Hi,
I need to create separate virtual ALSA devices for the left and right channel of a USB sound card. I do that with the following config:
pcm_slave.xxx_slave {
pcm "hw:CARD=xxx,DEV=0"
channels 2
rate 8000
buffer_size 2048
period_size 40
}
pcm.xxx_l {
type dshare
ipc_key 12345
slave xxx_slave
bindings.0 0
hint.description "left channel"
}
pcm.xxx_r {
type dshare
ipc_key 12345
slave xxx_slave
bindings.0 1
hint.description "right channel"
}
(For completeness I should note that via some udev configuration I make sure that no matter which audio device is plugged on the USB port, it will always be named "xxx"). This works fine with most USB audio devices. And if no USB audio device is plugged, I get an error from snd_pcm_open(), which is great too.
However, now I have a USB audio device, which only supports a single audio channel (mono). When I open the left channel virtual device (e.g. with the command: aplay -D xxx_l foo.wav), this also works fine. But when I do the same command with the right channel, I get a segmentation fault. After some investigation it seems that the snd_pcm_open() function does not return an error in this case, as I would expect. The segmentation fault happens later, when the (obviously invalid) PCM is being used.
This is a huge problem for me. I need to find out why snd_pcm_open() doesn't return an error, if I try to open it on a non-existing channel. Right now I'm trying to understand snd_pcm_dshare_open(). Maybe somebody has an idea what exactly to look for and can point me in the right direction? Any hint would be highly appreciated!
BR, Georg
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