Record (HDMI Rx) : Records the audio data into a file.
arecord -Dhw:0,1 -fS24_LE -r 48000 -c 2 -d 30 -t raw <output filename.raw>
Playback (HDMI Tx): Playing the recorded file from above step
aplay -D hw:0,0 -fS24_LE -r 48000 -c 2 -t raw <output filename.raw>
Device enumeration :
For record device:
arecord --device="hw:0,1" --dump-hw-params
For playback device:
aplay --device="hw:0,0" --dump-hw-params