[Qemu-devel] Audio latency

[Qemu-devel] Audio latency

[Alberich de megres]

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.
On the host side (suse), i changed the audio pci device latency to 99
but this only improves a little bit.

Other thing i noticed is when lowering video resolution, the audio
latency gets better and better.

I started played with source code, but i'm just a newbie on qemu.
Anyone can point some light to me please?

thanks guys!!

Re: [Qemu-devel] Audio latency

[malc]

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.
> On the host side (suse), i changed the audio pci device latency to 99
> but this only improves a little bit.
> 
> Other thing i noticed is when lowering video resolution, the audio
> latency gets better and better.
> 
> 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.

-- 
mailto:av1474@comtv.ru

Re: [Qemu-devel] Audio latency

[Alberich de megres]

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.



On Thu, Feb 11, 2010 at 1:03 AM, malc <av1474@comtv.ru> 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.
>> On the host side (suse), i changed the audio pci device latency to 99
>> but this only improves a little bit.
>>
>> Other thing i noticed is when lowering video resolution, the audio
>> latency gets better and better.
>>
>> 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.
>
> --
> mailto:av1474@comtv.ru
>

Re: [Qemu-devel] Audio latency

[malc]

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.
 
> 
> 
> On Thu, Feb 11, 2010 at 1:03 AM, malc <av1474@comtv.ru> 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?

> >> 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?

> >> Other thing i noticed is when lowering video resolution, the audio
> >> latency gets better and better.

Lowering video resolution of what? Guest, host?

> >> 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.

-- 
mailto:av1474@comtv.ru

Re: [Qemu-devel] Audio latency

[Alberich de megres]

On Thu, Feb 11, 2010 at 7:53 AM, malc <av1474@comtv.ru> 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 <av1474@comtv.ru> 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.

>
>> >> 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

>
> --
> mailto:av1474@comtv.ru
>


Thanks!!

Re: [Qemu-devel] Audio latency

[malc]

On Thu, 11 Feb 2010, Alberich de megres wrote:

> On Thu, Feb 11, 2010 at 7:53 AM, malc <av1474@comtv.ru> 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 <av1474@comtv.ru> 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

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

-- 
mailto:av1474@comtv.ru

Re: [Qemu-devel] Audio latency

[Alberich de megres]

On Thu, Feb 11, 2010 at 8:42 AM, malc <av1474@comtv.ru> wrote:
> On Thu, 11 Feb 2010, Alberich de megres wrote:
>
>> On Thu, Feb 11, 2010 at 7:53 AM, malc <av1474@comtv.ru> 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 <av1474@comtv.ru> 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
>
> --
> mailto:av1474@comtv.ru
>

Re: [Qemu-devel] Audio latency

[Alberich de megres]

Another interesting thing:

on guest side,
when i leave the screen quiet, for example just showing desktop with
no animations at all (so there's no change in what should be drawed)
things improve a lot of, and then i coudl hear a song perfectly.
The screen is 1680x1050. the same thing happens when i low screen
resolution to 800x600

Could be the emulated VGA graphic adapter latency? I suppose that i
haven't 2D acceleration so CPU has to paint the screen everytime a
change is done.


On Thu, Feb 11, 2010 at 7:07 PM, Alberich de megres
<alberich2k5@gmail.com> wrote:
> On Thu, Feb 11, 2010 at 8:42 AM, malc <av1474@comtv.ru> wrote:
>> On Thu, 11 Feb 2010, Alberich de megres wrote:
>>
>>> On Thu, Feb 11, 2010 at 7:53 AM, malc <av1474@comtv.ru> 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 <av1474@comtv.ru> 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
>>
>> --
>> mailto:av1474@comtv.ru
>>
>

Re: [Qemu-devel] Audio latency

[malc]

On Thu, 11 Feb 2010, Alberich de megres wrote:

> Another interesting thing:
> 
> on guest side,
> when i leave the screen quiet, for example just showing desktop with
> no animations at all (so there's no change in what should be drawed)
> things improve a lot of, and then i coudl hear a song perfectly.
> The screen is 1680x1050. the same thing happens when i low screen
> resolution to 800x600
> 
> Could be the emulated VGA graphic adapter latency? I suppose that i
> haven't 2D acceleration so CPU has to paint the screen everytime a
> change is done.
> 
> 
> On Thu, Feb 11, 2010 at 7:07 PM, Alberich de megres
> <alberich2k5@gmail.com> wrote:
> > On Thu, Feb 11, 2010 at 8:42 AM, malc <av1474@comtv.ru> wrote:
> >> On Thu, 11 Feb 2010, Alberich de megres wrote:
> >>
> >>> On Thu, Feb 11, 2010 at 7:53 AM, malc <av1474@comtv.ru> 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!!

