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<chapter id="encoding-guide">
<title>Kodowanie przy użyciu <application>MEncodera</application></title>
<sect1 id="menc-feat-dvd-mpeg4">
<title>Rippowanie DVD do wysokiej jakości pliku MPEG-4 ("DivX")</title>
<para>
Jednym z często zadawanych pytań jest "Jak zrobić rip najlepszej jakości
przy danej objętości?". Innym pytaniem jest "Jak zrobić najlepszy możliwy
rip? Nie ważne jaka będzie objętość, chcę najlepszej jakości."
</para>
<para>
To drugie pytanie jest przynajmniej źle postawione. W końcu, jeśli nie
przejmujesz się wielkością pliku, mógłbyć po prostu skopiować strumień
MPEG-2 z DVD. Pewnie, dostaniesz AVI wielkości około 5GB, ale jeśli chcesz
najlepszej jakości i nie przejmujesz się wielkością to jest to najlepsze
wyjście.
</para>
<para>
Tak na prawdę, powodem dla którego chcesz przekodować DVD na MPEG-4 jest to,
że <emphasis role="bold">przejmujesz</emphasis> się wielkością pliku.
</para>
<para>
Ciężko jest pokazać książkowy przepis na tworzenie ripu DVD bardzo wysokiej
jakości. Trzeba wziąć pod uwagę kilka czynników, i powinieneś rozumieć
szczegóły procesu, albo jest duża szansa że nie będziesz zadowolony z wyników.
Poniżej zbadamy niektóre problemy i pokażemy przykład. Zakładamy że używasz
<systemitem class="library">libavcodec</systemitem> do kodowania obrazu,
chociaż ta sama teoria działą też przy innych kodekach.
</para>
<para>
Jeśli to wydaje Ci się za dużo, to pewnie powinieneś użyć jednej z wielu
nakładek dostępnych w
<ulink url="http://mplayerhq.hu/homepage/design7/projects.html#mencoder_frontends">sekcji MEncodera</ulink>
naszej strony z powiązanymi projektami.
W ten sposób, powinno się udać otrzymać ripy wysokiej jakości bez zbyt
myślenia za dużo, ponieważ te narzędzia są projektowane by podejmować za
Ciebie mądre decyzje.
</para>
<!-- ********** -->
<sect2 id="menc-feat-dvd-mpeg4-preparing-encode">
<title>Przygotowanie do kodowania: Identyfikowanie materiału źródłowego
i framerate</title>
<para>
Zanim w ogóle zaczniesz myśleć o kodowaniu filmu, musisz przejść kilka
wstępnych kroków.
</para>
<para>
Pierwszym i najważniejszym krokiem przed kodowaniem powinno być
ustalenie jakim typem filmu się zajmujesz.
Jeśli Twój film jest z DVD albo telewizji (zwykłej, kablowej czy
satelitarnej), będzie w jednym z dwóch formatów: NTSC w Ameryce Północnej
i Japonii, PAL w Europie itp.
Trzeba sobie jednak zdawać sprawę z tego, że jest to tylko format do
prezentacji w telewizji, i często <emphasis role="bold">nie</emphasis> jest
oryginalnym formatem filmu.
Doświadczenie pokazuje że filmy NTSC są trudniejsze do kodowania, ponieważ
jest więcej elementów do zidentyfikowania w źródle.
Żeby zrobić odpowienie kodowanie musisz znać oryginalny format filmu.
Nieuwzględnienie tego skutkuje wieloma wadami wynikowego pliku, na przykład
brzydkie artefakty przeplotu i powtórzone albo zagubione klatki.
Poza tym że są brzydkie, artefakty są też szkodliwe dla kodowania:
Dostaniesz gorszą jakość na jednostkę bitrate.
</para>
<sect3 id="menc-feat-dvd-mpeg4-preparing-encode-fps">
<title>Ustalanie źródłowego framerate</title>
<para>
Poniżej jest lista popularnych typów materiału źródłowego, gdzie można je
najczęściej znaleźć i ich własności:
</para>
<itemizedlist>
<listitem><para>
<emphasis role="bold">Typowy film</emphasis>: Tworzony do wyświetlania przy
24fps.
</para></listitem>
<listitem><para>
<emphasis role="bold">Film PAL</emphasis>: Nagrywany kamerą video PAL
z prędkością 50 pól na sekundę.
Pole składa się tylko z parzystych albo nieparzystych linii klatki.
Telewizja była projektowana by odświerzać je naprzemiennie, w charakterze
taniej formy analogowej kompresji.
Ludzkie oko podobno kompensuje ten efekt, ale jeśli zrozumiesz przeplot
nauczysz się go widzieć też w telewizji i nigdy już nie będziesz z niej
ZADOWOLONY.
Dwa pola <emphasis role="bold">nie</emphasis> dają pełnej klatki, ponieważ
są uchwycone co 1/50 sekundy, więc nie pasują do siebie, chyba że nie ma
ruchu.
</para></listitem>
<listitem><para>
<emphasis role="bold">Film NTSC</emphasis>: Nagrany kamerą NTSC z prędkością
60000/1001 pól na sekundę, albo 60 pól na sekundę w erze przedkolorowej.
Poza tym podobny do PAL.
</para></listitem>
<listitem><para>
<emphasis role="bold">Animacja</emphasis>: Zazwyczaj rysowana przy 24fps,
ale zdarzają się też z mieszanym framerate.
</para></listitem>
<listitem><para>
<emphasis role="bold">Grafika komputerowa (CG)</emphasis>: Może być dowolny
framerate, ale niektóre są częstsze niż inne; wartości 24 i 30 klatek na
sekundę są typowe dla NTSC, a 25fps jest typowe dla PAL.
</para></listitem>
<listitem><para>
<emphasis role="bold">Stary film</emphasis>: Rozmaite niższe framerate.
</para></listitem>
</itemizedlist>
</sect3>
<sect3 id="menc-feat-dvd-mpeg4-preparing-encode-material">
<title>Identyfikowanie materiału źródłowego</title>
<para>
Filmy składające się z klatek nazywa się progresywnymi,
podczas gdy te składające się z niezależnych pól nazywa się
z przeplotem, albo filmem - chociaż ten drugi termin jest niejasny.
</para>
<para>
Żeby nie było za łatwo, niektóre filmy są kombinacją kilku powyższych typów.
</para>
<para>
Najważniejszą różnicą między tymi formatami, jest to że niektóre są oparte
na klatkach a inne na polach.
<emphasis role="bold">Zawsze</emphasis> gdy film jest przygotowywany do
wyświetlania w telewizji jest przekształcany na format oparty na polach.
Rozliczne metody którymi się tego dokonuje są wspólnie nazywane "telecine",
a niesławne "3:2 pulldown" z NTSC jest jednym z jego rodzajów.
Jeżeli oryginał nie był też oparty na polach (z tą samą prędkością),
dostajesz film w innym formacie niż oryginał.
</para>
<itemizedlist>
<title>Jest kilka popularnych typów pulldown:</title>
<listitem><para>
<emphasis role="bold">pulldown PAL 2:2</emphasis>: Najprzyjemniejszy z nich
wszystkich.
Każda klatka jest pokazywana przez czas dwóch pól, poprzez wydobycie
parzystych i nieparzystych linii i pokazywanie ich na przemian.
Jeśli oryginalny materiał miał 24fps, ten proces przyspiesza film o 4%.
</para></listitem>
<listitem><para>
<emphasis role="bold">pulldown PAL 2:2:2:2:2:2:2:2:2:2:2:3</emphasis>:
Każda 12ta klatka jest pokazywana przez czas trzech pól zamiast tylko dwóch.
Dzięki temu nie ma przyspieszenia o 4%, ale proces jest o wiele trudniejszy
do odtworzenia.
Zazwyczaj występuje w produkcjach muzycznych, gdzie zmiana prędkości o 4%
poważnie by uszkodziła muzykę.
</para></listitem>
<listitem><para>
<emphasis role="bold">NTSC 3:2 telecine</emphasis>: Klatki są pokazywane na
przemian przez czas 3ch albo 2ch pól.
To daje częstotliwość pól 2.5 raza większą niż oryginalna częstotliwość
klatek. Rezultat jest też lekko zwolniony z 60 pól na sekundę do 60000/1001
pól na sekundę by utrzymać częstotliwość pól w NTSC.
</para></listitem>
<listitem><para>
<emphasis role="bold">NTSC 2:2 pulldown</emphasis>: Używane do pokazywania
materiałów 30fps na NTSC.
Przyjemne, tak jak pulldown 2:2 PAL.
</para></listitem>
</itemizedlist>
<para>
Są też metody konwersji między filmami PAL i NTSC, ale ten temat
wykracza poza zakres tego podręcznika.
Jeśli natkniesz się na taki film i chcesz go zakodować, to największe
szanse masz robiąc kopię w oryginalnym formacie.
Konwersja między tymi dwoma formatami jest wysoce destrukcyjna i nie może
zostać ładnie odwrócona, więc kodowanie będzie o wiele gorszej jakości jeśli
jest robione z przekonwertowanego źródła.
</para>
<para>
Gdy film jest zapisywany na DVD, kolejne pary pól są zapisywane jako klatka,
pomimo tego że nie są przezaczone do wyświetlania razem.
Standard MPEG-2 używany na DVD i w cyfrowej TV pozwala na zakodowanie
oryginalnej progresywnej klatki i na przechowanie w nagłówku klatki ilości
pól przez które ta klatka powinna być pokazana.
Filmy zrobione przy użyciu tej metody są często określane mianem "miękkiego
telecine" (soft-telecine), ponieważ proces ten tylko informuje odtwarzacz że
ma on zastosować pulldown, a nie stosuje go samemu.
Tak jest o wiele lepiej, ponieważ może to zostać łatwo odwrócone (a tak na
prawdę zignorowane) przez koder i ponieważ zachowuje możliwie najwyższą
jakość.
Niestety, wielu producentów DVD i stacji nadawczych nie stosuje prawidłowych
technik kodowania ale w zamian produkuje filmy przy użyciu "twardego
telecine" (hard-telecine), gdzie pola są faktycznie powtórzone
w zakodowanym MPEG-2.
</para>
<para>
Procedury radzenia sobie z takimi przypadkami będą omówione
<link linkend="menc-feat-telecine">w dalszej części przewodnika</link>.
Teraz podamy tylko kilka wskazówek jak identyfikować z jakim typem materiału
mamy do czynienia.
</para>
<itemizedlist>
<title>Regiony NTSC:</title>
<listitem><para>
Jeśli <application>MPlayer</application> wyświetla w trakcie oglądania filmu
że framerate zostało zmienione na 24000/1001 i nigdy nie powraca, to jest
to prawie na pewno progresywny materiał na którym zastosowano "miękkie
telecine".
</para></listitem>
<listitem><para>
Jeśli <application>MPlayer</application> pokazuje że framerate zmienia się
między 24000/1001 i 30000/1001 i czasami widzisz "grzebienie" to jest kilka
możliwości.
<!-- Torinthiel: grzebienie mi najlepiej pasują, ale może jest oficjalne tłumaczenie -->
Kawałki 24000/1001fps są prawie na pewno progresywne, poddane "miękkiemu
telecine", ale fragmenty 30000/1001 fps mogą albo być 24000/1001 poddanym
"twardemu telecine" albo filmem NTCS o 60000/1001 polach na sekundę.
Używaj tych samych metod co w następnych dwóch przypadkach żeby je odróżnić.
</para></listitem>
<listitem><para>
Jeśli <application>MPlayer</application> nigdy nie pokazuje informacji
o zmianie framerate i każda klatka z ruchem wygląda jak grzebień, to masz
film NTSC z 60000/1001 polami na sekundę.
</para></listitem>
<listitem><para>
Jeśli <application>MPlayer</application> nigdy nie pokazuje informacji
o zmianie framerate i dwie klatki z każdych pięciu mają grzebienie, to film
jest 24000/1001 fps poddanym "twardemu telecine".
</para></listitem>
</itemizedlist>
<itemizedlist>
<title>Regiony PAL:</title>
<listitem><para>
Jeśli nie widzisz grzebieni, to jest to 2:2 pulldown.
</para></listitem>
<listitem><para>
Jeśli na przemian przez pół sekundy widzisz grzebienie a potem nie, to masz
2:2:2:2:2:2:2:2:2:2:2:3 pulldown.
</para></listitem>
<listitem><para>
Jeśli zawsze widzisz grzebienie w trakcie ruchu, to film jest filmem PAL
wyświetlanym z 50 polami na sekundę.
<!-- Torinthiel: wyświetlanym czy nagranym? -->
</para></listitem>
</itemizedlist>
<note><title>Podpowiedź:</title>
<para>
<application>MPlayer</application> może zwolnić odtwarzanie filmu opcją
-speed albo odtwarzać klatka po klatce.
Spróbuj użyć opcji <option>-speed</option> 0.2 żeby oglądać film bardzo
wolno, albo naciskaj wielokrotnie klawisz "<keycap>.</keycap>" żeby
wyświetlać klatka po klatce.
Może to pomóc zidentyfikować wzorzec jeśli
nie możesz go dostrzec przy pełnej prędkości.
</para>
</note>
</sect3>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-dvd-mpeg4-2pass">
<title>Stały kwantyzator a tryb wieloprzebiegowy</title>
<para>
Jest możliwe zakodowanie filmu z szeroką gamą jakości.
Z nowoczesnymi koderami i odrobiną kompresji przed kodekiem (zmniejszenie
rozdzielczości i usuwanie szumu), możliwe jest osiągnięcie bardzo dobrej
jakości przy 700 MB, dla 90-110 minutowego filmu kinowego.
Dodatkowo tylko najdłuższe filmy nie dają się zakodować na 1400 MB z prawie
doskonałą jakością.
</para>
<para>
Są trzy podejścia do kodowania video: stały bitrate (CBR),
stały kwantyzator i tryb wieloprzebiegowy (ABR, uśrednione bitrate).
</para>
<para>
Złożoność klatek filmu, a zatem i ilość bitów potrzebna na ich zakodowanie,
może się bardzo mocno zmieniać w zależności od sceny.
Nowoczesne kodery potrafią się dostosowywać do tych zmian i zmieniać
bitrate.
Jednak w prostych trybach, takich jak CBR, kodery nie znają zapotrzebowania
na bitrate w przyszłych scenach, więc nie mogą na długo przekraczać
wymaganego bitrate.
Bardziej zaawansowane tryby, takie jak kodowanie wieloprzebiegowe, potrafią
wziąć pod uwagę statystyki z poprzednich przebiegów, co naprawia ten problem.
</para>
<note><title>Uwaga:</title>
<para>
Większość kodeków obsługujących kodowanie ABR obsługuje tylko kodowanie
dwuprzebiegowe, podczas gdy niektóre inne, na przykład
<systemitem class="library">x264</systemitem> albo
<systemitem class="library">Xvid</systemitem> potrafią wykonywać wiele
przebiegów, z lekką poprawą jakości po każdym przebiegu. Jednak ta poprawa
nie jest zauważalna ani mierzalna po około 4tym przebiegu.
Dlatego też, w tej części, tryb dwuprzebiegowy i wieloprzebiegowy będą
używane zamiennie.
</para>
</note>
<para>
W każdym z tych trybów, kodek video (na przykład
<systemitem class="library">libavcodec</systemitem>)
dzieli klatkę obrazu na makrobloki 16x16 pikseli i stosuje do każdego z nich
kwantyzator. Im niższy kwantyzator, tym lepsza jakość i tym wyższe bitrate.
Metody jakiej koder używa do ustalenia kwantyzatora są różne i można nimi
sterować. (Jest to straszliwe uproszczenie, ale wystarcza do zrozumienia
podstaw.)
</para>
<para>
Kiedy podajesz stałe bitrate, kodek koduje usuwając tyle szczegółów ile musi
i tak mało jak to tylko możliwe żeby pozostać poniżej podanego bitrate.
Jeśli na prawdę nie obchodzi cię wielkość pliku, możesz użyć CBR i podać
nieskończone bitrate (W praktyce oznacza to bitrate na tyle wysokie że nie
stanowi bariery, na przykład 10000Kbit.) Bez żadnego ograniczenia na bitrate
kodek użyje najniższego możliwego kwantyzatora do każdej klatki (ustalonego
dla <systemitem class="library">libavcodec</systemitem> opcją
<option>vqmin</option>, domyślnie 2).
Gdy tylko podasz bitrate na tyle niskie że kodek musi używać wyższego
kwantyzatora, to prawie na pewno niszczysz film.
Żeby tego uniknąć, powinieneś pewnie zmniejszyć rozdzielczość filmu, metodą
opisaną dalej.
Ogólnie, jeśli zależy Ci na jakości, powinieneś unikać CBR.
</para>
<para>
Przy stałym kwantyzatorze, kodek używa na każdym makrobloku tego samego
kwantyzatora, podanego opcją <option>vqscale</option>
(w przypadku <systemitem class="library">libavcodec</systemitem>).
Jeśli chcesz możliwie najlepszy efekt, znów ignorując bitrate, możesz użyć
<option>vqscale=2</option>. Da to ten sam bitrate i PSNR (peak
signal-to-noise ratio, szczytowa proporcja sygnału do szumu) co CBR
z <option>vbitrate</option>=nieskończoność i domyślnym
<option>vqmin</option>.
</para>
<para>
Problemem przy stałym kwantyzatorze jest to, że używa podanego kwantyzatora
niezależnie od tego czy makroblok tego wymaga czy nie. To znaczy że można by
było zastosować do makrobloku wyższy kwantyzator bez utraty postrzegalnej
jakości. Dlaczego marnować bity na niepotrzebnie niski kwantyzator?
Mikroprocesor ma tyle cykli ile jest czasu, ale jest tylko ograniczona ilość
bitów na twardym dysku.
</para>
<para>
Przy kodowaniu dwuprzebiegowym, pierwszy przebieg potraktuje film jak przu
ustawieniu CBR, ale zachowa informacje o własnościach każdej klatki. Te dane
są później używane przy drugim przebiegu do podejmowania słusznych decyzji
o używanym kwantyzatorze. Przy szybkich scenach albo niewielu szczegółach
pewnie użyje większego kwantyzatora, podczas gdy dla powolnych,
szczegółowych scen będzie niższy kwantyzator.
</para>
<para>
Jeśli używasz <option>vqscale=2</option> to marnujesz bity. Jeśli używasz
<option>vqscale=3</option> to nie dostajesz najlepszej możliwej jakości.
Załóżmy że zakodowałeś swoje DVD przy <option>vqscale=3</option>
i dostałeś bitrate 1800Kbit. Jeśli zrobisz dwa przebiegi
z <option>vbitrate=1800</option> ostateczny wynik będzie miał
<emphasis role="bold">wyższą jakość</emphasis> przy
<emphasis role="bold">tym samym bitrate</emphasis>.
</para>
<para>
Ponieważ jesteś już przekonany że prawidłowym wyborem są dwa przebiegi,
prawdziwym pytaniem jest jakiego bitrate użyć. Nie ma jednej odpowiedzi.
Idealnie chcesz wybrać bitrate będący najlepszym kompromisem między jakością
a wielkością pliku. To się zmienia w zależności od filmu.
</para>
<para>
Jeśli wielkość nie ma znaczenia, dobrym punktem wyjściowym do bardzo
wysokiej jakości jest około 2000Kbit plus minus 200Kbit.
Jeśli jest dużo akcji albo szczegółów, albo po prostu masz bardzo wrażliwe
oko, możesz się zdecydować na 2400 albo 2600.
Przy niektórych DVD możesz nie zauważyć różnicy przy 1400Kbit. Dobrym
pomysłem jest poeksperymentowanie z kilkoma scenami i różnymi wartościami
bitrate żeby nabrać wyczucia.
</para>
<para>
Jeśli chcesz konkretnej wielkości, musisz jakoś obliczyć bitrare.
Ale zanim to zrobisz, musisz wiedzieć ile miejsca potrzebujesz na dźwięk,
więc powinieneś <link linkend="menc-feat-dvd-mpeg4-audio">ściągnąć go</link>
najpierw.
Możesz wyliczyć bitrate z następującego równania:
<systemitem>bitrate = (wielkość_docelowa_w_MBajtach - wielkość_dźwięku_w_MBajtach)
* 1024 * 1024 / długość_w_sekundach * 8 / 1000</systemitem>
Na przykład by wcisnąć dwugodzinny film na płytkę 702MB, z 60MB ścieżki
dźwiękowej, bitrate video musi być:
<systemitem>(702 - 60) * 1024 * 1024 / (120*60) * 8 / 1000
= 740kbps</systemitem>
</para>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-dvd-mpeg4-constraints">
<title>Ograniczenia efektywnego kodowania</title>
<para>
Ze względu na naturę kodowania typu MPEG istnieją różne ograniczenia których
warto się trzymać żeby osiągnąć najlepszą jakość.
MPEG dzieli obraz na kwadraty 16x16 pikseli nazywane makroblokami,
każdy z nich składa się z 4 bloków 8x8 informacji o jasności (luminancja, luma)
i dwóch 8x8 z połową rozdzielczości (jeden na składową czerwono-morską, drugi
na niebiesko-żółtą).
Nawet jeśli wysokość i szerokość filmu nie są wielokrotnościami 16,
koder użyje tyle makrobloków żeby przykryć cały obszar obrazu,
dodatkowa przestrzeń zostanie zmarnowana.
Zatem w interesie zwiększenai jakości przy utrzymaniu wielkości pliku kiepskim
pomysłem jest używanie wymiarów które nie są wielokrotnością 16.
</para>
<para>
Większość DVD ma też jakieś czarne ramki na brzegach.
Zostawienie ich tam <emphasis role="bold">mocno</emphasis> zaszkodzi jakości
na kilka sposobów.
</para>
<orderedlist>
<listitem>
<para>
Kompresje typu MPEG są zależne od transformat przestrzeni częstotliwości,
a dokładniej Dyskretnej Transformaty Cosinusowej (DCT), która jest podobna do
transformaty Fouriera.
Ten sposób kodowania jest efektywny przy wzorach i gładkich przejściach, ale
kiepsko sobie radzi z ostrymi krawędziami.
Żeby je zakoować, musi używać o wiele większej liczby bitów, albo wystąpią
artefakty znane jako pierścienie.
</para>
<para>
Transformacja częstotliwości (DCT) jest stosowana osobno do każdego
makrobloku (tak na prawdę do każdego bloku), więc ten problem istnieje tylko
gdy ostra krawędź jest wewnątrz bloku.
Jeśli czarna ramka zaczyna się dokładnie na krawędzi 16-pikselowego bloku,
nie stwarza problemów.
Jednakże, rzadko kiedy takie ramki są ładnie wyrównane, więc zazwyczaj będzie
trzeba przyciąć obraz żeby tego uniknąć.
</para>
</listitem>
</orderedlist>
<para>
Poza transformatami przestrzeni częstotliwości, kompresje typu MPEG używają
wektorów ruchu, by reprezentować zmiany między sąsiednimi klatkami.
Oczywiście wektory ruchu są mniej efektywne w stosunku do nowej treści
przychodzącej z brzegów obrazka, ponieważ nie było jej na poprzedniej klatce.
Jeśli obraz rozciąga się do krawędzi zakodowanego regionu,
wektory ruchu radzą sobie z treścią wychodzącą poza krawędzie.
Jednak jeśli są ramki, mogą być kłopoty:
</para>
<orderedlist continuation="continues">
<listitem>
<para>
Dla każdego makrobloku, kompresja typu MPEG przechowuje wektor opisujący
która część poprzedniej klatki powinna być skopiowana do tego makrobloku jako
podstawa do przewidzenia następnej klatki.
Zakodowane wtedy muszą być tylko różnice.
Jeśli makroblok zawiera fragment ramki, to wektory ruchu z pozostałych cześci
obrazu zamażą obramowanie.
Oznacza to że dużo bitów będzie zużytych albo na jej powtórne zaczernienie
albo (co bardziej prawdopodobne), wektor ruchu w ogóle nie będzie użyty
i wszystkie zmiany w tym makrobloku będzie trzeba zakodować bezpośrednio.
