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<div class="section" id="module-aifc">
<span id="aifc-read-and-write-aiff-and-aifc-files"></span><h1>21.2. <a class="reference internal" href="#module-aifc" title="aifc: Read and write audio files in AIFF or AIFC format."><tt class="xref py py-mod docutils literal"><span class="pre">aifc</span></tt></a> — Read and write AIFF and AIFC files<a class="headerlink" href="#module-aifc" title="Permalink to this headline">¶</a></h1>
<p id="index-0"><strong>Source code:</strong> <a class="reference external" href="http://hg.python.org/cpython/file/3.2/Lib/aifc.py">Lib/aifc.py</a></p>
<hr class="docutils" />
<p>This module provides support for reading and writing AIFF and AIFF-C files.
AIFF is Audio Interchange File Format, a format for storing digital audio
samples in a file. AIFF-C is a newer version of the format that includes the
ability to compress the audio data.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Some operations may only work under IRIX; these will raise <a class="reference internal" href="exceptions.html#ImportError" title="ImportError"><tt class="xref py py-exc docutils literal"><span class="pre">ImportError</span></tt></a>
when attempting to import the <tt class="xref py py-mod docutils literal"><span class="pre">cl</span></tt> module, which is only available on
IRIX.</p>
</div>
<p>Audio files have a number of parameters that describe the audio data. The
sampling rate or frame rate is the number of times per second the sound is
sampled. The number of channels indicate if the audio is mono, stereo, or
quadro. Each frame consists of one sample per channel. The sample size is the
size in bytes of each sample. Thus a frame consists of
<em>nchannels</em>**samplesize* bytes, and a second’s worth of audio consists of
<em>nchannels</em>**samplesize***framerate* bytes.</p>
<p>For example, CD quality audio has a sample size of two bytes (16 bits), uses two
channels (stereo) and has a frame rate of 44,100 frames/second. This gives a
frame size of 4 bytes (2*2), and a second’s worth occupies 2*2*44100 bytes
(176,400 bytes).</p>
<p>Module <a class="reference internal" href="#module-aifc" title="aifc: Read and write audio files in AIFF or AIFC format."><tt class="xref py py-mod docutils literal"><span class="pre">aifc</span></tt></a> defines the following function:</p>
<dl class="function">
<dt id="aifc.open">
<tt class="descclassname">aifc.</tt><tt class="descname">open</tt><big>(</big><em>file</em>, <em>mode=None</em><big>)</big><a class="headerlink" href="#aifc.open" title="Permalink to this definition">¶</a></dt>
<dd><p>Open an AIFF or AIFF-C file and return an object instance with methods that are
described below. The argument <em>file</em> is either a string naming a file or a
<a class="reference internal" href="../glossary.html#term-file-object"><em class="xref std std-term">file object</em></a>. <em>mode</em> must be <tt class="docutils literal"><span class="pre">'r'</span></tt> or <tt class="docutils literal"><span class="pre">'rb'</span></tt> when the file must be
opened for reading, or <tt class="docutils literal"><span class="pre">'w'</span></tt> or <tt class="docutils literal"><span class="pre">'wb'</span></tt> when the file must be opened for writing.