And there you go again :)

[..snip..]

QEMU is synchronous, if it takes too much time doing the video stuff
audio will be starved, i don't think i can help with that, what you
can do to test this theory of yours is to use VNC, set things up start
the song and then disconnect, if the audio is playing normally then
you are right.

-- 
mailto:av1474@comtv.ru

Re: [Qemu-devel] Audio latency

[Alberich de megres]

On Thu, Feb 11, 2010 at 10:45 PM, malc <av1474@comtv.ru> wrote:
> On Thu, 11 Feb 2010, Alberich de megres wrote:
>
>> Another interesting thing:
>>
>> on guest side,
>> when i leave the screen quiet, for example just showing desktop with
>> no animations at all (so there's no change in what should be drawed)
>> things improve a lot of, and then i coudl hear a song perfectly.
>> The screen is 1680x1050. the same thing happens when i low screen
>> resolution to 800x600
>>
>> Could be the emulated VGA graphic adapter latency? I suppose that i
>> haven't 2D acceleration so CPU has to paint the screen everytime a
>> change is done.
>>
>>
>> On Thu, Feb 11, 2010 at 7:07 PM, Alberich de megres
>> <alberich2k5@gmail.com> wrote:
>> > On Thu, Feb 11, 2010 at 8:42 AM, malc <av1474@comtv.ru> wrote:
>> >> On Thu, 11 Feb 2010, Alberich de megres wrote:
>> >>
>> >>> On Thu, Feb 11, 2010 at 7:53 AM, malc <av1474@comtv.ru> 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!!
>
> And there you go again :)
>
:( sorry once again

> [..snip..]
>
> QEMU is synchronous, if it takes too much time doing the video stuff
> audio will be starved, i don't think i can help with that, what you
> can do to test this theory of yours is to use VNC, set things up start
> the song and then disconnect, if the audio is playing normally then
> you are right.
>
You mean VNC conecting to guest OS? (windows in this case?)

> --
> mailto:av1474@comtv.ru
>

Qemu, uses some kind of 2D hardware acceleration to draw? or simply it
does with CPU?

It would be hard for me to implement a patch to make qemu
asynchronous? (i mean, if the qemu soft architecture allows it on a
easy way or not).

Thanks for all :))

Re: [Qemu-devel] Audio latency

[malc]

On Thu, 11 Feb 2010, Alberich de megres wrote:

> On Thu, Feb 11, 2010 at 10:45 PM, malc <av1474@comtv.ru> wrote:
> > On Thu, 11 Feb 2010, Alberich de megres wrote:
> >
> >> Another interesting thing:
> >>
> >> on guest side,
> >> when i leave the screen quiet, for example just showing desktop with
> >> no animations at all (so there's no change in what should be drawed)
> >> things improve a lot of, and then i coudl hear a song perfectly.
> >> The screen is 1680x1050. the same thing happens when i low screen
> >> resolution to 800x600
> >>
> >> Could be the emulated VGA graphic adapter latency? I suppose that i
> >> haven't 2D acceleration so CPU has to paint the screen everytime a
> >> change is done.
> >>
> >>
> >> On Thu, Feb 11, 2010 at 7:07 PM, Alberich de megres
> >> <alberich2k5@gmail.com> wrote:
> >> > On Thu, Feb 11, 2010 at 8:42 AM, malc <av1474@comtv.ru> wrote:
> >> >> On Thu, 11 Feb 2010, Alberich de megres wrote:
> >> >>
> >> >>> On Thu, Feb 11, 2010 at 7:53 AM, malc <av1474@comtv.ru> 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!!
> >
> > And there you go again :)
> >
> :( sorry once again
> 
> > [..snip..]
> >
> > QEMU is synchronous, if it takes too much time doing the video stuff
> > audio will be starved, i don't think i can help with that, what you
> > can do to test this theory of yours is to use VNC, set things up start
> > the song and then disconnect, if the audio is playing normally then
> > you are right.
> >
> You mean VNC conecting to guest OS? (windows in this case?)

No i mean QEMU's builtin vnc server:

I.e. n one terminal:

$ qemu [..args..] -vnc :0

And elsehwere:

$ vncclient localhost:0

> 
> Qemu, uses some kind of 2D hardware acceleration to draw? or simply it
> does with CPU?

Almost none with std-vga, btw you can also try -vga vmware

> 
> It would be hard for me to implement a patch to make qemu
> asynchronous? (i mean, if the qemu soft architecture allows it on a
> easy way or not).

Yes, it would be hard for you, for anyone even.

-- 
mailto:av1474@comtv.ru