Step 2 – At this point you should already see three new PCM devices. Run:
and you should see something similar to the following:
Discard all samples (playback) or generate zero samples (capture)
PulseAudio Sound Server
Default Audio Device
Direct sample mixing device
Direct sample snooping device
Direct hardware device without any conversions
Hardware device with all software conversions
we have added a swap device which invert the channels so that left goes to right and right to left.
Section 2 – Test the configuration
To test the configuration we can use either aplay or omxplayer. Run the following command for aplay and remember that it will only be able to play WAV files.
aplay -D mono_left <filename.wav>
This should play through the left speaker.
Similarly for omxplayer run:
omxplayer -o alsa:mono_left <filename.wav>
Appendix – Tips and gotchas.
If you want the configuration to apply system wide you will need to create a file under /etc instead of the .asoundrc mentioned above. As the folder is not writable by the user Pi you will need to run the command as root.