[alsa-devel] Still have choppy audio using 1.0.17

Gustavo da Silva Serra gustavo.serra at tet.com.br
Wed Jun 18 20:24:05 CEST 2008

I am tracing aloop execution and the choppy audio happens when an 
application (capture or playback) opens the device while another one is 
capturing or playing. It seems to me, I may be completely wrong, that 
the problem could be a synchronization issue (a critical region with no 
mutexes, for instance). I analysed the sound wave with Audacity while in 
choppy audio condition and I realized that there are silent gaps, 
miliseconds with no sound at all (as if some buffer pointer was lost, 
for example).

I haven't received any answer from you =(
What do you think that is happening?

Thanks in advance.

Gustavo da Silva Serra escreveu:
> I have been trying for many weeks to solve this problem, but with no 
> success. After updating to Alsa 1.0.17, which include changes to aloop, 
> I still have choppy audio. I will try to summarize what happens:
> - I need to use aloop, if I change to a sound card all the problems are 
> gone;
> - After some time of continuous play, applications start to reproduce 
> choppy audio. Choppy audio doesn't happens all the time;
> - If I repeatedly start and stop my sound capture application choppy 
> audio occur sooner;
> - Start/stop my application restores the sound quality (after some tryies);
> - This happens with ALSA applications (xine, vlc) and OSS emulated;
> - I have tryied many period_size and buffer_size in asound.conf, now I 
> am using 960 for period and 3840 for buffer. As I decrease period size, 
> the audio quality improves, but choppy audio still happens;
> - I test for overrun but no errors occur.
> - I am using block mode, interleaved, 44100, 16 bit, 2 channels
> - I am using dmix, dsnoop, removing them does not correct the audio
> These are some of the information I have, I don't know if is is enough. 
> If necessary I can provide any other information.
> What do you suggest that I do? Are there any known issues or 
> configuration requirements?
> Thanks in advance.
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Gustavo da Silva Serra        gustavo.serra at tet.com.br
Tools & Technologies - T&T Engenheiros Associados Ltda.
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http://www.tet.com.br/                                             tet at tet.com.br

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