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<a id="fof"></a>
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<a id="IndexFof" class="indexterm"></a>
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<h2>
<span class="refentrytitle">fof</span>
</h2>
<p>fof —
Produces sinusoid bursts useful for formant and granular synthesis.
</p>
</div>
<div class="refsect1" title="Description">
<a id="idp23784272"></a>
<h2>Description</h2>
<p>
Audio output is a succession of sinusoid bursts initiated at frequency <span class="emphasis"><em>xfund</em></span> with a spectral peak at <span class="emphasis"><em>xform</em></span>. For <span class="emphasis"><em>xfund</em></span> above 25 Hz these bursts produce a speech-like formant with spectral characteristics determined by the k-input parameters. For lower fundamentals this generator provides a special form of granular synthesis.
</p>
</div>
<div class="refsect1" title="Syntax">
<a id="idp23840208"></a>
<h2>Syntax</h2>
<pre class="synopsis">ares <span class="command"><strong>fof</strong></span> xamp, xfund, xform, koct, kband, kris, kdur, kdec, iolaps, \
ifna, ifnb, itotdur [, iphs] [, ifmode] [, iskip]</pre>
</div>
<div class="refsect1" title="Initialization">
<a id="idp23841528"></a>
<h2>Initialization</h2>
<p>
<span class="emphasis"><em>iolaps</em></span> -- number of preallocated spaces needed to hold overlapping burst data. Overlaps are frequency dependent, and the space required depends on the maximum value of <span class="emphasis"><em>xfund * kdur</em></span>. Can be over-estimated at no computation cost. Uses less than 50 bytes of memory per <span class="emphasis"><em>iolap</em></span>.
</p>
<p>
<span class="emphasis"><em>ifna, ifnb</em></span> -- table numbers of two stored functions. The first is a sine table for sineburst synthesis (size of at least 4096 recommended). The second is a rise shape, used forwards and backwards to shape the sineburst rise and decay; this may be linear (<a class="link" href="GEN07.html" title="GEN07"><em class="citetitle">GEN07</em></a>) or perhaps a sigmoid (<a class="link" href="GEN19.html" title="GEN19"><em class="citetitle">GEN19</em></a>).
</p>
<p>
<span class="emphasis"><em>itotdur</em></span> -- total time during which this <span class="emphasis"><em>fof</em></span> will be active. Normally set to p3. No new sineburst is created if it cannot complete its <span class="emphasis"><em>kdur</em></span> within the remaining <span class="emphasis"><em>itotdur</em></span>.
</p>
<p>
<span class="emphasis"><em>iphs</em></span> (optional, default=0) -- initial phase of the fundamental, expressed as a fraction of a cycle (0 to 1). The default value is 0.
</p>
<p>
<span class="emphasis"><em>ifmode</em></span> (optional, default=0) -- formant frequency mode. If zero, each sineburst keeps the <span class="emphasis"><em>xform</em></span> frequency it was launched with. If non-zero, each is influenced by <span class="emphasis"><em>xform</em></span> continuously. The default value is 0.
</p>
<p>
<span class="emphasis"><em>iskip</em></span> (optional, default=0) -- If non-zero, skip initialisation (allows legato use).
</p>
</div>
<div class="refsect1" title="Performance">
<a id="idp23848496"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>xamp</em></span> -- peak amplitude of each sineburst, observed at the true end of its rise pattern. The rise may exceed this value given a large bandwidth (say, Q < 10) and/or when the bursts are overlapping.
</p>
<p>
<span class="emphasis"><em>xfund</em></span> -- the fundamental frequency (in Hertz) of the impulses that create new sinebursts.
</p>
<p>
<span class="emphasis"><em>xform</em></span> -- the formant frequency, i.e. freq of the sinusoid burst induced by each <span class="emphasis"><em>xfund</em></span> impulse. This frequency can be fixed for each burst or can vary continuously (see <span class="emphasis"><em>ifmode</em></span>).
