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

[Jan Kiszka <jan.kiszka@web.de>]

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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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