Re: QEMU VNC Audio Patch

[Gerd Hoffmann <kraxel redhat com>]

  Hi,

> I started using a modified TightVNC Java Client from 
> http://www.paulsd.com/2009/VNC/   The client kept crashing and had significant 
> audio glitches.   And on top of things, it was a bit awkward to use.   I 
> hacked pulseaudio into the src.rpm for the SL61 gtk-vnc library so that I 
> could add audio output to the virt-manager without having to touch that code 
> as well (KISS principle).   Using this modified rpm, I am able to watch youtube 
> videos, full screen in the VM (1600x1200) and have occasional audio issues.   
> Maybe 1 detectable hiccup a minute.

Wow.  I guess you run vnc client and qemu-kvm on the same machine?  Does
it still work that great if the data stream has to travel over the network?

One fundamental issue the vnc audio extension has is that both audio and
video travel over the same tcp pipe.  So a bulky screen update can
easily disturb audio playback by delaying the audio stream.  With slower
network it will be more noticeable of course.

>    The previous patch was better in the skipping aspect, where the audio data 
> was dispatched to pulseaudio directly from the event loop, and not redirected 
> back via the GObject interface.   I am not entirely sure, why.   When I 
> slapped in some logging I would see batches of messages come in, then batches 
> being sent to pulse audio.   Are the Audio messages being batched and then 
> processed in some sort of idle loop?  (co-routines?)

The "batching" could be caused by both video and audio sharing the data
path too.

cheers,
  Gerd