W obu przypadkach, bardzo cierpi na tym efektywność kodowania.
</para>
<para>
Powtórnie, ten problem występuje tylko jeśli ramki nie są na krawędziach
16-pikselowych bloków.
</para>
</listitem>
<listitem>
<para>
W końcu, przypuśćmy że mamy makroblok wewnątrz obrazu i obiekt dostaje się do
niego z okolic krawędzi.
Kodowanie typu MPEG nie potrafi powiedzieć "skopiuj część która jeest
wewnątrz obraka, ale nie czarne obramowanie." Dlatego obramowanie też
zostanie skopiowane i trzeba będzie zużyć sporo bitów żeby zakodować fragment
obrazu który powinien tam być.
</para>
<para>
Jeśli obraz sięga do krawędzi zakodowanego obszaru, MPEG ma specjalne
optymalizacje do wielokrotnego kopiowania ostatniego rzędu pikseli jeśli
wektor ruchu przychodzi z poza zakodoanego obszaru.
Staje się to bezużyteczne gry obraz ma czarne obramowanie.
W odróżnieniu od problemów 1 i 2 tutaj nic nie pomoże ustawienie obramowania
w odpowiednim miejscu.
</para>
</listitem>
<listitem><para>
Mimo tego, że obramowanie jest całkowicie czarne i nigdy się nie zmienia,
zawsze jest pewien narzut związany z większą ilością makrobloków.
</para></listitem>
</orderedlist>
<para>
Ze wszystkich tych powodów zalecane jest całkowite wycięcie czarnych obramowań.
Dodatkowo, jeśli przy krawędziach jest obszar zakłóceń/zniekształceń, obcięcie
go również poprawi efektywność kodowania.
Puryści, którzy chcą możliwie dokładnie zachować oryginał mogą się sprzeciwiać,
ale jeśli nie planujesz używać stałego kwantyzatora to jakość uzyskana dzięki
skadrowaniu znacząco przewyższy utratę informacji przy brzegach.
</para>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-dvd-mpeg4-crop">
<title>Kadrowanie i skalowanie</title>
<para>
Przypomnijmy z poprzedniej części że ostateczna wielkość (wysokość i szerokość)
obrazu do kodowania powinna być wielokrotnością 16.
Można to osiągnąć kadrowaniem, skalowaniem albo kombinacją obydwu.
</para>
<para>
Przy kadrowaniu, jest kilka reguł których musimy przestrzegać by uniknąć
uszkodzenia filmu.
Zwykły format YUV, 4:2:0, przechowuje wartości koloru podpróbkowane, czyli
kolor jest próbkowany o połowę rzadziej w każdym kierunku niż jasność.
Spójrzmy na diagram, na którym L oznacza punkty próbkowania jasności (luma)
a C koloru (chroma).
</para>
<informaltable>
<?dbhtml table-width="40%" ?>
<?dbfo table-width="40%" ?>
<tgroup cols="8" align="center">
<colspec colnum="1" colname="col1"/>
<colspec colnum="2" colname="col2"/>
<colspec colnum="3" colname="col3"/>
<colspec colnum="4" colname="col4"/>
<colspec colnum="5" colname="col5"/>
<colspec colnum="6" colname="col6"/>
<colspec colnum="7" colname="col7"/>
<colspec colnum="8" colname="col8"/>
<spanspec spanname="spa1-2" namest="col1" nameend="col2"/>
<spanspec spanname="spa3-4" namest="col3" nameend="col4"/>
<spanspec spanname="spa5-6" namest="col5" nameend="col6"/>
<spanspec spanname="spa7-8" namest="col7" nameend="col8"/>
<tbody>
<row>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
</row>
<row>
<entry spanname="spa1-2">C</entry>
<entry spanname="spa3-4">C</entry>
<entry spanname="spa5-6">C</entry>
<entry spanname="spa7-8">C</entry>
</row>
<row>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
</row>
<row>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
</row>
<row>
<entry spanname="spa1-2">C</entry>
<entry spanname="spa3-4">C</entry>
<entry spanname="spa5-6">C</entry>
<entry spanname="spa7-8">C</entry>
</row>
<row>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<para>
Jak widać, wiersze i kolumny obrazu w sposób naturalny łączą się w pary.
Dlatego przesunięcia i wymiary kadrowania <emphasis>muszą</emphasis> być
liczbami parzystymi.
Jeśli nie są, barwa nie będzie już dobrze dopasowana do jasności.
Teoretycznie możliwe jest kadrowanie z nieparzystym przesunięciem, ale wymaga
to przepróbkowania kolorów, co jest potencjalnie stratną operacją nie
obsługiwaną przez filtr kadrowania.
</para>
<para>
Dalej, film z przeplotem jest kodowany jak poniżej:
</para>
<informaltable>
<?dbhtml table-width="80%" ?>
<?dbfo table-width="80%" ?>
<tgroup cols="16" align="center">
<colspec colnum="1" colname="col1"/>
<colspec colnum="2" colname="col2"/>
<colspec colnum="3" colname="col3"/>
<colspec colnum="4" colname="col4"/>
<colspec colnum="5" colname="col5"/>
<colspec colnum="6" colname="col6"/>
<colspec colnum="7" colname="col7"/>
<colspec colnum="8" colname="col8"/>
<colspec colnum="9" colname="col9"/>
<colspec colnum="10" colname="col10"/>
<colspec colnum="11" colname="col11"/>
<colspec colnum="12" colname="col12"/>
<colspec colnum="13" colname="col13"/>
<colspec colnum="14" colname="col14"/>
<colspec colnum="15" colname="col15"/>
<colspec colnum="16" colname="col16"/>
<spanspec spanname="spa1-2" namest="col1" nameend="col2"/>
<spanspec spanname="spa3-4" namest="col3" nameend="col4"/>
<spanspec spanname="spa5-6" namest="col5" nameend="col6"/>
<spanspec spanname="spa7-8" namest="col7" nameend="col8"/>
<spanspec spanname="spa9-10" namest="col9" nameend="col10"/>
<spanspec spanname="spa11-12" namest="col11" nameend="col12"/>
<spanspec spanname="spa13-14" namest="col13" nameend="col14"/>
<spanspec spanname="spa15-16" namest="col15" nameend="col16"/>
<tbody>
<row>
<entry namest="col1" nameend="col8">Górne pole</entry>
<entry namest="col9" nameend="col16">Dolne pole</entry>
</row>
<row>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry spanname="spa1-2">C</entry>
<entry spanname="spa3-4">C</entry>
<entry spanname="spa5-6">C</entry>
<entry spanname="spa7-8">C</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
</row>
<row>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry spanname="spa9-10">C</entry>
<entry spanname="spa11-12">C</entry>
<entry spanname="spa13-14">C</entry>
<entry spanname="spa15-16">C</entry>
</row>
<row>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
</row>
<row>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry spanname="spa1-2">C</entry>
<entry spanname="spa3-4">C</entry>
<entry spanname="spa5-6">C</entry>
<entry spanname="spa7-8">C</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
</row>
<row>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry spanname="spa9-10">C</entry>
<entry spanname="spa11-12">C</entry>
<entry spanname="spa13-14">C</entry>
<entry spanname="spa15-16">C</entry>
</row>
<row>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
<entry>L</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<para>
Jak widać, wzór powtarza się dopiero po 4 liniach.
Dlatego przy filmie z przeplotem, pionowa współrzędna i wysokość kadrowania
muszą być wielokrotnościami 4.
</para>
<para>
Podstawową rozdzielczością DVD jest 720x480 dla NTSC i 720x576 dla PAL, ale
jest też flaga proporcji, która określa czy obraz jest ekranowy (4:3) czy
panoramiczny (16:9).
Wiele (jeśli nie większość) panoramicznych DVD nie jest dokładnie 16:9 tylko
raczej 1,85:1 lub 2,35:1 (cinescope).
Oznacza to że będzie czarne obramowanie na filmie, które trzeba usunąć.
</para>
<para>
<application>MPlayer</application> dostarcza filtr wykrywania kadrowania
(<option>-vf cropdetect</option>), który określi prostokąt kadrowania.
Uruchom <application>MPlayera</application> z opcją <option>-vf
cropdetect</option> a wydrukuje on ustawienia kadrowania potrzebne do usunięcia
obramowania.
Powinieneś puścić film wystarczająco długo żeby został użyty cały obszar
obrazu, inaczej wartości będą niedokładne.
</para>
<para>
Potem przetestuj otrzymane wartości z użyciem
<application>MPlayera</application>, przekazując opcje podane przez
<option>cropdetect</option> i dostosowując prostokąt według potrzeb.
Filtr <option>rectangle</option> może w tym pomóc, pozwalając na interaktywne
ustawienie prostokąta kadrowania na filmie.
Pamiętaj, by trzymać się powyższych reguł podzielności, żeby nie przestawić
płaszczyzny koloru.
</para>
<para>
W pewnych przypadkach skalowanie może być niepożądane.
Skalowanie w kierunku pionowym jest trudne przy filmie z przeplotem, a jeśli
chcesz zachować przeplot, zazwyczaj powinieneś się wstrzymać od skalowania.
Jeśl nie chcesz skalować, ale nadal chcesz używać wymiarów będących wielokrotnościami 16 to musisz przekadrować.
NIe należy niedokadrowywać, bo obramowania są bardzo szkodliwe przy kodowaniu!
</para>
<para>
Ponieważ MPEG-4 używa makrobloków 16x16, powinieneś się upewnić,
że każdy wymiar kodowanego filmu jest wielokrotnością 16, inaczej
degradujemy jakość, zwłaszcza przy niższych bitrate.
Można tego dokonać zaokrąglając wysokość i szerokość prostokąta kadrowania do
najbliższej wielokrotności 16.
Jak powiedziano wcześniej, trzeba zwiększyć przesunięcie
pionowe o połowę różnicy między starą a nową wysokością,
żeby wynikowy film był brany ze środka klatki.
A ze względu na sposób w jaki próbkowane jest DVD, upewnij się że przesunięcie
jest parzyste (w zasadzie, stosuj się do reguły, żeby nigdy nie używać
nieparzystych wartości przy przycinaniu i skalowaniu obrazu).
Jeśli nie czujesz się dobrze odrzucając dodatkowe piksele,
może wolisz przeskalować video.
Przyjżymy się temu w przykładzie poniżej.
Możesz też pozwolić filtrowi <option>cropdetect</option> zrobić to wszystko za
Ciebie, jako że ma on opcjonalny parametr <option>round</option>
(zaokrąglenie), domyślnie równy 16.
</para>
<para>
Uważaj też na "poł-czarne" piksele na przegach. Też je wykadruj, albo będziesz
na nie marnował bity któ?e przydadzą się gdzie indziej.
</para>
<para>
Po tym wszystkim prawdopodobnie dostaniesz film który nie ma dokładnie
proporcji 1,85:1 ani 2,35:1 tylko coś podobnego.
Mógłbyś samemu policzyć nowe proporcje, ale <application>MEncoder</application>
ma pocję do <systemitem class="library">libavcodec</systemitem> nazywaną
<option>autoaspect</option> która zrobi to za Ciebie.
Nie powinieneś przeskalowywać video żeby wyrównać piksele, chyba że chcesz
marnować miejsce na dysku.
Skalowanie powinno być robione przy odtwarzaniu, a odtwarzacz używa informacji
o proporcjach zapisanych w AVI żeby określić prawidłową rozdzielczość.
Niestety, nie wszystkie odtwarzacze uznają te informacje,
dlatego mimo wszystko możesz chcieć przeskalować.
</para>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-dvd-mpeg4-resolution-bitrate">
<title>Dobieranie rozdzielczości i bitrate</title>
<para>
Jeśli nie kodujesz w trybie stałego kwantyzatora, musisz wybrać bitrate.
Jest to dość prosta rzecz – to (średnia) ilość bitów jaka będzie
używana do zakodowania jednej sekundy filmu.
Zazwyczaj bitrate mierzy się w kilobitach (1000 bitów) na sekundę.
Wielkość filmu na dysku to bitrate razy długość filmu,
plus drobne "dodatki" (patrz na przykład sekcja o
<link linkend="menc-feat-dvd-mpeg4-muxing-avi-limitations">kontenerze AVI</link>
).
Pozostałe parametry, takie jak skalowanie, kadrowanie itp.
<emphasis role="bold">nie</emphasis> zmienią wielkości pliku jeśli nie
zmienisz też bitrate!
</para>
<para>
Bitrate <emphasis role="bold">nie</emphasis> skaluje się proporcjonalnie do
rozdzielczości.
To znaczy, film 320x240 w 200 kbit/s nie będzie tej samej jakości co ten sam
film w 640x480 i 800 kbit/s!
Są ku temu dwie przyczyny:
<orderedlist>
<listitem><para>
<emphasis role="bold">Wizualna</emphasis>: Łatwiej zauważyć artefakty MPEG
jeśli są bardziej powiększone!
Artefakty powstają na poziomie bloków (8x8).
Ludzkie oko trudniej dostrzega błędy w 4800 małych blokach niż w 1200 dużych
(zakładając że skalujesz na pełny ekran).
</para></listitem>
<listitem><para>
<emphasis role="bold">Teoretyczna</emphasis>: Kiedy zmniejszasz obraz ale
nadal używasz tych samych bloków 8x8 do transformacji przestrzeni
częstotliwości. masz więcej danych w pasmach wyższych częstotliwości.
W pewien sposób każdy piksel ma więcej szczegółów niż poprzednio.
Dlatego, mimo że przeskalowany obraz zawiera 1/4 informacji jeśli chodzi
o wielkość, to nadal może zawierać większość informacji w przestrzeni
częstotliwości (zakładając że wysokie częstotliwości były mało używane
w oryginalnym filmie 640x480).
</para></listitem>
</orderedlist>
</para>
<para>
Poprzednie podręczniki zalecały dobranie bitrate i rozdzielczości w sposób
bazujący na podejściu "bity na piksel", ale z powyższych powodów zazwyczaj nie
jest to prawidłowe.
Lepszym przybliżeniem zdaje się skalowanie bitrate proporcjonalnie do
pierwiastka kwadratowego z rozdzielczości, czyli film 320x240 i 400 kbit/s
powinien być podobny do 640x480 i 800 kbit/s.
Nie zostało to jednak zweryfikowane ani teoretycznie ani empirycznie.
Dodatkowo, ponieważ filmy są bardzo zróżnicowane jeśli chodzi o szum,
szczegóły, ilość ruchu itp. bezsensowne jest podawanie ogólnych zaleceń na bity
na przekątą (analogia bitów na piksel używająca pierwiastka).
</para>
<para>
Omówiliśmy więc problemy z wyborem bitrate i rozdzielczości.
</para>
<sect3 id="menc-feat-dvd-mpeg4-resolution-bitrate-compute">
<title>Obliczanie rozdzielczości</title>
<para>
Następne kroki przeprowadzą Cię przez obliczenie rozdzielczości dla Twojego
filmu bez zniekształcania go za bardzo, biorąc pod uwagę kilka typów informacji
o źródłowym filmie.
Najpierw powinieneś policzyć zakodowane proporcje:
<systemitem>ARc = (Wc x (ARa / PRdvd )) / Hc</systemitem>
<itemizedlist>
<title>gdzie:</title>
<listitem><para>
Hc i Wc to wysokość i szerokość skadrowanego filmu.
</para></listitem>
<listitem><para>
ARa do wyświetlane proporcje, zazwyczaj 4/3 lub 16/9.
</para></listitem>
<listitem><para>
PRdvd to proporcje na DVD równe 1,25=(720*576) dla DVD PAL i 1,5=(720/480) dla
VD NTSC.
</para></listitem>
</itemizedlist>
</para>
<para>
Potem możesz policzyć rozdzielczość X i Y, zgodnie z dobranym wskażnikiem
Jakości Kompresji (Compression Quality, CQ):
<systemitem>RozY = INT(Pierw( 1000*Bitrate/25/ARc/CQ )/16) * 16</systemitem>
i
<systemitem>RozX = INT( ResY * ARc / 16) * 16</systemitem>,
gdzie INT oznacza zaokrąglenie do liczby całkowitej.
</para>
<para>
Dobrze, ale co to jest CQ?
CQ reprezentuje ilość bitów na piksel i klatkę kodowania.
Z grubsza biorąc, im większe CQ tym mniejsza szansa na zobaczenie artefaktów
kodowania.
Jednakże, jeśli masz docelową wielkość filmu (na przykład 1 lub 2 płyty CD),
masz ograniczoną ilość bitów do zużycia; dlatego musisz znaleźć równowagę
między poziomem kompresji i jakością.
</para>
<para>
CQ zależy od bitrate, efektywności kodeka video i rozdzielczości filmu.
Żeby podnieść CQ zazwyczej zmniejszysz film, ponieważ bitrate jest funkcją docelowej wielkości i długości filmu, które są stałe.
Przy użyciu kodeków MPEG-4 ASP, takich jak
<systemitem class="library">Xvid</systemitem> i
<systemitem class="library">libavcodec</systemitem>, CQ niższe niż 0,18
zazwyczaj daje kiepski obraz, ponieważ nie ma dość bitów by zakodować
informacje z każdego makrobloku.
(MPEG4, jak wiele innych kodeków, grupuje piksele w bloki żeby
skompresować obraz. Jeśli nie ma dość bitów widać krawędzie tych bloków.)
Dlatego też mądrze jest wybrać CQ w zakresie 0,20 do 0,22 na film jednopłytkowy
i 0,26-0,28 na dwupłytkowy przy standardowych opcjach kodowania.
Bardziej zaawansowane opcje kodowania, takie jak te podane tutaj dla
<link linkend="menc-feat-mpeg4-lavc-example-settings"><systemitem class="library">libavcodec</systemitem></link>
i
<link linkend="menc-feat-xvid-example-settings"><systemitem class="library">Xvid</systemitem></link>
powinny umożliwić otrzymanie takiej samej jakości z CQ w zakresie 0,18 do 0,20
na 1 CD i 0,24 do 0,26 na 2 CD.
Z kodekami MPEG-4 AVC, takimi jak
<systemitem class="library">x264</systemitem>, możesz używać CQ w zakresie
0,14 do 0,16 przy standardowych opcjach
a powinno się też udać zejść do 0,10 do 0,12 z
<link linkend="menc-feat-x264-example-settings">zaawansowanymi opcjami kodowania <systemitem class="library">x264</systemitem></link>.
</para>
<para>
Pamiętajmy, że CQ jest tylko przydatnym odnośnikiem, zależnym od kodowanego
filmu. CQ równe ,018 może wyglądać dobrze przy Bergmanie, w przeciwieństwie do
filmu takiego jak Martix, który zaawiera wiele bardzo ruchliwych scen.
Z drugiej strony, bezsensowne jest podnoszenie CQ powyżej 0,30 jako że marnuje się bity bez zauważalnej poprawy jakości.
Pamiętajmy też że, jak było wspomniane wcześniej, filmy w niższej
rozdzielczości potrzebują większego CQ (w porównaniu do na przykład
rozdzielczości DVD) żeby dobrze wyglądać.
</para>
</sect3>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-dvd-mpeg4-filtering">
<title>Filtrowanie</title>
<para>
Bardzo ważne do robienia dobrych kodowań jest nauczenie się posługiwania
systemem filtrów <application>MEncodera</application>.
Całe przetwarzanie video jest wykonywane przez filtry – kadrowanie, skalowanie,
dopasowywanie kolorów, usuwanie szumu, telecine, odwrócone telecine, usuwanie
bloków żeby wymienić choć część.
Poza dużą ilością obsługiwanych formatów wejściowych to właśnie zakres
dostępnych filtrów jest jedną z głównych przewag
<application>MEncodera</application> nad podobnymi programami.
</para>
<para>
Filtry są ładowane do łańcucha przy pomocy opcji -vf:
<screen>-vf filtr1=opcje,filtr2=opcje,...</screen>
Większość filtrów przyjmuje kilka parametrów numerycznych oddzielanych
dwukropkami, ale dokładna składnia zależy od filtru więc szczegóły odnośnie
filtrów, które chcesz zastosować, znajdziesz na stronie man.
</para>
<para>
Filtry działają na filmie w kolejnoścy w jakiej zostały załadowane.
Na przykład następujący łańcuch:
<screen>-vf crop=688:464:12:4,scale=640:464</screen>
najpierw skadruje fragment 688x464 filmu z lewym górnym rogiem na pozycji
(12,4) a potem zmniejszy rozdzielczość wyniku do 640x464.
</para>
<para>
Niektóre filtry trzeba ładować na początku lub blisko początku łańcucha,
ponieważ korzystają one z informacji którą następne filtry mogą zgubić lub
unieważnić.
Sztandarowym przykłądem jest <option>pp</option> (postprocessing, tylko gdy
wykonuje operacje usuwania bloków lub pierścieni),
<option>spp</option> (inny postprocessor do usuwania artefaktów MPEG),
<option>pullup</option> (odwrócone telecine) i
<option>softpulldown</option> (konwertuje miękkie telecine na twarde).
</para>
<para>
W ogólności chcesz przeprowadzać jak najmniej filtrowania żeby film pozostał
możliwie bliski oryginałowi.
Kadrowanie często jest niezbęne (jak opisano powyżej) ale staraj się uniknąć
skalowania.
Chociaż czasami zmniejszenie rozdzielczości jest lepszym wyjściem niż użycie
wyższego kwantyzatora, chcemy uniknąć obu: pamiętajmy, że od początku
zdecydowaliśmy się wybrać jakość kosztem wielkości.
</para>
<para>
Nie należy też dostosowywać gammy, kontrastu, jasności itp.
Co wygląda dobrze na Twoim ekranie może nie być tak dobre na innych.
Takie dostrojenia powinny być wykonywane tylko przy odtwarzaniu.
</para>
<para>
Jedną rzeczą którą możesz chcieć zrobić, jest przepuszczenie filmu przez bardzo
lekkie usuwanie szumów, takie jak <option>-vf hqdn3d=2:1:2</option>.
Znów, to kwestia lepszego zastosowania bitów: po co marnować je na zakodowanie
szumu skoro można dodać ten szum przy odtwarzaniu?
Zwiększenie parametrów dla <option>hqdn3d</option> jeszcze bardziej poprawi
kompresowalność, ale jeśli przesadzisz to zauważalnie zniekształcisz obraz.
Wartości sugerowane powyżej (<option>2:1:2</option>) są dość konserwatywne; nie
bój się eksperymentować z wyższymi wartościami i samemu oceniać wyniki.
</para>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-dvd-mpeg4-interlacing">
<title>Przeplot i telecine</title>
<para>
Prawie wszystkie filmy są kręcone przy 24 fps.
Ponieważ NTSC ma 30000/1001 fps potrzebna jest pewna przeróbka żeby film 24 fps
mógł być wyświetlany z prawidłową szybkością NTSC.
Ten proces nazywa się 3:2 pulldown, często zwany też telecine (ponieważ jest
używany przy konwersji z kina do telewizji) i, w uproszczeniu, jest to
spowolnienie filmu do 24000/1001 fps i powtórzenie co czwartej klatki.
</para>
<para>
Filmy DVD PAL, odtwarzanie przy 25 fps, nie wymagają żadnego specjalnego
traktowania.
(Technicznie rzecz ujmując, PAL może być poddany telecine, nazywanemu 2:2
pulldown, ale w praktyce nie jest to problemem.)
Po prostu film 24 fps jest odtwarzany przy 25 fps.
W wyniku tego film jest odtwarzany odrobinkę szybciej, ale jeśli nie masz
nieziemskich zmysłów to tego nie zauważysz.
Większość DVD PAL ma skorygowaną wysokość dźwięku, więc kiedy są odtwarzane
przy 25 fps dźwięk będzie brzmiał poprawnie, mimo tego że ścieżka dźwiekowa
(jak i cały film) jest o 4% krótsza niż DVD NTSC.
</para>
<para>
Ponieważ film na DVD PAL nie został zmieniony, nie ma powodu za bardzo
przejmować się framerate.
Oryginał ma 25 fps i Twój rip też będzie miał 25 fps.
Jednak jeśli ripujesz film z DVD NTSC możesz być zmuszony do zastosowania
odwrotnego telecine.
