[MPlayer-dev-eng] [PATCH] mencoder, B-frames, and video/audio delay

[Corey Hickey]

Nico Sabbi wrote:
> Are you sure that this patch fixes desync? Since the delay is constant 
> (and not per frame)
> mplayer will start with the first pts being correct (because it's 
> necessarily an I frame) but all
> B frames will still have  pts(b) > pts(p) because frames come out in 
> decoding order (P3 B1 B2).

Isn't that the reason muxer_lavf doesn't currently work with B-frames
correctly? It sets pts directly from the stream timer, which increases
linearly while at the same time frames arrive in decoding order.

pkt.pts = (stream->timer /
av_q2d(priv->oc->streams[pkt.stream_index]->time_base) + 0.5);

muxer_lavf will still work with the application of this patch because
the stream timer doesn't get adjusted in the absence of B-frames. The
other muxers (I think) don't care about the stream timers -- they just
write frames in the order they arrive. Am I mistaken? You know much more
about that than I do. How does mpeg handle a-v sync?

> All in all I think that your patch may somehow help, but it won't assign 
> the correct timestamp to
> frames.

In any case, I've been mulling over the idea of, instead of adjusting
the stream timer, leaving it be and having mencoder compensate when it
calculates the AV_delay variable. If there's an advantage to that
aproach, I can do it.

-Corey