Re: [Qemu-devel] Audio latency

[Alberich de megres]

On Thu, Feb 11, 2010 at 8:42 AM, malc <address@hidden> wrote:
> On Thu, 11 Feb 2010, Alberich de megres wrote:
>
>> On Thu, Feb 11, 2010 at 7:53 AM, malc <address@hidden> wrote:
>> > On Thu, 11 Feb 2010, Alberich de megres wrote:
>> >
>> >> I'm using the alsa driver.
>> >> Even I tried to change some values using the export and some flags
>> >> that -audio-help shows, but nothing significant.
>> >
>> > Please do not top post.
>>
>> Sorrry!!
>>
>> >
>> >>
>> >>
>> >> On Thu, Feb 11, 2010 at 1:03 AM, malc <address@hidden> wrote:
>> >> > On Thu, 11 Feb 2010, Alberich de megres wrote:
>> >> >
>> >> >> Hi!
>> >> >>
>> >> >> I'm running qemu on suse, and i got a very high audio latency. For
>> >> >> example, using windows latency is about 4s and audio gets distorted
>> >> >> with little cuts.
>> >
>> > How do you measure it?
>> With a program called dpc latency, it's for windows.
>>
>> >
>> >> >> On the host side (suse), i changed the audio pci device latency to 99
>> >> >> but this only improves a little bit.
>> >
>> > As in: with setpci?
>> Yes. I also tired, on host, to low latency to VGA to 10.
>
> That's completely unrelated latency [1]
>
>> >
>> >> >> Other thing i noticed is when lowering video resolution, the audio
>> >> >> latency gets better and better.
>> >
>> > Lowering video resolution of what? Guest, host?
>>
>> Yes, it was on guest. Even for example if i change the desktop or
>> switch to a text terminal when things works better what suggested me
>> that could be something with painting the screen. But i'm not shure if
>> its just only a side effect of a bad launch command, or something
>> else.
>>
>> >
>> >> >> I started played with source code, but i'm just a newbie on qemu.
>> >> >> Anyone can point some light to me please?
>> >> >>
>> >> >> thanks guys!!
>> >> >
>> >> > -audio-help is your friend, from there you can deduce (at the very 
>> >> > least)
>> >> > which audio driver your qemu uses.
>> >> >
>> >
>> > It would also help to know which version of QEMU you run and exactly how
>> > you invoke it.
>>
>> You're right..sorry:
>>
>> qemu-kvm -cpu core2duo -smp 2 -m 1024 -hda /home/nine/imgs/hda1.img
>> -vga std  -usbdevice tablet
>>                -name t1  -net nic,macaddr=55:54:00:12:34:56 -net
>> tap,ifname=tap1,script=no
>>                -soundhw ac97
>
> I can't help you with kvm and windows, that said here are the things
> to try:
>  a. Vanilla qemu
>  b. No smp
>
The same thing.
When playing sounds, i get little cuts.


> And i'm not saying that those will help, just trying to collect more
> data points.
>
> P.S. 4 seconds of latency is sortof insane, especially given that
>     default buffering for ALSA is nowhere near that, not by a
>     longest shot.
>
> [1] http://www.reric.net/linux/pci_latency.html
>
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>