[alsa-devel] device naming
Andrew Kohlsmith (Mailing List Account)
aklists at mixdown.ca
Wed Jan 20 17:35:11 CET 2010
Is there a definitive guide to device naming with ALSA? I'm trying to use a
single device for simultaneous capture and playback but opening different
device names gives different results and I'm trying to determine which is the
best to use.
aplay -L output gives front, surround40, surround41, surround50, surround51,
null and pulse.
Trying to register a playback callback using "pulse" gives a "function not
implemented" error, although I can open and set all the parameters I need
(8kHz, 2 channels, 20ms buffers).
I get the same result with "default". If I use "plughw:0,0" I can capture and
play audio, but the driver (intel HDA) seems to be very prone to either not
calling either the playback or capture callback, or throwing an xrun and not
being able to recover. This is an otherwise idle core2 machine running Ubuntu
9.10. Playing with nice or ionice does not seem to affect this "brittleness."
I do not have an ~/.asoundrc, nor do I have anything related to asound in
/etc. Moving pulseaudio out of the way doesn't seem to do anything either.
Is there a definitive list of devices and their device filenames so I can stop
guessing? /proc/asound/cards just shows card 0 as an Intel HDA, and
/proc/asound/devices shows the following:
$ cat /proc/asound/devices
2: : timer
3: : sequencer
4: [ 0- 2]: digital audio capture
5: [ 0- 0]: digital audio playback
6: [ 0- 0]: digital audio capture
7: [ 0- 1]: hardware dependent
8: [ 0- 0]: hardware dependent
9: [ 0] : control
(0-0 is the only device showing both playback and capture, which is why I'm
using it, but how do I know that plughw is the correct device filename? I just
guessed at it due to previous experience trying to get bt audio working with
I'm sure I'm doing something incredibly stupid, but I can't seem to find out
what it is.
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