If omitted, <tt class="docutils literal"><span class="pre">file.mode</span></tt> is used if it exists, otherwise <tt class="docutils literal"><span class="pre">'rb'</span></tt> is used. When
used for writing, the file object should be seekable, unless you know ahead of
time how many samples you are going to write in total and use
<tt class="xref py py-meth docutils literal"><span class="pre">writeframesraw()</span></tt> and <tt class="xref py py-meth docutils literal"><span class="pre">setnframes()</span></tt>.</p>
</dd></dl>
<p>Objects returned by <a class="reference internal" href="#aifc.open" title="aifc.open"><tt class="xref py py-func docutils literal"><span class="pre">open()</span></tt></a> when a file is opened for reading have the
following methods:</p>
<dl class="method">
<dt id="aifc.aifc.getnchannels">
<tt class="descclassname">aifc.</tt><tt class="descname">getnchannels</tt><big>(</big><big>)</big><a class="headerlink" href="#aifc.aifc.getnchannels" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the number of audio channels (1 for mono, 2 for stereo).</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.getsampwidth">
<tt class="descclassname">aifc.</tt><tt class="descname">getsampwidth</tt><big>(</big><big>)</big><a class="headerlink" href="#aifc.aifc.getsampwidth" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the size in bytes of individual samples.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.getframerate">
<tt class="descclassname">aifc.</tt><tt class="descname">getframerate</tt><big>(</big><big>)</big><a class="headerlink" href="#aifc.aifc.getframerate" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the sampling rate (number of audio frames per second).</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.getnframes">
<tt class="descclassname">aifc.</tt><tt class="descname">getnframes</tt><big>(</big><big>)</big><a class="headerlink" href="#aifc.aifc.getnframes" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the number of audio frames in the file.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.getcomptype">
<tt class="descclassname">aifc.</tt><tt class="descname">getcomptype</tt><big>(</big><big>)</big><a class="headerlink" href="#aifc.aifc.getcomptype" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a bytes array of length 4 describing the type of compression
used in the audio file. For AIFF files, the returned value is
<tt class="docutils literal"><span class="pre">b'NONE'</span></tt>.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.getcompname">
<tt class="descclassname">aifc.</tt><tt class="descname">getcompname</tt><big>(</big><big>)</big><a class="headerlink" href="#aifc.aifc.getcompname" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a bytes array convertible to a human-readable description
of the type of compression used in the audio file. For AIFF files,
the returned value is <tt class="docutils literal"><span class="pre">b'not</span> <span class="pre">compressed'</span></tt>.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.getparams">
<tt class="descclassname">aifc.</tt><tt class="descname">getparams</tt><big>(</big><big>)</big><a class="headerlink" href="#aifc.aifc.getparams" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a tuple consisting of all of the above values in the above order.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.getmarkers">
<tt class="descclassname">aifc.</tt><tt class="descname">getmarkers</tt><big>(</big><big>)</big><a class="headerlink" href="#aifc.aifc.getmarkers" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a list of markers in the audio file. A marker consists of a tuple of
three elements. The first is the mark ID (an integer), the second is the mark
position in frames from the beginning of the data (an integer), the third is the
name of the mark (a string).</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.getmark">
<tt class="descclassname">aifc.</tt><tt class="descname">getmark</tt><big>(</big><em>id</em><big>)</big><a class="headerlink" href="#aifc.aifc.getmark" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the tuple as described in <a class="reference internal" href="#aifc.aifc.getmarkers" title="aifc.aifc.getmarkers"><tt class="xref py py-meth docutils literal"><span class="pre">getmarkers()</span></tt></a> for the mark with the given
<em>id</em>.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.readframes">
<tt class="descclassname">aifc.</tt><tt class="descname">readframes</tt><big>(</big><em>nframes</em><big>)</big><a class="headerlink" href="#aifc.aifc.readframes" title="Permalink to this definition">¶</a></dt>
<dd><p>Read and return the next <em>nframes</em> frames from the audio file. The returned
data is a string containing for each frame the uncompressed samples of all
channels.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.rewind">
<tt class="descclassname">aifc.</tt><tt class="descname">rewind</tt><big>(</big><big>)</big><a class="headerlink" href="#aifc.aifc.rewind" title="Permalink to this definition">¶</a></dt>
