opcodes/clip.xml


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<refentry id="clip">
<indexterm id="IndexClip"><primary>clip</primary></indexterm>
  <refentryinfo><title>Signal Modifiers:Amplitude Modifiers</title></refentryinfo>
  <refmeta>
    <refentrytitle>clip</refentrytitle>
  </refmeta>


  <refnamediv>
    <refname>clip</refname>
    <refpurpose>
      Clips a signal to a predefined limit.
          </refpurpose>
  </refnamediv>
 
  <refsect1>
    <title>Description</title>
    <para>
      Clips an a-rate signal to a predefined limit, in a <quote>soft</quote> manner, using one of three methods.
   </para>
  </refsect1>
 
  <refsect1>
    <title>Syntax</title>
    <synopsis>ares <command>clip</command> asig, imeth, ilimit [, iarg]</synopsis>
  </refsect1>
 
  <refsect1>
    <title>Initialization</title>
    <para>
      <emphasis>imeth</emphasis> -- selects the clipping method. The default is 0. The methods are:
      <itemizedlist>
        <listitem>
            <para>0 = Bram de Jong method (default)</para>
        </listitem>

        <listitem>
            <para>1 = sine clipping</para>
        </listitem>

        <listitem>
            <para>2 = tanh clipping</para>
        </listitem>
      </itemizedlist>
    </para>

    <para>
      <emphasis>ilimit</emphasis> -- limiting value
    </para>

    <para>
      <emphasis>iarg</emphasis> (optional, default=0.5) -- when <emphasis>imeth</emphasis> = 0, indicates the point at which clipping starts, in the range 0 - 1. Not used when <emphasis>imeth</emphasis> = 1 or <emphasis>imeth</emphasis> = 2. Default is 0.5.
    </para>
  </refsect1>
 
  <refsect1>
    <title>Performance</title>
    <para>
      <emphasis>asig</emphasis> -- a-rate input signal
    </para>

    <para>
      The Bram de Jong method (<emphasis>imeth</emphasis> = 0) applies the algorithm:
    </para>

    <para>
      <informalexample>
        <programlisting>
|<emphasis>x</emphasis>| &gt; <emphasis>a</emphasis>:     f(<emphasis>x</emphasis>) = sin(<emphasis>x</emphasis>) * (a+(<emphasis>x-a</emphasis>)/(1+((<emphasis>x-a</emphasis>)/(1-<emphasis>a</emphasis>))<superscript>2</superscript> |<emphasis>x</emphasis>| &gt; 1: f(<emphasis>x</emphasis>) = sin(<emphasis>x</emphasis>) * (<emphasis>a</emphasis>+1)/2
        </programlisting>
      </informalexample>
    </para>

    <para>
      This method requires that <emphasis>asig</emphasis> be normalized to 1.
    </para>

    <para>
      The second method (<emphasis>imeth</emphasis> = 1) is the sine clip:
    </para>

    <para>
      <informalexample>
        <programlisting>
|<emphasis>x</emphasis>| &lt; <emphasis>limit</emphasis>: f(<emphasis>x</emphasis>) = <emphasis>limit</emphasis> * sin(&pi;*<emphasis>x</emphasis>/(2*<emphasis>limit</emphasis>)) f(<emphasis>x</emphasis>) = <emphasis>limit</emphasis> * sin(<emphasis>x</emphasis>)
        </programlisting>
      </informalexample>
    </para>

    <para>
      The third method (imeth = 3) is the tanh clip:
    </para>

    <para>
      <informalexample>
        <programlisting>
|<emphasis>x</emphasis>| &lt; <emphasis>limit</emphasis>: f(<emphasis>x</emphasis>) = <emphasis>limit</emphasis> * tanh(<emphasis>x/limit</emphasis>)/tanh(1) f(<emphasis>x</emphasis>) = <emphasis>limit</emphasis> * sin(<emphasis>x</emphasis>)
        </programlisting>
      </informalexample>
    </para>

    <note>
      <title>Note</title>
      <para>
        Method 1 appears to be non-functional at release of Csound version 4.07.
      </para>
    </note>
  </refsect1>
 
  <refsect1>
    <title>Examples</title>
    <para>
      Here is an example of the clip opcode. It uses the file <ulink url="examples/clip.csd"><citetitle>clip.csd</citetitle></ulink>.

      <example>
        <title>Example of the clip opcode.</title>

        
        <para>See the sections <link linkend="UsingRealTime"><citetitle>Real-time Audio</citetitle></link> and <link linkend="CommandFlags"><citetitle>Command Line Flags</citetitle></link> for more information on using command line flags.</para>
          <xi:include href="examples-xml/clip.csd.xml" xmlns:xi="http://www.w3.org/2001/XInclude"/>
      </example>
    </para>
  </refsect1>
 
  <refsect1>
    <title>Credits</title>
    <para>
      <simplelist>
        <member>Author: &namejohn;</member>
        <member>University of Bath, Codemist Ltd.</member>
        <member>Bath, UK</member>
        <member>August, 2000</member>
      </simplelist>
    </para>

    <para>New in Csound version 4.07</para>
  </refsect1>
</refentry>