====== Alsa ======
Official Alsa pages:
  * [[http://www.alsa-project.org/main/index.php/Asoundrc|Asoundrc]]
  * [[http://alsa.opensrc.org/Asoundrc]]
  * [[http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html|Alsa PCM plugins]]

Very precious notes from users:
  * [[http://www.volkerschatz.com/noise/alsa.html]]
  * [[http://www.sabi.co.uk/Notes/linuxSoundALSA.html|Linux ALSA sound notes]]

===== asoundrc / asound.conf =====

By default sound is processed through dmix plugin which handles rate and channels conversion.



==== Plugin: hw ====
This plugin communicates directly with the ALSA kernel driver. It is a raw communication without any conversions.

To override "default" pcm device and route outputdirectly into hardware:
<code>
pcm.!default {
    type hw
    card 0
    format S16_LE
}
</code>
With settings above, there is no possiblity to play mono sound (channel=1), when there is stereo audio device.

Change default card:
<code>
pcm.!default {
  type hw
  card 1
  device 3
}

ctl.!default {
  type hw
  card 1
  device 3
}
</code>

==== Plguin: plug ====
Is a plugin responsible for rate and format conversion.
<code>
pcm.!default {
    type plug
    slave {
        pcm "hw:0,0"
        format S16_LE
    }

}
</code>
There might be problems with some programs though. Some applications always try to open a control device with the same name as the pcm device they are given, so you may also need to create a dummy control device with the same name:
<code>
ctl.!default {
    type hw
    card 0
}
</code>

==== Plugin: asym ====
asym is an ALSA PCM plugin that combines half-duplex PCM plugins like dsnoop and dmix into one full-duplex device.
[[http://alsa.opensrc.org/Asym]]

==== Plugin: dmix ====
PCM plugins extend the functionality of PCM devices allowing low-level sample conversions and copying between channels, files and soundcard devices. The dmix plugin provides for direct mixing of multiple streams.
[[http://alsa.opensrc.org/Dmix]]