Change number of channels

[RuABraun]

I'm trying to use soundcard on raspberry pi. I can play a stereo wavfile using aplay and hear that it's really using stereo. But when I want to use soundcard the channels of the speaker is set to 1 and I can't change that, and I guess that is also why when I play the corresponding numpy array it mixes the two channels together and I can hear output in both of my earphones (even though I've set one channel to 0.).

Is there something I can do to get around this constraint?

[bastibe]

SoundCard Speakers report the number of channels configured in pulseaudio. This can't be changed. You can change the number of channels you want to use in play or player, but only up to the number of channels reported by the Speaker.

But SoundCard is really only a thin wrapper around pulseaudio. Most likely, your pulseaudio is configured wrongly or you are using the wrong soundcard.

[RuABraun]

Thank you for the response!

I know this is out of scope... but I'd really appreciate if you could give me a hint: Based on this I changed /etc/pulse/default.pa by commenting

if foo
load-module module-udev-detect
else
load-module module-detect
endif

And added a line

load-module module-alsa-sink device=default:CARD=Headphones channels=2 rate=44100 channel_map=left,right

Based on the output of aplay -L

But this results in an error

...pulseaudio.py" line 72
assert self._pa_context_get_state(self.context) == _pa.PA_CONTEXT_READY

Any idea?

edit: Not getting the error anymore, no sound playing. Guess I need to figure out how write the load-module line correctly.

edit2: Got it to work!! had to use the hw syntax and no default:

[bastibe]

I'm glad you were able to figure out a solution. Could you post the solution here, so as to help me and other people who might experience a similar issue in the future?

[RuABraun]

I already mentioned the important details. To be more explicit, what worked was

load-module module-alsa-sink device=hw:1,0 channels=2 rate=44100 channel_map=left,right

restart pulse audio with pulseaudio --kill and pulseaudio --start. One should already be able to see if things are working correctly by calling pacmd list-sinks (if it's not there'll be a "dummy" sink instead of the correct one, for me headphones).

[RuABraun]

Let me also use the opportunity to say I love this library! :)

[bastibe]

Thank you very much for your kind words, and for documenting this solution.