On 2012-04-25 09:34, Gerd Hoffmann wrote: > 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.
Yep, would work fine - if the issue below allowed me to use it. > >> 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). I found another workaround: audio hw passthrough. Works nicely. And this indicates that there should be still some room for improvement in the device model so that Windows chooses a proper ring buffer size, no? Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
