VNC audio extension, was Re: [Qemu-devel] Re: [RFC] qemu-gui based on wxWidgets and libvncclient

[Johannes Schindelin]

Hi,

On Wed, 18 Oct 2006, Anthony Liguori wrote:

> Johannes Schindelin wrote:
> > Hi,
> > 
> > On Tue, 17 Oct 2006, Fabrice Bellard wrote:
> > 
> > > Another point is that you should consider adding audio support. I can help
> > > you on that (maybe malc would be interested too !). A simple format could
> > > be 4 bit ADPCM at fixed frequency. Optionally A more advanced codec such
> > > as Vorbis could be used.
> > 
> > Please, please not _another_ vnc hack! The RFB protocol loses all of its
> > appeal if everybody has proprietary, incompatible extensions! If you bother
> > to search Google for prior art, here is a link:
> > 
> > http://www.ks.uni-freiburg.de/php_arbeitdet.php?id=75
> > 
> > Yes, it is in German, but it already works. No need to add yet another
> > obscure extension.
> 
> My German is not very good, but from what I was able to read, it seems like
> they are just using VNC to transmit the port information for doing esd
> forwarding.  Presumably this saved a lot of work because no server side code
> was needed.

Actually, it does not use ESD forwarding. The ESD part was meant for audio 
_capture_, since the project was to transport also audio from a real 
computer.

But you are correct about the opening a port part. It uses RTP, not TCP, 
to ensure that the latency is low (which makes sense). The essence of this 
work is (AFAIUI) that

        - Java is not the right language to do the job (which I don't 
          agree with), and
        - it makes no sense to integrate the data stream into the VNC
          data stream, since you cannot sensibly multiplex the video
          and audio stream (because they have different goals).

Hth,
Dscho