[Qemu-devel] Re: [PATCH] alsaaudio: increase default buffer sizes

[malc]

On Mon, 5 May 2008, Jan Kiszka wrote:

> malc wrote:
> > On Sun, 4 May 2008, Jan Kiszka wrote:
> >
> > > Jan Kiszka wrote:
> > > > malc wrote:
> > > > > On Sun, 4 May 2008, Jan Kiszka wrote:
> >
> > [..snip..]
> >
> > > > Yeah, great, that was the key! Find below the version that works for me
> > > > (on 64 bit 8) ). It even obsoletes my buffer size patch. Please merge!
> > >
> > > Declaring the buffer size tweak obsolete was too quick. I still need
> > > more under certain guest load, but now I'm already fine with
> > > DEFAULT_BUFFER_SIZE=4096. Or all in one:
> >
> > I wonder if everyone will be happy with quadrupled latency, apart from
>
> Hmm, I wonder about the scenario where this latency may actually hurt.
> QEMU is not /that/ fast anyway. ;)

You would be surprised.

> > you and this other user on some (kvm was it) mailing list there are no
> > huge outcries of dissatisfaction, then again i'm not sure how many people
> > use ALSA+QEMU or QEMUs+AUDIO in general.
>
> I don't think many users are actually running QEMU (or KVM) against
> ALSA. You have to
> - manually enable it during configure
> - pass QEMU_AUDIO_DRV=alsa (OSS remains default even if ALSA is on - I
>   ran into this trap first.)

I don't see how it's a trap. You can also enable esd or fmod drivers
in configure along with alsa, which one should be the default?

> - possibly have to fix up your configuration with FIXED_FREQ and
>   BUFFER_SIZE (as reported by >1 kvm users) until
>
> As OSS does not give us shared sound device access and, in the end, is a
> deprecated API under Linux, my goal is to overcome remaining issues of
> the ALSA support and then make /this/ the default one (under Linux).

Huh? Even OSS/lite that is/was shipping with default Linux gave me
"shared" sound, though i had a decent sound card with possibility to
open the same /dev/dsp 16 times (it actually had 16 sigmatel chips on
board). And the real OSS has vmix. And fwiw to have this wonderful
"shared" sound you have to configure "dmix" (or whatever its called)
too.

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