</para>
<para>
Dla filmów nagrywanych przy 24 fps obraz na DVD NTSC jest albo poddany telecine
na 30000/1001 albo jest progresywny przy 24000/1001 i przeznaczony do poddania
telecine w locie przez odtwarzacz DVD.
Z drugiej strony seriale telewizyjne zazwyczaj mają tylko przeplot, nie są poddane telecine.
Nie jest to reguła: Niektóre seriale (na przykład Buffy Łowca Wampirów) mają
przeplot, a inne są mieszanką progresywnego i przeplotu (Angel, 24).
</para>
<para>
Jest wysoce zalecane żebyś przeczytał sekcję
<!-- TODO przetłumaczyć tytuł -->
<link linkend="menc-feat-telecine">How to deal with telecine and interlacing in NTSC DVDs</link>
żeby dowiedzieć się jak sobie radzić z różnymi możliwościami.
</para>
<para>
Jednak jeśli zazwyczaj tylko ripujesz filmy, prawdopodobnie masz doczynienia
z filmem 24 fps progresywnym lub poddanym telecine, a w takim przypadku możesz
użyć filtra <option>pullup</option> podając parametr
<option>-vf pullup,softskip</option>.
</para>
</sect2>
<!-- ********** -->
<!-- synced 'till here -->
<sect2 id="menc-feat-dvd-mpeg4-encoding-interlaced">
<title>Encoding interlaced video</title>
<para>
If the movie you want to encode is interlaced (NTSC video or
PAL video), you will need to choose whether you want to
deinterlace or not.
While deinterlacing will make your movie usable on progressive
scan displays such a computer monitors and projectors, it comes
at a cost: The fieldrate of 50 or 60000/1001 fields per second
is halved to 25 or 30000/1001 frames per second, and roughly half of
the information in your movie will be lost during scenes with
significant motion.
</para>
<para>
Therefore, if you are encoding for high quality archival purposes,
it is recommended not to deinterlace.
You can always deinterlace the movie at playback time when
displaying it on progressive scan devices.
The power of currently available computers forces players to use a
deinterlacing filter, which results in a slight degradation in
image quality.
But future players will be able to mimic the interlaced display of
a TV, deinterlacing to full fieldrate and interpolating 50 or
60000/1001 entire frames per second from the interlaced video.
</para>
<para>
Special care must be taken when working with interlaced video:
</para>
<orderedlist>
<listitem><para>
Crop height and y-offset must be multiples of 4.
</para></listitem>
<listitem><para>
Any vertical scaling must be performed in interlaced mode.
</para></listitem>
<listitem><para>
Postprocessing and denoising filters may not work as expected
unless you take special care to operate them a field at a time,
and they may damage the video if used incorrectly.
</para></listitem>
</orderedlist>
<para>
With these things in mind, here is our first example:
<screen>
mencoder <replaceable>capture.avi</replaceable> -mc 0 -oac lavc -ovc lavc -lavcopts \
vcodec=mpeg2video:vbitrate=6000:ilme:ildct:acodec=mp2:abitrate=224
</screen>
Note the <option>ilme</option> and <option>ildct</option> options.
</para>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-dvd-mpeg4-av-sync">
<title>Notes on Audio/Video synchronization</title>
<para>
<application>MEncoder</application>'s audio/video synchronization
algorithms were designed with the intention of recovering files with
broken sync.
However, in some cases they can cause unnecessary skipping and duplication of
frames, and possibly slight A/V desync, when used with proper input
(of course, A/V sync issues apply only if you process or copy the
audio track while transcoding the video, which is strongly encouraged).
Therefore, you may have to switch to basic A/V sync with
the <option>-mc 0</option> option, or put this in your
<systemitem>~/.mplayer/mencoder</systemitem> config file, as long as
you are only working with good sources (DVD, TV capture, high quality
MPEG-4 rips, etc) and not broken ASF/RM/MOV files.
</para>
<para>
If you want to further guard against strange frame skips and
duplication, you can use both <option>-mc 0</option> and
<option>-noskip</option>.
This will prevent <emphasis>all</emphasis> A/V sync, and copy frames
one-to-one, so you cannot use it if you will be using any filters that
unpredictably add or drop frames, or if your input file has variable
framerate!
Therefore, using <option>-noskip</option> is not in general recommended.
</para>
<para>
The so-called "three-pass" audio encoding which
<application>MEncoder</application> supports has been reported to cause A/V
desync.
This will definitely happen if it is used in conjunction with certain
filters, therefore, it is now recommended <emphasis>not</emphasis> to
use three-pass audio mode.
This feature is only left for compatibility purposes and for expert
users who understand when it is safe to use and when it is not.
If you have never heard of three-pass mode before, forget that we
even mentioned it!
</para>
<para>
There have also been reports of A/V desync when encoding from stdin
with <application>MEncoder</application>.
Do not do this! Always use a file or CD/DVD/etc device as input.
</para>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-dvd-mpeg4-codec">
<title>Choosing the video codec</title>
<para>
Which video codec is best to choose depends on several factors,
like size, quality, streamability, usability and popularity, some of
which widely depend on personal taste and technical constraints.
</para>
<itemizedlist>
<listitem>
<para>
<emphasis role="bold">Compression efficiency</emphasis>:
It is quite easy to understand that most newer-generation codecs are
made to increase quality and compression.
Therefore, the authors of this guide and many other people suggest that
you cannot go wrong
<footnote id='fn-menc-feat-dvd-mpeg4-codec-cpu'><para>
Be careful, however: Decoding DVD-resolution MPEG-4 AVC videos
requires a fast machine (i.e. a Pentium 4 over 1.5GHz or a Pentium M
over 1GHz).
</para></footnote>
when choosing MPEG-4 AVC codecs like
<systemitem class="library">x264</systemitem> instead of MPEG-4 ASP codecs
such as <systemitem class="library">libavcodec</systemitem> MPEG-4 or
<systemitem class="library">Xvid</systemitem>.
(Advanced codec developers may be interested in reading Michael
Niedermayer's opinion on
"<ulink url="http://guru.multimedia.cx/?p=10">why MPEG4-ASP sucks</ulink>".)
Likewise, you should get better quality using MPEG-4 ASP than you
would with MPEG-2 codecs.
</para>
<para>
However, newer codecs which are in heavy development can suffer from
bugs which have not yet been noticed and which can ruin an encode.
This is simply the tradeoff for using bleeding-edge technology.
</para>
<para>
What is more, beginning to use a new codec requires that you spend some
time becoming familiar with its options, so that you know what
to adjust to achieve a desired picture quality.
</para>
</listitem>
<listitem><para>
<emphasis role="bold">Hardware compatibility</emphasis>:
It usually takes a long time for standalone video players to begin to
include support for the latest video codecs.
As a result, most only support MPEG-1 (like VCD, XVCD and KVCD), MPEG-2
(like DVD, SVCD and KVCD) and MPEG-4 ASP (like DivX,
<systemitem class="library">libavcodec</systemitem>'s LMP4 and
<systemitem class="library">Xvid</systemitem>)
(Beware: Usually, not all MPEG-4 ASP features are supported).
Please refer to the technical specs of your player (if they are available),
or google around for more information.
</para></listitem>
<listitem>
<para>
<emphasis role="bold">Best quality per encoding time</emphasis>:
Codecs that have been around for some time (such as
<systemitem class="library">libavcodec</systemitem> MPEG-4 and
<systemitem class="library">Xvid</systemitem>) are usually heavily
optimized with all kinds of smart algorithms and SIMD assembly code.
That is why they tend to yield the best quality per encoding time ratio.
However, they may have some very advanced options that, if enabled,
will make the encode really slow for marginal gains.
</para>
<para>
If you are after blazing speed you should stick around the default
settings of the video codec (although you should still try the other
options which are mentioned in other sections of this guide).
</para>
<para>
You may also consider choosing a codec which can do multi-threaded
processing, though this is only useful for users of machines with
several CPUs.
<systemitem class="library">libavcodec</systemitem> MPEG-4 does
allow that, but speed gains are limited, and there is a slight
negative effect on picture quality.
<systemitem class="library">Xvid</systemitem>'s multi-threaded encoding,
activated by the <option>threads</option> option, can be used to
boost encoding speed — by about 40-60% in typical cases —
with little if any picture degradation.
<systemitem class="library">x264</systemitem> also allows multi-threaded
encoding, which currently speeds up encoding by 94% per CPU core while
lowering PSNR between 0.005dB and 0.01dB on a typical setup.
</para>
</listitem>
<listitem>
<para>
<emphasis role="bold">Personal taste</emphasis>:
This is where it gets almost irrational: For the same reason that some
hung on to DivX 3 for years when newer codecs were already doing wonders,
some folks will prefer <systemitem class="library">Xvid</systemitem>
or <systemitem class="library">libavcodec</systemitem> MPEG-4 over
<systemitem class="library">x264</systemitem>.
</para>
<para>
You should make your own judgement; do not take advice from people who
swear by one codec.
Take a few sample clips from raw sources and compare different
encoding options and codecs to find one that suits you best.
The best codec is the one you master, and the one that looks
best to your eyes on your display
<footnote id='fn-menc-feat-dvd-mpeg4-codec-playback'><para>
The same encode may not look the same on someone else's monitor or
when played back by a different decoder, so future-proof your encodes by
playing them back on different setups.
</para></footnote>!
</para>
</listitem>
</itemizedlist>
<para>
Please refer to the section
<link linkend="menc-feat-selecting-codec">selecting codecs and container formats</link>
to get a list of supported codecs.
</para>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-dvd-mpeg4-audio">
<title>Audio</title>
<para>
Audio is a much simpler problem to solve: if you care about quality, just
leave it as is.
Even AC-3 5.1 streams are at most 448Kbit/s, and they are worth every bit.
You might be tempted to transcode the audio to high quality Vorbis, but
just because you do not have an A/V receiver for AC-3 pass-through today
does not mean you will not have one tomorrow. Future-proof your DVD rips by
preserving the AC-3 stream.
You can keep the AC-3 stream either by copying it directly into the video
stream <link linkend="menc-feat-mpeg4">during the encoding</link>.
You can also extract the AC-3 stream in order to mux it into containers such
as NUT or Matroska.
<screen>
mplayer <replaceable>source_file.vob</replaceable> -aid 129 -dumpaudio -dumpfile <replaceable>sound.ac3</replaceable>
</screen>
will dump into the file <replaceable>sound.ac3</replaceable> the
audio track number 129 from the file
<replaceable>source_file.vob</replaceable> (NB: DVD VOB files
usually use a different audio numbering,
which means that the VOB audio track 129 is the 2nd audio track of the file).
</para>
<para>
But sometimes you truly have no choice but to further compress the
sound so that more bits can be spent on the video.
Most people choose to compress audio with either MP3 or Vorbis audio codecs.
While the latter is a very space-efficient codec, MP3 is better supported
by hardware players, although this trend is changing.
</para>
<para>
Do <emphasis>not</emphasis> use <option>-nosound</option> when encoding
a file with audio, even if you will be encoding and muxing audio
separately later.
Though it may work in ideal cases, using <option>-nosound</option> is
likely to hide some problems in your encoding command line setting.
In other words, having a soundtrack during your encode assures you that,
provided you do not see messages such as
<quote>Too many audio packets in the buffer</quote>, you will be able
to get proper sync.
</para>
<para>
You need to have <application>MEncoder</application> process the sound.
You can for example copy the original soundtrack during the encode with
<option>-oac copy</option> or convert it to a "light" 4 kHz mono WAV
PCM with <option>-oac pcm -channels 1 -srate 4000</option>.
Otherwise, in some cases, it will generate a video file that will not sync
with the audio.
Such cases are when the number of video frames in the source file does
not match up to the total length of audio frames or whenever there
are discontinuities/splices where there are missing or extra audio frames.
The correct way to handle this kind of problem is to insert silence or
cut audio at these points.
However <application>MPlayer</application> cannot do that, so if you
demux the AC-3 audio and encode it with a separate app (or dump it to PCM with
<application>MPlayer</application>), the splices will be left incorrect
and the only way to correct them is to drop/duplicate video frames at the
splice.
As long as <application>MEncoder</application> sees the audio when it is
encoding the video, it can do this dropping/duping (which is usually OK
since it takes place at full black/scene change), but if
<application>MEncoder</application> cannot see the audio, it will just
process all frames as-is and they will not fit the final audio stream when
you for example merge your audio and video track into a Matroska file.
</para>
<para>
First of all, you will have to convert the DVD sound into a WAV file that the
audio codec can use as input.
For example:
<screen>
mplayer <replaceable>source_file.vob</replaceable> -ao pcm:file=<replaceable>destination_sound.wav</replaceable> \
-vc dummy -aid 1 -vo null
</screen>
will dump the second audio track from the file
<replaceable>source_file.vob</replaceable> into the file
<replaceable>destination_sound.wav</replaceable>.
You may want to normalize the sound before encoding, as DVD audio tracks
are commonly recorded at low volumes.
You can use the tool <application>normalize</application> for instance,
which is available in most distributions.
If you are using Windows, a tool such as <application>BeSweet</application>
can do the same job.
You will compress in either Vorbis or MP3.
For example:
<screen>oggenc -q1 <replaceable>destination_sound.wav</replaceable></screen>
will encode <replaceable>destination_sound.wav</replaceable> with
the encoding quality 1, which is roughly equivalent to 80Kb/s, and
is the minimum quality at which you should encode if you care about
quality.
Please note that <application>MEncoder</application> currently cannot
mux Vorbis audio tracks
into the output file because it only supports AVI and MPEG
containers as an output, each of which may lead to audio/video
playback synchronization problems with some players when the AVI file
contain VBR audio streams such as Vorbis.
Do not worry, this document will show you how you can do that with third
party programs.
</para>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-dvd-mpeg4-muxing">
<title>Muxing</title>
<para>
Now that you have encoded your video, you will most likely want
to mux it with one or more audio tracks into a movie container, such
as AVI, MPEG, Matroska or NUT.
<application>MEncoder</application> is currently only able to natively output
audio and video into MPEG and AVI container formats.
for example:
<screen>
mencoder -oac copy -ovc copy -o <replaceable>output_movie.avi</replaceable> \
-audiofile <replaceable>input_audio.mp2</replaceable> <replaceable>input_video.avi</replaceable>
</screen>
This would merge the video file <replaceable>input_video.avi</replaceable>
and the audio file <replaceable>input_audio.mp2</replaceable>
into the AVI file <replaceable>output_movie.avi</replaceable>.
This command works with MPEG-1 layer I, II and III (more commonly known
as MP3) audio, WAV and a few other audio formats too.
</para>
<para>
<application>MEncoder</application> features experimental support for
<systemitem class="library">libavformat</systemitem>, which is a
library from the FFmpeg project that supports muxing and demuxing
a variety of containers.
For example:
<screen>
mencoder -oac copy -ovc copy -o <replaceable>output_movie.asf</replaceable> -audiofile <replaceable>input_audio.mp2</replaceable> \
<replaceable>input_video.avi</replaceable> -of lavf -lavfopts format=asf
</screen>
This will do the same thing as the previous example, except that
the output container will be ASF.
Please note that this support is highly experimental (but getting
better every day), and will only work if you compiled
<application>MPlayer</application> with the support for
<systemitem class="library">libavformat</systemitem> enabled (which
means that a pre-packaged binary version will not work in most cases).
</para>
<sect3 id="menc-feat-dvd-mpeg4-muxing-filter-issues">
<title>Improving muxing and A/V sync reliability</title>
<para>
You may experience some serious A/V sync problems while trying to mux
your video and some audio tracks, where no matter how you adjust the
audio delay, you will never get proper sync.
That may happen when you use some video filters that will drop or
duplicate some frames, like the inverse telecine filters.
It is strongly encouraged to append the <option>harddup</option> video
filter at the end of the filter chain to avoid this kind of problem.
</para>
<para>
Without <option>harddup</option>, if <application>MEncoder</application>
wants to duplicate a frame, it relies on the muxer to put a mark on the
container so that the last frame will be displayed again to maintain
sync while writing no actual frame.
With <option>harddup</option>, <application>MEncoder</application>
will instead just push the last frame displayed again into the filter
chain.
This means that the encoder receives the <emphasis>exact</emphasis>
same frame twice, and compresses it.
This will result in a slightly bigger file, but will not cause problems
when demuxing or remuxing into other container formats.
</para>
<para>
You may also have no choice but to use <option>harddup</option> with
container formats that are not too tightly linked with
<application>MEncoder</application> such as the ones supported through
<systemitem class="library">libavformat</systemitem>, which may not
support frame duplication at the container level.
</para>
</sect3>
<sect3 id="menc-feat-dvd-mpeg4-muxing-avi-limitations">
<title>Limitations of the AVI container</title>
<para>
Although it is the most widely-supported container format after MPEG-1,
AVI also has some major drawbacks.
Perhaps the most obvious is the overhead.
For each chunk of the AVI file, 24 bytes are wasted on headers and index.
This translates into a little over 5 MB per hour, or 1-2.5%
overhead for a 700 MB movie. This may not seem like much, but it could
mean the difference between being able to use 700 kbit/sec video or
714 kbit/sec, and every bit of quality counts.
</para>
<para>
In addition this gross inefficiency, AVI also has the following major
limitations:
</para>
<orderedlist>
<listitem><para>
Only fixed-fps content can be stored. This is particularly limiting
if the original material you want to encode is mixed content, for
example a mix of NTSC video and film material.
Actually there are hacks that can be used to store mixed-framerate
content in AVI, but they increase the (already huge) overhead
fivefold or more and so are not practical.
</para></listitem>
<listitem><para>
Audio in AVI files must be either constant-bitrate (CBR) or
constant-framesize (i.e. all frames decode to the same number of
samples).
Unfortunately, the most efficient codec, Vorbis, does not meet
either of these requirements.
Therefore, if you plan to store your movie in AVI, you will have to
use a less efficient codec such as MP3 or AC-3.
</para></listitem>
</orderedlist>
<para>
Having said all that, <application>MEncoder</application> does not
currently support variable-fps output or Vorbis encoding.
Therefore, you may not see these as limitations if
<application>MEncoder</application> is the
only tool you will be using to produce your encodes.
However, it is possible to use <application>MEncoder</application>
only for video encoding, and then use external tools to encode
audio and mux it into another container format.
</para>
</sect3>
<sect3 id="menc-feat-dvd-mpeg4-muxing-matroska">
<title>Muxing into the Matroska container</title>
<para>
Matroska is a free, open standard container format, aiming
to offer a lot of advanced features, which older containers
like AVI cannot handle.
For example, Matroska supports variable bitrate audio content
(VBR), variable framerates (VFR), chapters, file attachments,
error detection code (EDC) and modern A/V Codecs like "Advanced Audio
Coding" (AAC), "Vorbis" or "MPEG-4 AVC" (H.264), next to nothing
handled by AVI.
</para>
<para>
The tools required to create Matroska files are collectively called
<application>mkvtoolnix</application>, and are available for most
Unix platforms as well as <application>Windows</application>.
Because Matroska is an open standard you may find other
tools that suit you better, but since mkvtoolnix is the most
common, and is supported by the Matroska team itself, we will
only cover its usage.
</para>
<para>
Probably the easiest way to get started with Matroska is to use
<application>MMG</application>, the graphical frontend shipped with
<application>mkvtoolnix</application>, and follow the
<ulink url="http://www.bunkus.org/videotools/mkvtoolnix/doc/mkvmerge-gui.html">guide to mkvmerge GUI (mmg)</ulink>
</para>
<para>
You may also mux audio and video files using the command line:
<screen>
mkvmerge -o <replaceable>output.mkv</replaceable> <replaceable>input_video.avi</replaceable> <replaceable>input_audio1.mp3</replaceable> <replaceable>input_audio2.ac3</replaceable>
</screen>
This would merge the video file <replaceable>input_video.avi</replaceable>
and the two audio files <replaceable>input_audio1.mp3</replaceable>
and <replaceable>input_audio2.ac3</replaceable> into the Matroska
file <replaceable>output.mkv</replaceable>.
Matroska, as mentioned earlier, is able to do much more than that, like
multiple audio tracks (including fine-tuning of audio/video
synchronization), chapters, subtitles, splitting, etc...
Please refer to the documentation of those applications for
more details.
</para>
</sect3>
</sect2>
</sect1>
<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
<sect1 id="menc-feat-telecine">
<title>How to deal with telecine and interlacing within NTSC DVDs</title>
<sect2 id="menc-feat-telecine-intro">
<title>Introduction</title>
<formalpara>
<title>What is telecine?</title>
<para>
If you do not understand much of what is written in this document, read the
<ulink url="http://en.wikipedia.org/wiki/Telecine">Wikipedia entry on telecine</ulink>.
It is an understandable and reasonably comprehensive
description of what telecine is.
</para></formalpara>
<formalpara>
<title>A note about the numbers.</title>
<para>
Many documents, including the article linked above, refer to the fields
per second value of NTSC video as 59.94 and the corresponding frames
per second values as 29.97 (for telecined and interlaced) and 23.976
(for progressive). For simplicity, some documents even round these
numbers to 60, 30, and 24.
</para></formalpara>
<para>
Strictly speaking, all those numbers are approximations. Black and
white NTSC video was exactly 60 fields per second, but 60000/1001
was later chosen to accommodate color data while remaining compatible
with contemporary black and white televisions. Digital NTSC video
(such as on a DVD) is also 60000/1001 fields per second. From this,
interlaced and telecined video are derived to be 30000/1001 frames
per second; progressive video is 24000/1001 frames per second.
</para>
<para>
Older versions of the <application>MEncoder</application> documentation
and many archived mailing list posts refer to 59.94, 29.97, and 23.976.
All <application>MEncoder</application> documentation has been updated
to use the fractional values, and you should use them too.
</para>
<para>
<option>-ofps 23.976</option> is incorrect.
<option>-ofps 24000/1001</option> should be used instead.
</para>
<formalpara>
<title>How telecine is used.</title>
<para>
All video intended to be displayed on an NTSC
television set must be 60000/1001 fields per second. Made-for-TV movies
and shows are often filmed directly at 60000/1001 fields per second, but
the majority of cinema is filmed at 24 or 24000/1001 frames per
second. When cinematic movie DVDs are mastered, the video is then
converted for television using a process called telecine.
</para></formalpara>
<para>
On a DVD, the video is never actually stored as 60000/1001 fields per
second. For video that was originally 60000/1001, each pair of fields is
combined to form a frame, resulting in 30000/1001 frames per
second. Hardware DVD players then read a flag embedded in the video
stream to determine whether the odd- or even-numbered lines should
form the first field.
</para>
<para>
Usually, 24000/1001 frames per second content stays as it is when
encoded for a DVD, and the DVD player must perform telecining
on-the-fly. Sometimes, however, the video is telecined
<emphasis>before</emphasis> being stored on the DVD; even though it
was originally 24000/1001 frames per second, it becomes 60000/1001 fields per
second. When it is stored on the DVD, pairs of fields are combined to form
30000/1001 frames per second.
</para>
<para>
When looking at individual frames formed from 60000/1001 fields per
second video, telecined or otherwise, interlacing is clearly visible
wherever there is any motion, because one field (say, the
even-numbered lines) represents a moment in time 1/(60000/1001)
seconds later than the other. Playing interlaced video on a computer
looks ugly both because the monitor is higher resolution and because
the video is shown frame-after-frame instead of field-after-field.
</para>
<itemizedlist>
<title>Notes:</title>
<listitem><para>
This section only applies to NTSC DVDs, and not PAL.
</para></listitem>
<listitem><para>
The example <application>MEncoder</application> lines throughout the
document are <emphasis role="bold">not</emphasis> intended for
actual use. They are simply the bare minimum required to encode the
pertaining video category. How to make good DVD rips or fine-tune
<systemitem class="library">libavcodec</systemitem> for maximal
quality is not within the scope of this section; refer to other
sections within the <link linkend="encoding-guide">MEncoder encoding
guide</link>.
