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| 55 | <H1><A NAME="SECTION0016400000000000000000"> |
| 56 | 14.4 <tt class="module">sunau</tt> -- |
| 57 | Read and write Sun AU files</A> |
| 58 | </H1> |
| 59 | |
| 60 | <P> |
| 61 | <A NAME="module-sunau"></A> |
| 62 | |
| 63 | <P> |
| 64 | The <tt class="module">sunau</tt> module provides a convenient interface to the Sun |
| 65 | AU sound format. Note that this module is interface-compatible with |
| 66 | 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>. |
| 67 | |
| 68 | <P> |
| 69 | An audio file consists of a header followed by the data. The fields |
| 70 | of the header are: |
| 71 | |
| 72 | <P> |
| 73 | <div class="center"><table class="realtable"> |
| 74 | <thead> |
| 75 | <tr> |
| 76 | <th class="left" >Field</th> |
| 77 | <th class="left" >Contents</th> |
| 78 | </tr> |
| 79 | </thead> |
| 80 | <tbody> |
| 81 | <tr><td class="left" valign="baseline">magic word</td> |
| 82 | <td class="left" >The four bytes "<tt class="samp">.snd</tt>".</td></tr> |
| 83 | <tr><td class="left" valign="baseline">header size</td> |
| 84 | <td class="left" >Size of the header, including info, in bytes.</td></tr> |
| 85 | <tr><td class="left" valign="baseline">data size</td> |
| 86 | <td class="left" >Physical size of the data, in bytes.</td></tr> |
| 87 | <tr><td class="left" valign="baseline">encoding</td> |
| 88 | <td class="left" >Indicates how the audio samples are encoded.</td></tr> |
| 89 | <tr><td class="left" valign="baseline">sample rate</td> |
| 90 | <td class="left" >The sampling rate.</td></tr> |
| 91 | <tr><td class="left" valign="baseline"># of channels</td> |
| 92 | <td class="left" >The number of channels in the samples.</td></tr> |
| 93 | <tr><td class="left" valign="baseline">info</td> |
| 94 | <td class="left" >ASCII string giving a description of the audio |
| 95 | file (padded with null bytes).</td></tr></tbody> |
| 96 | </table></div> |
| 97 | |
| 98 | <P> |
| 99 | Apart from the info field, all header fields are 4 bytes in size. |
| 100 | They are all 32-bit unsigned integers encoded in big-endian byte |
| 101 | order. |
| 102 | |
| 103 | <P> |
| 104 | The <tt class="module">sunau</tt> module defines the following functions: |
| 105 | |
| 106 | <P> |
| 107 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 108 | <td><nobr><b><tt id='l2h-4667' xml:id='l2h-4667' class="function">open</tt></b>(</nobr></td> |
| 109 | <td><var>file, mode</var>)</td></tr></table></dt> |
| 110 | <dd> |
| 111 | If <var>file</var> is a string, open the file by that name, otherwise treat it |
| 112 | as a seekable file-like object. <var>mode</var> can be any of |
| 113 | <DL> |
| 114 | <DT><STRONG><code>'r'</code></STRONG></DT> |
| 115 | <DD>Read only mode. |
| 116 | |
| 117 | </DD> |
| 118 | <DT><STRONG><code>'w'</code></STRONG></DT> |
| 119 | <DD>Write only mode. |
| 120 | </DD> |
| 121 | </DL> |
| 122 | Note that it does not allow read/write files. |
| 123 | |
| 124 | <P> |
| 125 | A <var>mode</var> of <code>'r'</code> returns a <tt class="class">AU_read</tt> |
| 126 | object, while a <var>mode</var> of <code>'w'</code> or <code>'wb'</code> returns |
| 127 | a <tt class="class">AU_write</tt> object. |
