[Qemu-devel] Linux KVM, Windows 7 guest choppy sound

[Qemu-devel] Linux KVM, Windows 7 guest choppy sound

[Erik Lotspeich]

Hi,

I apologize if this isn't the right venue for this message, but this
mailing list seems a bit more active than qemu-discuss.

Background:
I am running OpenSUSE 12.1. I fixed audio issues in VM guests by setting
the following in qemu.conf:

vnc_allow_host_audio = 1

I also set user= and group= to allow qemu-kvm to run as the same user as
I am logged in as. This allowed qemu-kvm to send audio to pulseaudio.

My issue:
I am using the ICH6 virtual audio driver in my VMs. In my Linux VMs, the
sound works perfectly without any issues. In my Windows 7 VM, the sound
works with the exception of static and choppiness in the audio. Has
anyone else seen this or have any ideas for a fix?

Thanks!

Regards

Erik

Re: [Qemu-devel] Linux KVM, Windows 7 guest choppy sound

[Jan Kiszka]

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On 2012-09-07 18:09, Erik Lotspeich wrote:
> Hi,
> 
> I apologize if this isn't the right venue for this message, but this
> mailing list seems a bit more active than qemu-discuss.
> 
> Background:
> I am running OpenSUSE 12.1. I fixed audio issues in VM guests by setting
> the following in qemu.conf:
> 
> vnc_allow_host_audio = 1
> 
> I also set user= and group= to allow qemu-kvm to run as the same user as
> I am logged in as. This allowed qemu-kvm to send audio to pulseaudio.
> 
> My issue:
> I am using the ICH6 virtual audio driver in my VMs. In my Linux VMs, the
> sound works perfectly without any issues. In my Windows 7 VM, the sound
> works with the exception of static and choppiness in the audio. Has
> anyone else seen this or have any ideas for a fix?

Known issue, likely unfixable in QEMU due to hard-coded constraints of
the driver Windows uses (too small playback buffers).

I gave up on hda, I'm happily using a passed-through USB headset now.
Another known-to-work alternative is PCI passthrough of the host sound
hardware. However, both approaches are no option when the host is out of
reach.

What seems to work better - but is lacking input support - is usb-audio.
Maybe worth a try when you don't need a microphone.

Jan


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Re: [Qemu-devel] Linux KVM, Windows 7 guest choppy sound

[Avi Kivity]

On 09/08/2012 01:53 PM, Jan Kiszka wrote:
> On 2012-09-07 18:09, Erik Lotspeich wrote:
>> Hi,
>> 
>> I apologize if this isn't the right venue for this message, but this
>> mailing list seems a bit more active than qemu-discuss.
>> 
>> Background:
>> I am running OpenSUSE 12.1. I fixed audio issues in VM guests by setting
>> the following in qemu.conf:
>> 
>> vnc_allow_host_audio = 1
>> 
>> I also set user= and group= to allow qemu-kvm to run as the same user as
>> I am logged in as. This allowed qemu-kvm to send audio to pulseaudio.
>> 
>> My issue:
>> I am using the ICH6 virtual audio driver in my VMs. In my Linux VMs, the
>> sound works perfectly without any issues. In my Windows 7 VM, the sound
>> works with the exception of static and choppiness in the audio. Has
>> anyone else seen this or have any ideas for a fix?
> 
> Known issue, likely unfixable in QEMU due to hard-coded constraints of
> the driver Windows uses (too small playback buffers).

Would using real-time priority for the guest improve things?

Of course that can be dangerous if the guest decides to spin and has as
many vcpus as you have cores.


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error compiling committee.c: too many arguments to function

Re: [Qemu-devel] Linux KVM, Windows 7 guest choppy sound

[Jan Kiszka]

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On 2012-09-09 16:50, Avi Kivity wrote:
> On 09/08/2012 01:53 PM, Jan Kiszka wrote:
>> On 2012-09-07 18:09, Erik Lotspeich wrote:
>>> Hi,
>>>
>>> I apologize if this isn't the right venue for this message, but this
>>> mailing list seems a bit more active than qemu-discuss.
>>>
>>> Background:
>>> I am running OpenSUSE 12.1. I fixed audio issues in VM guests by setting
>>> the following in qemu.conf:
>>>
>>> vnc_allow_host_audio = 1
>>>
>>> I also set user= and group= to allow qemu-kvm to run as the same user as
>>> I am logged in as. This allowed qemu-kvm to send audio to pulseaudio.
>>>
>>> My issue:
>>> I am using the ICH6 virtual audio driver in my VMs. In my Linux VMs, the
>>> sound works perfectly without any issues. In my Windows 7 VM, the sound
>>> works with the exception of static and choppiness in the audio. Has
>>> anyone else seen this or have any ideas for a fix?
>>
>> Known issue, likely unfixable in QEMU due to hard-coded constraints of
>> the driver Windows uses (too small playback buffers).
> 
> Would using real-time priority for the guest improve things?
> 
> Of course that can be dangerous if the guest decides to spin and has as
> many vcpus as you have cores.

We need to decouple the data path of that device from the rest of QEMU
first. Just prioritizing likely doesn't help. And then the problem might
be getting sufficient reactivity from the QEMU-external audio data path
as well.

Jan



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Re: [Qemu-devel] Linux KVM, Windows 7 guest choppy sound

[Avi Kivity]

On 09/10/2012 12:06 PM, Jan Kiszka wrote:

>>> Known issue, likely unfixable in QEMU due to hard-coded constraints of
>>> the driver Windows uses (too small playback buffers).
>> 
>> Would using real-time priority for the guest improve things?
>> 
>> Of course that can be dangerous if the guest decides to spin and has as
>> many vcpus as you have cores.
> 
> We need to decouple the data path of that device from the rest of QEMU
> first. Just prioritizing likely doesn't help. 

Depends on what the guest is doing, but likely you are right.  Luckily
we're already doing that.

> And then the problem might
> be getting sufficient reactivity from the QEMU-external audio data path
> as well.

Those already have realtime priority.  Doesn't guarantee the path is
short enough but it may work.

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error compiling committee.c: too many arguments to function

Re: [Qemu-devel] Linux KVM, Windows 7 guest choppy sound

[Jan Kiszka]

[re-adding the list]

On 2012-09-11 16:23, Erik Lotspeich wrote:
> On 09/08/2012 05:53 AM, Jan Kiszka wrote:
>> Known issue, likely unfixable in QEMU due to hard-coded constraints of
>> the driver Windows uses (too small playback buffers).
> 
> Thanks so much for your response on this. Even though there is no
> immediate fix, it is good to know that it is a known issue.
> 
> I appreciate your suggestion regarding USB devices as well. I believe
> that requires VT-d support which I cannot enable since I am one of those
> unlucky users who experiences the lockups on boot with Nvidia and VT-d
> enabled on my Lenovo W520.

Host sound controller pass-through requires VT-d, USB device
pass-through does not.

Jan

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