See bug 13884

The configuration of various ALSA PCM parameters in the audio stacks on Baby & Fab4 is very sensitive to the specific details and will fail if other combinations of values are used that should, on the face of it, be acceptable.

Currently we set sample-rate(x), channels(2), periods(2), buffer-time(20ms) and this works across all standard sample rates from 8000-96000. Changing the buffer time to 40ms, for example, or setting period-time instead of buffer-time will cause configuration to fail for one or more sample-rates:

(1) decode_alsa_backend() should be made robust against failues of _pcmopen(), at least for anything other than 44100 samples/s and should return an error -> STMn in such cases;

(2) we need to get to the bottom of why configuration fails in these cases.