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<div class="refentry" title="clip">
<a id="clip"></a>
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<a id="IndexClip" class="indexterm"></a>
<div class="refnamediv">
<h2>
<span class="refentrytitle">clip</span>
</h2>
<p>clip —
Clips a signal to a predefined limit.
</p>
</div>
<div class="refsect1" title="Description">
<a id="idp16052016"></a>
<h2>Description</h2>
<p>
Clips an a-rate signal to a predefined limit, in a <span class="quote">“<span class="quote">soft</span>”</span> manner, using one of three methods.
</p>
</div>
<div class="refsect1" title="Syntax">
<a id="idp16061792"></a>
<h2>Syntax</h2>
<pre class="synopsis">ares <span class="command"><strong>clip</strong></span> asig, imeth, ilimit [, iarg]</pre>
</div>
<div class="refsect1" title="Initialization">
<a id="idp16062928"></a>
<h2>Initialization</h2>
<p>
<span class="emphasis"><em>imeth</em></span> -- selects the clipping method. The default is 0. The methods are:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" type="disc">
<li class="listitem">
<p>0 = Bram de Jong method (default)</p>
</li>
<li class="listitem">
<p>1 = sine clipping</p>
</li>
<li class="listitem">
<p>2 = tanh clipping</p>
</li>
</ul>
</div>
<p>
</p>
<p>
<span class="emphasis"><em>ilimit</em></span> -- limiting value
</p>
<p>
<span class="emphasis"><em>iarg</em></span> (optional, default=0.5) -- when <span class="emphasis"><em>imeth</em></span> = 0, indicates the point at which clipping starts, in the range 0 - 1. Not used when <span class="emphasis"><em>imeth</em></span> = 1 or <span class="emphasis"><em>imeth</em></span> = 2. Default is 0.5.
</p>
</div>
<div class="refsect1" title="Performance">
<a id="idp16106456"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>asig</em></span> -- a-rate input signal
</p>
<p>
The Bram de Jong method (<span class="emphasis"><em>imeth</em></span> = 0) applies the algorithm (denoting <span class="emphasis"><em>ilimit</em></span> as <span class="emphasis"><em>limit</em></span> and <span class="emphasis"><em>iarg</em></span> as <span class="emphasis"><em>a</em></span>):
</p>
<p>
</p>
<div class="informalexample">
<pre class="programlisting">
|<span class="emphasis"><em>x</em></span>| >= 0 and |<span class="emphasis"><em>x</em></span>| <= (<span class="emphasis"><em>limit*a</em></span>): f(<span class="emphasis"><em>x</em></span>) = f(<span class="emphasis"><em>x</em></span>)
|<span class="emphasis"><em>x</em></span>| > (<span class="emphasis"><em>limit*a</em></span>) and |<span class="emphasis"><em>x</em></span>| <= <span class="emphasis"><em>limit</em></span>: f(<span class="emphasis"><em>x</em></span>) = sign(<span class="emphasis"><em>x</em></span>) * (<span class="emphasis"><em>limit*a</em></span>+(<span class="emphasis"><em>x-limit*a</em></span>)/(1+((<span class="emphasis"><em>x-limit*a</em></span>)/(<span class="emphasis"><em>limit</em></span>*(1-<span class="emphasis"><em>a</em></span>)))<sup>2</sup>))
|<span class="emphasis"><em>x</em></span>| > <span class="emphasis"><em>limit</em></span>: f(<span class="emphasis"><em>x</em></span>) = sign(<span class="emphasis"><em>x</em></span>) * (<span class="emphasis"><em>limit</em></span>*(<span class="emphasis"><em>1+a</em></span>))/2</pre>
</div>
<p>
</p>
<p>
The second method (<span class="emphasis"><em>imeth</em></span> = 1) is the sine clip:
</p>
<p>
</p>
<div class="informalexample">
<pre class="programlisting">
