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<div class="refentry" title="vco">
<a id="vco"></a>
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<a id="IndexVco" class="indexterm"></a>
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<h2>
<span class="refentrytitle">vco</span>
</h2>
<p>vco —
Implementation of a band limited, analog modeled oscillator.
</p>
</div>
<div class="refsect1" title="Description">
<a id="idp50832872"></a>
<h2>Description</h2>
<p>
Implementation of a band limited, analog modeled oscillator, based on integration of band limited impulses. <span class="emphasis"><em>vco</em></span> can be used to simulate a variety of analog wave forms.
</p>
</div>
<div class="refsect1" title="Syntax">
<a id="idp50833920"></a>
<h2>Syntax</h2>
<pre class="synopsis">ares <span class="command"><strong>vco</strong></span> xamp, xcps, iwave, kpw [, ifn] [, imaxd] [, ileak] [, inyx] \
[, iphs] [, iskip]</pre>
</div>
<div class="refsect1" title="Initialization">
<a id="idp50887616"></a>
<h2>Initialization</h2>
<p>
<span class="emphasis"><em>iwave</em></span> -- determines the waveform:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" type="disc">
<li class="listitem">
<p><span class="emphasis"><em>iwave</em></span> = 1 - sawtooth</p>
</li>
<li class="listitem">
<p><span class="emphasis"><em>iwave</em></span> = 2 - square/PWM</p>
</li>
<li class="listitem">
<p><span class="emphasis"><em>iwave</em></span> = 3 - triangle/saw/ramp</p>
</li>
</ul>
</div>
<p>
</p>
<p>
<span class="emphasis"><em>ifn</em></span> (optional, default = 1) -- should be the table number of a of a stored sine wave. Must point to a valid table which contains a sine wave. Csound will report an error if this parameter is not set and table 1 doesn't exist.
</p>
<p>
<span class="emphasis"><em>imaxd</em></span> (optional, default = 1) -- is the maximum delay time. A time of 1/<span class="emphasis"><em>ifqc</em></span> may be required for the PWM and triangle waveform. To bend the pitch down this value must be as large as 1/(minimum frequency).
</p>
<p>
<span class="emphasis"><em>ileak</em></span> (optional, default = 0) -- if <span class="emphasis"><em>ileak</em></span> is between zero and one (0 < ileak < 1) then <span class="emphasis"><em>ileak</em></span> is used as the leaky integrator value. Otherwise a leaky integrator value of .999 is used for the saw and square waves and .995 is used for the triangle wave. This can be used to <span class="quote">“<span class="quote">flatten</span>”</span> the square wave or <span class="quote">“<span class="quote">straighten</span>”</span> the saw wave at low frequencies by setting <span class="emphasis"><em>ileak</em></span> to .99999 or a similar value. This should give a hollower sounding square wave.
</p>
<p>
<span class="emphasis"><em>inyx</em></span> (optional, default = .5) -- this is used to determine the number of harmonics in the band limited pulse. All overtones up to <span class="emphasis"><em>sr</em></span> * <span class="emphasis"><em>inyx</em></span> will be used. The default gives <span class="emphasis"><em>sr</em></span> * .5 (<span class="emphasis"><em>sr</em></span>/2). For <span class="emphasis"><em>sr</em></span>/4 use <span class="emphasis"><em>inyx</em></span> = .25. This can generate a <span class="quote">“<span class="quote">fatter</span>”</span> sound in some cases.
</p>
<p>
<span class="emphasis"><em>iphs</em></span> (optional, default = 0) -- this is a phase value. There is an artifact (bug-like feature) in <span class="emphasis"><em>vco</em></span> which occurs during the first half cycle of the square wave which causes the waveform to be greater in magnitude than all others. The value of <span class="emphasis"><em>iphs</em></span> has an effect on this artifact. In particular setting <span class="emphasis"><em>iphs</em></span> to .5 will cause the first half cycle of the square wave to resemble a small triangle wave. This may be more desirable than the large wave artifact which is the current default.
</p>
<p>
<span class="emphasis"><em>iskip</em></span> (optional, default = 0) -- if non zero
skip the initialisation of the filter. (New in Csound version
4.23f13 and 5.0)
</p>
</div>
<div class="refsect1" title="Performance">
<a id="idp50898704"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>kpw</em></span> -- determines either the pulse width (if <span class="emphasis"><em>iwave</em></span> is 2) or the saw/ramp character (if <span class="emphasis"><em>iwave</em></span> is 3) The value of <span class="emphasis"><em>kpw</em></span> should be greater than 0 and less than 1. A value of 0.5 will generate either a square wave (if <span class="emphasis"><em>iwave</em></span> is 2) or a triangle wave (if <span class="emphasis"><em>iwave</em></span> is 3).
