Re: [Qemu-devel] [PATCH] hw/usb/dev-audio.c: make USB audio card sound perfect

[Stefan Hajnoczi]

On Wed, Oct 28, 2015 at 09:59:32AM -0400, Programmingkid wrote:
> 
> On Oct 28, 2015, at 6:58 AM, Stefan Hajnoczi wrote:
> 
> > On Mon, Oct 26, 2015 at 01:24:00PM +0100, Gerd Hoffmann wrote:
> >>> So this change would make real-time audio feel laggy.
> >> 
> >> That is secondary if the sound quality is bad due to constant overruns
> >> and underruns ...
> > 
> > This is like sweeping network performance problems under the rug by
> > increasing queue size.
> > 
> > Before bumping the buffer size and breaking real-time applications (i.e.
> > 128-512 samples per buffer), there should be a little performance
> > investigation to understand the root cause.
> > 
> > Why are overruns/underruns occurring?
> > 
> > Is the problem the host sound API, QEMU's audio/mixing infrastructure,
> > or guest responsiveness?
> 
> I think a better question is who is going to spend the time and energy 
> trying to answer these questions?

To push patches like this is arrogant because your patch makes a
trade-off: smooth playback on *your* system vs worse latency for
*everyone*.

You don't want to spend time understanding why playback is choppy on
your system.  That's fine.

What bothers me is that you have no qualms about making latency on
everyone's system worse.

If you don't have time, that's fine.  Just send an email to report the
symptom and in the meantime use the qdev property to increase the buffer
size for yourself:

  -device usb-audio,buffer=6144

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