</p>
<p>
<span class="emphasis"><em>koct</em></span> -- octaviation index, normally zero. If greater than zero, lowers the effective <span class="emphasis"><em>xfund</em></span> frequency by attenuating odd-numbered sinebursts. Whole numbers are full octaves, fractions transitional.
</p>
<p>
<span class="emphasis"><em>kband</em></span> -- the formant bandwidth (at -6dB), expressed in Hz. The bandwidth determines the rate of exponential decay throughout the sineburst, before the enveloping described below is applied.
</p>
<p>
<span class="emphasis"><em>kris, kdur, kdec</em></span> -- rise, overall duration, and decay times (in seconds) of the sinusoid burst. These values apply an enveloped duration to each burst, in similar fashion to a Csound <span class="emphasis"><em>linen</em></span> generator but with rise and decay shapes derived from the <span class="emphasis"><em>ifnb</em></span> input. <span class="emphasis"><em>kris</em></span> inversely determines the skirtwidth (at -40 dB) of the induced formant region. <span class="emphasis"><em>kdur</em></span> affects the density of sineburst overlaps, and thus the speed of computation. Typical values for vocal imitation are .003,.02,.007.
</p>
<p>
Csound's <span class="emphasis"><em>fof</em></span> generator is loosely based on Michael Clarke's C-coding of IRCAM's <span class="emphasis"><em>CHANT</em></span> program (Xavier Rodet et al.). Each fof produces a single formant, and the output of four or more of these can be summed to produce a rich vocal imitation. <span class="emphasis"><em>fof</em></span> synthesis is a special form of granular synthesis, and this implementation aids transformation between vocal imitation and granular textures. Computation speed depends on <span class="emphasis"><em>kdur, xfund</em></span>, and the density of any overlaps.
</p>
</div>
<div class="refsect1" title="Examples">
<a id="idp23856416"></a>
<h2>Examples</h2>
<p>
Here is an example of the fof opcode. It uses the file <a class="ulink" href="examples/fof.csd" target="_top"><em class="citetitle">fof.csd</em></a>.
</p>
<div class="example">
<a id="idp23857392"></a>
<p class="title">
<strong>Example 280. Example of the fof opcode.</strong>
</p>
<div class="example-contents">
<p>See the sections <a class="link" href="UsingRealTime.html" title="Real-Time Audio"><em class="citetitle">Real-time Audio</em></a> and <a class="link" href="CommandFlags.html" title="Csound command line"><em class="citetitle">Command Line Flags</em></a> for more information on using command line flags.</p>
<pre class="programlisting">
<span class="csdtag"><CsoundSynthesizer></span>
<span class="csdtag"><CsOptions></span>
<span class="comment">; Select audio/midi flags here according to platform</span>
-odac <span class="comment">;;;realtime audio out</span>
<span class="comment">;-iadc ;;;uncomment -iadc if realtime audio input is needed too</span>
<span class="comment">; For Non-realtime ouput leave only the line below:</span>
<span class="comment">; -o fof.wav -W ;;; for file output any platform</span>
<span class="csdtag"></CsOptions></span>
<span class="csdtag"><CsInstruments></span>
<span class="ohdr">sr</span> <span class="op">=</span> 44100
<span class="ohdr">ksmps</span> <span class="op">=</span> 32
<span class="ohdr">nchnls</span> <span class="op">=</span> 2
<span class="oblock">instr</span> 1
<span class="comment">; Combine five formants together to create </span>
<span class="comment">; a transformation from an alto-"a" sound</span>
<span class="comment">; to an alto-"i" sound.</span>
<span class="comment">; Values common to all of the formants.</span>
kfund <span class="opc">init</span> 261.659
koct <span class="opc">init</span> 0
