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Re: [Qemu-devel] [HACK] hda: expose microphone instead of line-in
From: |
Gerd Hoffmann |
Subject: |
Re: [Qemu-devel] [HACK] hda: expose microphone instead of line-in |
Date: |
Wed, 25 Apr 2012 14:34:01 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:10.0.3) Gecko/20120307 Thunderbird/10.0.3 |
On 04/25/12 13:03, Jan Kiszka wrote:
> Hi Gerd,
>
> I had problems with Windows LiveMeeting expecting a microphone as
> input. But the HDA model only exposes a line-in port. The following hack
> works for me, but I bet there is a cleaner solution. Any suggestions?
Good to know this works. /me has patches ready to go, was just waiting
for testing feedback ...
Pushed to git://git.kraxel.org/qemu audio.1
They do essentially the same, except that they leave the existing
hda-duplex code as-is and add a new hda-micro codec instead which
advertises the input as micro to the guest.
> BTW, sound output quality of a Win7 guest on my Linux hosts sucks while
> it's fine for a Linux guest. I vaguely recall that Windows requests a
> too small DAC buffer, is that true? Is there anything one can do about
> this?
Yes. The buffer is ~ one page and can hold 20 ms of sound data, so
considering buffer flipping intel-hda has to shuffle data every 10ms,
and the windows guest needs to be scheduled too so it can re-fill the
other half of the buffer. Which obviously makes sound playback *very*
sensitive to latencies anywhere in the qemu.
What you can do about it? Dunno whenever windows allows to tweak the
buffer size somehow. When I looked deeper at that a while back the
biggest latency issues in qemu used to be qxl, ide/qcow2 and vnc. qcow2
should be fixed now with the switch to coroutines and full async i/o.
Likewise qxl, although this depends on recent guest drivers. For vnc
enabling the threaded vnc server helps alot (without it moving around
windows leads to sound dropouts).
cheers,
Gerd