[MPlayer-users] x264 and loss of sync with B-frames

Rich Felker dalias at aerifal.cx
Tue May 17 02:36:41 CEST 2005

On Mon, May 16, 2005 at 09:05:12AM -0400, Jason Tackaberry wrote:
> On Mon, 2005-05-16 at 03:50 -0400, Rich Felker wrote:
> > in mencoder. a/v sync has absolutely nothing to do with codec.
> At least with respect to x264, isn't the real issue here then that
> mencoder can't handle B-frames, rather than that B-frames suck?

the problem with the a/v desync is that mencoder can't handle b
frames, yes...

> B-frames might add complexity, but your opinion in the past seems to be
> that they suck, or are inherently bad or something.  I'm just not sure I
> see that argument.

...however, b frames do suck in general. they significantly increase
the working set size for decoding, which means you need more
processing speed to decode them, and they create a nightmare for
efficient buffer management when filtering the video at runtime.
anyone making a player is forced to choose between abysmal performance
and ugly hacks that aren't guaranteed to work.

> Anyway, I haven't noticed similar sync problems when using lavc.  With
> x264, using B-frames actually causes an increased frame count in the
> resulting output.  So it doesn't seem to me to be an architecture issue
> if lavc doesn't have this problem.  Unless mencoder has those ugly hacks
> you mentioned for lavc but not x264?

it's probably a bug in the ve_x264 wrapper, writing a bogus "frame" at
the beginning. if you fix this, maybe the problem would go away..?


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