[Spice-devel] [PATCH spice-gtk 0/2] Disabling mmtime adjustment in the client (from audio backend)

[Victor Toso]

Hi,

On Thu, Aug 03, 2017 at 10:13:10AM -0400, Marc-André Lureau wrote:
> Hi
>
> ----- Original Message -----
> > > I start to be worried about all of our streaming tweaks and issues. Is
> > > there any effort to use RTP/SRTP instead? I think this would be a big
> > > opportunity to improve the situation going forward.
> >
> > There is not effort on that AFAIK.
> >
>
> I would put my effort there.

Okay, I'll check it out.

> > But I'm interested on improving the mmtime in server side but it'll be
> > hard if I can't disable this long-term workaround.
> >
> > If it isn't a workaround, I would like to understand why.
> >
> >   commit fbe3b5ec32e3d93f0a0f41239b85be723d8d91c5
> >   Author: Marc-André Lureau <marcandre.lureau at redhat.com>
> >   Date:   Wed Dec 22 15:32:45 2010 +0100
> >
> >       gtk: update mm time based on playback time+delay
> >
>
> This is not a workaround, iirc.
>
> The way I remember it, video frames have ts, based on audio time (or
> supposed to I think server implementation is lacking there).
>
> When we receive audio packets, we are supposed to set the current
> mmtime. We asked the audio backend what is the current audio delay,
> and update mmtime = last_packet.time - audio_delay, so we can sync the
> video frames on audio.
>
> Wrong? Yeah probably, video streaming is not an easy subject, that's
> why effort should be put on using the real thing that gstreamer can
> provide us (almost) for free.

Not easy, yeah. But I doubt that changing to different protocol will
solve our synchronization issues without extra effort because the video
could be encoded in different ways in the host or it could be encoded in
the guest and spice-server only needs to wrap it under its protocol.

Too many possibilities which makes fixing mmtime on the client
error-prone.

I'll investigate a bit how to improve mmtime in the server and look into
rtp/srtp and how can we use it with GStreamer.

If I can improve the mmtime generation, we could change the default of
this proposed property (sync-video-on-audio) to FALSE instead.

Thanks again for the discussion,
    toso
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