[MPlayer-dev-eng] libmpeg2 and lavc don't agree on PTS values

[Michael Niedermayer]

Hi

On Mon, Nov 27, 2006 at 12:38:03AM +0200, Uoti Urpala wrote:
> On Sun, 2006-11-26 at 12:40 -0800, Trent Piepho wrote:
> > I've spent hours trying to get a 2-pass filter working correctly until I
> > finally figured out it's not my fault.  It's either lavc's fault or
> > libmpeg2's fault!
> 
> The decoders do not track pts directly.
> 
> > This is the first few frames of an ATSC ts stream as decoded with -vc
> > mpeg12, listing pts value, frame type, and mean qscale value:
> 
> > This is the same file with -vc ffmpeg2:
> 
> > You see the frame type and mean qscale match exactly, but the pts values
> > have been shifted down by one.
> 
> Without -correct-pts mplayer (or mencoder) does not handle decoder lag
> correctly. Probably libmpeg2 and ffmpeg12 have different decoder lag for
> some reason and thus give different results.
> 
> If you try using -correct-pts with the internal or lavf mpeg demuxer it
> probably won't work right (though lavf can work for some videos),
> basically because those demuxers behave badly (internal has hacky
> special cases different from other demuxers and the lavf mpeg demuxer
> doesn't calculate any pts values for some frames). Muxing the mpeg video

maybe -correct-pts should set AVFMT_FLAG_GENPTS
?

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In the past you could go to a library and read, borrow or copy any book
Today you'd get arrested for mere telling someone where the library is