[alsa-devel] snd_pcm_writei() -last value sustained
gineera at aspect135.co.uk
Fri Jul 4 10:38:53 CEST 2008
Working on an app I am seeing several strange effects, and this is one of
It can be demonstrated with the pcm.c example program, and I have attempted to
attach a small shot of Audacity capturing the effect.
After writing to the pcm with snd_pcm_writei() a certain amount of data (I
have pcm.c doing 2 periods) the value captured from the soundcard remains at
the last value thereafter; clearly this card doesn't have DC elimination or
this would not be seen.
The sound card is ice1712 (DMX6fire); I had always noticed the PCM meters in
envy24control often stayed high if something like XMMS was stopped or paused
during play, but thought it a metering fault. Now it appears to be actual
pcm value that 'gets stuck'.
Close examination with Audacity shows it is in fact the last-but-one value
that is sustained.
Is this expected behaviour, configuration fault, driver bug or other problem?
I had expected that after the block of data had been written out as audio the
signal would return to zero straightaway. Can anyone give me any clues?
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