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Julian Porter
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py/doc/pyalsaaudio.rst
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py/doc/pyalsaaudio.rst
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************
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Introduction
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************
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:Author: Casper Wilstrup <cwi@aves.dk>
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:Author: Lars Immisch <lars@ibp.de>
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.. |release| replace:: version
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.. % At minimum, give your name and an email address. You can include a
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.. % snail-mail address if you like.
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.. % This makes the Abstract go on a separate page in the HTML version;
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.. % if a copyright notice is used, it should go immediately after this.
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.. %
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.. _front:
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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.
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.. % Copyright statement should go here, if needed.
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.. % The abstract should be a paragraph or two long, and describe the
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.. % scope of the document.
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.. topic:: Abstract
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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.
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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.
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************
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What is ALSA
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************
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The Advanced Linux Sound Architecture (ALSA) provides audio and MIDI
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functionality to the Linux operating system.
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Logically ALSA consists of these components:
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* 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
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* A kernel level API for manipulating the ALSA devices.
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* A user-space C library for simplified access to the sound hardware from
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userspace applications. This library is called *libasound* and is required by
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all ALSA capable applications.
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More information about ALSA may be found on the project homepage
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`<http://www.alsa-project.org>`_
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ALSA and Python
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===============
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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.
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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.
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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.
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PyAlsaAudio has full support for sound capture, playback of sound, as well as
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the ALSA Mixer API.
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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.
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************
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Installation
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************
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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.
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*On Debian (and probably Ubuntu), install libasound2-dev.*
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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.
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To install, execute the following: --- ::
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$ python setup.py build
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And then as root: --- ::
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# python setup.py install
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*******
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Testing
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*******
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Make sure that :code:`aplay` plays a file through the soundcard you want, then
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try::
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$ python playwav.py <filename.wav>
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If :code:`aplay` needs a device argument, like
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:code:`aplay -D hw:CARD=sndrpihifiberry,DEV=0`, use::
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$ python playwav.py -d hw:CARD=sndrpihifiberry,DEV=0 <filename.wav>
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To test PCM recordings (on your default soundcard), verify your
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microphone works, then do::
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$ python recordtest.py -d <device> <filename>
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Speak into the microphone, and interrupt the recording at any time
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with ``Ctl-C``.
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Play back the recording with::
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$ python playbacktest.py-d <device> <filename>
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There is a minimal test suite in :code:`test.py`, 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.
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If you find bugs/problems, please file a `bug report
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<https://github.com/larsimmisch/pyalsaaudio/issues>`_.
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