<dd><p>Rewind the read pointer. The next <a class="reference internal" href="#aifc.aifc.readframes" title="aifc.aifc.readframes"><tt class="xref py py-meth docutils literal"><span class="pre">readframes()</span></tt></a> will start from the
beginning.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.setpos">
<tt class="descclassname">aifc.</tt><tt class="descname">setpos</tt><big>(</big><em>pos</em><big>)</big><a class="headerlink" href="#aifc.aifc.setpos" title="Permalink to this definition">¶</a></dt>
<dd><p>Seek to the specified frame number.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.tell">
<tt class="descclassname">aifc.</tt><tt class="descname">tell</tt><big>(</big><big>)</big><a class="headerlink" href="#aifc.aifc.tell" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the current frame number.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.close">
<tt class="descclassname">aifc.</tt><tt class="descname">close</tt><big>(</big><big>)</big><a class="headerlink" href="#aifc.aifc.close" title="Permalink to this definition">¶</a></dt>
<dd><p>Close the AIFF file. After calling this method, the object can no longer be
used.</p>
</dd></dl>
<p>Objects returned by <a class="reference internal" href="#aifc.open" title="aifc.open"><tt class="xref py py-func docutils literal"><span class="pre">open()</span></tt></a> when a file is opened for writing have all the
above methods, except for <tt class="xref py py-meth docutils literal"><span class="pre">readframes()</span></tt> and <tt class="xref py py-meth docutils literal"><span class="pre">setpos()</span></tt>. In addition
the following methods exist. The <tt class="xref py py-meth docutils literal"><span class="pre">get*()</span></tt> methods can only be called after
the corresponding <tt class="xref py py-meth docutils literal"><span class="pre">set*()</span></tt> methods have been called. Before the first
<tt class="xref py py-meth docutils literal"><span class="pre">writeframes()</span></tt> or <tt class="xref py py-meth docutils literal"><span class="pre">writeframesraw()</span></tt>, all parameters except for the
number of frames must be filled in.</p>
<dl class="method">
<dt id="aifc.aifc.aiff">
<tt class="descclassname">aifc.</tt><tt class="descname">aiff</tt><big>(</big><big>)</big><a class="headerlink" href="#aifc.aifc.aiff" title="Permalink to this definition">¶</a></dt>
<dd><p>Create an AIFF file. The default is that an AIFF-C file is created, unless the
name of the file ends in <tt class="docutils literal"><span class="pre">'.aiff'</span></tt> in which case the default is an AIFF file.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.aifc">
<tt class="descclassname">aifc.</tt><tt class="descname">aifc</tt><big>(</big><big>)</big><a class="headerlink" href="#aifc.aifc.aifc" title="Permalink to this definition">¶</a></dt>
<dd><p>Create an AIFF-C file. The default is that an AIFF-C file is created, unless
the name of the file ends in <tt class="docutils literal"><span class="pre">'.aiff'</span></tt> in which case the default is an AIFF
file.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.setnchannels">
<tt class="descclassname">aifc.</tt><tt class="descname">setnchannels</tt><big>(</big><em>nchannels</em><big>)</big><a class="headerlink" href="#aifc.aifc.setnchannels" title="Permalink to this definition">¶</a></dt>
<dd><p>Specify the number of channels in the audio file.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.setsampwidth">
<tt class="descclassname">aifc.</tt><tt class="descname">setsampwidth</tt><big>(</big><em>width</em><big>)</big><a class="headerlink" href="#aifc.aifc.setsampwidth" title="Permalink to this definition">¶</a></dt>
<dd><p>Specify the size in bytes of audio samples.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.setframerate">
<tt class="descclassname">aifc.</tt><tt class="descname">setframerate</tt><big>(</big><em>rate</em><big>)</big><a class="headerlink" href="#aifc.aifc.setframerate" title="Permalink to this definition">¶</a></dt>
<dd><p>Specify the sampling frequency in frames per second.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.setnframes">
<tt class="descclassname">aifc.</tt><tt class="descname">setnframes</tt><big>(</big><em>nframes</em><big>)</big><a class="headerlink" href="#aifc.aifc.setnframes" title="Permalink to this definition">¶</a></dt>
<dd><p>Specify the number of frames that are to be written to the audio file. If this
parameter is not set, or not set correctly, the file needs to support seeking.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.setcomptype">
<tt class="descclassname">aifc.</tt><tt class="descname">setcomptype</tt><big>(</big><em>type</em>, <em>name</em><big>)</big><a class="headerlink" href="#aifc.aifc.setcomptype" title="Permalink to this definition">¶</a></dt>
<dd><p id="index-1">Specify the compression type. If not specified, the audio data will
not be compressed. In AIFF files, compression is not possible.
