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<h2>
<span class="refentrytitle">hetro</span>
</h2>
<p>hetro —
Decomposes an input soundfile into component sinusoids.
<a id="IndexHetro" class="indexterm"></a>
</p>
</div>
<div class="refsect1" title="Description">
<a id="idp81246576"></a>
<h2>Description</h2>
<p>
Hetrodyne filter analysis for the Csound <a class="link" href="adsyn.html" title="adsyn"><em class="citetitle">adsyn</em></a> generator.
</p>
</div>
<div class="refsect1" title="Syntax">
<a id="idp81257120"></a>
<h2>Syntax</h2>
<pre class="synopsis"><span class="command"><strong>csound -U hetro</strong></span> [flags] infilename outfilename</pre>
<pre class="synopsis"><span class="command"><strong>hetro</strong></span> [flags] infilename outfilename</pre>
</div>
<div class="refsect1" title="Initialization">
<a id="idp81258840"></a>
<h2>Initialization</h2>
<p>
<span class="emphasis"><em>hetro</em></span> takes an input soundfile, decomposes it into component sinusoids, and outputs a description of the components in the form of breakpoint amplitude and frequency tracks. Analysis is conditioned by the control flags below. A space is optional between flag and value.
</p>
<p>
<span class="emphasis"><em>-s srate</em></span> -- sampling rate of the audio input file. This will over-ride the srate of the soundfile header, which otherwise applies. If neither is present, the default is 10000. Note that for <span class="emphasis"><em>adsyn</em></span> synthesis the srate of the source file and the generating orchestra need not be the same.
</p>
<p>
<span class="emphasis"><em>-c channel</em></span> -- channel number sought. The default is 1.
</p>
<p>
<span class="emphasis"><em>-b begin</em></span> -- beginning time (in seconds) of the audio segment to be analyzed. The default is 0.0
</p>
<p>
<span class="emphasis"><em>-d duration</em></span> -- duration (in seconds) of the audio segment to be analyzed. The default of 0.0 means to the end of the file. Maximum length is 32.766 seconds.
</p>
<p>
<span class="emphasis"><em>-f begfreq</em></span> -- estimated starting frequency of the fundamental, necessary to initialize the filter analysis. The default is 100 (cps).
</p>
<p>
<span class="emphasis"><em>-h partials</em></span> -- number of harmonic partials sought in the audio file. Default is 10, maximum is a function of memory available.
</p>
<p>
<span class="emphasis"><em>-M maxamp</em></span> -- maximum amplitude summed across all concurrent tracks. The default is 32767.
</p>
<p>
<span class="emphasis"><em>-m minamp</em></span> -- amplitude threshold below which a single pair of amplitude/frequency tracks is considered dormant and will not contribute to output summation. Typical values: 128 (48 db down from full scale), 64 (54 db down), 32 (60 db down), 0 (no thresholding). The default threshold is 64 (54 db down).
</p>
<p>
<span class="emphasis"><em>-n brkpts</em></span> -- initial number of analysis
breakpoints in each amplitude and frequency track, prior to
thresholding (<span class="emphasis"><em>-m</em></span>) and linear breakpoint
consolidation. The initial points are spread evenly over the
duration. The default is 256.
</p>
<p>
<span class="emphasis"><em>-l cutfreq</em></span> -- substitute a 3rd order
Butterworth low-pass filter with cutoff frequency
<span class="emphasis"><em>cutfreq</em></span> (in Hz), in place of the default
averaging comb filter. The default is 0 (don't use).
</p>
</div>
<div class="refsect1" title="Performance">
<a id="idp81299664"></a>
<h2>Performance</h2>
<p>
As of Csound 4.08, <span class="emphasis"><em>hetro</em></span> can write SDIF
output files if the output file name ends with
".sdif" or ".SDIF". See the <a class="link" href="sdif2ad.html" title="sdif2ad"><em class="citetitle">sdif2ad utility</em></a>
for more information about the Csound's SDIF support.
</p>
</div>
<div class="refsect1" title="Examples">
<a id="idp81301264"></a>
<h2>Examples</h2>
<p>
</p>
<pre class="programlisting">
<span class="emphasis"><em>hetro</em></span> -s44100 -b.5 -d2.5 -h16 -M24000 audiofile.test adsynfile7</pre>
<p>
This will analyze 2.5 seconds of channel 1 of a file
"audiofile.test", recorded at 44.1 kHz, beginning .5
seconds from the start, and place the result in a file
"adsynfile7". We request just the first 16 harmonics of
the sound, with 256 initial breakpoint values per amplitude or
frequency track, and a peak summation amplitude of 24000. The
fundamental is estimated to begin at 100 Hz. Amplitude
thresholding is at 54 db down.
</p>
<p>
The Butterworth LPF is not enabled.
</p>
<div class="refsect2" title="File Format">
<a id="HetroFileFormat"></a>
<h3>File Format</h3>
<p>
The output file contains time-sequenced amplitude and
frequency values for each partial of an additive complex audio
source. The information is in the form of breakpoints (time,
value, time, value, ....) using 16-bit integers in the range 0 -
32767. Time is given in milliseconds, and frequency in Hertz
(cps). The breakpoint data is exclusively non-negative, and the
values -1 and -2 uniquely signify the start of new amplitude and
frequency tracks. A track is terminated by the value
32767. Before being written out, each track is data-reduced by
amplitude thresholding and linear breakpoint consolidation.
</p>
<p>
A component partial is defined by two breakpoint sets: an
amplitude set, and a frequency set. Within a composite file
these sets may appear in any order (amplitude, frequency,
amplitude ....; or amplitude, amplitude..., then frequency,
frequency,...). During <a class="link" href="adsyn.html" title="adsyn"><em class="citetitle">adsyn</em></a> resynthesis
the sets are automatically paired (amplitude, frequency) from
the order in which they were found. There should be an equal
number of each.
</p>
<p>
A legal <span class="emphasis"><em>adsyn</em></span> control file could have
following format:
</p>
<div class="informalexample">
<pre class="programlisting">
-1 time1 value1 ... timeK valueK 32767 ; amplitude breakpoints for partial 1
-2 time1 value1 ... timeL valueL 32767 ; frequency breakpoints for partial 1
-1 time1 value1 ... timeM valueM 32767 ; amplitude breakpoints for partial 2
-2 time1 value1 ... timeN valueN 32767 ; frequency breakpoints for partial 2
-2 time1 value1 ..........
-2 time1 value1 .......... ; pairable tracks for partials 3 and 4
-1 time1 value1 ..........
-1 time2 value1 ..........</pre>
</div>
<p>
</p>
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</div>
<div class="refsect1" title="Credits">
<a id="idp81308728"></a>
<h2>Credits</h2>
<p>
</p>
<table border="0" summary="Simple list" class="simplelist">
<tr>
<td>Author: Tom Sullivan</td>
</tr>
<tr>
<td>1992</td>
</tr>
<tr>
<td>Author: John ffitch</td>
</tr>
<tr>
<td>1994</td>
</tr>
<tr>
<td>Author: Richard Dobson</td>
</tr>
<tr>
<td>2000</td>
</tr>
</table>
<p>
</p>
<p>
October 2002. Thanks to Rasmus Ekman, added a note about the SDIF format.
</p>
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