|<span class="emphasis"><em>x</em></span>| < <span class="emphasis"><em>limit</em></span>: f(<span class="emphasis"><em>x</em></span>) = <span class="emphasis"><em>limit</em></span> * sin(π*<span class="emphasis"><em>x</em></span>/(2*<span class="emphasis"><em>limit</em></span>)), |<span class="emphasis"><em>x</em></span>| >= <span class="emphasis"><em>limit</em></span>: f(<span class="emphasis"><em>x</em></span>) = <span class="emphasis"><em>limit</em></span> * sign(<span class="emphasis"><em>x</em></span>)</pre>
</div>
<p>
</p>
<p>
The third method (<span class="emphasis"><em>imeth = 2</em></span>) is the tanh clip:
</p>
<p>
</p>
<div class="informalexample">
<pre class="programlisting">
|<span class="emphasis"><em>x</em></span>| < <span class="emphasis"><em>limit</em></span>: f(<span class="emphasis"><em>x</em></span>) = <span class="emphasis"><em>limit</em></span> * tanh(<span class="emphasis"><em>x/limit</em></span>)/tanh(1), |<span class="emphasis"><em>x</em></span>| >= <span class="emphasis"><em>limit</em></span>: f(<span class="emphasis"><em>x</em></span>) = <span class="emphasis"><em>limit</em></span> * sign(<span class="emphasis"><em>x</em></span>)</pre>
</div>
<p>
</p>
<div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note: Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25">
<img alt="[Note]" src="images/note.png" />
</td>
<th align="left">Note</th>
</tr>
<tr>
<td align="left" valign="top">
<p>
Method 1 appears to be non-functional at release of Csound version 4.07.
</p>
</td>
</tr>
</table>
</div>
</div>
<div class="refsect1" title="Examples">
<a id="idp16122472"></a>
<h2>Examples</h2>
<p>
Here is an example of the clip opcode. It uses the file <a class="ulink" href="examples/clip.csd" target="_top"><em class="citetitle">clip.csd</em></a>.
</p>
<div class="example">
<a id="idp16123440"></a>
<p class="title">
<strong>Example 112. Example of the clip 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">;;;RT audio out</span>
<span class="comment">;-iadc ;;;uncomment -iadc if RT audio input is needed too</span>
<span class="comment">; For Non-realtime ouput leave only the line below:</span>
<span class="comment">; -o clip.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="ohdr">0dbfs</span> <span class="op">=</span> 1
<span class="oblock">instr</span> 1 <span class="comment">; white noise</span>
arnd <span class="opc">rand</span> 1 <span class="comment">; full amlitude</span>
<span class="comment">; Clip the noisy waveform's amplitude to 0.5</span>
a1 <span class="opc">clip</span> arnd, 2, 0.5
<span class="opc">outs</span> a1, a1
<span class="oblock">endin</span>
<span class="oblock">instr</span> 2 <span class="comment">; white noise</span>
arnd <span class="opc">rand</span> 1 <span class="comment">; full amlitude</span>
<span class="comment">; Clip the noisy waveform's amplitude to 0.1</span>
a1 <span class="opc">clip</span> arnd, 2, 0.1
<span class="opc">outs</span> a1, a1
<span class="oblock">endin</span>
<span class="csdtag"></CsInstruments></span>
<span class="csdtag"><CsScore></span>
<span class="comment">; Play Instrument #1 for one second.</span>
<span class="stamnt">i</span> 1 0 1
<span class="comment">; Play Instrument #2 for one second.</span>
<span class="stamnt">i</span> 2 1 1
<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="Credits">
<a id="idp16125616"></a>
<h2>Credits</h2>
<p>
</p>
<table border="0" summary="Simple list" class="simplelist">
<tr>
<td>Author: John ffitch</td>
</tr>
<tr>
<td>University of Bath, Codemist Ltd.</td>
</tr>
<tr>
<td>Bath, UK</td>
</tr>
<tr>
<td>August, 2000</td>
</tr>
</table>
<p>
</p>
<p>New in Csound version 4.07</p>
<p>September 2009: Thanks to a note from Paolo Dell'Osso, corrected the formula.</p>
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