kris <span class="opc">init</span> 0.003
kdur <span class="opc">init</span> 0.02
kdec <span class="opc">init</span> 0.007
iolaps <span class="op">=</span> 100
ifna <span class="op">=</span> 1
ifnb <span class="op">=</span> 2
itotdur <span class="op">=</span> p3
<span class="comment">; First formant.</span>
k1amp <span class="op">=</span> <span class="opc">ampdb</span>(0)
k1form <span class="opc">line</span> 800, p3, 350
k1band <span class="opc">line</span> 80, p3, 50
<span class="comment">; Second formant.</span>
k2amp <span class="opc">line</span> <span class="opc">ampdb</span>(<span class="op">-</span>4), p3, <span class="opc">ampdb</span>(<span class="op">-</span>20)
k2form <span class="opc">line</span> 1150, p3, 1700
k2band <span class="opc">line</span> 90, p3, 100
<span class="comment">; Third formant.</span>
k3amp <span class="opc">line</span> <span class="opc">ampdb</span>(<span class="op">-</span>20), p3, <span class="opc">ampdb</span>(<span class="op">-</span>30)
k3form <span class="opc">line</span> 2800, p3, 2700
k3band <span class="opc">init</span> 120
<span class="comment">; Fourth formant.</span>
k4amp <span class="opc">init</span> <span class="opc">ampdb</span>(<span class="op">-</span>36)
k4form <span class="opc">line</span> 3500, p3, 3700
k4band <span class="opc">line</span> 130, p3, 150
<span class="comment">; Fifth formant.</span>
k5amp <span class="opc">init</span> <span class="opc">ampdb</span>(<span class="op">-</span>60)
k5form <span class="opc">init</span> 4950
k5band <span class="opc">line</span> 140, p3, 200
a1 <span class="opc">fof</span> k1amp, kfund, k1form, koct, k1band, kris, \
kdur, kdec, iolaps, ifna, ifnb, itotdur
a2 <span class="opc">fof</span> k2amp, kfund, k2form, koct, k2band, kris, \
kdur, kdec, iolaps, ifna, ifnb, itotdur
a3 <span class="opc">fof</span> k3amp, kfund, k3form, koct, k3band, kris, \
kdur, kdec, iolaps, ifna, ifnb, itotdur
a4 <span class="opc">fof</span> k4amp, kfund, k4form, koct, k4band, kris, \
kdur, kdec, iolaps, ifna, ifnb, itotdur
a5 <span class="opc">fof</span> k5amp, kfund, k5form, koct, k5band, kris, \
kdur, kdec, iolaps, ifna, ifnb, itotdur
<span class="comment">; Combine all of the formants together</span>
asig <span class="opc">sum</span> (a1<span class="op">+</span>a2<span class="op">+</span>a3<span class="op">+</span>a4<span class="op">+</span>a5) <span class="op">*</span> 13000
<span class="opc">outs</span> asig, asig
<span class="oblock">endin</span>
<span class="csdtag"></CsInstruments></span>
<span class="csdtag"><CsScore></span>
<span class="comment">; sine wave</span>
<span class="stamnt">f</span> 1 0 4096 10 1
<span class="comment">; sigmoid wave</span>
<span class="stamnt">f</span> 2 0 1024 19 0.5 0.5 270 0.5
<span class="stamnt">i</span> 1 0 1
<span class="stamnt">i</span> 1 2 5 <span class="comment">; same but slower</span>
<span class="stamnt">e</span>
<span class="csdtag"></CsScore></span>
<span class="csdtag"></CsoundSynthesizer></span>
</pre>
</div>
</div>
<p><br class="example-break" />
The formant values for the alto-"a" sound were taken from the <a class="link" href="MiscFormants.html" title="Appendix D. Formant Values"><em class="citetitle">Formant Values Appendix</em></a>.
</p>
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<div class="refsect1" title="See Also">
<a id="idp23860344"></a>
<h2>See Also</h2>
<p>
<a class="link" href="fof2.html" title="fof2"><em class="citetitle">fof2</em></a>,
<a class="link" href="MiscFormants.html" title="Appendix D. Formant Values"><em class="citetitle">Formant Values Appendix</em></a>
</p>
</div>
<div class="refsect1" title="Credits">
<a id="idp23861920"></a>
<h2>Credits</h2>
<p>Added in version 1 (1990)</p>
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