[MPlayer-dev-eng] Sync problems switching mpeg1 streams

[David Toso]

Hi mplayer developers,

Arpi <arpi at thot.banki.hu> wrote:
> no wonder - have you ever heard/think of audio buffering? :)
> and it's not even in mplayer, it's done by the soundcard (hw or driver).

Ok I think I now have some idea of what is happening, but have no idea of how 
to fix it. (It does not appear to be audio buffering in HW/driver).

A little background for those who have not followed the previous related thread: 

     ./feeder | mplayer -delay 0.216 -demuxer 2 -

  The feeder program presents a prompt, to which I enter:

      load 1.mpg

  The feeder program opens 1.mpg, reads from it and sends the data to mplayer,
  which starts playing, which also causes mplayer to initialise its vo module, and 
  displays 1.mpg playing in its window.

  At some point (say 30 seconds) later I type at the feeder prompt:

      load 2.mpg

  Internally, feeder closes 1.mpg, opens 2.mpg and starts sending that to mplayer 
  instead. Since these are mpeg files, mplayer hapilly treats the 2nd file as a 
  (slightly broken) part of the original stream, and just skips ahead to valid frames. 
  There is no noticable artifact on the switch between streams.
 
The "-delay -0.216" is to compensate for PAL 3:2 pulldown, as these mpeg files 
are actually rips from PAL (region 4) DVD's. This does not have any effect on the 
problem I am having (other than to correct lip-sync).

The problem is that when I switch from stream 1 to stream 2, mplayer takes a 
_long_ time, say 10-15 seconds, to regain synchronisation between the video 
and audio.

I have verified this by looking at the A-V field from the running statistics output 
of mplayer. I would normally see rapid fluctuation between say "A-V:  0.022" and 
"A-V: -0.045", when the audio and video _are_ in sync. 

Upon switching to the second stream (30 seconds later) that field goes up to 
some abnormally high figure like "A-V:  0.725" and gradually (over 10-15 
seconds) settles back down to the normal range, after which the video &
audio do look to be in sync again.

I wonder if there is any way to ensure that there will be no large loss of sync
when switching mpeg streams? 

I have tried -cache but, of course, that just results in the effect of the feeder 
commands being delayed by some time proportional to the cache size.

Any help would be much apreciated.

David Toso.