[Matroska-devel] Rejig (for spyder)
spyder at matroska.org
Thu Oct 16 17:09:05 CEST 2003
On Wednesday 15 October 2003 03:37, Steve Lhomme wrote:
> Did you check that out ?
It's a transcoder...a quite complex one too since it doesn't fully decode, it
only drops the bitrate of the streams by adjusting quants etc. I think. My
code now lets me get the timestamps off of GOP headers(really useless though)
and it properly chops the streams into frames. I can determine frame
type(I,P,or B), and also framerate, resolution, and aspect ratio of the clip.
The problem I have hit now is how to create timecodes for the streams.
MPEG2 video allows a mixture of 23.976 and 29.97fps video that creates big
problems for calculating timestamps. I can break the stream down further to
determine if the frames are supposed to be 23.976 w/ playback-pulldown or if
they are real 29.97fps. Then the new problem is, will decoders care if they
get 23.976fps timestamps for some frames and then 29.97fps timestamps for
others. I think that the decoders don't really need the timestamp info
anyway as there is none in the raw ES. I will look at the PS specs today and
see if we could reuse the timestamps directly from it. I think it doesn't
stamp every frame necessarily though.
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