[MPlayer-dev-eng] [PATCH] Fix for mpeg2 A/V sync bug.

Steaphan Greene sgreene at cs.binghamton.edu
Tue Jul 12 03:17:44 CEST 2011

On 06/26/2011 02:49 PM, Reimar Döffinger wrote:
> On Fri, Jun 24, 2011 at 09:30:57AM -0400, Steaphan Greene wrote:
>> The attached patch fixes the bug with vob files (and, presumably other
>> mpeg2 content) caused by the A/V sync code added with r32055/32056.  I
>> believe this solution should cause no other harm.
>> Basically, it now just removes the last_pts data when one of these pts
>> changes occurs in the mpeg2 stream.  That way, the A/V resync code in
>> question ignores this frame, and no longer breaks anything.
> But this is not code for non-uniform time-stamps really but it is
> reordering.
> And my suspicion is that your change only makes it so that non-B-frames
> which MPlayer can detect break the other correction code you pointed out before.
> If so you could just avoid the obfuscation and put the whole other code
> under "if codec != MPEG-2" for exactly the same effect.

I've attached an updated version of my band-aid for this bug based on
current svn (r33877).  I believe this is still correct, as, if I am
understanding you correctly, this case is due to an out-of-order frame,
which means that the time stored in last_pts really was not correct, as
it did not actually store the pts of the truly-previous frame.

...I hope that explanation made sense to more people than just me.

I have updated the comment to reflect this.  Of course, I could still be
wrong about exactly what's happening here.  I am only confident from my
traces that this fixes the problem I found, and only this problem, and
causes no other harm.

Without this patch, the current version of mplayer in SVN is not able to
properly play most of my DVDs.  So, unless a better solution is obvious,
I'd request this patch be applied.


Steaphan Greene <sgreene at cs.binghamton.edu>
Lecturer, Computer Science, Binghamton University
GPG public key: http://www.cs.binghamton.edu/~sgreene/gpg.key.txt
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