====== Audio ======

=== Issues ===

  * Play mp3 in command line
    * Packages - alsa alsa-lib
    * Only root can read the audio device - Add regular user to "audio" group
    * Volume control - "alsamixer", left/right, up/down to adjust the volume
    * Play mp3 in command line - ffplay from ffmpeg, play from sox with libsox-fmt-mp3<code>
$ ffplay file.mp3
$ play file.mp3
</code>

  * Play sound through digital output - SPDIF
    * List playback devices<code>
$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: ALC892 Analog [ALC892 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 1: ALC892 Digital [ALC892 Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 7: HDMI 1 [HDMI 1]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

$ cat /proc/asound/devices
  1:        : sequencer
  2: [ 0- 7]: digital audio playback
  3: [ 0- 3]: digital audio playback
  4: [ 0- 2]: digital audio capture
  5: [ 0- 1]: digital audio playback
  6: [ 0- 0]: digital audio playback
  7: [ 0- 0]: digital audio capture
  8: [ 0- 3]: hardware dependent
  9: [ 0- 2]: hardware dependent
 10: [ 0]   : control
 33:        : timer

//device 0,1 is the digital output.
</code>
    * Unmute the S/PDIF, run "alsamixer", switch to "S/PDIF", press "m".
    * "play" "ffplay" mp3 should work.
    * Play raw sound specifying the device.<code>
$ aplay -D plughw:0,1 ./woman.wav
</code>


=== Reference ===
 * http://alsa.opensrc.org/DigitalOut