[Qemu-devel] Re: Audio

[malc <av1474@comtv.ru>]

On Mon, 14 Sep 2009, Jan Kiszka wrote:

> malc wrote:
> > On Sun, 13 Sep 2009, Jan Kiszka wrote:
> > 
> >> Jan Kiszka wrote:
> >>> malc wrote:
> >>>> Does following help?
> > 
> > [..snip.]
> > 
> >>> Nope, still full CPU load.
> >> Forgot to mention: I also tried OSS before, but it suffered the same
> >> way, and polling had to be disabled.
> >>
> > 
> > Aha, i've commited this patch and another which correct premature
> > closure of audio device (for both OSS and ALSA), can not notice
> > anything particularly wrong when running with poll enabled now, can
> > you please retest things on your end, once again it would be nice to
> > have both audio systems, tested. Thanks in advance.
> > 
> 
> Sorry, both audio systems still require to disable polling for a normal
> cpu load.

I believe the problem is within wm8750(/musicpal combination?)
wm8750_set_format creates a bunch of ADC voices and enables them, but
no reads are ever performed, so ALSA/OSS quickly fills the buffers
and then stops reading into them thus leaving respective fd's in a
selectable state. My main machine lacks ADC so i was unable to reproduce
the behaviour you've seen on it on another box the issue is indeed very
visible. Setting QEMU_OSS_ADC_DEV to /dev/moo or commenting out
AUD_set_active_in in wm8750.c cures the problem as does, contrary to
your report, setting QEMU_AUDIO_ADC_TRY_POLL to 0.

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