On Oct 29, 2015, at 11:08 AM, Stefan Hajnoczi wrote: > 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*.
I'm sorry you are taking this so personally. I would never have submitted this patch if it causes a lot of problems to others. > You don't want to spend time understanding why playback is choppy on > your system. That's fine. I have been working on a sound output related problem for years. > What bothers me is that you have no qualms about making latency on > everyone's system worse. How do you know it makes sound on other people's systems worse? If you have actually done any testing, I would like to see the results. Here is a format I suggest you could use: Host operating system: Guest operating system: emulated machine: Tests conducted: video playback, game sound playback, ... > 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 The thing is I am certain is this patch makes sound play better. Before this patch the sound played back from the usb audio device was very poor. With this patch it sounds great. I have played video files in QEMU and if the latency was really high, then I would have noticed the audio not being in sync with the video. You have shown calculations, but you haven't given any real world examples of why this patch is bad.
