[alsa-devel] Use of default device with snd_pcm_link()
I am working on some code which captures from one PCM device and plays to another, based off of the latency.c found in alsa-lib. I noticed something strange:
The code works if I set the capture device to hw:1,0 and playback device to hw:0,0. However, if I change the playback device to "default:0", the snd_pcm_link() call fails with -ENOSYS (error 38).
If I dump out the properties, I can see that the the default device *is* mapped to device 0,0, so it's not clear why the behaviour would differ.
My goal was just to playback to whatever the default device is, and I was under the impression that default:0 should be equivalent to "hw:0,0". Can anyone offer any brief explanation as to why the snd_pcm_link() call would fail?
Thanks in advance,
Devin
O Sun, 27 Dec 2009, Devin Heitmueller wrote:
I am working on some code which captures from one PCM device and plays to another, based off of the latency.c found in alsa-lib. I noticed something strange:
The code works if I set the capture device to hw:1,0 and playback device to hw:0,0. However, if I change the playback device to "default:0", the snd_pcm_link() call fails with -ENOSYS (error 38).
If I dump out the properties, I can see that the the default device *is* mapped to device 0,0, so it's not clear why the behaviour would differ.
My goal was just to playback to whatever the default device is, and I was under the impression that default:0 should be equivalent to "hw:0,0". Can anyone offer any brief explanation as to why the snd_pcm_link() call would fail?
Some alsa-lib plugins do not have the link feature implemented. If you use snd_pcm_dump(), you may list all plugins in chain. I think that dmix is in path. And no, "default:0" is NOT equivalent to "hw:0,0".
Jaroslav
----- Jaroslav Kysela perex@perex.cz Linux Kernel Sound Maintainer ALSA Project, Red Hat, Inc.
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Devin Heitmueller -
Jaroslav Kysela