[alsa-devel] noise and consume pcm faster

Nie Jun niej0001 at gmail.com
Tue Sep 2 11:40:01 CEST 2008

In addition, OSS API emulated by ALSA has not this issue.

2008/9/2 Nie Jun <niej0001 at gmail.com>:
> Hi,
>    I found a strange issue that ALSA consume pcm data faster than
> normal. Does any one had come across it?
>    When I sychronize video frame against audio, the video thread will
> check how much pcm data has been written to ALSA API but has not been
> fetched by DMA. This query causes ALSA consume pcm data faster than
> normal, noise appears too. A stream that is 131 seconds will playback
> just 112 seconds. It only appears when audio is stereo and sampling
> rate is directly supported by hardware.
> This bug can be reproduced with aplay. To reproduce it with aplay, you
> just need to add a thread and query the ALSA latency 20~30times every
> second.
> My system: XSCALE PXA300/zylonite, Linux2.6.25, alsa-lib-1.0.13(I
> tried alsa-lib-1.0.17, bugs too), codec: wm9713. Linux2.6.14 has this
> issue too, but I did not find it in 2.6.21 and 2.6.24.
> Does anyone has idea about it? Thanks!
> Jun Nie

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