Re: QEMU VNC Audio Patch

[Steven Carr <Steven Carr scaa-usa com>]

On Wednesday 30 November 2011 11:44:46 Daniel P. Berrange wrote:
> Moving the message to the gtk-vnc-devel mailing list....
> 
> On Tue, Nov 29, 2011 at 04:50:22PM -0500, Steven Carr wrote:
> > Hello,
> >    My name is Steven Carr.   I have written a patch to gtk-vnc to support
> > QEMU/KVM Audio over VNC (outputs to PulseAudio).   As with all things
> > Open Source, I had a need and scratched it.   I needed audio supported
> > for virt- manager.   I use RHEL 6.1, so audio output uses PulseAudio.  
> > The patch is based on the contents of the git repository as of
> > 2011-11-29.   This was the easiest approach to transparently enabling
> > audio on virt-manager.
> 
> Thanks for hacking on this. I too have hacked on audio support myself but
> I always ended up down a rathole trying to wire it up to gstreamer, so
>  never ended up finishing it. What you have done with pulseaudio is much
>  simpler and shows me a nicer direction for us to take :-)
> 
> >    Taking into consideration the various distributions and sound outputs,
> > it might be better to simply have a callback to deliver the audio data
> > packets to the user application.   This way, it is up to the calling
> > application to implement proper audio output (ESD, Pulse, written to a
> > mpeg file, whatever).
> >
> > int do_audio(void *private, int state, int bytes, char *data)
> > {
> >        my_private_t *priv = (my_private_t *)private;
> >
> > 	switch(state) {
> > 	case VNC_QEMU_AUDIO_START:
> > 	case VNC_QEMU_AUDIO_STOP:
> > 	case VNC_QEMU_AUDIO_DATA:
> > 		/* magic happens here */
> > 	}
> > }
> >
> > /* register audio handler */
> > void vnc_connection_audio_callback(conn, do_audio, (void
> > *)private_struct); void vnc_connection_audio_enable(conn, sample_size,
> > channels, rate); void vnc_connection_audio_disable(conn);
> 
> I think what I'd  do is to create a new GObject interface
> 
>     VncAudioSink *
> 
> which have a couple of methods
> 
>      vnc_audio_sink_start(VncAudioSink *sink, VncAudioFormat *format);;
>      vnc_audio_sink_write(VncAudioSink *sink, void *data, gszie len)
>      vnc_audio_sink_stop(VncAudioSink *sink);
> 
> VncAudiobuffer is a simple struct, much like VncPixelformat, just for
> holding the sample size / channels / rate
> 
> Then, create an implementation of that interface for pulseaudio
> 
>     VncAudioSinkPulse *
> 
> To complete things we just need an API to allow attaching of
> an VncAudioSink * to a VncConnection *.
> 
>   vnc_connection_set_audio_sink(VncConnection *conn, VncAudiSink *sink);
> 
> 
> Is this something you have more time to work on ?  If not I'll use you
> patch as the basis for doing this myself in the future.
> 
> Regards,
> Daniel
> 

I think I have some spare time this week,
~Steven