forked from auracaster/pyalsaaudio
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217 lines
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<title>Introduction — alsaaudio documentation 0.9.2 documentation</title>
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<link rel="next" title="PCM Terminology and Concepts" href="terminology.html" />
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<section id="introduction">
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<h1>Introduction<a class="headerlink" href="#introduction" title="Permalink to this headline">¶</a></h1>
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<dl class="field-list simple">
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<dt class="field-odd">Author</dt>
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<dd class="field-odd"><p>Casper Wilstrup <<a class="reference external" href="mailto:cwi%40aves.dk">cwi<span>@</span>aves<span>.</span>dk</a>></p>
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</dd>
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<dt class="field-even">Author</dt>
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<dd class="field-even"><p>Lars Immisch <<a class="reference external" href="mailto:lars%40ibp.de">lars<span>@</span>ibp<span>.</span>de</a>></p>
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</dd>
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</dl>
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<p id="front">This software is licensed under the PSF license - the same one used by the
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majority of the python distribution. Basically you can use it for anything you
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wish (even commercial purposes). There is no warranty whatsoever.</p>
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<div class="topic">
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<p class="topic-title">Abstract</p>
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<p>This package contains wrappers for accessing the ALSA API from Python. It is
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currently fairly complete for PCM devices and Mixer access. MIDI sequencer
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support is low on our priority list, but volunteers are welcome.</p>
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<p>If you find bugs in the wrappers please use thegithub issue tracker.
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Please don’t send bug reports regarding ALSA specifically. There are several
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bugs in this API, and those should be reported to the ALSA team - not me.</p>
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</div>
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</section>
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<section id="what-is-alsa">
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<h1>What is ALSA<a class="headerlink" href="#what-is-alsa" title="Permalink to this headline">¶</a></h1>
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<p>The Advanced Linux Sound Architecture (ALSA) provides audio and MIDI
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functionality to the Linux operating system.</p>
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<p>Logically ALSA consists of these components:</p>
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<ul class="simple">
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<li><p>A set of kernel drivers. — These drivers are responsible for handling the
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physical sound hardware from within the Linux kernel, and have been the
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standard sound implementation in Linux since kernel version 2.5</p></li>
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<li><p>A kernel level API for manipulating the ALSA devices.</p></li>
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<li><p>A user-space C library for simplified access to the sound hardware from
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userspace applications. This library is called <em>libasound</em> and is required by
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all ALSA capable applications.</p></li>
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</ul>
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<p>More information about ALSA may be found on the project homepage
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<a class="reference external" href="http://www.alsa-project.org">http://www.alsa-project.org</a></p>
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<section id="alsa-and-python">
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<h2>ALSA and Python<a class="headerlink" href="#alsa-and-python" title="Permalink to this headline">¶</a></h2>
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<p>The older Linux sound API (OSS) which is now deprecated is well supported from
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the standard Python library, through the ossaudiodev module. No native ALSA
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support exists in the standard library.</p>
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<p>There are a few other “ALSA for Python” projects available, including at least
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two different projects called pyAlsa. Neither of these seem to be under active
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development at the time - and neither are very feature complete.</p>
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<p>I wrote PyAlsaAudio to fill this gap. My long term goal is to have the module
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included in the standard Python library, but that looks currently unlikely.</p>
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<p>PyAlsaAudio has full support for sound capture, playback of sound, as well as
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the ALSA Mixer API.</p>
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<p>MIDI support is not available, and since I don’t own any MIDI hardware, it’s
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difficult for me to implement it. Volunteers to work on this would be greatly
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appreciated.</p>
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</section>
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</section>
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<section id="installation">
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<h1>Installation<a class="headerlink" href="#installation" title="Permalink to this headline">¶</a></h1>
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<p>Note: the wrappers link with the alsasound library (from the alsa-lib package)
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and need the ALSA headers for compilation. Verify that you have
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/usr/lib/libasound.so and /usr/include/alsa (or similar paths) before building.</p>
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<p><em>On Debian (and probably Ubuntu), install libasound2-dev.</em></p>
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<p>Naturally you also need to use a kernel with proper ALSA support. This is the
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default in Linux kernel 2.6 and later. If you are using kernel version 2.4 you
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may need to install the ALSA patches yourself - although most distributions
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ship with ALSA kernels.</p>
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<p>To install, execute the following: —</p>
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<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>$ python setup.py build
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</pre></div>
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</div>
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<p>And then as root: —</p>
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<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="c1"># python setup.py install</span>
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</pre></div>
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</div>
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</section>
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<section id="testing">
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<h1>Testing<a class="headerlink" href="#testing" title="Permalink to this headline">¶</a></h1>
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<p>Make sure that <code class="code docutils literal notranslate"><span class="pre">aplay</span></code> plays a file through the soundcard you want, then
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try:</p>
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<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>$ python playwav.py <filename.wav>
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</pre></div>
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</div>
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<p>If <code class="code docutils literal notranslate"><span class="pre">aplay</span></code> needs a device argument, like
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<code class="code docutils literal notranslate"><span class="pre">aplay</span> <span class="pre">-D</span> <span class="pre">hw:CARD=sndrpihifiberry,DEV=0</span></code>, use:</p>
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<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>$ python playwav.py -d hw:CARD=sndrpihifiberry,DEV=0 <filename.wav>
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</pre></div>
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</div>
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<p>To test PCM recordings (on your default soundcard), verify your
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microphone works, then do:</p>
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<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>$ python recordtest.py -d <device> <filename>
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</pre></div>
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</div>
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<p>Speak into the microphone, and interrupt the recording at any time
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with <code class="docutils literal notranslate"><span class="pre">Ctl-C</span></code>.</p>
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<p>Play back the recording with:</p>
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<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>$ python playbacktest.py-d <device> <filename>
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</pre></div>
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</div>
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<p>There is a minimal test suite in <code class="code docutils literal notranslate"><span class="pre">test.py</span></code>, but it is
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a bit dependent on the ALSA configuration and may fail without indicating
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a real problem.</p>
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<p>If you find bugs/problems, please file a <a class="reference external" href="https://github.com/larsimmisch/pyalsaaudio/issues">bug report</a>.</p>
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</section>
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<h1 class="logo"><a href="index.html">alsaaudio documentation</a></h1>
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<h3>Navigation</h3>
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<p class="caption" role="heading"><span class="caption-text">Contents:</span></p>
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<ul class="current">
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<li class="toctree-l1 current"><a class="current reference internal" href="#">Introduction</a></li>
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<li class="toctree-l1"><a class="reference internal" href="#what-is-alsa">What is ALSA</a><ul>
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<li class="toctree-l2"><a class="reference internal" href="#alsa-and-python">ALSA and Python</a></li>
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</ul>
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</li>
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<li class="toctree-l1"><a class="reference internal" href="#installation">Installation</a></li>
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<li class="toctree-l1"><a class="reference internal" href="#testing">Testing</a></li>
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<li class="toctree-l1"><a class="reference internal" href="terminology.html">PCM Terminology and Concepts</a></li>
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<li class="toctree-l1"><a class="reference internal" href="libalsaaudio.html"><code class="xref py py-mod docutils literal notranslate"><span class="pre">alsaaudio</span></code></a></li>
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</ul>
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<div class="relations">
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<h3>Related Topics</h3>
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<ul>
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<li><a href="index.html">Documentation overview</a><ul>
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<li>Previous: <a href="index.html" title="previous chapter">alsaaudio documentation</a></li>
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<li>Next: <a href="terminology.html" title="next chapter">PCM Terminology and Concepts</a></li>
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</ul></li>
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©2017, Lars Immisch & Casper Wilstrup.
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