[MPlayer-dev-eng] A/V sync filter

[D Richard Felker III]

On Mon, Feb 07, 2005 at 11:30:08AM +0100, Diego Biurrun wrote:
> Tony Houghton writes:
> > I have a problem with loss of A/V sync since I started using the dfbmga
> > driver. The picture starts to increasingly lag behind sound, and
> > changing the audio delay with the +/- keys has no effect for some
> > reason. I think it's caused by using vsync, but vsync is vital for
> > watching interlaced TV, and seems to make the picture smoother for
> > non-interlaced videos too.  Enabling framedrop drops far too many
> > frames. -ao sdl makes a big improvement in the time it takes before the
> > gap becomes noticeable but doesn't cure it altogether.
> 
> Have you already experimented with the -mc and -autosync options?

They won't help. The problem is that video out drivers are not
supposed to be synchronous like this in MPlayer's design, but they
have to be for playing interlaced video on an interlaced device. It
_might_ work ok with -framedrop and -autosync together (better than
-framedrop without -autosync) but I'm not sure. The real solution is a
decent player design.

Anyway the fundamental cause for the drift is that the audio and video
clocks aren't quite in sync to real time. You might be able to fix the
problem just by forcing MPlayer to do some resampling based on
empirical data (overriding fps/samplerate) or by getting a better
sound card with an accurate clock.

Rich