[alsa-devel] Still have choppy audio using 1.0.17

stan ghjeold_i_mwee at cox.net
Tue Jul 15 02:50:26 CEST 2008

Gustavo da Silva Serra wrote:
> I have discovered something else. Choppy audio occurs when 
> snd_pcm_playback_silence, in pcm_lib.c, will silence the same period 
> than the capture pointer is pointing at. I am printing this variables 
> "ofs" in snd_pcm_playback_silence and what is returned from 
> snd_card_loopback_pointer when the substream is capture.
> How snd_pcm_playback_silence is supposed to work? Must it silence the 
> next period from the playback pointer? How is ensured that this 
> situation (ofs == capture pointer) does not happen with sound cards?
> Thanks ANY help... any...
The way the API docs describe it the silence function 
fills the play buffer with a set amount of silence when 
the buffer has fewer than threshold frames to play. 
So, if your playback is running close to that 
threshold, it will be continuously injecting chunks of 
silence into the stream.  That would certainly sound 
choppy.  From the docs it sounds like the silence is 
always injected into the existing stream at the current 

Note:  this is just from reading the docs.  I haven't 
actually used this.

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