On 4 Dec 2002, Pontus Lidman wrote:
> Hello,
>
> I'm experiencing audio overruns when recording with an ALSA
> application, but after investigation I'm inclined to consider them
> 'bogus' because I believe there is no way that the buffer can be
> overrun in such a short time. I don't know how I can avoid them, I
> hope somebody can help me troubleshoot this.
>
> The application, 'avview' (TV capture software), runs fine for some
> time, randomly between 5-30 seconds, independent of sampling rate,
> after every snd_pcm_prepare, but then I get an audio overrun
> reported. This is invariably when a very short time elapsed since the
> last successful read.
>
> I tried to record about 10 minutes, and I got 37 overruns. I measured
> the time since the last read, when the buffer is supposedly near
> empty, and the intervals are between 3 and 36 microseconds, the
> average being 18 microseconds. Obviously something strange is going
> on.
>
> When the reading loop is successful, the time between successful reads
> depends on the blocksize; since the read call has to block to wait for
> data, I assume I'm calling the read function often enough. Since I'm
> recording video at the same time, the system is a bit loaded, but
> 'top' reports constantly more than 50% idle.
>
> My hardware is a MSI KT3 Ultra2 motherboard with 'VIA Technologies,
> Inc. VT8233 AC97 Audio Controller (rev 80)' (source: cat /proc/pci).
>
> For ALSA, stop threshold is set to 65536, buffer time is set to
> 100020, I'm doing blocking reads. I've tried varying these settings,
Could you send me full dump of sw and hw params? see *dump() functions in
pcm.h header file. Also, could you check lines coming from the sound
driver in /var/log/messages (if any)?
Jaroslav
-----
Jaroslav Kysela <[EMAIL PROTECTED]>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs
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