</para></listitem>
<listitem><para>
There are a couple footnotes specific to this guide, linked like this:
<link linkend="menc-feat-telecine-footnotes">[1]</link>
</para></listitem>
</itemizedlist>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-telecine-ident">
<title>How to tell what type of video you have</title>
<sect3 id="menc-feat-telecine-ident-progressive">
<title>Progressive</title>
<para>
Progressive video was originally filmed at 24000/1001 fps, and stored
on the DVD without alteration.
</para>
<para>
When you play a progressive DVD in <application>MPlayer</application>,
<application>MPlayer</application> will print the following line as
soon as the movie begins to play:
<screen>
demux_mpg: 24000/1001 fps progressive NTSC content detected, switching framerate.
</screen>
From this point forward, demux_mpg should never say it finds
"30000/1001 fps NTSC content."
</para>
<para>
When you watch progressive video, you should never see any
interlacing. Beware, however, because sometimes there is a tiny bit
of telecine mixed in where you would not expect. I have encountered TV
show DVDs that have one second of telecine at every scene change, or
at seemingly random places. I once watched a DVD that had a
progressive first half, and the second half was telecined. If you
want to be <emphasis>really</emphasis> thorough, you can scan the
entire movie:
<screen>mplayer dvd://1 -nosound -vo null -benchmark</screen>
Using <option>-benchmark</option> makes
<application>MPlayer</application> play the movie as quickly as it
possibly can; still, depending on your hardware, it can take a
while. Every time demux_mpg reports a framerate change, the line
immediately above will show you the time at which the change
occurred.
</para>
<para>
Sometimes progressive video on DVDs is referred to as
"soft-telecine" because it is intended to
be telecined by the DVD player.
</para>
</sect3>
<sect3 id="menc-feat-telecine-ident-telecined">
<title>Telecined</title>
<para>
Telecined video was originally filmed at 24000/1001, but was telecined
<emphasis>before</emphasis> it was written to the DVD.
</para>
<para>
<application>MPlayer</application> does not (ever) report any
framerate changes when it plays telecined video.
</para>
<para>
Watching a telecined video, you will see interlacing artifacts that
seem to "blink": they repeatedly appear and disappear.
You can look closely at this by
<orderedlist>
<listitem><screen>mplayer dvd://1</screen></listitem>
<listitem><para>
Seek to a part with motion.
</para></listitem>
<listitem><para>
Use the <keycap>.</keycap> key to step forward one frame at a time.
</para></listitem>
<listitem><para>
Look at the pattern of interlaced-looking and progressive-looking
frames. If the pattern you see is PPPII,PPPII,PPPII,... then the
video is telecined. If you see some other pattern, then the video
may have been telecined using some non-standard method;
<application>MEncoder</application> cannot losslessly convert
non-standard telecine to progressive. If you do not see any
pattern at all, then it is most likely interlaced.
</para></listitem>
</orderedlist>
</para>
<para>
Sometimes telecined video on DVDs is referred to as
"hard-telecine". Since hard-telecine is already 60000/1001 fields
per second, the DVD player plays the video without any manipulation.
</para>
<para>
Another way to tell if your source is telecined or not is to play
the source with the <option>-vf pullup</option> and <option>-v</option>
command line options to see how <option>pullup</option> matches frames.
If the source is telecined, you should see on the console a 3:2 pattern
with <systemitem>0+.1.+2</systemitem> and <systemitem>0++1</systemitem>
alternating.
This technique has the advantage that you do not need to watch the
source to identify it, which could be useful if you wish to automate
the encoding procedure, or to carry out said procedure remotely via
a slow connection.
</para>
</sect3>
<sect3 id="menc-feat-telecine-ident-interlaced">
<title>Interlaced</title>
<para>
Interlaced video was originally filmed at 60000/1001 fields per second,
and stored on the DVD as 30000/1001 frames per second. The interlacing effect
(often called "combing") is a result of combining pairs of
fields into frames. Each field is supposed to be 1/(60000/1001) seconds apart,
and when they are displayed simultaneously the difference is apparent.
</para>
<para>
As with telecined video, <application>MPlayer</application> should
not ever report any framerate changes when playing interlaced content.
</para>
<para>
When you view an interlaced video closely by frame-stepping with the
<keycap>.</keycap> key, you will see that every single frame is interlaced.
</para>
</sect3>
<sect3 id="menc-feat-telecine-ident-mixedpt">
<title>Mixed progressive and telecine</title>
<para>
All of a "mixed progressive and telecine" video was originally
24000/1001 frames per second, but some parts of it ended up being telecined.
</para>
<para>
When <application>MPlayer</application> plays this category, it will
(often repeatedly) switch back and forth between "30000/1001 fps NTSC"
and "24000/1001 fps progressive NTSC". Watch the bottom of
<application>MPlayer</application>'s output to see these messages.
</para>
<para>
You should check the "30000/1001 fps NTSC" sections to make sure
they are actually telecine, and not just interlaced.
</para>
</sect3>
<sect3 id="menc-feat-telecine-ident-mixedpi">
<title>Mixed progressive and interlaced</title>
<para>
In "mixed progressive and interlaced" content, progressive
and interlaced video have been spliced together.
</para>
<para>
This category looks just like "mixed progressive and telecine",
until you examine the 30000/1001 fps sections and see that they do not have the
telecine pattern.
</para>
</sect3>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-telecine-encode">
<title>How to encode each category</title>
<para>
As I mentioned in the beginning, example <application>MEncoder</application>
lines below are <emphasis role="bold">not</emphasis> meant to actually be used;
they only demonstrate the minimum parameters to properly encode each category.
</para>
<sect3 id="menc-feat-telecine-encode-progressive">
<title>Progressive</title>
<para>
Progressive video requires no special filtering to encode. The only
parameter you need to be sure to use is <option>-ofps 24000/1001</option>.
Otherwise, <application>MEncoder</application>
will try to encode at 30000/1001 fps and will duplicate frames.
</para>
<para>
<screen>mencoder dvd://1 -oac copy -ovc lavc -ofps 24000/1001</screen>
</para>
<para>
It is often the case, however, that a video that looks progressive
actually has very short parts of telecine mixed in. Unless you are
sure, it is safest to treat the video as
<link linkend="menc-feat-telecine-encode-mixedpt">mixed progressive and telecine</link>.
The performance loss is small
<link linkend="menc-feat-telecine-footnotes">[3]</link>.
</para>
</sect3>
<sect3 id="menc-feat-telecine-encode-telecined">
<title>Telecined</title>
<para>
Telecine can be reversed to retrieve the original 24000/1001 content,
using a process called inverse-telecine.
<application>MPlayer</application> contains several filters to
accomplish this; the best filter, <option>pullup</option>, is described
in the <link linkend="menc-feat-telecine-encode-mixedpt">mixed
progressive and telecine</link> section.
</para>
</sect3>
<sect3 id="menc-feat-telecine-encode-interlaced">
<title>Interlaced</title>
<para>
For most practical cases it is not possible to retrieve a complete
progressive video from interlaced content. The only way to do so
without losing half of the vertical resolution is to double the
framerate and try to "guess" what ought to make up the
corresponding lines for each field (this has drawbacks - see method 3).
</para>
<orderedlist>
<listitem><para>
Encode the video in interlaced form. Normally, interlacing wreaks
havoc with the encoder's ability to compress well, but
<systemitem class="library">libavcodec</systemitem> has two
parameters specifically for dealing with storing interlaced video a
bit better: <option>ildct</option> and <option>ilme</option>. Also,
using <option>mbd=2</option> is strongly recommended
<link linkend="menc-feat-telecine-footnotes">[2] </link> because it
will encode macroblocks as non-interlaced in places where there is
no motion. Note that <option>-ofps</option> is NOT needed here.
<screen>mencoder dvd://1 -oac copy -ovc lavc -lavcopts ildct:ilme:mbd=2</screen>
</para></listitem>
<listitem><para>
Use a deinterlacing filter before encoding. There are several of
these filters available to choose from, each with its own advantages
and disadvantages. Consult <option>mplayer -pphelp</option> and
<option>mplayer -vf help</option> to see what is available
(grep for "deint"), read Michael Niedermayer's
<ulink url="http://guru.multimedia.cx/deinterlacing-filters/">Deinterlacing filters comparison</ulink>,
and search the
<ulink url="http://www.mplayerhq.hu/design7/mailing_lists.html">
MPlayer mailing lists</ulink> to find many discussions about the
various filters.
Again, the framerate is not changing, so no
<option>-ofps</option>. Also, deinterlacing should be done after
cropping <link linkend="menc-feat-telecine-footnotes">[1]</link> and
before scaling.
<screen>mencoder dvd://1 -oac copy -vf yadif -ovc lavc</screen>
</para></listitem>
<listitem><para>
Unfortunately, this option is buggy with
<application>MEncoder</application>; it ought to work well with
<application>MEncoder G2</application>, but that is not here yet. You
might experience crashes. Anyway, the purpose of <option> -vf
tfields</option> is to create a full frame out of each field, which
makes the framerate 60000/1001. The advantage of this approach is that no
data is ever lost; however, since each frame comes from only one
field, the missing lines have to be interpolated somehow. There are
no very good methods of generating the missing data, and so the
result will look a bit similar to when using some deinterlacing
filters. Generating the missing lines creates other issues, as well,
simply because the amount of data doubles. So, higher encoding
bitrates are required to maintain quality, and more CPU power is
used for both encoding and decoding. tfields has several different
options for how to create the missing lines of each frame. If you
use this method, then Reference the manual, and chose whichever
option looks best for your material. Note that when using
<option>tfields</option> you
<emphasis role="bold">have to</emphasis> specify both
<option>-fps</option> and <option>-ofps</option> to be twice the
framerate of your original source.
<screen>
mencoder dvd://1 -oac copy -vf tfields=2 -ovc lavc \
-fps 60000/1001 -ofps 60000/1001<!--
--></screen>
</para></listitem>
<listitem><para>
If you plan on downscaling dramatically, you can extract and encode
only one of the two fields. Of course, you will lose half the vertical
resolution, but if you plan on downscaling to at most 1/2 of the
original, the loss will not matter much. The result will be a
progressive 30000/1001 frames per second file. The procedure is to use
<option>-vf field</option>, then crop
<link linkend="menc-feat-telecine-footnotes">[1]</link> and scale
appropriately. Remember that you will have to adjust the scale to
compensate for the vertical resolution being halved.
<screen>mencoder dvd://1 -oac copy -vf field=0 -ovc lavc</screen>
</para></listitem>
</orderedlist>
</sect3>
<sect3 id="menc-feat-telecine-encode-mixedpt">
<title>Mixed progressive and telecine</title>
<para>
In order to turn mixed progressive and telecine video into entirely
progressive video, the telecined parts have to be
inverse-telecined. There are three ways to accomplish this,
described below. Note that you should
<emphasis role="bold">always</emphasis> inverse-telecine before any
rescaling; unless you really know what you are doing,
inverse-telecine before cropping, too
<link linkend="menc-feat-telecine-footnotes">[1]</link>.
<option>-ofps 24000/1001</option> is needed here because the output video
will be 24000/1001 frames per second.
</para>
<itemizedlist>
<listitem><para>
<option>-vf pullup</option> is designed to inverse-telecine
telecined material while leaving progressive data alone. In order to
work properly, <option>pullup</option> <emphasis role="bold">must</emphasis>
be followed by the <option>softskip</option> filter or
else <application>MEncoder</application> will crash.
<option>pullup</option> is, however, the cleanest and most
accurate method available for encoding both telecine and
"mixed progressive and telecine".
<screen>
mencoder dvd://1 -oac copy -vf pullup,softskip
-ovc lavc -ofps 24000/1001<!--
--></screen>
</para></listitem>
<listitem><para>
<option>-vf filmdint</option> is similar to
<option>-vf pullup</option>: both filters attempt to match a pair of
fields to form a complete frame. <option>filmdint</option> will
deinterlace individual fields that it cannot match, however, whereas
<option>pullup</option> will simply drop them. Also, the two filters
have separate detection code, and <option>filmdint</option> may tend to match fields a
bit less often. Which filter works better may depend on the input
video and personal taste; feel free to experiment with fine-tuning
the filters' options if you encounter problems with either one (see
the man page for details). For most well-mastered input video,
however, both filters work quite well, so either one is a safe choice
to start with.
<screen>
mencoder dvd://1 -oac copy -vf filmdint -ovc lavc -ofps 24000/1001<!--
--></screen>
</para></listitem>
<listitem><para>
An older method
is to, rather than inverse-telecine the telecined parts, telecine
the non-telecined parts and then inverse-telecine the whole
video. Sound confusing? softpulldown is a filter that goes through
a video and makes the entire file telecined. If we follow
softpulldown with either <option>detc</option> or
<option>ivtc</option>, the final result will be entirely
progressive. <option>-ofps 24000/1001</option> is needed.
<screen>
mencoder dvd://1 -oac copy -vf softpulldown,ivtc=1 -ovc lavc -ofps 24000/1001
</screen>
</para></listitem>
</itemizedlist>
</sect3>
<sect3 id="menc-feat-telecine-encode-mixedpi">
<title>Mixed progressive and interlaced</title>
<para>
There are two options for dealing with this category, each of
which is a compromise. You should decide based on the
duration/location of each type.
</para>
<itemizedlist>
<listitem>
<para>
Treat it as progressive. The interlaced parts will look interlaced,
and some of the interlaced fields will have to be dropped, resulting
in a bit of uneven jumpiness. You can use a postprocessing filter if
you want to, but it may slightly degrade the progressive parts.
</para>
<para>
This option should definitely not be used if you want to eventually
display the video on an interlaced device (with a TV card, for
example). If you have interlaced frames in a 24000/1001 frames per
second video, they will be telecined along with the progressive
frames. Half of the interlaced "frames" will be displayed for three
fields' duration (3/(60000/1001) seconds), resulting in a flicking
"jump back in time" effect that looks quite bad. If you
even attempt this, you <emphasis role="bold">must</emphasis> use a
deinterlacing filter like <option>lb</option> or
<option>l5</option>.
</para>
<para>
It may also be a bad idea for progressive display, too. It will drop
pairs of consecutive interlaced fields, resulting in a discontinuity
that can be more visible than with the second method, which shows
some progressive frames twice. 30000/1001 frames per second interlaced
video is already a bit choppy because it really should be shown at
60000/1001 fields per second, so the duplicate frames do not stand out as
much.
</para>
<para>
Either way, it is best to consider your content and how you intend to
display it. If your video is 90% progressive and you never intend to
show it on a TV, you should favor a progressive approach. If it is
only half progressive, you probably want to encode it as if it is all
interlaced.
</para>
</listitem>
<listitem><para>
Treat it as interlaced. Some frames of the progressive parts will
need to be duplicated, resulting in uneven jumpiness. Again,
deinterlacing filters may slightly degrade the progressive parts.
</para></listitem>
</itemizedlist>
</sect3>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-telecine-footnotes">
<title>Footnotes</title>
<orderedlist>
<listitem>
<formalpara>
<title>About cropping:</title>
<para>
Video data on DVDs are stored in a format called YUV 4:2:0. In YUV
video, luma ("brightness") and chroma ("color")
are stored separately. Because the human eye is somewhat less
sensitive to color than it is to brightness, in a YUV 4:2:0 picture
there is only one chroma pixel for every four luma pixels. In a
progressive picture, each square of four luma pixels (two on each
side) has one common chroma pixel. You must crop progressive YUV
4:2:0 to even resolutions, and use even offsets. For example,
<option>crop=716:380:2:26</option> is OK but
<option>crop=716:380:3:26 </option> is not.
</para>
</formalpara>
<para>
When you are dealing with interlaced YUV 4:2:0, the situation is a
bit more complicated. Instead of every four luma pixels in the
<emphasis>frame</emphasis> sharing a chroma pixel, every four luma
pixels in each <emphasis> field</emphasis> share a chroma
pixel. When fields are interlaced to form a frame, each scanline is
one pixel high. Now, instead of all four luma pixels being in a
square, there are two pixels side-by-side, and the other two pixels
are side-by-side two scanlines down. The two luma pixels in the
intermediate scanline are from the other field, and so share a
different chroma pixel with two luma pixels two scanlines away. All
this confusion makes it necessary to have vertical crop dimensions
and offsets be multiples of four. Horizontal can stay even.
</para>
<para>
For telecined video, I recommend that cropping take place after
inverse telecining. Once the video is progressive you only need to
crop by even numbers. If you really want to gain the slight speedup
that cropping first may offer, you must crop vertically by multiples
of four or else the inverse-telecine filter will not have proper data.
</para>
<para>
For interlaced (not telecined) video, you must always crop
vertically by multiples of four unless you use <option>-vf
field</option> before cropping.
</para>
</listitem>
<listitem><formalpara>
<title>About encoding parameters and quality:</title>
<para>
Just because I recommend <option>mbd=2</option> here does not mean it
should not be used elsewhere. Along with <option>trell</option>,
<option>mbd=2</option> is one of the two
<systemitem class="library">libavcodec</systemitem> options that
increases quality the most, and you should always use at least those
two unless the drop in encoding speed is prohibitive (e.g. realtime
encoding). There are many other options to
<systemitem class="library">libavcodec</systemitem> that increase
encoding quality (and decrease encoding speed) but that is beyond
the scope of this document.
</para>
</formalpara></listitem>
<listitem><formalpara>
<title>About the performance of pullup:</title>
<para>
It is safe to use <option>pullup</option> (along with <option>softskip
</option>) on progressive video, and is usually a good idea unless
the source has been definitively verified to be entirely progressive.
The performance loss is small for most cases. On a bare-minimum encode,
<option>pullup</option> causes <application>MEncoder</application> to
be 50% slower. Adding sound processing and advanced <option>lavcopts
</option> overshadows that difference, bringing the performance
decrease of using <option>pullup</option> down to 2%.
</para>
</formalpara></listitem>
</orderedlist>
</sect2>
</sect1>
<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
<sect1 id="menc-feat-enc-libavcodec">
<title>Encoding with the <systemitem class="library">libavcodec</systemitem>
codec family</title>
<para>
<systemitem class="library">libavcodec</systemitem>
provides simple encoding to a lot of interesting video and audio formats.
You can encode to the following codecs (more or less up to date):
</para>
<!-- ********** -->
<sect2 id="menc-feat-enc-libavcodec-video-codecs">
<title><systemitem class="library">libavcodec</systemitem>'s
video codecs</title>
<para>
<informaltable frame="all">
<tgroup cols="2">
<thead>
<row><entry>Video codec name</entry><entry>Description</entry></row>
</thead>
<tbody>
<row>
<entry>mjpeg</entry>
<entry>Motion JPEG</entry>
</row>
<row>
<entry>ljpeg</entry>
<entry>lossless JPEG</entry>
</row>
<row>
<entry>jpegls</entry>
<entry>JPEG LS</entry>
</row>
<row>
<entry>targa</entry>
<entry>Targa image</entry>
</row>
<row>
<entry>gif</entry>
<entry>GIF image</entry>
</row>
<row>
<entry>bmp</entry>
<entry>BMP image</entry>
</row>
<row>
<entry>png</entry>
<entry>PNG image</entry>
</row>
<row>
<entry>h261</entry>
<entry>H.261</entry>
</row>
<row>
<entry>h263</entry>
<entry>H.263 </entry>
</row>
<row>
<entry>h263p</entry>
<entry>H.263+</entry>
</row>
<row>
<entry>mpeg4</entry>
<entry>ISO standard MPEG-4 (DivX, Xvid compatible)</entry>
</row>
<row>
<entry>msmpeg4</entry>
<entry>pre-standard MPEG-4 variant by MS, v3 (AKA DivX3)</entry>
</row>
<row>
<entry>msmpeg4v2</entry>
<entry>pre-standard MPEG-4 by MS, v2 (used in old ASF files)</entry>
</row>
<row>
<entry>wmv1</entry>
<entry>Windows Media Video, version 1 (AKA WMV7)</entry>
</row>
<row>
<entry>wmv2</entry>
<entry>Windows Media Video, version 2 (AKA WMV8)</entry>
</row>
<row>
<entry>rv10</entry>
<entry>RealVideo 1.0</entry>
</row>
<row>
<entry>rv20</entry>
<entry>RealVideo 2.0</entry>
</row>
<row>
<entry>mpeg1video</entry>
<entry>MPEG-1 video</entry>
</row>
<row>
<entry>mpeg2video</entry>
<entry>MPEG-2 video</entry>
</row>
<row>
<entry>huffyuv</entry>
<entry>lossless compression</entry>
</row>
<row>
<entry>ffvhuff</entry>
<entry>FFmpeg modified huffyuv lossless</entry>
</row>
<row>
<entry>asv1</entry>
<entry>ASUS Video v1</entry>
</row>
<row>
<entry>asv2</entry>
<entry>ASUS Video v2</entry>
</row>
<row>
<entry>ffv1</entry>
<entry>FFmpeg's lossless video codec</entry>
</row>
<row>
<entry>svq1</entry>
<entry>Sorenson video 1</entry>
</row>
<row>
<entry>flv</entry>
<entry>Sorenson H.263 used in Flash Video</entry>
</row>
<row>
<entry>flashsv</entry>
<entry>Flash Screen Video</entry>
</row>
<row>
<entry>dvvideo</entry>
<entry>Sony Digital Video</entry>
</row>
<row>
<entry>snow</entry>
<entry>FFmpeg's experimental wavelet-based codec</entry>
</row>
<row>
<entry>zmbv</entry>
<entry>Zip Motion Blocks Video</entry>
</row>
<row>
<entry>dnxhd</entry>
<entry>AVID DNxHD</entry>
</row>
</tbody>
</tgroup>
</informaltable>
The first column contains the codec names that should be passed after the
<literal>vcodec</literal> config,
like: <option>-lavcopts vcodec=msmpeg4</option>
</para>
<informalexample><para>
An example with MJPEG compression:
<screen>
mencoder dvd://2 -o <replaceable>title2.avi</replaceable> -ovc lavc -lavcopts vcodec=mjpeg -oac copy
</screen>
</para></informalexample>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-enc-libavcodec-audio-codecs">
<title><systemitem class="library">libavcodec</systemitem>'s
audio codecs</title>
<para>
<informaltable frame="all">
<tgroup cols="2">
<thead>
<row><entry>Audio codec name</entry><entry>Description</entry></row>
</thead>
<tbody>
<row>
<entry>ac3</entry>
<entry>Dolby Digital (AC-3)</entry>
</row>
<row>
<entry>adpcm_*</entry>
<entry>Adaptive PCM formats - see supplementary table</entry>
</row>
<row>
<entry>flac</entry>
<entry>Free Lossless Audio Codec (FLAC)</entry>
</row>
<row>
<entry>g726</entry>
<entry>G.726 ADPCM</entry>
</row>
<row>
<entry>libamr_nb</entry>
<entry>3GPP Adaptive Multi-Rate (AMR) narrow-band</entry>
</row>
<row>
<entry>libamr_wb</entry>
<entry>3GPP Adaptive Multi-Rate (AMR) wide-band</entry>
</row>
<row>
<entry>libfaac</entry>
<entry>Advanced Audio Coding (AAC) - using FAAC</entry>
</row>
<row>
<entry>libgsm</entry>
<entry>ETSI GSM 06.10 full rate</entry>
</row>
<row>
<entry>libgsm_ms</entry>
<entry>Microsoft GSM</entry>
</row>
<row>
<entry>libmp3lame</entry>
<entry>MPEG-1 audio layer 3 (MP3) - using LAME</entry>
</row>
<row>
<entry>mp2</entry>
<entry>MPEG-1 audio layer 2 (MP2)</entry>
</row>
<row>
<entry>pcm_*</entry>
<entry>PCM formats - see supplementary table</entry>
</row>
<row>
<entry>roq_dpcm</entry>
<entry>Id Software RoQ DPCM</entry>
</row>
<row>
<entry>sonic</entry>
<entry>experimental FFmpeg lossy codec</entry>
</row>
<row>
<entry>sonicls</entry>
<entry>experimental FFmpeg lossless codec</entry>
</row>
<row>
<entry>vorbis</entry>
<entry>Vorbis</entry>
</row>
<row>
<entry>wmav1</entry>
<entry>Windows Media Audio v1</entry>
</row>
<row>
<entry>wmav2</entry>
<entry>Windows Media Audio v2</entry>
</row>
</tbody>
</tgroup>
</informaltable>
The first column contains the codec names that should be passed after the
<literal>acodec</literal> option, like: <option>-lavcopts acodec=ac3</option>
</para>
<informalexample><para>
An example with AC-3 compression:
<screen>
mencoder dvd://2 -o <replaceable>title2.avi</replaceable> -oac lavc -lavcopts acodec=ac3 -ovc copy
</screen>
</para></informalexample>
<para>
Contrary to <systemitem class="library">libavcodec</systemitem>'s video
codecs, its audio codecs do not make a wise usage of the bits they are
given as they lack some minimal psychoacoustic model (if at all)
which most other codec implementations feature.
