I'm trying to understand snd-aloop and whether my experiences are of buggy 
software or I'm doing something wrong.

  # modprobe snd-aloop
  # echo "Layla3G,0,0" > /proc/asound/Loopback/timer_source

For example; if I try the simplest action of playing some audio and 
recording it:

  $ aplay -D hw:Loopback,0,0 music-48k.wav
  $ arecord -D hw:Loopback,1,0 -f dat recorded.wav

I get a 44 byte WAV header and a hang, until the processes exit after a 
few seconds with:

  aplay: pcm_write:2061: write error: Input/output error
  arecord: pcm_read:2153: read error: Input/output error

Thinking that maybe the device 'timer source' needs to be rolling, I try 
"aplay" to hw:Layla3G,0,0 but this has no effect.

Information in /proc "cable#0" shows things open but no buffer movement 
(btw. I deduce that the "size" here is bytes, not frames)

Kernel is v5.6.6.

There seems to be zero docs on Loopback in general, alsaloop and snd-aloop 
(am I correct?) so I can't be sure what the "expected" behaviour is.

I do intend to use with alsaloop & dmix, but both of these seem to be 
introducing idiosynracies of their own making it hard to pin down where 
the problems are, so I started with this one.

Should I expect the commands above to work? If not... why not?


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