[Gta04-owner] Sound playback

[Neil Jerram]

In my continuing mission to re-understand things that everyone else
probably understood ages ago... :-)

I've noticed on my GTA04, with a plain ALSA setup, that sound playback
sometimes works and sometimes doesn't.  For example, if I do:

root at neo:~# for n in `seq 1 5`; do aplay -D hw:0 -f S16_LE -c 1 
test.wav; done

the stdout looks good:

Playing WAVE 'test.wav' : Signed 16 bit Little Endian, Rate 8000 Hz, 
Stereo
Playing WAVE 'test.wav' : Signed 16 bit Little Endian, Rate 8000 Hz, 
Stereo
Playing WAVE 'test.wav' : Signed 16 bit Little Endian, Rate 8000 Hz, 
Stereo
Playing WAVE 'test.wav' : Signed 16 bit Little Endian, Rate 8000 Hz, 
Stereo
Playing WAVE 'test.wav' : Signed 16 bit Little Endian, Rate 8000 Hz, 
Stereo

but I only hear the content of 'test.wav' 2 or 3 times out of 5.

If I do the same test again, still only 2 or 3 times out of 5, but in a
different pattern.  (E.g. just now: #1 ok, #2 silence, #3 ok, #4
silence, #5 ok.)

If I set the ALSA controls for playback through the earpiece, and listen
very closely to individual playback attempts, some more observations:

1. I can clearly hear two levels of 'silence' after the end of a
successful playback.  There's a slight click that I assume marks the end
of the .wav file, then around 5 seconds of low volume white noise, then
a sudden drop to much better silence.

2. During an unsuccessful playback I can hear some very faint noises,
with a relative volume pattern roughly like the message that I should be
hearing properly.

3. It doesn't seem to make any difference, to whether the next playback
will be successful or not, if I wait longer before starting it.

Does anyone have any ideas about:

- how I can understand what is happening here?

- if there is any practical thing / workaround I can do to guarantee
   that the following playback attempt will be successful?

Many thanks,

      Neil