However, note that all these audio codecs are very fast and work
out-of-the-box everywhere <application>MEncoder</application> has been
compiled with <systemitem class="library">libavcodec</systemitem> (which
is the case most of time), and do not depend on external libraries.
</para>
<sect3 id="menc-feat-enc-libavcodec-audio-codecs-pcmadpcm">
<title>PCM/ADPCM format supplementary table</title>
<para>
<informaltable frame="all">
<tgroup cols="2">
<thead>
<row><entry>PCM/ADPCM codec name</entry><entry>Description</entry></row>
</thead>
<tbody>
<row>
<entry>pcm_s32le</entry>
<entry>signed 32-bit little-endian</entry>
</row>
<row>
<entry>pcm_s32be</entry>
<entry>signed 32-bit big-endian</entry>
</row>
<row>
<entry>pcm_u32le</entry>
<entry>unsigned 32-bit little-endian</entry>
</row>
<row>
<entry>pcm_u32be</entry>
<entry>unsigned 32-bit big-endian</entry>
</row>
<row>
<entry>pcm_s24le</entry>
<entry>signed 24-bit little-endian</entry>
</row>
<row>
<entry>pcm_s24be</entry>
<entry>signed 24-bit big-endian</entry>
</row>
<row>
<entry>pcm_u24le</entry>
<entry>unsigned 24-bit little-endian</entry>
</row>
<row>
<entry>pcm_u24be</entry>
<entry>unsigned 24-bit big-endian</entry>
</row>
<row>
<entry>pcm_s16le</entry>
<entry>signed 16-bit little-endian</entry>
</row>
<row>
<entry>pcm_s16be</entry>
<entry>signed 16-bit big-endian</entry>
</row>
<row>
<entry>pcm_u16le</entry>
<entry>unsigned 16-bit little-endian</entry>
</row>
<row>
<entry>pcm_u16be</entry>
<entry>unsigned 16-bit big-endian</entry>
</row>
<row>
<entry>pcm_s8</entry>
<entry>signed 8-bit</entry>
</row>
<row>
<entry>pcm_u8</entry>
<entry>unsigned 8-bit</entry>
</row>
<row>
<entry>pcm_alaw</entry>
<entry>G.711 A-LAW </entry>
</row>
<row>
<entry>pcm_mulaw</entry>
<entry>G.711 μ-LAW</entry>
</row>
<row>
<entry>pcm_s24daud</entry>
<entry>signed 24-bit D-Cinema Audio format</entry>
</row>
<row>
<entry>pcm_zork</entry>
<entry>Activision Zork Nemesis</entry>
</row>
<row>
<entry>adpcm_ima_qt</entry>
<entry>Apple QuickTime</entry>
</row>
<row>
<entry>adpcm_ima_wav</entry>
<entry>Microsoft/IBM WAVE</entry>
</row>
<row>
<entry>adpcm_ima_dk3</entry>
<entry>Duck DK3</entry>
</row>
<row>
<entry>adpcm_ima_dk4</entry>
<entry>Duck DK4</entry>
</row>
<row>
<entry>adpcm_ima_ws</entry>
<entry>Westwood Studios</entry>
</row>
<row>
<entry>adpcm_ima_smjpeg</entry>
<entry>SDL Motion JPEG</entry>
</row>
<row>
<entry>adpcm_ms</entry>
<entry>Microsoft</entry>
</row>
<row>
<entry>adpcm_4xm</entry>
<entry>4X Technologies</entry>
</row>
<row>
<entry>adpcm_xa</entry>
<entry>Phillips Yellow Book CD-ROM eXtended Architecture</entry>
</row>
<row>
<entry>adpcm_ea</entry>
<entry>Electronic Arts</entry>
</row>
<row>
<entry>adpcm_ct</entry>
<entry>Creative 16->4-bit</entry>
</row>
<row>
<entry>adpcm_swf</entry>
<entry>Adobe Shockwave Flash</entry>
</row>
<row>
<entry>adpcm_yamaha</entry>
<entry>Yamaha</entry>
</row>
<row>
<entry>adpcm_sbpro_4</entry>
<entry>Creative VOC SoundBlaster Pro 8->4-bit</entry>
</row>
<row>
<entry>adpcm_sbpro_3</entry>
<entry>Creative VOC SoundBlaster Pro 8->2.6-bit</entry>
</row>
<row>
<entry>adpcm_sbpro_2</entry>
<entry>Creative VOC SoundBlaster Pro 8->2-bit</entry>
</row>
<row>
<entry>adpcm_thp</entry>
<entry>Nintendo GameCube FMV THP</entry>
</row>
<row>
<entry>adpcm_adx</entry>
<entry>Sega/CRI ADX</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
</sect3>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-dvd-mpeg4-lavc-encoding-options">
<title>Encoding options of libavcodec</title>
<para>
Ideally, you would probably want to be able to just tell the encoder to switch
into "high quality" mode and move on.
That would probably be nice, but unfortunately hard to implement as different
encoding options yield different quality results depending on the source
material. That is because compression depends on the visual properties of the
video in question.
For example, Anime and live action have very different properties and
thus require different options to obtain optimum encoding.
The good news is that some options should never be left out, like
<option>mbd=2</option>, <option>trell</option>, and <option>v4mv</option>.
See below for a detailed description of common encoding options.
</para>
<itemizedlist>
<title>Options to adjust:</title>
<listitem><para>
<emphasis role="bold">vmax_b_frames</emphasis>: 1 or 2 is good, depending on
the movie.
Note that if you need to have your encode be decodable by DivX5, you
need to activate closed GOP support, using
<systemitem class="library">libavcodec</systemitem>'s <option>cgop</option>
option, but you need to deactivate scene detection, which
is not a good idea as it will hurt encode efficiency a bit.
</para></listitem>
<listitem><para>
<emphasis role="bold">vb_strategy=1</emphasis>: helps in high-motion scenes.
On some videos, vmax_b_frames may hurt quality, but vmax_b_frames=2 along
with vb_strategy=1 helps.
</para></listitem>
<listitem><para>
<emphasis role="bold">dia</emphasis>: motion search range. Bigger is better
and slower.
Negative values are a completely different scale.
Good values are -1 for a fast encode, or 2-4 for slower.
</para></listitem>
<listitem><para>
<emphasis role="bold">predia</emphasis>: motion search pre-pass.
Not as important as dia. Good values are 1 (default) to 4. Requires preme=2
to really be useful.
</para></listitem>
<listitem><para>
<emphasis role="bold">cmp, subcmp, precmp</emphasis>: Comparison function for
motion estimation.
Experiment with values of 0 (default), 2 (hadamard), 3 (dct), and 6 (rate
distortion).
0 is fastest, and sufficient for precmp.
For cmp and subcmp, 2 is good for Anime, and 3 is good for live action.
6 may or may not be slightly better, but is slow.
</para></listitem>
<listitem><para>
<emphasis role="bold">last_pred</emphasis>: Number of motion predictors to
take from the previous frame.
1-3 or so help at little speed cost.
Higher values are slow for no extra gain.
</para></listitem>
<listitem><para>
<emphasis role="bold">cbp, mv0</emphasis>: Controls the selection of
macroblocks. Small speed cost for small quality gain.
</para></listitem>
<listitem><para>
<emphasis role="bold">qprd</emphasis>: adaptive quantization based on the
macroblock's complexity.
May help or hurt depending on the video and other options.
This can cause artifacts unless you set vqmax to some reasonably small value
(6 is good, maybe as low as 4); vqmin=1 should also help.
</para></listitem>
<listitem><para>
<emphasis role="bold">qns</emphasis>: very slow, especially when combined
with qprd.
This option will make the encoder minimize noise due to compression
artifacts instead of making the encoded video strictly match the source.
Do not use this unless you have already tweaked everything else as far as it
will go and the results still are not good enough.
</para></listitem>
<listitem><para>
<emphasis role="bold">vqcomp</emphasis>: Tweak ratecontrol.
What values are good depends on the movie.
You can safely leave this alone if you want.
Reducing vqcomp puts more bits on low-complexity scenes, increasing it puts
them on high-complexity scenes (default: 0.5, range: 0-1. recommended range:
0.5-0.7).
</para></listitem>
<listitem><para>
<emphasis role="bold">vlelim, vcelim</emphasis>: Sets the single coefficient
elimination threshold for luminance and chroma planes.
These are encoded separately in all MPEG-like algorithms.
The idea behind these options is to use some good heuristics to determine
when the change in a block is less than the threshold you specify, and in
such a case, to just encode the block as "no change".
This saves bits and perhaps speeds up encoding. vlelim=-4 and vcelim=9
seem to be good for live movies, but seem not to help with Anime;
when encoding animation, you should probably leave them unchanged.
</para></listitem>
<listitem><para>
<emphasis role="bold">qpel</emphasis>: Quarter pixel motion estimation.
MPEG-4 uses half pixel precision for its motion search by default,
therefore this option comes with an overhead as more information will be
stored in the encoded file.
The compression gain/loss depends on the movie, but it is usually not very
effective on Anime.
qpel always incurs a significant cost in CPU decode time (+25% in
practice).
</para></listitem>
<listitem><para>
<emphasis role="bold">psnr</emphasis>: does not affect the actual encoding,
but writes a log file giving the type/size/quality of each frame, and
prints a summary of PSNR (Peak Signal to Noise Ratio) at the end.
</para></listitem>
</itemizedlist>
<itemizedlist>
<title>Options not recommended to play with:</title>
<listitem><para>
<emphasis role="bold">vme</emphasis>: The default is best.
</para></listitem>
<listitem><para>
<emphasis role="bold">lumi_mask, dark_mask</emphasis>: Psychovisual adaptive
quantization.
You do not want to play with those options if you care about quality.
Reasonable values may be effective in your case, but be warned this is very
subjective.
</para></listitem>
<listitem><para>
<emphasis role="bold">scplx_mask</emphasis>: Tries to prevent blocky
artifacts, but postprocessing is better.
</para></listitem>
</itemizedlist>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-mpeg4-lavc-example-settings">
<title>Encoding setting examples</title>
<para>
The following settings are examples of different encoding
option combinations that affect the speed vs quality tradeoff
at the same target bitrate.
</para>
<para>
All the encoding settings were tested on a 720x448 @30000/1001 fps
video sample, the target bitrate was 900kbps, and the machine was an
AMD-64 3400+ at 2400 MHz in 64 bits mode.
Each encoding setting features the measured encoding speed (in
frames per second) and the PSNR loss (in dB) compared to the "very
high quality" setting.
Please understand that depending on your source, your machine type
and development advancements, you may get very different results.
</para>
<para>
<informaltable frame="all">
<tgroup cols="4">
<thead>
<row>
<entry>Description</entry>
<entry>Encoding options</entry>
<entry>speed (in fps)</entry>
<entry>Relative PSNR loss (in dB)</entry>
</row>
</thead>
<tbody>
<row>
<entry>Very high quality</entry>
<entry><option>vcodec=mpeg4:mbd=2:mv0:trell:v4mv:cbp:last_pred=3:predia=2:dia=2:vmax_b_frames=2:vb_strategy=1:precmp=2:cmp=2:subcmp=2:preme=2:qns=2</option></entry>
<entry>6fps</entry>
<entry>0dB</entry>
</row>
<row>
<entry>High quality</entry>
<entry><option>vcodec=mpeg4:mbd=2:trell:v4mv:last_pred=2:dia=-1:vmax_b_frames=2:vb_strategy=1:cmp=3:subcmp=3:precmp=0:vqcomp=0.6:turbo</option></entry>
<entry>15fps</entry>
<entry>-0.5dB</entry>
</row>
<row>
<entry>Fast</entry>
<entry><option>vcodec=mpeg4:mbd=2:trell:v4mv:turbo</option></entry>
<entry>42fps</entry>
<entry>-0.74dB</entry>
</row>
<row>
<entry>Realtime</entry>
<entry><option>vcodec=mpeg4:mbd=2:turbo</option></entry>
<entry>54fps</entry>
<entry>-1.21dB</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
</sect2>
<!-- ********** -->
<sect2 id="custommatrices">
<title>Custom inter/intra matrices</title>
<para>
With this feature of
<systemitem class="library">libavcodec</systemitem>
you are able to set custom inter (I-frames/keyframes) and intra
(P-frames/predicted frames) matrices. It is supported by many of the codecs:
<systemitem>mpeg1video</systemitem> and <systemitem>mpeg2video</systemitem>
are reported as working.
</para>
<para>
A typical usage of this feature is to set the matrices preferred by the
<ulink url="http://www.kvcd.net/">KVCD</ulink> specifications.
</para>
<para>
The <emphasis role="bold">KVCD "Notch" Quantization Matrix:</emphasis>
</para>
<para>
Intra:
<screen>
8 9 12 22 26 27 29 34
9 10 14 26 27 29 34 37
12 14 18 27 29 34 37 38
22 26 27 31 36 37 38 40
26 27 29 36 39 38 40 48
27 29 34 37 38 40 48 58
29 34 37 38 40 48 58 69
34 37 38 40 48 58 69 79
</screen>
Inter:
<screen>
16 18 20 22 24 26 28 30
18 20 22 24 26 28 30 32
20 22 24 26 28 30 32 34
22 24 26 30 32 32 34 36
24 26 28 32 34 34 36 38
26 28 30 32 34 36 38 40
28 30 32 34 36 38 42 42
30 32 34 36 38 40 42 44
</screen>
</para>
<para>
Usage:
<screen>
mencoder <replaceable>input.avi</replaceable> -o <replaceable>output.avi</replaceable> -oac copy -ovc lavc \
-lavcopts inter_matrix=...:intra_matrix=...
</screen>
</para>
<para>
<screen>
mencoder <replaceable>input.avi</replaceable> -ovc lavc -lavcopts \
vcodec=mpeg2video:intra_matrix=8,9,12,22,26,27,29,34,9,10,14,26,27,29,34,37,\
12,14,18,27,29,34,37,38,22,26,27,31,36,37,38,40,26,27,29,36,39,38,40,48,27,\
29,34,37,38,40,48,58,29,34,37,38,40,48,58,69,34,37,38,40,48,58,69,79\
:inter_matrix=16,18,20,22,24,26,28,30,18,20,22,24,26,28,30,32,20,22,24,26,\
28,30,32,34,22,24,26,30,32,32,34,36,24,26,28,32,34,34,36,38,26,28,30,32,34,\
36,38,40,28,30,32,34,36,38,42,42,30,32,34,36,38,40,42,44 -oac copy -o svcd.mpg
</screen>
</para>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-dvd-mpeg4-example">
<title>Example</title>
<para>
So, you have just bought your shiny new copy of Harry Potter and the Chamber
of Secrets (widescreen edition, of course), and you want to rip this DVD
so that you can add it to your Home Theatre PC. This is a region 1 DVD,
so it is NTSC. The example below will still apply to PAL, except you will
omit <option>-ofps 24000/1001</option> (because the output framerate is the
same as the input framerate), and of course the crop dimensions will be
different.
</para>
<para>
After running <option>mplayer dvd://1</option>, we follow the process
detailed in the section <link linkend="menc-feat-telecine">How to deal
with telecine and interlacing in NTSC DVDs</link> and discover that it is
24000/1001 fps progressive video, which means that we need not use an inverse
telecine filter, such as <option>pullup</option> or
<option>filmdint</option>.
</para>
<para id="menc-feat-dvd-mpeg4-example-crop">
Next, we want to determine the appropriate crop rectangle, so we use the
cropdetect filter:
<screen>mplayer dvd://1 -vf cropdetect</screen>
Make sure you seek to a fully filled frame (such as a bright scene,
past the opening credits and logos), and
you will see in <application>MPlayer</application>'s console output:
<screen>crop area: X: 0..719 Y: 57..419 (-vf crop=720:362:0:58)</screen>
We then play the movie back with this filter to test its correctness:
<screen>mplayer dvd://1 -vf crop=720:362:0:58</screen>
And we see that it looks perfectly fine. Next, we ensure the width and
height are a multiple of 16. The width is fine, however the height is
not. Since we did not fail 7th grade math, we know that the nearest
multiple of 16 lower than 362 is 352.
</para>
<para>
We could just use <option>crop=720:352:0:58</option>, but it would be nice
to take a little off the top and a little off the bottom so that we
retain the center. We have shrunk the height by 10 pixels, but we do not
want to increase the y-offset by 5-pixels since that is an odd number and
will adversely affect quality. Instead, we will increase the y-offset by
4 pixels:
<screen>mplayer dvd://1 -vf crop=720:352:0:62</screen>
Another reason to shave pixels from both the top and the bottom is that we
ensure we have eliminated any half-black pixels if they exist. Note that if
your video is telecined, make sure the <option>pullup</option> filter (or
whichever inverse telecine filter you decide to use) appears in the filter
chain before you crop. If it is interlaced, deinterlace before cropping.
(If you choose to preserve the interlaced video, then make sure your
vertical crop offset is a multiple of 4.)
</para>
<para>
If you are really concerned about losing those 10 pixels, you might
prefer instead to scale the dimensions down to the nearest multiple of 16.
The filter chain would look like:
<screen>-vf crop=720:362:0:58,scale=720:352</screen>
Scaling the video down like this will mean that some small amount of
detail is lost, though it probably will not be perceptible. Scaling up will
result in lower quality (unless you increase the bitrate). Cropping
discards those pixels altogether. It is a tradeoff that you will want to
consider for each circumstance. For example, if the DVD video was made
for television, you might want to avoid vertical scaling, since the line
sampling corresponds to the way the content was originally recorded.
</para>
<para>
On inspection, we see that our movie has a fair bit of action and high
amounts of detail, so we pick 2400Kbit for our bitrate.
</para>
<para>
We are now ready to do the two pass encode. Pass one:
<screen>
mencoder dvd://1 -ofps 24000/1001 -oac copy -o <replaceable>Harry_Potter_2.avi</replaceable> -ovc lavc \
-lavcopts vcodec=mpeg4:vbitrate=2400:v4mv:mbd=2:trell:cmp=3:subcmp=3:autoaspect:vpass=1 \
-vf pullup,softskip,crop=720:352:0:62,hqdn3d=2:1:2
</screen>
And pass two is the same, except that we specify <option>vpass=2</option>:
<screen>
mencoder dvd://1 -ofps 24000/1001 -oac copy -o <replaceable>Harry_Potter_2.avi</replaceable> -ovc lavc \
-lavcopts vcodec=mpeg4:vbitrate=2400:v4mv:mbd=2:trell:cmp=3:subcmp=3:autoaspect:vpass=2 \
-vf pullup,softskip,crop=720:352:0:62,hqdn3d=2:1:2
</screen>
</para>
<para>
The options <option>v4mv:mbd=2:trell</option> will greatly increase the
quality at the expense of encoding time. There is little reason to leave
these options out when the primary goal is quality. The options
<option>cmp=3:subcmp=3</option> select a comparison function that
yields higher quality than the defaults. You might try experimenting with
this parameter (refer to the man page for the possible values) as
different functions can have a large impact on quality depending on the
source material. For example, if you find
<systemitem class="library">libavcodec</systemitem> produces too much
blocky artifacts, you could try selecting the experimental NSSE as
comparison function via <option>*cmp=10</option>.
</para>
<para>
For this movie, the resulting AVI will be 138 minutes long and nearly
3GB. And because you said that file size does not matter, this is a
perfectly acceptable size. However, if you had wanted it smaller, you
could try a lower bitrate. Increasing bitrates have diminishing
returns, so while we might clearly see an improvement from 1800Kbit to
2000Kbit, it might not be so noticeable above 2000Kbit. Feel
free to experiment until you are happy.
</para>
<para>
Because we passed the source video through a denoise filter, you may want
to add some of it back during playback. This, along with the
<option>spp</option> post-processing filter, drastically improves the
perception of quality and helps eliminate blocky artifacts in the video.
With <application>MPlayer</application>'s <option>autoq</option> option,
you can vary the amount of post-processing done by the spp filter
depending on available CPU. Also, at this point, you may want to apply
gamma and/or color correction to best suit your display. For example:
<screen>
mplayer <replaceable>Harry_Potter_2.avi</replaceable> -vf spp,noise=9ah:5ah,eq2=1.2 -autoq 3
</screen>
</para>
</sect2>
</sect1>
<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
<sect1 id="menc-feat-xvid">
<title>Encoding with the <systemitem class="library">Xvid</systemitem>
codec</title>
<para>
<systemitem class="library">Xvid</systemitem> is a free library for
encoding MPEG-4 ASP video streams.
Before starting to encode, you need to <link linkend="xvid">
set up <application>MEncoder</application> to support it</link>.
</para>
<para>
This guide mainly aims at featuring the same kind of information
as x264's encoding guide.
Therefore, please begin by reading
<link linkend="menc-feat-x264-encoding-options-intro">the first part</link>
of that guide.
</para>
<!-- ********** -->
<sect2 id="menc-feat-xvid-intro">
<title>What options should I use to get the best results?</title>
<para>
Please begin by reviewing the
<systemitem class="library">Xvid</systemitem> section of
<application>MPlayer</application>'s man page.
This section is intended to be a supplement to the man page.
</para>
<para>
The Xvid default settings are already a good tradeoff between
speed and quality, therefore you can safely stick to them if
the following section puzzles you.
</para>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-xvid-encoding-options">
<title>Encoding options of <systemitem class="library">Xvid</systemitem></title>
<itemizedlist>
<listitem><para>
<emphasis role="bold">vhq</emphasis>
This setting affects the macroblock decision algorithm, where the
higher the setting, the wiser the decision.
The default setting may be safely used for every encode, while
higher settings always help PSNR but are significantly slower.
Please note that a better PSNR does not necessarily mean
that the picture will look better, but tells you that it is
closer to the original.
Turning it off will noticeably speed up encoding; if speed is
critical for you, the tradeoff may be worth it.
</para></listitem>
<listitem><para>
<emphasis role="bold">bvhq</emphasis>
This does the same job as vhq, but does it on B-frames.
It has a negligible impact on speed, and slightly improves quality
(around +0.1dB PSNR).
</para></listitem>
<listitem><para>
<emphasis role="bold">max_bframes</emphasis>
A higher number of consecutive allowed B-frames usually improves
compressibility, although it may also lead to more blocking artifacts.
The default setting is a good tradeoff between compressibility and
quality, but you may increase it up to 3 if you are bitrate-starved.
You may also decrease it to 1 or 0 if you are aiming at perfect
quality, though in that case you should make sure your
target bitrate is high enough to ensure that the encoder does not
have to increase quantizers to reach it.
</para></listitem>
<listitem><para>
<emphasis role="bold">bf_threshold</emphasis>
This controls the B-frame sensitivity of the encoder, where a higher
value leads to more B-frames being used (and vice versa).
This setting is to be used together with <option>max_bframes</option>;
if you are bitrate-starved, you should increase both
<option>max_bframes</option> and <option>bf_threshold</option>,
while you may increase <option>max_bframes</option> and reduce
<option>bf_threshold</option> so that the encoder may use more
B-frames in places that only <emphasis role="bold">really</emphasis>
need them.
A low number of <option>max_bframes</option> and a high value of
<option>bf_threshold</option> is probably not a wise choice as it
will force the encoder to put B-frames in places that would not
benefit from them, therefore reducing visual quality.
However, if you need to be compatible with standalone players that
only support old DivX profiles (which only supports up to 1
consecutive B-frame), this would be your only way to
increase compressibility through using B-frames.