</p>
<p>
<span class="emphasis"><em>xamp</em></span> -- determines the amplitude
</p>
<p>
<span class="emphasis"><em>xcps</em></span> -- is the frequency of the wave in cycles per second.
</p>
</div>
<div class="refsect1" title="Examples">
<a id="idp50901872"></a>
<h2>Examples</h2>
<p>
Here is an example of the vco opcode. It uses the file <a class="ulink" href="examples/vco.csd" target="_top"><em class="citetitle">vco.csd</em></a>.
</p>
<div class="example">
<a id="idp50902848"></a>
<p class="title">
<strong>Example 929. Example of the vco 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>
<span class="comment">; Audio out Audio in</span>
-odac -iadc <span class="comment">;;;RT audio I/O</span>
<span class="comment">; For Non-realtime ouput leave only the line below:</span>
<span class="comment">; -o vco.wav -W ;;; for file output any platform</span>
<span class="csdtag"></CsOptions></span>
<span class="csdtag"><CsInstruments></span>
<span class="comment">; Initialize the global variables.</span>
<span class="ohdr">sr</span> <span class="op">=</span> 44100
<span class="ohdr">kr</span> <span class="op">=</span> 44100
<span class="ohdr">ksmps</span> <span class="op">=</span> 1
<span class="ohdr">nchnls</span> <span class="op">=</span> 1
<span class="comment">; Instrument #1</span>
<span class="oblock">instr</span> 1
<span class="comment">; Set the amplitude.</span>
kamp <span class="op">=</span> p4
<span class="comment">; Set the frequency.</span>
kcps <span class="op">=</span> <span class="opc">cpspch</span>(p5)
<span class="comment">; Select the wave form.</span>
iwave <span class="op">=</span> p6
<span class="comment">; Set the pulse-width/saw-ramp character.</span>
kpw <span class="opc">init</span> 0.5
<span class="comment">; Use Table #1.</span>
ifn <span class="op">=</span> 1
<span class="comment">; Generate the waveform.</span>
asig <span class="opc">vco</span> kamp, kcps, iwave, kpw, ifn
<span class="comment">; Output and amplification.</span>
<span class="opc">out</span> asig
<span class="oblock">endin</span>
<span class="csdtag"></CsInstruments></span>
<span class="csdtag"><CsScore></span>
<span class="comment">; Table #1, a sine wave.</span>
<span class="stamnt">f</span> 1 0 65536 10 1
<span class="comment">; Define the score.</span>
<span class="comment">; p4 = raw amplitude (0-32767)</span>
<span class="comment">; p5 = frequency, in pitch-class notation.</span>
<span class="comment">; p6 = the waveform (1=Saw, 2=Square/PWM, 3=Tri/Saw-Ramp-Mod)</span>
<span class="stamnt">i</span> 1 00 02 20000 05.00 1
<span class="stamnt">i</span> 1 02 02 20000 05.00 2
<span class="stamnt">i</span> 1 04 02 20000 05.00 3
<span class="stamnt">i</span> 1 06 02 20000 07.00 1
<span class="stamnt">i</span> 1 08 02 20000 07.00 2
<span class="stamnt">i</span> 1 10 02 20000 07.00 3
<span class="stamnt">i</span> 1 12 02 20000 09.00 1
<span class="stamnt">i</span> 1 14 02 20000 09.00 2
<span class="stamnt">i</span> 1 16 02 20000 09.00 3
<span class="stamnt">i</span> 1 18 02 20000 11.00 1
<span class="stamnt">i</span> 1 20 02 20000 11.00 2
<span class="stamnt">i</span> 1 22 02 20000 11.00 3
<span class="stamnt">e</span>
<span class="csdtag"></CsScore></span>
<span class="csdtag"></CsoundSynthesizer></span>
</pre>
</div>
</div>
<p><br class="example-break" />
</p>
</div>
<div class="refsect1" title="See Also">
<a id="idp50905144"></a>
<h2>See Also</h2>
<p>
<a class="link" href="vco2.html" title="vco2"><em class="citetitle">vco2</em></a>
</p>
</div>
<div class="refsect1" title="Credits">
<a id="idp50906192"></a>
<h2>Credits</h2>
<p>
</p>
<table border="0" summary="Simple list" class="simplelist">
<tr>
<td>Author: Hans Mikelson</td>
</tr>
<tr>
<td>December 1998</td>
</tr>
</table>
<p>
</p>
<p>New in Csound version 3.50</p>
<p>November 2002. Corrected the documentation for the <span class="emphasis"><em>kpw</em></span> parameter thanks to Luis Jure and Hans Mikelson.</p>
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