The name parameter should be a human-readable description of the
compression type as a bytes array, the type parameter should be a
bytes array of length 4. Currently the following compression types
are supported: <tt class="docutils literal"><span class="pre">b'NONE'</span></tt>, <tt class="docutils literal"><span class="pre">b'ULAW'</span></tt>, <tt class="docutils literal"><span class="pre">b'ALAW'</span></tt>, <tt class="docutils literal"><span class="pre">b'G722'</span></tt>.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.setparams">
<tt class="descclassname">aifc.</tt><tt class="descname">setparams</tt><big>(</big><em>nchannels</em>, <em>sampwidth</em>, <em>framerate</em>, <em>comptype</em>, <em>compname</em><big>)</big><a class="headerlink" href="#aifc.aifc.setparams" title="Permalink to this definition">¶</a></dt>
<dd><p>Set all the above parameters at once. The argument is a tuple consisting of the
various parameters. This means that it is possible to use the result of a
<a class="reference internal" href="#aifc.aifc.getparams" title="aifc.aifc.getparams"><tt class="xref py py-meth docutils literal"><span class="pre">getparams()</span></tt></a> call as argument to <a class="reference internal" href="#aifc.aifc.setparams" title="aifc.aifc.setparams"><tt class="xref py py-meth docutils literal"><span class="pre">setparams()</span></tt></a>.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.setmark">
<tt class="descclassname">aifc.</tt><tt class="descname">setmark</tt><big>(</big><em>id</em>, <em>pos</em>, <em>name</em><big>)</big><a class="headerlink" href="#aifc.aifc.setmark" title="Permalink to this definition">¶</a></dt>
<dd><p>Add a mark with the given id (larger than 0), and the given name at the given
position. This method can be called at any time before <a class="reference internal" href="#aifc.aifc.close" title="aifc.aifc.close"><tt class="xref py py-meth docutils literal"><span class="pre">close()</span></tt></a>.</p>
</dd></dl>
<dl class="method">
<dt>
<tt class="descclassname">aifc.</tt><tt class="descname">tell</tt><big>(</big><big>)</big></dt>
<dd><p>Return the current write position in the output file. Useful in combination
with <a class="reference internal" href="#aifc.aifc.setmark" title="aifc.aifc.setmark"><tt class="xref py py-meth docutils literal"><span class="pre">setmark()</span></tt></a>.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.writeframes">
<tt class="descclassname">aifc.</tt><tt class="descname">writeframes</tt><big>(</big><em>data</em><big>)</big><a class="headerlink" href="#aifc.aifc.writeframes" title="Permalink to this definition">¶</a></dt>
<dd><p>Write data to the output file. This method can only be called after the audio
file parameters have been set.</p>
</dd></dl>
<dl class="method">
<dt id="aifc.aifc.writeframesraw">
<tt class="descclassname">aifc.</tt><tt class="descname">writeframesraw</tt><big>(</big><em>data</em><big>)</big><a class="headerlink" href="#aifc.aifc.writeframesraw" title="Permalink to this definition">¶</a></dt>
<dd><p>Like <a class="reference internal" href="#aifc.aifc.writeframes" title="aifc.aifc.writeframes"><tt class="xref py py-meth docutils literal"><span class="pre">writeframes()</span></tt></a>, except that the header of the audio file is not
updated.</p>
</dd></dl>
<dl class="method">
<dt>
<tt class="descclassname">aifc.</tt><tt class="descname">close</tt><big>(</big><big>)</big></dt>
<dd><p>Close the AIFF file. The header of the file is updated to reflect the actual
size of the audio data. After calling this method, the object can no longer be
used.</p>
</dd></dl>
</div>
</div>
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distrib
>
Mandriva
>
2010.1
>
x86_64
>
media
>
contrib-backports
>
by-pkgid
>
3ba3bd1608c672ba2129b098a48e9e4d
>
files
>
609