</para></listitem>
<listitem><para>
<emphasis role="bold">trellis</emphasis>
Optimizes the quantization process to get an optimal tradeoff
between PSNR and bitrate, which allows significant bit saving.
These bits will in return be spent elsewhere on the video,
raising overall visual quality.
You should always leave it on as its impact on quality is huge.
Even if you are looking for speed, do not disable it until you
have turned down <option>vhq</option> and all other more
CPU-hungry options to the minimum.
</para></listitem>
<listitem><para>
<emphasis role="bold">hq_ac</emphasis>
Activates a better coefficient cost estimation method, which slightly
reduces file size by around 0.15 to 0.19% (which corresponds to less
than 0.01dB PSNR increase), while having a negligible impact on speed.
It is therefore recommended to always leave it on.
</para></listitem>
<listitem><para>
<emphasis role="bold">cartoon</emphasis>
Designed to better encode cartoon content, and has no impact on
speed as it just tunes the mode decision heuristics for this type
of content.
</para></listitem>
<listitem>
<para>
<emphasis role="bold">me_quality</emphasis>
This setting is to control the precision of the motion estimation.
The higher <option>me_quality</option>, the more
precise the estimation of the original motion will be, and the
better the resulting clip will capture the original motion.
</para>
<para>
The default setting is best in all cases;
thus it is not recommended to turn it down unless you are
really looking for speed, as all the bits saved by a good motion
estimation would be spent elsewhere, raising overall quality.
Therefore, do not go any lower than 5, and even that only as a last
resort.
</para>
</listitem>
<listitem><para>
<emphasis role="bold">chroma_me</emphasis>
Improves motion estimation by also taking the chroma (color)
information into account, whereas <option>me_quality</option>
alone only uses luma (grayscale).
This slows down encoding by 5-10% but improves visual quality
quite a bit by reducing blocking effects and reduces file size by
around 1.3%.
If you are looking for speed, you should disable this option before
starting to consider reducing <option>me_quality</option>.
</para></listitem>
<listitem><para>
<emphasis role="bold">chroma_opt</emphasis>
Is intended to increase chroma image quality around pure
white/black edges, rather than improving compression.
This can help to reduce the "red stairs" effect.
</para></listitem>
<listitem><para>
<emphasis role="bold">lumi_mask</emphasis>
Tries to give less bitrate to part of the picture that the
human eye cannot see very well, which should allow the encoder
to spend the saved bits on more important parts of the picture.
The quality of the encode yielded by this option highly depends
on personal preferences and on the type and monitor settings
used to watch it (typically, it will not look as good if it is
bright or if it is a TFT monitor).
</para></listitem>
<listitem>
<para>
<emphasis role="bold">qpel</emphasis>
Raise the number of candidate motion vectors by increasing
the precision of the motion estimation from halfpel to
quarterpel.
The idea is to find better motion vectors which will in return
reduce bitrate (hence increasing quality).
However, motion vectors with quarterpel precision require a
few extra bits to code, but the candidate vectors do not always
give (much) better results.
Quite often, the codec still spends bits on the extra precision,
but little or no extra quality is gained in return.
Unfortunately, there is no way to foresee the possible gains of
<option>qpel</option>, so you need to actually encode with and
without it to know for sure.
</para>
<para>
<option>qpel</option> can be almost double encoding time, and
requires as much as 25% more processing power to decode.
It is not supported by all standalone players.
</para>
</listitem>
<listitem><para>
<emphasis role="bold">gmc</emphasis>
Tries to save bits on panning scenes by using a single motion
vector for the whole frame.
This almost always raises PSNR, but significantly slows down
encoding (as well as decoding).
Therefore, you should only use it when you have turned
<option>vhq</option> to the maximum.
<systemitem class="library">Xvid</systemitem>'s GMC is more
sophisticated than DivX's, but is only supported by few
standalone players.
</para></listitem>
</itemizedlist>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-xvid-encoding-profiles">
<title>Encoding profiles</title>
<para>
Xvid supports encoding profiles through the <option>profile</option> option,
which are used to impose restrictions on the properties of the Xvid video
stream such that it will be playable on anything which supports the
chosen profile.
The restrictions relate to resolutions, bitrates and certain MPEG-4
features.
The following table shows what each profile supports.
</para>
<informaltable>
<tgroup cols="16" align="center">
<colspec colnum="1" colname="col1"/>
<colspec colnum="2" colname="col2"/>
<colspec colnum="3" colname="col3"/>
<colspec colnum="4" colname="col4"/>
<colspec colnum="5" colname="col5"/>
<colspec colnum="6" colname="col6"/>
<colspec colnum="7" colname="col7"/>
<colspec colnum="8" colname="col8"/>
<colspec colnum="9" colname="col9"/>
<colspec colnum="10" colname="col10"/>
<colspec colnum="11" colname="col11"/>
<colspec colnum="12" colname="col12"/>
<colspec colnum="13" colname="col13"/>
<colspec colnum="14" colname="col14"/>
<colspec colnum="15" colname="col15"/>
<colspec colnum="16" colname="col16"/>
<colspec colnum="17" colname="col17"/>
<spanspec spanname="spa2-5" namest="col2" nameend="col5"/>
<spanspec spanname="spa6-11" namest="col6" nameend="col11"/>
<spanspec spanname="spa12-17" namest="col12" nameend="col17"/>
<tbody>
<row>
<entry></entry>
<entry spanname="spa2-5">Simple</entry>
<entry spanname="spa6-11">Advanced Simple</entry>
<entry spanname="spa12-17">DivX</entry>
</row>
<row>
<entry>Profile name</entry>
<entry>0</entry>
<entry>1</entry>
<entry>2</entry>
<entry>3</entry>
<entry>0</entry>
<entry>1</entry>
<entry>2</entry>
<entry>3</entry>
<entry>4</entry>
<entry>5</entry>
<entry>Handheld</entry>
<entry>Portable NTSC</entry>
<entry>Portable PAL</entry>
<entry>Home Theater NTSC</entry>
<entry>Home Theater PAL</entry>
<entry>HDTV</entry>
</row>
<row>
<entry>Width [pixels]</entry>
<entry>176</entry>
<entry>176</entry>
<entry>352</entry>
<entry>352</entry>
<entry>176</entry>
<entry>176</entry>
<entry>352</entry>
<entry>352</entry>
<entry>352</entry>
<entry>720</entry>
<entry>176</entry>
<entry>352</entry>
<entry>352</entry>
<entry>720</entry>
<entry>720</entry>
<entry>1280</entry>
</row>
<row>
<entry>Height [pixels]</entry>
<entry>144</entry>
<entry>144</entry>
<entry>288</entry>
<entry>288</entry>
<entry>144</entry>
<entry>144</entry>
<entry>288</entry>
<entry>288</entry>
<entry>576</entry>
<entry>576</entry>
<entry>144</entry>
<entry>240</entry>
<entry>288</entry>
<entry>480</entry>
<entry>576</entry>
<entry>720</entry>
</row>
<row>
<entry>Frame rate [fps]</entry>
<entry>15</entry>
<entry>15</entry>
<entry>15</entry>
<entry>15</entry>
<entry>30</entry>
<entry>30</entry>
<entry>15</entry>
<entry>30</entry>
<entry>30</entry>
<entry>30</entry>
<entry>15</entry>
<entry>30</entry>
<entry>25</entry>
<entry>30</entry>
<entry>25</entry>
<entry>30</entry>
</row>
<row>
<entry>Max average bitrate [kbps]</entry>
<entry>64</entry>
<entry>64</entry>
<entry>128</entry>
<entry>384</entry>
<entry>128</entry>
<entry>128</entry>
<entry>384</entry>
<entry>768</entry>
<entry>3000</entry>
<entry>8000</entry>
<entry>537.6</entry>
<entry>4854</entry>
<entry>4854</entry>
<entry>4854</entry>
<entry>4854</entry>
<entry>9708.4</entry>
</row>
<row>
<entry>Peak average bitrate over 3 secs [kbps]</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry>800</entry>
<entry>8000</entry>
<entry>8000</entry>
<entry>8000</entry>
<entry>8000</entry>
<entry>16000</entry>
</row>
<row>
<entry>Max. B-frames</entry>
<entry>0</entry>
<entry>0</entry>
<entry>0</entry>
<entry>0</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry>0</entry>
<entry>1</entry>
<entry>1</entry>
<entry>1</entry>
<entry>1</entry>
<entry>2</entry>
</row>
<row>
<entry>MPEG quantization</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry>Adaptive quantization</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
</row>
<row>
<entry>Interlaced encoding</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
</row>
<row>
<entry>Quarterpixel</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry>Global motion compensation</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry></entry>
</row>
</tbody>
</tgroup>
</informaltable>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-xvid-example-settings">
<title>Encoding setting examples</title>
<para>
The following settings are examples of different encoding
option combinations that affect the speed vs quality tradeoff
at the same target bitrate.
</para>
<para>
All the encoding settings were tested on a 720x448 @30000/1001 fps
video sample, the target bitrate was 900kbps, and the machine was an
AMD-64 3400+ at 2400 MHz in 64 bits mode.
Each encoding setting features the measured encoding speed (in
frames per second) and the PSNR loss (in dB) compared to the "very
high quality" setting.
Please understand that depending on your source, your machine type
and development advancements, you may get very different results.
</para>
<informaltable frame="all">
<tgroup cols="4">
<thead>
<row><entry>Description</entry><entry>Encoding options</entry><entry>speed (in fps)</entry><entry>Relative PSNR loss (in dB)</entry></row>
</thead>
<tbody>
<row>
<entry>Very high quality</entry>
<entry><option>chroma_opt:vhq=4:bvhq=1:quant_type=mpeg</option></entry>
<entry>16fps</entry>
<entry>0dB</entry>
</row>
<row>
<entry>High quality</entry>
<entry><option>vhq=2:bvhq=1:chroma_opt:quant_type=mpeg</option></entry>
<entry>18fps</entry>
<entry>-0.1dB</entry>
</row>
<row>
<entry>Fast</entry>
<entry><option>turbo:vhq=0</option></entry>
<entry>28fps</entry>
<entry>-0.69dB</entry>
</row>
<row>
<entry>Realtime</entry>
<entry><option>turbo:nochroma_me:notrellis:max_bframes=0:vhq=0</option></entry>
<entry>38fps</entry>
<entry>-1.48dB</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</sect2>
</sect1>
<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
<sect1 id="menc-feat-x264">
<title>Encoding with the
<systemitem class="library">x264</systemitem> codec</title>
<para>
<systemitem class="library">x264</systemitem> is a free library for
encoding H.264/AVC video streams.
Before starting to encode, you need to
<link linkend="x264">set up <application>MEncoder</application> to support it</link>.
</para>
<!-- ********** -->
<sect2 id="menc-feat-x264-encoding-options">
<title>Encoding options of x264</title>
<para>
Please begin by reviewing the
<systemitem class="library">x264</systemitem> section of
<application>MPlayer</application>'s man page.
This section is intended to be a supplement to the man page.
Here you will find quick hints about which options are most
likely to interest most people. The man page is more terse,
but also more exhaustive, and it sometimes offers much better
technical detail.
</para>
<sect3 id="menc-feat-x264-encoding-options-intro">
<title>Introduction</title>
<para>
This guide considers two major categories of encoding options:
</para>
<orderedlist>
<listitem><para>
Options which mainly trade off encoding time vs. quality
</para></listitem>
<listitem><para>
Options which may be useful for fulfilling various personal
preferences and special requirements
</para></listitem>
</orderedlist>
<para>
Ultimately, only you can decide which options are best for your
purposes. The decision for the first class of options is the simplest:
you only have to decide whether you think the quality differences
justify the speed differences. For the second class of options,
preferences may be far more subjective, and more factors may be
involved. Note that some of the "personal preferences and special
requirements" options can still have large impacts on speed or quality,
but that is not what they are primarily useful for. A couple of the
"personal preference" options may even cause changes that look better
to some people, but look worse to others.
</para>
<para>
Before continuing, you need to understand that this guide uses only one
quality metric: global PSNR.
For a brief explanation of what PSNR is, see
<ulink url="http://en.wikipedia.org/wiki/PSNR">the Wikipedia article on PSNR</ulink>.
Global PSNR is the last PSNR number reported when you include
the <option>psnr</option> option in <option>x264encopts</option>.
Any time you read a claim about PSNR, one of the assumptions
behind the claim is that equal bitrates are used.
</para>
<para>
Nearly all of this guide's comments assume you are using two pass.
When comparing options, there are two major reasons for using
two pass encoding.
First, using two pass often gains around 1dB PSNR, which is a
very big difference.
Secondly, testing options by doing direct quality comparisons
with one pass encodes introduces a major confounding
factor: bitrate often varies significantly with each encode.
It is not always easy to tell whether quality changes are due
mainly to changed options, or if they mostly reflect essentially
random differences in the achieved bitrate.
</para>
</sect3>
<sect3 id="menc-feat-x264-encoding-options-speedvquality">
<title>Options which primarily affect speed and quality</title>
<itemizedlist>
<listitem>
<para>
<emphasis role="bold">subq</emphasis>:
Of the options which allow you to trade off speed for quality,
<option>subq</option> and <option>frameref</option> (see below) are usually
by far the most important.
If you are interested in tweaking either speed or quality, these
are the first options you should consider.
On the speed dimension, the <option>frameref</option> and
<option>subq</option> options interact with each other fairly
strongly.
Experience shows that, with one reference frame,
<option>subq=5</option> (the default setting) takes about 35% more time than
<option>subq=1</option>.
With 6 reference frames, the penalty grows to over 60%.
<option>subq</option>'s effect on PSNR seems fairly constant
regardless of the number of reference frames.
Typically, <option>subq=5</option> achieves 0.2-0.5 dB higher global
PSNR in comparison <option>subq=1</option>.
This is usually enough to be visible.
</para>
<para>
<option>subq=6</option> is slower and yields better quality at a reasonable
cost.
In comparison to <option>subq=5</option>, it usually gains 0.1-0.4 dB
global PSNR with speed costs varying from 25%-100%.
Unlike other levels of <option>subq</option>, the behavior of
<option>subq=6</option> does not depend much on <option>frameref</option>
and <option>me</option>. Instead, the effectiveness of <option>subq=6
</option> depends mostly upon the number of B-frames used. In normal
usage, this means <option>subq=6</option> has a large impact on both speed
and quality in complex, high motion scenes, but it may not have much effect
in low-motion scenes. Note that it is still recommended to always set
<option>bframes</option> to something other than zero (see below).
</para>
<para>
<option>subq=7</option> is the slowest, highest quality mode.
In comparison to <option>subq=6</option>, it usually gains 0.01-0.05 dB
global PSNR with speed costs varying from 15%-33%.
Since the tradeoff encoding time vs. quality is quite low, you should
only use it if you are after every bit saving and if encoding time is
not an issue.
</para>
</listitem>
<listitem>
<para>
<emphasis role="bold">frameref</emphasis>:
<option>frameref</option> is set to 1 by default, but this
should not be taken to imply that it is reasonable to set it to 1.
Merely raising <option>frameref</option> to 2 gains around
0.15dB PSNR with a 5-10% speed penalty; this seems like a good tradeoff.
<option>frameref=3</option> gains around 0.25dB PSNR over
<option>frameref=1</option>, which should be a visible difference.
<option>frameref=3</option> is around 15% slower than
<option>frameref=1</option>.
Unfortunately, diminishing returns set in rapidly.
<option>frameref=6</option> can be expected to gain only
0.05-0.1 dB over <option>frameref=3</option> at an additional
15% speed penalty.
Above <option>frameref=6</option>, the quality gains are
usually very small (although you should keep in mind throughout
this whole discussion that it can vary quite a lot depending on your source).
In a fairly typical case, <option>frameref=12</option>
will improve global PSNR by a tiny 0.02dB over
<option>frameref=6</option>, at a speed cost of 15%-20%.
At such high <option>frameref</option> values, the only really
good thing that can be said is that increasing it even further will
almost certainly never <emphasis role="bold">harm</emphasis>
PSNR, but the additional quality benefits are barely even
measurable, let alone perceptible.
</para>
<note><title>Note:</title>
<para>
Raising <option>frameref</option> to unnecessarily high values
<emphasis role="bold">can</emphasis> and
<emphasis role="bold">usually does</emphasis>
hurt coding efficiency if you turn CABAC off.
With CABAC on (the default behavior), the possibility of setting
<option>frameref</option> "too high" currently seems too remote
to even worry about, and in the future, optimizations may remove
the possibility altogether.
</para></note>
<para>
If you care about speed, a reasonable compromise is to use low
<option>subq</option> and <option>frameref</option> values on
the first pass, and then raise them on the second pass.
Typically, this has a negligible negative effect on the final
quality: You will probably lose well under 0.1dB PSNR, which
should be much too small of a difference to see.
However, different values of <option>frameref</option> can
occasionally affect frame type decision.
Most likely, these are rare outlying cases, but if you want to
be pretty sure, consider whether your video has either
fullscreen repetitive flashing patterns or very large temporary
occlusions which might force an I-frame.
Adjust the first-pass <option>frameref</option> so it is large
enough to contain the duration of the flashing cycle (or occlusion).
For example, if the scene flashes back and forth between two images
over a duration of three frames, set the first pass
<option>frameref</option> to 3 or higher.
This issue is probably extremely rare in live action video material,
but it does sometimes come up in video game captures.
</para>
</listitem>
<listitem>
<para>
<emphasis role="bold">me</emphasis>:
This option is for choosing the motion estimation search method.
Altering this option provides a straightforward quality-vs-speed
tradeoff. <option>me=dia</option> is only a few percent faster than
the default search, at a cost of under 0.1dB global PSNR. The
default setting (<option>me=hex</option>) is a reasonable tradeoff
between speed and quality. <option>me=umh</option> gains a little under
0.1dB global PSNR, with a speed penalty that varies depending on
<option>frameref</option>. At high values of
<option>frameref</option> (e.g. 12 or so), <option>me=umh</option>
is about 40% slower than the default <option> me=hex</option>. With
<option>frameref=3</option>, the speed penalty incurred drops to
25%-30%.
</para>
<para>
<option>me=esa</option> uses an exhaustive search that is too slow for
practical use.
</para>
</listitem>
<listitem><para>
<emphasis role="bold">partitions=all</emphasis>:
This option enables the use of 8x4, 4x8 and 4x4 subpartitions in
predicted macroblocks (in addition to the default partitions).
Enabling it results in a fairly consistent
10%-15% loss of speed. This option is rather useless in source
containing only low motion, however in some high-motion source,
particularly source with lots of small moving objects, gains of
about 0.1dB can be expected.
</para></listitem>
<listitem>
<para>
<emphasis role="bold">bframes</emphasis>:
If you are used to encoding with other codecs, you may have found
that B-frames are not always useful.
In H.264, this has changed: there are new techniques and block
types that are possible in B-frames.
Usually, even a naive B-frame choice algorithm can have a
significant PSNR benefit.
It is interesting to note that using B-frames usually speeds up
the second pass somewhat, and may also speed up a single
pass encode if adaptive B-frame decision is turned off.
</para>
<para>
With adaptive B-frame decision turned off
(<option>x264encopts</option>'s <option>nob_adapt</option>),
the optimal value for this setting is usually no more than
<option>bframes=1</option>, or else high-motion scenes can suffer.
With adaptive B-frame decision on (the default behavior), it is
safe to use higher values; the encoder will reduce the use of
B-frames in scenes where they would hurt compression.
The encoder rarely chooses to use more than 3 or 4 B-frames;
setting this option any higher will have little effect.
</para>
</listitem>
<listitem>
<para>
<emphasis role="bold">b_adapt</emphasis>:
Note: This is on by default.
</para>
<para>
With this option enabled, the encoder will use a reasonably fast
decision process to reduce the number of B-frames used in scenes that
might not benefit from them as much.
You can use <option>b_bias</option> to tweak how B-frame-happy
the encoder is.
The speed penalty of adaptive B-frames is currently rather modest,
but so is the potential quality gain.
It usually does not hurt, however.
Note that this only affects speed and frame type decision on the
first pass.
<option>b_adapt</option> and <option>b_bias</option> have no
effect on subsequent passes.
</para>
</listitem>
<listitem><para>
<emphasis role="bold">b_pyramid</emphasis>:
You might as well enable this option if you are using >=2 B-frames;
as the man page says, you get a little quality improvement at no
speed cost.
Note that these videos cannot be read by libavcodec-based decoders
older than about March 5, 2005.
</para></listitem>
<listitem>
<para>
<emphasis role="bold">weight_b</emphasis>:
In typical cases, there is not much gain with this option.
However, in crossfades or fade-to-black scenes, weighted
prediction gives rather large bitrate savings.
In MPEG-4 ASP, a fade-to-black is usually best coded as a series
of expensive I-frames; using weighted prediction in B-frames
makes it possible to turn at least some of these into much smaller
B-frames.
Encoding time cost is minimal, as no extra decisions need to be made.
Also, contrary to what some people seem to guess, the decoder
CPU requirements are not much affected by weighted prediction,
all else being equal.
</para>
<para>
Unfortunately, the current adaptive B-frame decision algorithm
has a strong tendency to avoid B-frames during fades.
Until this changes, it may be a good idea to add
<option>nob_adapt</option> to your x264encopts, if you expect
fades to have a large effect in your particular video
clip.
</para>
</listitem>
<listitem id="menc-feat-x264-encoding-options-speedvquality-threads">
<para>
<emphasis role="bold">threads</emphasis>:
This option allows to spawn threads to encode in parallel on multiple CPUs.
You can manually select the number of threads to be created or, better, set
<option>threads=auto</option> and let
<systemitem class="library">x264</systemitem> detect how many CPUs are
available and pick an appropriate number of threads.
If you have a multi-processor machine, you should really consider using it
as it can to increase encoding speed linearly with the number of CPU cores
(about 94% per CPU core), with very little quality reduction (about 0.005dB
for dual processor, about 0.01dB for a quad processor machine).
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3 id="menc-feat-x264-encoding-options-misc-preferences">
<title>Options pertaining to miscellaneous preferences</title>
<itemizedlist>
<listitem>
<para>
<emphasis role="bold">Two pass encoding</emphasis>:
Above, it was suggested to always use two pass encoding, but there
are still reasons for not using it. For instance, if you are capturing
live TV and encoding in realtime, you are forced to use single-pass.
Also, one pass is obviously faster than two passes; if you use the
exact same set of options on both passes, two pass encoding is almost
twice as slow.
</para>
<para>
Still, there are very good reasons for using two pass encoding. For
one thing, single pass ratecontrol is not psychic, and it often makes
unreasonable choices because it cannot see the big picture. For example,
suppose you have a two minute long video consisting of two distinct
halves. The first half is a very high-motion scene lasting 60 seconds
which, in isolation, requires about 2500kbps in order to look decent.
Immediately following it is a much less demanding 60-second scene
that looks good at 300kbps. Suppose you ask for 1400kbps on the theory
that this is enough to accommodate both scenes. Single pass ratecontrol
will make a couple of "mistakes" in such a case. First of all, it
will target 1400kbps in both segments. The first segment may end up
heavily overquantized, causing it to look unacceptably and unreasonably
blocky. The second segment will be heavily underquantized; it may look
perfect, but the bitrate cost of that perfection will be completely
unreasonable. What is even harder to avoid is the problem at the
transition between the two scenes. The first seconds of the low motion
half will be hugely over-quantized, because the ratecontrol is still
expecting the kind of bitrate requirements it met in the first half
of the video. This "error period" of heavily over-quantized low motion
will look jarringly bad, and will actually use less than the 300kbps
it would have taken to make it look decent. There are ways to
mitigate the pitfalls of single-pass encoding, but they may tend to
increase bitrate misprediction.
</para>
<para>
Multipass ratecontrol can offer huge advantages over a single pass.
Using the statistics gathered from the first pass encode, the encoder
can estimate, with reasonable accuracy, the "cost" (in bits) of
encoding any given frame, at any given quantizer. This allows for
a much more rational, better planned allocation of bits between the
expensive (high-motion) and cheap (low-motion) scenes. See
<option>qcomp</option> below for some ideas on how to tweak this
allocation to your liking.
