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I'm successfully rendering audio with alsa, however I'm completely incapable of determining the channel mapping. As various sources have stated, I'm calling snd_pcm_get_chmap after the hw & sw params are set and the device is prepared.

snd_config_get_string returns 'pulse' for this device which I'm presuming means it's an alsa/pulseaudio bridge for want of a better term.

Calling snd_strerror(errno) after snd_pcm_get_chmap fails is returning 'Socket operation on non-socket'. I should probably add that I'm debugging remotely from Visual Studio 2017 as that may be related.

I'd really like to be able to get the channel mapping. Any suggestions appreciated.

user1424890
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Pulse audio's list of ALSA issues states that it isn't currently possible to obtain the channel map. https://www.freedesktop.org/wiki/Software/PulseAudio/Backends/ALSA/Issues/

There's no way to query the active channel map for a device

user1424890
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  • Consolidating comments I made here: 1. Coming late to this question but I wonder if the pulse audio guys have seen this: https://docs.kernel.org/sound/designs/channel-mapping-api.html -- seems this documentation was introduced to the Linux kernel tree in 2012. 2. Following up, I did find some alsa lib code that seems to retrieve the map from the ctl interface. Maybe actual implementation differs by kernel driver. https://github.com/alsa-project/alsa-lib/blob/7f2d6c3aac3505ceee4b0d3e8b3ca423ce29b070/src/pcm/pcm_hw.c#L1320 3. I was indeed able to query the channel map on my own machine. – asveikau Nov 14 '22 at 20:48