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<title>14.4 sunau -- Read and write Sun AU files</title>
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<H1><A NAME="SECTION0016400000000000000000">
14.4 <tt class="module">sunau</tt> --
         Read and write Sun AU files</A>
</H1>

<P>
<A NAME="module-sunau"></A>

<P>
The <tt class="module">sunau</tt> module provides a convenient interface to the Sun
AU sound format.  Note that this module is interface-compatible with
the modules <tt class="module"><a href="module-aifc.html">aifc</a></tt> and <tt class="module"><a href="module-wave.html">wave</a></tt>.

<P>
An audio file consists of a header followed by the data.  The fields
of the header are:

<P>
<div class="center"><table class="realtable">
  <thead>
    <tr>
      <th class="left"  >Field</th>
      <th class="left"  >Contents</th>
      </tr>
    </thead>
  <tbody>
    <tr><td class="left"   valign="baseline">magic word</td>
        <td class="left"  >The four bytes "<tt class="samp">.snd</tt>".</td></tr>
    <tr><td class="left"   valign="baseline">header size</td>
        <td class="left"  >Size of the header, including info, in bytes.</td></tr>
    <tr><td class="left"   valign="baseline">data size</td>
        <td class="left"  >Physical size of the data, in bytes.</td></tr>
    <tr><td class="left"   valign="baseline">encoding</td>
        <td class="left"  >Indicates how the audio samples are encoded.</td></tr>
    <tr><td class="left"   valign="baseline">sample rate</td>
        <td class="left"  >The sampling rate.</td></tr>
    <tr><td class="left"   valign="baseline"># of channels</td>
        <td class="left"  >The number of channels in the samples.</td></tr>
    <tr><td class="left"   valign="baseline">info</td>
        <td class="left"  >ASCII string giving a description of the audio
                file (padded with null bytes).</td></tr></tbody>
</table></div>

<P>
Apart from the info field, all header fields are 4 bytes in size.
They are all 32-bit unsigned integers encoded in big-endian byte
order.

<P>
The <tt class="module">sunau</tt> module defines the following functions:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4667' xml:id='l2h-4667' class="function">open</tt></b>(</nobr></td>
  <td><var>file, mode</var>)</td></tr></table></dt>
<dd>
If <var>file</var> is a string, open the file by that name, otherwise treat it
as a seekable file-like object. <var>mode</var> can be any of
<DL>
<DT><STRONG><code>'r'</code></STRONG></DT>
<DD>Read only mode.

</DD>
<DT><STRONG><code>'w'</code></STRONG></DT>
<DD>Write only mode.
</DD>
</DL>
Note that it does not allow read/write files.

<P>
A <var>mode</var> of <code>'r'</code> returns a <tt class="class">AU_read</tt>
object, while a <var>mode</var> of <code>'w'</code> or <code>'wb'</code> returns
a <tt class="class">AU_write</tt> object.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4668' xml:id='l2h-4668' class="function">openfp</tt></b>(</nobr></td>
  <td><var>file, mode</var>)</td></tr></table></dt>
<dd>
A synonym for <tt class="function">open</tt>, maintained for backwards compatibility.
</dl>

<P>
The <tt class="module">sunau</tt> module defines the following exception:

<P>
<dl><dt><b><span class="typelabel">exception</span>&nbsp;<tt id='l2h-4669' xml:id='l2h-4669' class="exception">Error</tt></b></dt>
<dd>
An error raised when something is impossible because of Sun AU specs or
implementation deficiency.
</dd></dl>

<P>
The <tt class="module">sunau</tt> module defines the following data items:

<P>
<dl><dt><b><tt id='l2h-4670' xml:id='l2h-4670'>AUDIO_FILE_MAGIC</tt></b></dt>
<dd>
An integer every valid Sun AU file begins with, stored in big-endian
form.  This is the string "<tt class="samp">.snd</tt>" interpreted as an integer.
</dd></dl>

<P>
<dl><dt><b><tt id='l2h-4671' xml:id='l2h-4671'>AUDIO_FILE_ENCODING_MULAW_8</tt></b></dt>
<dd>
<dt><b><tt id='l2h-4673' xml:id='l2h-4673'>AUDIO_FILE_ENCODING_LINEAR_8</tt></b></dt><dd>
<dt><b><tt id='l2h-4674' xml:id='l2h-4674'>AUDIO_FILE_ENCODING_LINEAR_16</tt></b></dt><dd>
<dt><b><tt id='l2h-4675' xml:id='l2h-4675'>AUDIO_FILE_ENCODING_LINEAR_24</tt></b></dt><dd>
<dt><b><tt id='l2h-4676' xml:id='l2h-4676'>AUDIO_FILE_ENCODING_LINEAR_32</tt></b></dt><dd>
<dt><b><tt id='l2h-4677' xml:id='l2h-4677'>AUDIO_FILE_ENCODING_ALAW_8</tt></b></dt><dd>
Values of the encoding field from the AU header which are supported by
this module.
</dd></dl>

<P>
<dl><dt><b><tt id='l2h-4672' xml:id='l2h-4672'>AUDIO_FILE_ENCODING_FLOAT</tt></b></dt>
<dd>
<dt><b><tt id='l2h-4678' xml:id='l2h-4678'>AUDIO_FILE_ENCODING_DOUBLE</tt></b></dt><dd>
<dt><b><tt id='l2h-4679' xml:id='l2h-4679'>AUDIO_FILE_ENCODING_ADPCM_G721</tt></b></dt><dd>
<dt><b><tt id='l2h-4680' xml:id='l2h-4680'>AUDIO_FILE_ENCODING_ADPCM_G722</tt></b></dt><dd>
<dt><b><tt id='l2h-4681' xml:id='l2h-4681'>AUDIO_FILE_ENCODING_ADPCM_G723_3</tt></b></dt><dd>
<dt><b><tt id='l2h-4682' xml:id='l2h-4682'>AUDIO_FILE_ENCODING_ADPCM_G723_5</tt></b></dt><dd>
Additional known values of the encoding field from the AU header, but
which are not supported by this module.
</dd></dl>

<P>

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<LI><A href="au-read-objects.html">14.4.1 AU_read Objects</a>
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<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
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