</para>
<para>
Moreover, two passes need not take twice as long as one pass. You can
tweak the options in the first pass for higher speed and lower quality.
If you choose your options well, you can get a very fast first pass.
The resulting quality in the second pass will be slightly lower because size
prediction is less accurate, but the quality difference is normally much
too small to be visible. Try, for example, adding
<option>subq=1:frameref=1</option> to the first pass
<option>x264encopts</option>. Then, on the second pass, use slower,
higher-quality options:
<option>subq=6:frameref=15:partitions=all:me=umh</option>
</para>
</listitem>
<listitem><para>
<emphasis role="bold">Three pass encoding</emphasis>?
x264 offers the ability to make an arbitrary number of consecutive
passes. If you specify <option>pass=1</option> on the first pass,
then use <option>pass=3</option> on a subsequent pass, the subsequent
pass will both read the statistics from the previous pass, and write
its own statistics. An additional pass following this one will have
a very good base from which to make highly accurate predictions of
frame sizes at a chosen quantizer. In practice, the overall quality
gain from this is usually close to zero, and quite possibly a third
pass will result in slightly worse global PSNR than the pass before
it. In typical usage, three passes help if you get either bad bitrate
prediction or bad looking scene transitions when using only two passes.
This is somewhat likely to happen on extremely short clips. There are
also a few special cases in which three (or more) passes are handy
for advanced users, but for brevity, this guide omits discussing those
special cases.
</para></listitem>
<listitem><para>
<emphasis role="bold">qcomp</emphasis>:
<option>qcomp</option> trades off the number of bits allocated
to "expensive" high-motion versus "cheap" low-motion frames. At
one extreme, <option>qcomp=0</option> aims for true constant
bitrate. Typically this would make high-motion scenes look completely
awful, while low-motion scenes would probably look absolutely
perfect, but would also use many times more bitrate than they
would need in order to look merely excellent. At the other extreme,
<option>qcomp=1</option> achieves nearly constant quantization parameter
(QP). Constant QP does not look bad, but most people think it is more
reasonable to shave some bitrate off of the extremely expensive scenes
(where the loss of quality is not as noticeable) and reallocate it to
the scenes that are easier to encode at excellent quality.
<option>qcomp</option> is set to 0.6 by default, which may be slightly
low for many peoples' taste (0.7-0.8 are also commonly used).
</para></listitem>
<listitem><para>
<emphasis role="bold">keyint</emphasis>:
<option>keyint</option> is solely for trading off file seekability against
coding efficiency. By default, <option>keyint</option> is set to 250. In
25fps material, this guarantees the ability to seek to within 10 seconds
precision. If you think it would be important and useful to be able to
seek within 5 seconds of precision, set <option>keyint=125</option>;
this will hurt quality/bitrate slightly. If you care only about quality
and not about seekability, you can set it to much higher values
(understanding that there are diminishing returns which may become
vanishingly low, or even zero). The video stream will still have seekable
points as long as there are some scene changes.
</para></listitem>
<listitem>
<para>
<emphasis role="bold">deblock</emphasis>:
This topic is going to be a bit controversial.
</para>
<para>
H.264 defines a simple deblocking procedure on I-blocks that uses
pre-set strengths and thresholds depending on the QP of the block
in question.
By default, high QP blocks are filtered heavily, and low QP blocks
are not deblocked at all.
The pre-set strengths defined by the standard are well-chosen and
the odds are very good that they are PSNR-optimal for whatever
video you are trying to encode.
The <option>deblock</option> allow you to specify offsets to the preset
deblocking thresholds.
</para>
<para>
Many people seem to think it is a good idea to lower the deblocking
filter strength by large amounts (say, -3).
This is however almost never a good idea, and in most cases,
people who are doing this do not understand very well how
deblocking works by default.
</para>
<para>
The first and most important thing to know about the in-loop
deblocking filter is that the default thresholds are almost always
PSNR-optimal.
In the rare cases that they are not optimal, the ideal offset is
plus or minus 1.
Adjusting deblocking parameters by a larger amount is almost
guaranteed to hurt PSNR.
Strengthening the filter will smear more details; weakening the
filter will increase the appearance of blockiness.
</para>
<para>
It is definitely a bad idea to lower the deblocking thresholds if
your source is mainly low in spacial complexity (i.e., not a lot
of detail or noise).
The in-loop filter does a rather excellent job of concealing
the artifacts that occur.
If the source is high in spacial complexity, however, artifacts
are less noticeable.
This is because the ringing tends to look like detail or noise.
Human visual perception easily notices when detail is removed,
but it does not so easily notice when the noise is wrongly
represented.
When it comes to subjective quality, noise and detail are somewhat
interchangeable.
By lowering the deblocking filter strength, you are most likely
increasing error by adding ringing artifacts, but the eye does
not notice because it confuses the artifacts with detail.
</para>
<para>
This <emphasis role="bold">still</emphasis> does not justify
lowering the deblocking filter strength, however.
You can generally get better quality noise from postprocessing.
If your H.264 encodes look too blurry or smeared, try playing with
<option>-vf noise</option> when you play your encoded movie.
<option>-vf noise=8a:4a</option> should conceal most mild
artifacts.
It will almost certainly look better than the results you
would have gotten just by fiddling with the deblocking filter.
</para>
</listitem>
</itemizedlist>
</sect3>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-x264-example-settings">
<title>Encoding setting examples</title>
<para>
The following settings are examples of different encoding
option combinations that affect the speed vs quality tradeoff
at the same target bitrate.
</para>
<para>
All the encoding settings were tested on a 720x448 @30000/1001 fps
video sample, the target bitrate was 900kbps, and the machine was an
AMD-64 3400+ at 2400 MHz in 64 bits mode.
Each encoding setting features the measured encoding speed (in
frames per second) and the PSNR loss (in dB) compared to the "very
high quality" setting.
Please understand that depending on your source, your machine type
and development advancements, you may get very different results.
</para>
<informaltable frame="all">
<tgroup cols="4">
<thead>
<row>
<entry>Description</entry>
<entry>Encoding options</entry>
<entry>speed (in fps)</entry>
<entry>Relative PSNR loss (in dB)</entry>
</row>
</thead>
<tbody>
<row>
<entry>Very high quality</entry>
<entry><option>subq=6:partitions=all:8x8dct:me=umh:frameref=5:bframes=3:b_pyramid=normal:weight_b</option></entry>
<entry>6fps</entry>
<entry>0dB</entry>
</row>
<row>
<entry>High quality</entry>
<entry><option>subq=5:8x8dct:frameref=2:bframes=3:b_pyramid=normal:weight_b</option></entry>
<entry>13fps</entry>
<entry>-0.89dB</entry>
</row>
<row>
<entry>Fast</entry>
<entry><option>subq=4:bframes=2:b_pyramid=normal:weight_b</option></entry>
<entry>17fps</entry>
<entry>-1.48dB</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</sect2>
</sect1>
<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
<sect1 id="menc-feat-video-for-windows">
<title>
Encoding with the <systemitem class="library">Video For Windows</systemitem>
codec family
</title>
<para>
Video for Windows provides simple encoding by means of binary video codecs.
You can encode with the following codecs (if you have more, please tell us!)
</para>
<para>
Note that support for this is very experimental and some codecs may not work
correctly. Some codecs will only work in certain colorspaces, try
<option>-vf format=bgr24</option> and <option>-vf format=yuy2</option>
if a codec fails or gives wrong output.
</para>
<!-- ********** -->
<sect2 id="menc-feat-enc-vfw-video-codecs">
<title>Video for Windows supported codecs</title>
<para>
<informaltable frame="all">
<tgroup cols="4">
<thead>
<row>
<entry>Video codec file name</entry>
<entry>Description (FourCC)</entry>
<entry>md5sum</entry>
<entry>Comment</entry>
</row>
</thead>
<tbody>
<row>
<entry>aslcodec_vfw.dll</entry>
<entry>Alparysoft lossless codec vfw (ASLC)</entry>
<entry>608af234a6ea4d90cdc7246af5f3f29a</entry>
<entry></entry>
</row>
<row>
<entry>avimszh.dll</entry>
<entry>AVImszh (MSZH)</entry>
<entry>253118fe1eedea04a95ed6e5f4c28878</entry>
<entry>needs <option>-vf format</option></entry>
</row>
<row>
<entry>avizlib.dll</entry>
<entry>AVIzlib (ZLIB)</entry>
<entry>2f1cc76bbcf6d77d40d0e23392fa8eda</entry>
<entry></entry>
</row>
<row>
<entry>divx.dll</entry>
<entry>DivX4Windows-VFW</entry>
<entry>acf35b2fc004a89c829531555d73f1e6</entry>
<entry></entry>
</row>
<row>
<entry>huffyuv.dll</entry>
<entry>HuffYUV (lossless) (HFYU)</entry>
<entry>b74695b50230be4a6ef2c4293a58ac3b</entry>
<entry></entry>
</row>
<row>
<entry>iccvid.dll</entry>
<entry>Cinepak Video (cvid)</entry>
<entry>cb3b7ee47ba7dbb3d23d34e274895133</entry>
<entry></entry>
</row>
<row>
<entry>icmw_32.dll</entry>
<entry>Motion Wavelets (MWV1)</entry>
<entry>c9618a8fc73ce219ba918e3e09e227f2</entry>
<entry></entry>
</row>
<row>
<entry>jp2avi.dll</entry>
<entry>ImagePower MJPEG2000 (IPJ2)</entry>
<entry>d860a11766da0d0ea064672c6833768b</entry>
<entry><option>-vf flip</option></entry>
</row>
<row>
<entry>m3jp2k32.dll</entry>
<entry>Morgan MJPEG2000 (MJ2C)</entry>
<entry>f3c174edcbaef7cb947d6357cdfde7ff</entry>
<entry></entry>
</row>
<row>
<entry>m3jpeg32.dll</entry>
<entry>Morgan Motion JPEG Codec (MJPEG)</entry>
<entry>1cd13fff5960aa2aae43790242c323b1</entry>
<entry></entry>
</row>
<row>
<entry>mpg4c32.dll</entry>
<entry>Microsoft MPEG-4 v1/v2</entry>
<entry>b5791ea23f33010d37ab8314681f1256</entry>
<entry></entry>
</row>
<row>
<entry>tsccvid.dll</entry>
<entry>TechSmith Camtasia Screen Codec (TSCC)</entry>
<entry>8230d8560c41d444f249802a2700d1d5</entry>
<entry>shareware error on windows</entry>
</row>
<row>
<entry>vp31vfw.dll</entry>
<entry>On2 Open Source VP3 Codec (VP31)</entry>
<entry>845f3590ea489e2e45e876ab107ee7d2</entry>
<entry></entry>
</row>
<row>
<entry>vp4vfw.dll</entry>
<entry>On2 VP4 Personal Codec (VP40)</entry>
<entry>fc5480a482ccc594c2898dcc4188b58f</entry>
<entry></entry>
</row>
<row>
<entry>vp6vfw.dll</entry>
<entry>On2 VP6 Personal Codec (VP60)</entry>
<entry>04d635a364243013898fd09484f913fb</entry>
<entry></entry>
</row>
<row>
<entry>vp7vfw.dll</entry>
<entry>On2 VP7 Personal Codec (VP70)</entry>
<entry>cb4cc3d4ea7c94a35f1d81c3d750bc8d</entry>
<entry><option>-ffourcc VP70</option></entry>
</row>
<row>
<entry>ViVD2.dll</entry>
<entry>SoftMedia ViVD V2 codec VfW (GXVE)</entry>
<entry>a7b4bf5cac630bb9262c3f80d8a773a1</entry>
<entry></entry>
</row>
<row>
<entry>msulvc06.DLL</entry>
<entry>MSU Lossless codec (MSUD)</entry>
<entry>294bf9288f2f127bb86f00bfcc9ccdda</entry>
<entry>
Decodable by <application>Window Media Player</application>,
not <application>MPlayer</application> (yet).
</entry>
</row>
<row>
<entry>camcodec.dll</entry>
<entry>CamStudio lossless video codec (CSCD)</entry>
<entry>0efe97ce08bb0e40162ab15ef3b45615</entry>
<entry>sf.net/projects/camstudio</entry>
</row>
</tbody>
</tgroup>
</informaltable>
The first column contains the codec names that should be passed after the
<literal>codec</literal> parameter,
like: <option>-xvfwopts codec=divx.dll</option>
The FourCC code used by each codec is given in the parentheses.
</para>
<informalexample>
<para>
An example to convert an ISO DVD trailer to a VP6 flash video file
using compdata bitrate settings:
<screen>
mencoder -dvd-device <replaceable>zeiram.iso</replaceable> dvd://7 -o <replaceable>trailer.flv</replaceable> \
-ovc vfw -xvfwopts codec=vp6vfw.dll:compdata=onepass.mcf -oac mp3lame \
-lameopts cbr:br=64 -af lavcresample=22050 -vf yadif,scale=320:240,flip \
-of lavf
</screen>
</para>
</informalexample>
</sect2>
<sect2 id="menc-feat-video-for-windows-bitrate-settings">
<title>Using vfw2menc to create a codec settings file.</title>
<para>
To encode with the Video for Windows codecs, you will need to set bitrate
and other options. This is known to work on x86 on both *NIX and Windows.
</para>
<para>
First you must build the <application>vfw2menc</application> program.
It is located in the <filename class="directory">TOOLS</filename> subdirectory
of the MPlayer source tree.
To build on Linux, this can be done using <application>Wine</application>:
<screen>winegcc vfw2menc.c -o vfw2menc -lwinmm -lole32</screen>
To build on Windows in <application>MinGW</application> or
<application>Cygwin</application> use:
<screen>gcc vfw2menc.c -o vfw2menc.exe -lwinmm -lole32</screen>
To build on <application>MSVC</application> you will need getopt.
Getopt can be found in the original <application>vfw2menc</application>
archive available at:
The <ulink url="http://oss.netfarm.it/mplayer-win32.php">MPlayer on win32</ulink> project.
</para>
<informalexample>
<para>
Below is an example with the VP6 codec.
<screen>
vfw2menc -f VP62 -d vp6vfw.dll -s firstpass.mcf
</screen>
This will open the VP6 codec dialog window.
Repeat this step for the second pass
and use <option>-s <replaceable>secondpass.mcf</replaceable></option>.
</para>
</informalexample>
<para>
Windows users can use
<option>-xvfwopts codec=vp6vfw.dll:compdata=dialog</option> to have
the codec dialog display before encoding starts.
</para>
</sect2>
</sect1>
<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
<sect1 id="menc-feat-quicktime-7">
<title>Using <application>MEncoder</application> to create
<application>QuickTime</application>-compatible files</title>
<sect2 id="menc-feat-quicktime-7-why-use-it">
<title>Why would one want to produce <application>QuickTime</application>-compatible Files?</title>
<para>
There are several reasons why producing
<application>QuickTime</application>-compatible files can be desirable.
</para>
<itemizedlist>
<listitem><para>
You want any computer illiterate to be able to watch your encode on
any major platform (Windows, Mac OS X, Unices …).
</para></listitem>
<listitem><para>
<application>QuickTime</application> is able to take advantage of more
hardware and software acceleration features of Mac OS X than
platform-independent players like <application>MPlayer</application>
or <application>VLC</application>.
That means that your encodes have a chance to be played smoothly by older
G4-powered machines.
</para></listitem>
<listitem><para>
<application>QuickTime</application> 7 supports the next-generation codec H.264,
which yields significantly better picture quality than previous codec
generations (MPEG-2, MPEG-4 …).
</para></listitem>
</itemizedlist>
</sect2>
<sect2 id="menc-feat-quicktime-7-constraints">
<title><application>QuickTime</application> 7 limitations</title>
<para>
<application>QuickTime</application> 7 supports H.264 video and AAC audio,
but it does not support them muxed in the AVI container format.
However, you can use <application>MEncoder</application> to encode
the video and audio, and then use an external program such as
<application>mp4creator</application> (part of the
<ulink url="http://mpeg4ip.sourceforge.net/">MPEG4IP suite</ulink>)
to remux the video and audio tracks into an MP4 container.
</para>
<para>
<application>QuickTime</application>'s support for H.264 is limited,
so you will need to drop some advanced features.
If you encode your video with features that
<application>QuickTime</application> 7 does not support,
<application>QuickTime</application>-based players will show you a pretty
white screen instead of your expected video.
</para>
<itemizedlist>
<listitem><para>
<emphasis role="bold">B-frames</emphasis>:
<application>QuickTime</application> 7 supports a maximum of 1 B-frame, i.e.
<option>-x264encopts bframes=1</option>. This means that
<option>b_pyramid</option> and <option>weight_b</option> will have no
effect, since they require <option>bframes</option> to be greater than 1.
</para></listitem>
<listitem><para>
<emphasis role="bold">Macroblocks</emphasis>:
<application>QuickTime</application> 7 does not support 8x8 DCT macroblocks.
This option (<option>8x8dct</option>) is off by default, so just be sure
not to explicitly enable it. This also means that the <option>i8x8</option>
option will have no effect, since it requires <option>8x8dct</option>.
</para></listitem>
<listitem><para>
<emphasis role="bold">Aspect ratio</emphasis>:
<application>QuickTime</application> 7 does not support SAR (sample
aspect ratio) information in MPEG-4 files; it assumes that SAR=1. Read
<link linkend="menc-feat-quicktime-7-scale">the section on scaling</link>
for a workaround.
</para></listitem>
</itemizedlist>
</sect2>
<sect2 id="menc-feat-quicktime-7-crop">
<title>Cropping</title>
<para>
Suppose you want to rip your freshly bought copy of "The Chronicles of
Narnia". Your DVD is region 1,
which means it is NTSC. The example below would still apply to PAL,
except you would omit <option>-ofps 24000/1001</option> and use slightly
different <option>crop</option> and <option>scale</option> dimensions.
</para>
<para>
After running <option>mplayer dvd://1</option>, you follow the process
detailed in the section <link linkend="menc-feat-telecine">How to deal
with telecine and interlacing in NTSC DVDs</link> and discover that it is
24000/1001 fps progressive video. This simplifies the process somewhat,
since you do not need to use an inverse telecine filter such as
<option>pullup</option> or a deinterlacing filter such as
<option>yadif</option>.
</para>
<para>
Next, you need to crop out the black bars from the top and bottom of the
video, as detailed in <link linkend="menc-feat-dvd-mpeg4-example-crop">this</link>
previous section.
</para>
</sect2>
<sect2 id="menc-feat-quicktime-7-scale">
<title>Scaling</title>
<para>
The next step is truly heartbreaking.
<application>QuickTime</application> 7 does not support MPEG-4 videos
with a sample aspect ratio other than 1, so you will need to upscale
(which wastes a lot of disk space) or downscale (which loses some
details of the source) the video to square pixels.
Either way you do it, this is highly inefficient, but simply cannot
be avoided if you want your video to be playable by
<application>QuickTime</application> 7.
<application>MEncoder</application> can apply the appropriate upscaling
or downscaling by specifying respectively <option>-vf scale=-10:-1</option>
or <option>-vf scale=-1:-10</option>.
This will scale your video to the correct width for the cropped height,
rounded to the closest multiple of 16 for optimal compression.
Remember that if you are cropping, you should crop first, then scale:
<screen>-vf crop=720:352:0:62,scale=-10:-1</screen>
</para>
</sect2>
<sect2 id="menc-feat-quicktime-7-avsync">
<title>A/V sync</title>
<para>
Because you will be remuxing into a different container, you should
always use the <option>harddup</option> option to ensure that duplicated
frames are actually duplicated in the video output. Without this option,
<application>MEncoder</application> will simply put a marker in the video
stream that a frame was duplicated, and rely on the client software to
show the same frame twice. Unfortunately, this "soft duplication" does
not survive remuxing, so the audio would slowly lose sync with the video.
</para>
<para>
The final filter chain looks like this:
<screen>-vf crop=720:352:0:62,scale=-10:-1,harddup</screen>
</para>
</sect2>
<sect2 id="menc-feat-quicktime-7-bitrate">
<title>Bitrate</title>
<para>
As always, the selection of bitrate is a matter of the technical properties
of the source, as explained
<link linkend="menc-feat-dvd-mpeg4-resolution-bitrate">here</link>, as
well as a matter of taste.
This movie has a fair bit of action and lots of detail, but H.264 video
looks good at much lower bitrates than XviD or other MPEG-4 codecs.
After much experimentation, the author of this guide chose to encode
this movie at 900kbps, and thought that it looked very good.
You may decrease bitrate if you need to save more space, or increase
it if you need to improve quality.
</para>
</sect2>
<sect2 id="menc-feat-quicktime-7-example">
<title>Encoding example</title>
<para>
You are now ready to encode the video. Since you care about
quality, of course you will be doing a two-pass encode. To shave off
some encoding time, you can specify the <option>turbo</option> option
on the first pass; this reduces <option>subq</option> and
<option>frameref</option> to 1. To save some disk space, you can
use the <option>ss</option> option to strip off the first few seconds
of the video. (I found that this particular movie has 32 seconds of
credits and logos.) <option>bframes</option> can be 0 or 1.
The other options are documented in <link
linkend="menc-feat-x264-encoding-options-speedvquality">Encoding with
the <systemitem class="library">x264</systemitem> codec</link> and
the man page.
<screen>mencoder dvd://1 -o /dev/null -ss 32 -ovc x264 \
-x264encopts pass=1:turbo:bitrate=900:bframes=1:\
me=umh:partitions=all:trellis=1:qp_step=4:qcomp=0.7:direct_pred=auto:keyint=300 \
-vf crop=720:352:0:62,scale=-10:-1,harddup \
-oac faac -faacopts br=192:mpeg=4:object=2 -channels 2 -srate 48000 \
-ofps 24000/1001</screen>
If you have a multi-processor machine, don't miss the opportunity to
dramatically speed-up encoding by enabling
<link linkend="menc-feat-x264-encoding-options-speedvquality-threads">
<systemitem class="library">x264</systemitem>'s multi-threading mode</link>
by adding <option>threads=auto</option> to your <option>x264encopts</option>
command-line.
</para>
<para>
The second pass is the same, except that you specify the output file
and set <option>pass=2</option>.
<screen>mencoder dvd://1 <emphasis role="bold">-o narnia.avi</emphasis> -ss 32 -ovc x264 \
-x264encopts <emphasis role="bold">pass=2</emphasis>:turbo:bitrate=900:frameref=5:bframes=1:\
me=umh:partitions=all:trellis=1:qp_step=4:qcomp=0.7:direct_pred=auto:keyint=300 \
-vf crop=720:352:0:62,scale=-10:-1,harddup \
-oac faac -faacopts br=192:mpeg=4:object=2 -channels 2 -srate 48000 \
-ofps 24000/1001</screen>
</para>
<para>
The resulting AVI should play perfectly in
<application>MPlayer</application>, but of course
<application>QuickTime</application> can not play it because it does
not support H.264 muxed in AVI.
So the next step is to remux the video into an MP4 container.
</para>
</sect2>
<sect2 id="menc-feat-quicktime-7-remux">
<title>Remuxing as MP4</title>
<para>
There are several ways to remux AVI files to MP4. You can use
<application>mp4creator</application>, which is part of the
<ulink url="http://mpeg4ip.sourceforge.net/">MPEG4IP suite</ulink>.
</para>
<para>
First, demux the AVI into separate audio and video streams using
<application>MPlayer</application>.
<screen>mplayer narnia.avi -dumpaudio -dumpfile narnia.aac
mplayer narnia.avi -dumpvideo -dumpfile narnia.h264</screen>
The file names are important; <application>mp4creator</application>
requires that AAC audio streams be named <systemitem>.aac</systemitem>
and H.264 video streams be named <systemitem>.h264</systemitem>.
</para>
<para>
Now use <application>mp4creator</application> to create a new
MP4 file out of the audio and video streams.
<screen>mp4creator -create=narnia.aac narnia.mp4
mp4creator -create=narnia.h264 -rate=23.976 narnia.mp4</screen>
Unlike the encoding step, you must specify the framerate as a
decimal (such as 23.976), not a fraction (such as 24000/1001).
