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<div class="refentry" title="fofilter">
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<h2>
<span class="refentrytitle">fofilter</span>
</h2>
<p>fofilter —
Formant filter.
</p>
</div>
<div class="refsect1" title="Description">
<a id="id2911186"></a>
<h2>Description</h2>
<p>
Fofilter generates a stream of overlapping sinewave grains, when fed with
a pulse train. Each grain is the impulse response of a combination of
two BP filters. The grains are defined by their attack time (determining
the skirtwidth of the formant region at -60dB) and decay time
(-6dB bandwidth). Overlapping will occur when 1/freq < decay, but,
unlike FOF, there is no upper limit on the number of overlaps.
The original idea for this opcode came from J McCartney's formlet class
in SuperCollider, but this is possibly implemented differently(?).
</p>
</div>
<div class="refsect1" title="Syntax">
<a id="id2911196"></a>
<h2>Syntax</h2>
<pre class="synopsis">asig <span class="command"><strong>fofilter</strong></span> ain, kcf, kris, kdec[, istor]</pre>
</div>
<div class="refsect1" title="Initialization">
<a id="id2912214"></a>
<h2>Initialization</h2>
<p>
<span class="emphasis"><em>istor</em></span> --initial disposition of internal data space. Since
filtering incorporates a feedback loop of previous output,
the initial status of the storage space used is significant.
A zero value will clear the space; a non-zero value will allow
previous information to remain. The default value is 0.
</p>
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<div class="refsect1" title="Performance">
<a id="id2912232"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>asig</em></span> -- input signal.
</p>
<p>
<span class="emphasis"><em>kcf</em></span> -- filter centre frequency
</p>
<p>
<span class="emphasis"><em>kris</em></span> -- impulse response attack time (secs).
</p>
<p>
<span class="emphasis"><em>kdec</em></span> -- impulse response decay time (secs).
</p>
</div>
<div class="refsect1" title="Examples">
<a id="id2912269"></a>
<h2>Examples</h2>
<p>
</p>
<div class="example">
<a id="id2912276"></a>
<p class="title">
<b>Example 256. Example</b>
</p>
<div class="example-contents">
<pre class="programlisting">
kfe <span class="opc">expseg</span> 10, p3<span class="op">*</span>0.9, 180, p3<span class="op">*</span>0.1, 175
kenv <span class="opc">linen</span> 1000, 0.05, p3, 0.05
asig <span class="opc">buzz</span> kenv, kfe, sr<span class="op">/</span>(2<span class="op">*</span>kfe), 1
afil <span class="opc">fofilter</span> asig, 900, 0.007, 0.04
<span class="opc">out</span> afil</pre>
</div>
</div>
<p><br class="example-break" />
</p>
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<div class="refsect1" title="Credits">
<a id="id2912344"></a>
<h2>Credits</h2>
<p>
</p>
<table border="0" summary="Simple list" class="simplelist">
<tr>
<td>Author: Victor Lazzarini</td>
</tr>
<tr>
<td>January 2005</td>
</tr>
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<p>
</p>
<p>New plugin in version 5</p>
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