| 128 | </dl> |
| 129 | |
| 130 | <P> |
| 131 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 132 | <td><nobr><b><tt id='l2h-4668' xml:id='l2h-4668' class="function">openfp</tt></b>(</nobr></td> |
| 133 | <td><var>file, mode</var>)</td></tr></table></dt> |
| 134 | <dd> |
| 135 | A synonym for <tt class="function">open</tt>, maintained for backwards compatibility. |
| 136 | </dl> |
| 137 | |
| 138 | <P> |
| 139 | The <tt class="module">sunau</tt> module defines the following exception: |
| 140 | |
| 141 | <P> |
| 142 | <dl><dt><b><span class="typelabel">exception</span> <tt id='l2h-4669' xml:id='l2h-4669' class="exception">Error</tt></b></dt> |
| 143 | <dd> |
| 144 | An error raised when something is impossible because of Sun AU specs or |
| 145 | implementation deficiency. |
| 146 | </dd></dl> |
| 147 | |
| 148 | <P> |
| 149 | The <tt class="module">sunau</tt> module defines the following data items: |
| 150 | |
| 151 | <P> |
| 152 | <dl><dt><b><tt id='l2h-4670' xml:id='l2h-4670'>AUDIO_FILE_MAGIC</tt></b></dt> |
| 153 | <dd> |
| 154 | An integer every valid Sun AU file begins with, stored in big-endian |
| 155 | form. This is the string "<tt class="samp">.snd</tt>" interpreted as an integer. |
| 156 | </dd></dl> |
| 157 | |
| 158 | <P> |
| 159 | <dl><dt><b><tt id='l2h-4671' xml:id='l2h-4671'>AUDIO_FILE_ENCODING_MULAW_8</tt></b></dt> |
| 160 | <dd> |
| 161 | <dt><b><tt id='l2h-4673' xml:id='l2h-4673'>AUDIO_FILE_ENCODING_LINEAR_8</tt></b></dt><dd> |
| 162 | <dt><b><tt id='l2h-4674' xml:id='l2h-4674'>AUDIO_FILE_ENCODING_LINEAR_16</tt></b></dt><dd> |
| 163 | <dt><b><tt id='l2h-4675' xml:id='l2h-4675'>AUDIO_FILE_ENCODING_LINEAR_24</tt></b></dt><dd> |
| 164 | <dt><b><tt id='l2h-4676' xml:id='l2h-4676'>AUDIO_FILE_ENCODING_LINEAR_32</tt></b></dt><dd> |
| 165 | <dt><b><tt id='l2h-4677' xml:id='l2h-4677'>AUDIO_FILE_ENCODING_ALAW_8</tt></b></dt><dd> |
| 166 | Values of the encoding field from the AU header which are supported by |
| 167 | this module. |
| 168 | </dd></dl> |
| 169 | |
| 170 | <P> |
| 171 | <dl><dt><b><tt id='l2h-4672' xml:id='l2h-4672'>AUDIO_FILE_ENCODING_FLOAT</tt></b></dt> |
| 172 | <dd> |
| 173 | <dt><b><tt id='l2h-4678' xml:id='l2h-4678'>AUDIO_FILE_ENCODING_DOUBLE</tt></b></dt><dd> |
| 174 | <dt><b><tt id='l2h-4679' xml:id='l2h-4679'>AUDIO_FILE_ENCODING_ADPCM_G721</tt></b></dt><dd> |
| 175 | <dt><b><tt id='l2h-4680' xml:id='l2h-4680'>AUDIO_FILE_ENCODING_ADPCM_G722</tt></b></dt><dd> |
| 176 | <dt><b><tt id='l2h-4681' xml:id='l2h-4681'>AUDIO_FILE_ENCODING_ADPCM_G723_3</tt></b></dt><dd> |
| 177 | <dt><b><tt id='l2h-4682' xml:id='l2h-4682'>AUDIO_FILE_ENCODING_ADPCM_G723_5</tt></b></dt><dd> |
| 178 | Additional known values of the encoding field from the AU header, but |
| 179 | which are not supported by this module. |
| 180 | </dd></dl> |
| 181 | |
| 182 | <P> |
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| 190 | <LI><A href="au-read-objects.html">14.4.1 AU_read Objects</a> |
| 191 | <LI><A href="au-write-objects.html">14.4.2 AU_write Objects</a> |
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| 230 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> |
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