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<H1><A NAME="SECTION0016400000000000000000">
14.4 <tt class="module">sunau</tt> --
Read and write Sun AU files</A>
</H1>
<P>
<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>
<table border align="center" style="border-collapse: collapse">
<thead>
<tr class="tableheader">
<th align="left"><b>Field</b> </th>
<th align="left"><b>Contents</b> </th>
</tr>
</thead>
<tbody valign="baseline">
<tr><td align="left" valign="baseline">magic word</td>
<td align="left">The four bytes "<tt class="samp">.snd</tt>".</td>
<tr><td align="left" valign="baseline">header size</td>
<td align="left">Size of the header, including info, in bytes.</td>
<tr><td align="left" valign="baseline">data size</td>
<td align="left">Physical size of the data, in bytes.</td>
<tr><td align="left" valign="baseline">encoding</td>
<td align="left">Indicates how the audio samples are encoded.</td>
<tr><td align="left" valign="baseline">sample rate</td>
<td align="left">The sampling rate.</td>
<tr><td align="left" valign="baseline"># of channels</td>
<td align="left">The number of channels in the samples.</td>
<tr><td align="left" valign="baseline">info</td>
<td align="left">ASCII string giving a description of the audio
file (padded with null bytes).</td></tbody>
</table>
<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><b><a name="l2h-3508"><tt class="function">open</tt></a></b>(<var>file, mode</var>)
<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><b><a name="l2h-3509"><tt class="function">openfp</tt></a></b>(<var>file, mode</var>)
<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> <a name="l2h-3510"><tt class="exception">Error</tt></a></b>
<dd>
An error raised when something is impossible because of Sun AU specs or
implementation deficiency.
</dl>
<P>
The <tt class="module">sunau</tt> module defines the following data items:
<P>
<dl><dt><b><a name="l2h-3511"><tt>AUDIO_FILE_MAGIC</tt></a></b>
<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.
</dl>
<P>
<dl><dt><b><a name="l2h-3512"><tt>AUDIO_FILE_ENCODING_MULAW_8</tt></a></b>
<dd>
<dt><b><a name="l2h-3514"><tt>AUDIO_FILE_ENCODING_LINEAR_8</tt></a></b><dd>
<dt><b><a name="l2h-3515"><tt>AUDIO_FILE_ENCODING_LINEAR_16</tt></a></b><dd>
<dt><b><a name="l2h-3516"><tt>AUDIO_FILE_ENCODING_LINEAR_24</tt></a></b><dd>
<dt><b><a name="l2h-3517"><tt>AUDIO_FILE_ENCODING_LINEAR_32</tt></a></b><dd>
<dt><b><a name="l2h-3518"><tt>AUDIO_FILE_ENCODING_ALAW_8</tt></a></b><dd>
Values of the encoding field from the AU header which are supported by
this module.
</dl>
<P>
<dl><dt><b><a name="l2h-3513"><tt>AUDIO_FILE_ENCODING_FLOAT</tt></a></b>
<dd>
<dt><b><a name="l2h-3519"><tt>AUDIO_FILE_ENCODING_DOUBLE</tt></a></b><dd>
<dt><b><a name="l2h-3520"><tt>AUDIO_FILE_ENCODING_ADPCM_G721</tt></a></b><dd>
<dt><b><a name="l2h-3521"><tt>AUDIO_FILE_ENCODING_ADPCM_G722</tt></a></b><dd>
<dt><b><a name="l2h-3522"><tt>AUDIO_FILE_ENCODING_ADPCM_G723_3</tt></a></b><dd>
<dt><b><a name="l2h-3523"><tt>AUDIO_FILE_ENCODING_ADPCM_G723_5</tt></a></b><dd>
Additional known values of the encoding field from the AU header, but
which are not supported by this module.
</dl>
<P>
<p><hr>
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<LI><A href="au-read-objects.html">14.4.1 AU_read Objects</a>
<LI><A href="au-write-objects.html">14.4.2 AU_write Objects</a>
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<span class="release-info">Release 2.2, documentation updated on December 21, 2001.</span>
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