0dbfs.xml


<refentry id="Zerodbfs">
<indexterm id="Index0dbfs"><primary>0dbfs</primary></indexterm>
<refentryinfo><title>Orchestra Syntax:Header</title></refentryinfo>
  <refmeta>
    <refentrytitle>0dbfs</refentrytitle>
  </refmeta>

  <refnamediv>
    <refname>0dbfs</refname>
    <refpurpose>
      Sets the value of 0 decibels using full scale amplitude.
    </refpurpose>
  </refnamediv>

  <refsect1>
    <title>Description</title>
    <para>
      Sets the value of 0 decibels using full scale amplitude.
    </para>
  </refsect1>

  <refsect1>
    <title>Syntax</title>
    <synopsis><command>0dbfs</command> = iarg</synopsis>
    <synopsis><command>0dbfs</command> </synopsis>
  </refsect1>

  <refsect1>
    <title>Initialization</title>
    <para>
      <emphasis>iarg</emphasis> -- the value of 0 decibels using full scale amplitude.
    </para>
  </refsect1>

  <refsect1>
    <title>Performance</title>
    <para>
      The default is 32767, so all existing orcs <emphasis>should</emphasis> work.
    </para>

    <para>
      Amplitude values in Csound are always relative to a "<link linkend="Zerodbfs"><citetitle>0dbfs</citetitle></link>" value representing the peak available amplitude before clipping. In the original Csound, this value was always 32767, corresponding to the bipolar range of a 16bit soundfile or 16bit AD/DA codec. This remains the <emphasis>default</emphasis> peak amplitude for Csound, for backward compatibility. The <link linkend="Zerodbfs"><citetitle>0dbfs</citetitle></link> value enables Csound to produce appropriately scaled values to whatever output format is being used, whether 16bit integer, 24bit integer, 32bit floats, or even 32bit integers.
    </para>
    <para>
      OdBFS can be defined in the header, to set the amplitude reference Csound will use, but it can also be used as a varible inside instruments like this:

      <informalexample>
        <programlisting>ipeak <emphasis role="op">=</emphasis> <emphasis role="ohdr">0dbfs</emphasis></programlisting>
      </informalexample>

      <informalexample>
        <programlisting>
asig <emphasis role="opc">oscil</emphasis> <emphasis role="ohdr">0dbfs</emphasis>, freq, 1
     <emphasis role="opc">out</emphasis>   asig * 0.3 * <emphasis role="ohdr">0dbfs</emphasis></programlisting>
      </informalexample>

    </para>

    <para>
      The purpose of the <emphasis>0dbfs</emphasis> opcode is for people to start to code 0dbfs-relatively (and use the <link linkend="ampdbfs"><citetitle>ampdbfs()</citetitle></link> opcodes a lot more!), rather than use explicit sample values. Using 0dbfs=1 is in accordance to industry practice, as ranges from -1 to 1 are used in most commercial plugin formats and in most other synthesis systems like Pure Data.
    </para>

    <para>
      Floats written to a file, when <emphasis>0dbfs = 1</emphasis>, will in effect go through no range translation at all. So the numbers in the file are exactly what the orc says they are.
    </para>
    <para>For more details on amplitude values in Csound, see the section <link linkend="AmplitudeCsound"><citetitle>Amplitude values in Csound</citetitle></link></para>

  </refsect1>

  <refsect1>
    <title>Example</title>
    <para>
      Here is an example of the 0dbfs opcode. It uses the file <ulink url="examples/0dbfs.csd"><citetitle>0dbfs.csd</citetitle></ulink>.

      <example>
        <title>Example of the 0dbfs 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/0dbfs.csd.xml" xmlns:xi="http://www.w3.org/2001/XInclude"/>
      </example>
    </para>
  </refsect1>
  <refsect1>
    <title>See also</title>
    <para><link linkend="ampdbfs"><citetitle>ampdbfs()</citetitle></link></para>
  </refsect1>

  <refsect1>
    <title>Credits</title>
    <para>
      <simplelist>
        <member>Author: Richard Dobson</member>
        <member>May 2002</member>
      </simplelist>
    </para>
    <para>New in version 4.10</para>
  </refsect1>
</refentry>