[NUT-devel] Frame/Field problem

[Michael Niedermayer]

On Tue, Feb 19, 2008 at 11:51:40PM -0500, Rich Felker wrote:
> On Wed, Feb 20, 2008 at 05:23:14AM +0100, Michael Niedermayer wrote:
> > Hi
> > 
> > When we designed the pts->dts reorder algorithm we considered arbitrary
> > frame reorderings, but there was something we missed, that are mixes of
> > frame and field pictures, like:
> > 
> >     i1 p2 P3 p4 P5 p7 P8   (lower case is a field, upper is a frame)
> > PTS 2  3  4  6  7  9  10
> > DTS 0  1  2  4  5  7  8
> > 
> > As you can see no reordering of PTS can result in the DTS values.
> 
> I'm confused by this example. As there are no B frames, dts==pts is
> just fine.

Fine in what respect? Certainly not fine in the respect of being a valid
decoding timestamp for an mpeg2 decoder.

Anyway after some sleep it seems the example above is invalid as mpeg2 says:
"If field pictures are used then they shall occur in  pairs"
This also gives us an easy solution, just put both fields in a single nut
frame. I also should likely try that in ffmpeg the code i commited yesterday
to interpolate field picture timestamps is ugly, though it should work with
any possible mixture ...


also here are a few examples with b frames:

i  p  P  B  B  B  B
0  1 10  2  4  6  8
-  -  0  2  4  6  8

i  P  p  B  B  B  B     (invalid in mpeg2 i dunno about h.264)
0  1 11  2  4  6  8
-  -  1  2  4  6  8

I  p  p  B  B  B  B
0 10 11  2  4  6  8
-  0  1  2  4  6  8

i  p  p  p  B  B  B  B
0  1 10 11  2  4  6  8
-  -  0  1  2  4  6  8

I  P  b  b  b  b  b  b  b  b
0 10  2  3  4  5  6  7  8  9
-  0  2  3  4  5  6  7  8  9


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Frequently ignored awnser#1 FFmpeg bugs should be sent to our bugtracker. User
questions about the command line tools should be sent to the ffmpeg-user ML.
And questions about how to use libav* should be sent to the libav-user ML.
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