</para>
<para>
This <systemitem>narnia.mp4</systemitem> file should now be playable
with any <application>QuickTime</application> 7 application, such as
<application>QuickTime Player</application> or
<application>iTunes</application>. If you are planning to view the
video in a web browser with the <application>QuickTime</application>
plugin, you should also hint the movie so that the
<application>QuickTime</application> plugin can start playing it
while it is still downloading. <application>mp4creator</application>
can create these hint tracks:
<screen>mp4creator -hint=1 narnia.mp4
mp4creator -hint=2 narnia.mp4
mp4creator -optimize narnia.mp4</screen>
You can check the final result to ensure that the hint tracks were
created successfully:
<screen>mp4creator -list narnia.mp4</screen>
You should see a list of tracks: 1 audio, 1 video, and 2 hint tracks.
<screen>Track Type Info
1 audio MPEG-4 AAC LC, 8548.714 secs, 190 kbps, 48000 Hz
2 video H264 Main@5.1, 8549.132 secs, 899 kbps, 848x352 @ 23.976001 fps
3 hint Payload mpeg4-generic for track 1
4 hint Payload H264 for track 2
</screen>
</para>
</sect2>
<sect2 id="menc-feat-quicktime-7-metadata">
<title>Adding metadata tags</title>
<para>
If you want to add tags to your video that show up in iTunes, you can use
<ulink url="http://atomicparsley.sourceforge.net/">AtomicParsley</ulink>.
<screen>AtomicParsley narnia.mp4 --metaEnema --title "The Chronicles of Narnia" --year 2005 --stik Movie --freefree --overWrite</screen>
The <option>--metaEnema</option> option removes any existing metadata
(<application>mp4creator</application> inserts its name in the
"encoding tool" tag), and <option>--freefree</option> reclaims the
space from the deleted metadata.
The <option>--stik</option> option sets the type of video (such as Movie
or TV Show), which iTunes uses to group related video files.
The <option>--overWrite</option> option overwrites the original file;
without it, <application>AtomicParsley</application> creates a new
auto-named file in the same directory and leaves the original file
untouched.
</para>
</sect2>
</sect1>
<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
<sect1 id="menc-feat-vcd-dvd">
<title>Using <application>MEncoder</application>
to create VCD/SVCD/DVD-compliant files</title>
<sect2 id="menc-feat-vcd-dvd-constraints">
<title>Format Constraints</title>
<para>
<application>MEncoder</application> is capable of creating VCD, SCVD
and DVD format MPEG files using the
<systemitem class="library">libavcodec</systemitem> library.
These files can then be used in conjunction with
<ulink url="http://www.gnu.org/software/vcdimager/vcdimager.html">vcdimager</ulink>
or
<ulink url="http://dvdauthor.sourceforge.net/">dvdauthor</ulink>
to create discs that will play on a standard set-top player.
</para>
<para>
The DVD, SVCD, and VCD formats are subject to heavy constraints.
Only a small selection of encoded picture sizes and aspect ratios are
available.
If your movie does not already meet these requirements, you may have
to scale, crop or add black borders to the picture to make it
compliant.
</para>
<sect3 id="menc-feat-vcd-dvd-constraints-resolution">
<title>Format Constraints</title>
<informaltable frame="all">
<tgroup cols="9">
<thead>
<row>
<entry>Format</entry>
<entry>Resolution</entry>
<entry>V. Codec</entry>
<entry>V. Bitrate</entry>
<entry>Sample Rate</entry>
<entry>A. Codec</entry>
<entry>A. Bitrate</entry>
<entry>FPS</entry>
<entry>Aspect</entry>
</row>
</thead>
<tbody>
<row>
<entry>NTSC DVD</entry>
<entry>720x480, 704x480, 352x480, 352x240</entry>
<entry>MPEG-2</entry>
<entry>9800 kbps</entry>
<entry>48000 Hz</entry>
<entry>AC-3,PCM</entry>
<entry>1536 kbps (max)</entry>
<entry>30000/1001, 24000/1001</entry>
<entry>4:3, 16:9 (only for 720x480)</entry>
</row>
<row>
<entry>NTSC DVD</entry>
<entry>352x240<footnote id='fn-rare-resolutions'><para>
These resolutions are rarely used for DVDs because
they are fairly low quality.</para></footnote></entry>
<entry>MPEG-1</entry>
<entry>1856 kbps</entry>
<entry>48000 Hz</entry>
<entry>AC-3,PCM</entry>
<entry>1536 kbps (max)</entry>
<entry>30000/1001, 24000/1001</entry>
<entry>4:3, 16:9</entry>
</row>
<row>
<entry>NTSC SVCD</entry>
<entry>480x480</entry>
<entry>MPEG-2</entry>
<entry>2600 kbps</entry>
<entry>44100 Hz</entry>
<entry>MP2</entry>
<entry>384 kbps (max)</entry>
<entry>30000/1001</entry>
<entry>4:3</entry>
</row>
<row>
<entry>NTSC VCD</entry>
<entry>352x240</entry>
<entry>MPEG-1</entry>
<entry>1150 kbps</entry>
<entry>44100 Hz</entry>
<entry>MP2</entry>
<entry>224 kbps</entry>
<entry>24000/1001, 30000/1001</entry>
<entry>4:3</entry>
</row>
<row>
<entry>PAL DVD</entry>
<entry>720x576, 704x576, 352x576, 352x288</entry>
<entry>MPEG-2</entry>
<entry>9800 kbps</entry>
<entry>48000 Hz</entry>
<entry>MP2,AC-3,PCM</entry>
<entry>1536 kbps (max)</entry>
<entry>25</entry>
<entry>4:3, 16:9 (only for 720x576)</entry>
</row>
<row>
<entry>PAL DVD</entry>
<entry>352x288<footnoteref linkend='fn-rare-resolutions'/></entry>
<entry>MPEG-1</entry>
<entry>1856 kbps</entry>
<entry>48000 Hz</entry>
<entry>MP2,AC-3,PCM</entry>
<entry>1536 kbps (max)</entry>
<entry>25</entry>
<entry>4:3, 16:9</entry>
</row>
<row>
<entry>PAL SVCD</entry>
<entry>480x576</entry>
<entry>MPEG-2</entry>
<entry>2600 kbps</entry>
<entry>44100 Hz</entry>
<entry>MP2</entry>
<entry>384 kbps (max)</entry>
<entry>25</entry>
<entry>4:3</entry>
</row>
<row>
<entry>PAL VCD</entry>
<entry>352x288</entry>
<entry>MPEG-1</entry>
<entry>1152 kbps</entry>
<entry>44100 Hz</entry>
<entry>MP2</entry>
<entry>224 kbps</entry>
<entry>25</entry>
<entry>4:3</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<para>
If your movie has 2.35:1 aspect (most recent action movies), you will
have to add black borders or crop the movie down to 16:9 to make a DVD or VCD.
If you add black borders, try to align them at 16-pixel boundaries in
order to minimize the impact on encoding performance.
Thankfully DVD has sufficiently excessive bitrate that you do not have
to worry too much about encoding efficiency, but SVCD and VCD are
highly bitrate-starved and require effort to obtain acceptable quality.
</para>
</sect3>
<sect3 id="menc-feat-vcd-dvd-constraints-gop">
<title>GOP Size Constraints</title>
<para>
DVD, VCD, and SVCD also constrain you to relatively low
GOP (Group of Pictures) sizes.
For 30 fps material the largest allowed GOP size is 18.
For 25 or 24 fps, the maximum is 15.
The GOP size is set using the <option>keyint</option> option.
</para>
</sect3>
<sect3 id="menc-feat-vcd-dvd-constraints-bitrate">
<title>Bitrate Constraints</title>
<para>
VCD video is required to be CBR at 1152 kbps.
This highly limiting constraint also comes along with an extremely low vbv
buffer size of 327 kilobits.
SVCD allows varying video bitrates up to 2500 kbps, and a somewhat less
restrictive vbv buffer size of 917 kilobits is allowed.
DVD video bitrates may range anywhere up to 9800 kbps (though typical
bitrates are about half that), and the vbv buffer size is 1835 kilobits.
</para>
</sect3>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-vcd-dvd-output">
<title>Output Options</title>
<para>
<application>MEncoder</application> has options to control the output
format.
Using these options we can instruct it to create the correct type of
file.
</para>
<para>
The options for VCD and SVCD are called xvcd and xsvcd, because they
are extended formats.
They are not strictly compliant, mainly because the output does not
contain scan offsets.
If you need to generate an SVCD image, you should pass the output file to
<ulink url="http://www.gnu.org/software/vcdimager/vcdimager.html">vcdimager</ulink>.
</para>
<para>
VCD:
<screen>-of mpeg -mpegopts format=xvcd</screen>
</para>
<para>
SVCD:
<screen>-of mpeg -mpegopts format=xsvcd</screen>
</para>
<para>
DVD (with timestamps on every frame, if possible):
<screen>-of mpeg -mpegopts format=dvd:tsaf</screen>
</para>
<para>
DVD with NTSC Pullup:
<screen>-of mpeg -mpegopts format=dvd:tsaf:telecine -ofps 24000/1001</screen>
This allows 24000/1001 fps progressive content to be encoded at 30000/1001
fps whilst maintaining DVD-compliance.
</para>
<sect3 id="menc-feat-vcd-dvd-output-aspect">
<title>Aspect Ratio</title>
<para>
The aspect argument of <option>-lavcopts</option> is used to encode
the aspect ratio of the file.
During playback the aspect ratio is used to restore the video to the
correct size.
</para>
<para>
16:9 or "Widescreen"
<screen>-lavcopts aspect=16/9</screen>
</para>
<para>
4:3 or "Fullscreen"
<screen>-lavcopts aspect=4/3</screen>
</para>
<para>
2.35:1 or "Cinemascope" NTSC
<screen>-vf scale=720:368,expand=720:480 -lavcopts aspect=16/9</screen>
To calculate the correct scaling size, use the expanded NTSC width of
854/2.35 = 368
</para>
<para>
2.35:1 or "Cinemascope" PAL
<screen>-vf scale=720:432,expand=720:576 -lavcopts aspect=16/9</screen>
To calculate the correct scaling size, use the expanded PAL width of
1024/2.35 = 432
</para>
</sect3>
<sect3 id="menc-feat-vcd-dvd-a-v-sync">
<title>Maintaining A/V sync</title>
<para>
In order to maintain audio/video synchronization throughout the encode,
<application>MEncoder</application> has to drop or duplicate frames.
This works rather well when muxing into an AVI file, but is almost
guaranteed to fail to maintain A/V sync with other muxers such as MPEG.
This is why it is necessary to append the
<option>harddup</option> video filter at the end of the filter chain
to avoid this kind of problem.
You can find more technical information about <option>harddup</option>
in the section
<link linkend="menc-feat-dvd-mpeg4-muxing-filter-issues">Improving muxing and A/V sync reliability</link>
or in the manual page.
</para>
</sect3>
<sect3 id="menc-feat-vcd-dvd-output-srate">
<title>Sample Rate Conversion</title>
<para>
If the audio sample rate in the original file is not the same as
required by the target format, sample rate conversion is required.
This is achieved using the <option>-srate</option> option and
the <option>-af lavcresample</option> audio filter together.
</para>
<para>
DVD:
<screen>-srate 48000 -af lavcresample=48000</screen>
</para>
<para>
VCD and SVCD:
<screen>-srate 44100 -af lavcresample=44100</screen>
</para>
</sect3>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-vcd-dvd-lavc">
<title>Using libavcodec for VCD/SVCD/DVD Encoding</title>
<sect3 id="menc-feat-vcd-dvd-lavc-intro">
<title>Introduction</title>
<para>
<systemitem class="library">libavcodec</systemitem> can be used to
create VCD/SVCD/DVD compliant video by using the appropriate options.
</para>
</sect3>
<sect3 id="menc-feat-vcd-dvd-lavc-options">
<title>lavcopts</title>
<para>
This is a list of fields in <option>-lavcopts</option> that you may
be required to change in order to make a complaint movie for VCD, SVCD,
or DVD:
</para>
<itemizedlist>
<listitem><para>
<emphasis role="bold">acodec</emphasis>:
<option>mp2</option> for VCD, SVCD, or PAL DVD;
<option>ac3</option> is most commonly used for DVD.
PCM audio may also be used for DVD, but this is mostly a big waste of
space.
Note that MP3 audio is not compliant for any of these formats, but
players often have no problem playing it anyway.
</para></listitem>
<listitem><para>
<emphasis role="bold">abitrate</emphasis>:
224 for VCD; up to 384 for SVCD; up to 1536 for DVD, but commonly
used values range from 192 kbps for stereo to 384 kbps for 5.1 channel
sound.
</para></listitem>
<listitem><para>
<emphasis role="bold">vcodec</emphasis>:
<option>mpeg1video</option> for VCD;
<option>mpeg2video</option> for SVCD;
<option>mpeg2video</option> is usually used for DVD but you may also use
<option>mpeg1video</option> for CIF resolutions.
</para></listitem>
<listitem><para>
<emphasis role="bold">keyint</emphasis>:
Used to set the GOP size.
18 for 30fps material, or 15 for 25/24 fps material.
Commercial producers seem to prefer keyframe intervals of 12.
It is possible to make this much larger and still retain compatibility
with most players.
A <option>keyint</option> of 25 should never cause any problems.
</para></listitem>
<listitem><para>
<emphasis role="bold">vrc_buf_size</emphasis>:
327 for VCD, 917 for SVCD, and 1835 for DVD.
</para></listitem>
<listitem><para>
<emphasis role="bold">vrc_minrate</emphasis>:
1152, for VCD. May be left alone for SVCD and DVD.
</para></listitem>
<listitem><para>
<emphasis role="bold">vrc_maxrate</emphasis>:
1152 for VCD; 2500 for SVCD; 9800 for DVD.
For SVCD and DVD, you might wish to use lower values depending on your
own personal preferences and requirements.
</para></listitem>
<listitem><para>
<emphasis role="bold">vbitrate</emphasis>:
1152 for VCD;
up to 2500 for SVCD;
up to 9800 for DVD.
For the latter two formats, vbitrate should be set based on personal
preference.
For instance, if you insist on fitting 20 or so hours on a DVD, you
could use vbitrate=400.
The resulting video quality would probably be quite bad.
If you are trying to squeeze out the maximum possible quality on a DVD,
use vbitrate=9800, but be warned that this could constrain you to less
than an hour of video on a single-layer DVD.
</para></listitem>
<listitem><para>
<emphasis role="bold">vstrict</emphasis>:
<option>vstrict</option>=0 should be used to create DVDs.
Without this option, <application>MEncoder</application> creates a
stream that cannot be correctly decoded by some standalone DVD
players.
</para></listitem>
</itemizedlist>
</sect3>
<sect3 id="menc-feat-vcd-dvd-lavc-examples">
<title>Examples</title>
<para>
This is a typical minimum set of <option>-lavcopts</option> for
encoding video:
</para>
<para>
VCD:
<screen>
-lavcopts vcodec=mpeg1video:vrc_buf_size=327:vrc_minrate=1152:\
vrc_maxrate=1152:vbitrate=1152:keyint=15:acodec=mp2
</screen>
</para>
<para>
SVCD:
<screen>
-lavcopts vcodec=mpeg2video:vrc_buf_size=917:vrc_maxrate=2500:vbitrate=1800:\
keyint=15:acodec=mp2
</screen>
</para>
<para>
DVD:
<screen>
-lavcopts vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=9800:vbitrate=5000:\
keyint=15:vstrict=0:acodec=ac3
</screen>
</para>
</sect3>
<sect3 id="menc-feat-vcd-dvd-lavc-advanced">
<title>Advanced Options</title>
<para>
For higher quality encoding, you may also wish to add quality-enhancing
options to lavcopts, such as <option>trell</option>,
<option>mbd=2</option>, and others.
Note that <option>qpel</option> and <option>v4mv</option>, while often
useful with MPEG-4, are not usable with MPEG-1 or MPEG-2.
Also, if you are trying to make a very high quality DVD encode, it may
be useful to add <option>dc=10</option> to lavcopts.
Doing so may help reduce the appearance of blocks in flat-colored areas.
Putting it all together, this is an example of a set of lavcopts for a
higher quality DVD:
</para>
<para>
<screen>
-lavcopts vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=9800:vbitrate=8000:\
keyint=15:trell:mbd=2:precmp=2:subcmp=2:cmp=2:dia=-10:predia=-10:cbp:mv0:\
vqmin=1:lmin=1:dc=10:vstrict=0
</screen>
</para>
</sect3>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-vcd-dvd-audio">
<title>Encoding Audio</title>
<para>
VCD and SVCD support MPEG-1 layer II audio, using one of
<systemitem class="library">toolame</systemitem>,
<systemitem class="library">twolame</systemitem>,
or <systemitem class="library">libavcodec</systemitem>'s MP2 encoder.
The libavcodec MP2 is far from being as good as the other two libraries,
however it should always be available to use.
VCD only supports constant bitrate audio (CBR) whereas SVCD supports
variable bitrate (VBR), too.
Be careful when using VBR because some bad standalone players might not
support it too well.
</para>
<para>
For DVD audio, <systemitem class="library">libavcodec</systemitem>'s
AC-3 codec is used.
</para>
<sect3 id="menc-feat-vcd-dvd-audio-toolame">
<title>toolame</title>
<para>
For VCD and SVCD:
<screen>-oac toolame -toolameopts br=224</screen>
</para>
</sect3>
<sect3 id="menc-feat-vcd-dvd-audio-twolame">
<title>twolame</title>
<para>
For VCD and SVCD:
<screen>-oac twolame -twolameopts br=224</screen>
</para>
</sect3>
<sect3 id="menc-feat-vcd-dvd-audio-lavc">
<title>libavcodec</title>
<para>
For DVD with 2 channel sound:
<screen>-oac lavc -lavcopts acodec=ac3:abitrate=192</screen>
</para>
<para>
For DVD with 5.1 channel sound:
<screen>-channels 6 -oac lavc -lavcopts acodec=ac3:abitrate=384</screen>
</para>
<para>
For VCD and SVCD:
<screen>-oac lavc -lavcopts acodec=mp2:abitrate=224</screen>
</para>
</sect3>
</sect2>
<!-- ********** -->
<sect2 id="menc-feat-vcd-dvd-all">
<title>Putting it all Together</title>
<para>
This section shows some complete commands for creating VCD/SVCD/DVD
compliant videos.
</para>
<sect3 id="menc-feat-vcd-dvd-all-pal-dvd">
<title>PAL DVD</title>
<para>
<screen>
mencoder -oac lavc -ovc lavc -of mpeg -mpegopts format=dvd:tsaf \
-vf scale=720:576,harddup -srate 48000 -af lavcresample=48000 \
-lavcopts vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=9800:vbitrate=5000:\
keyint=15:vstrict=0:acodec=ac3:abitrate=192:aspect=16/9 -ofps 25 \
-o <replaceable>movie.mpg</replaceable> <replaceable>movie.avi</replaceable>
</screen>
</para>
</sect3>
<sect3 id="menc-feat-vcd-dvd-all-ntsc-dvd">
<title>NTSC DVD</title>
<para>
<screen>
mencoder -oac lavc -ovc lavc -of mpeg -mpegopts format=dvd:tsaf \
-vf scale=720:480,harddup -srate 48000 -af lavcresample=48000 \
-lavcopts vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=9800:vbitrate=5000:\
keyint=18:vstrict=0:acodec=ac3:abitrate=192:aspect=16/9 -ofps 30000/1001 \
-o <replaceable>movie.mpg</replaceable> <replaceable>movie.avi</replaceable>
</screen>
</para>
</sect3>
<sect3 id="menc-feat-vcd-dvd-all-pal-ac3-copy">
<title>PAL AVI Containing AC-3 Audio to DVD</title>
<para>
If the source already has AC-3 audio, use -oac copy instead of re-encoding it.
<screen>
mencoder -oac copy -ovc lavc -of mpeg -mpegopts format=dvd:tsaf \
-vf scale=720:576,harddup -ofps 25 \
-lavcopts vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=9800:vbitrate=5000:\
keyint=15:vstrict=0:aspect=16/9 -o <replaceable>movie.mpg</replaceable> <replaceable>movie.avi</replaceable>
</screen>
</para>
</sect3>
<sect3 id="menc-feat-vcd-dvd-all-ntsc-ac3-copy">
<title>NTSC AVI Containing AC-3 Audio to DVD</title>
<para>
If the source already has AC-3 audio, and is NTSC @ 24000/1001 fps:
<screen>
mencoder -oac copy -ovc lavc -of mpeg -mpegopts format=dvd:tsaf:telecine \
-vf scale=720:480,harddup -lavcopts vcodec=mpeg2video:vrc_buf_size=1835:\
vrc_maxrate=9800:vbitrate=5000:keyint=15:vstrict=0:aspect=16/9 -ofps 24000/1001 \
-o <replaceable>movie.mpg</replaceable> <replaceable>movie.avi</replaceable>
</screen>
</para>
</sect3>
<sect3 id="menc-feat-vcd-dvd-all-pal-svcd">
<title>PAL SVCD</title>
<para>
<screen>
mencoder -oac lavc -ovc lavc -of mpeg -mpegopts format=xsvcd -vf \
scale=480:576,harddup -srate 44100 -af lavcresample=44100 -lavcopts \
vcodec=mpeg2video:mbd=2:keyint=15:vrc_buf_size=917:vrc_minrate=600:\
vbitrate=2500:vrc_maxrate=2500:acodec=mp2:abitrate=224:aspect=16/9 -ofps 25 \
-o <replaceable>movie.mpg</replaceable> <replaceable>movie.avi</replaceable>
</screen>
</para>
</sect3>
<sect3 id="menc-feat-vcd-dvd-all-ntsc-svcd">
<title>NTSC SVCD</title>
<para>
<screen>
mencoder -oac lavc -ovc lavc -of mpeg -mpegopts format=xsvcd -vf \
scale=480:480,harddup -srate 44100 -af lavcresample=44100 -lavcopts \
vcodec=mpeg2video:mbd=2:keyint=18:vrc_buf_size=917:vrc_minrate=600:\
vbitrate=2500:vrc_maxrate=2500:acodec=mp2:abitrate=224:aspect=16/9 -ofps 30000/1001 \
-o <replaceable>movie.mpg</replaceable> <replaceable>movie.avi</replaceable>
</screen>
</para>
</sect3>
<sect3 id="menc-feat-vcd-dvd-all-pal-vcd">
<title>PAL VCD</title>
<para>
<screen>
mencoder -oac lavc -ovc lavc -of mpeg -mpegopts format=xvcd -vf \
scale=352:288,harddup -srate 44100 -af lavcresample=44100 -lavcopts \
vcodec=mpeg1video:keyint=15:vrc_buf_size=327:vrc_minrate=1152:\
vbitrate=1152:vrc_maxrate=1152:acodec=mp2:abitrate=224:aspect=16/9 -ofps 25 \
-o <replaceable>movie.mpg</replaceable> <replaceable>movie.avi</replaceable>
</screen>
</para>
</sect3>
<sect3 id="menc-feat-vcd-dvd-all-ntsc-vcd">
<title>NTSC VCD</title>
<para>
<screen>
mencoder -oac lavc -ovc lavc -of mpeg -mpegopts format=xvcd -vf \
scale=352:240,harddup -srate 44100 -af lavcresample=44100 -lavcopts \
vcodec=mpeg1video:keyint=18:vrc_buf_size=327:vrc_minrate=1152:\
vbitrate=1152:vrc_maxrate=1152:acodec=mp2:abitrate=224:aspect=16/9 -ofps 30000/1001 \
-o <replaceable>movie.mpg</replaceable> <replaceable>movie.avi</replaceable>
</screen>
</para>
</sect3>
</sect2>
</sect1>
</chapter>
distrib
>
Mageia
>
5
>
x86_64
>
media
>
core-release
>
by-pkgid
>
b4f24aed537813ec1c72d9ce1ce54d62
>
files
>
144
