[FFmpeg-devel] Matroska demuxer gives presentation order in dts

elupus elupus
Wed Feb 27 14:06:55 CET 2008

Thorsten Jordan <tjordan <at> macrosystem.de> writes:

> Hello,
> i just stumbled over some strange behaviour when reading Matroska files,
> the reported pts are in expected presentation order (non-monotonous),
> but the dts values of the packet are as well!
> Beside that the Matroska demuxer reports several issues with that file, like
> Ignoring seekhead entry for ID=0x1549a966
> (many)
> Unknown entry 0x73a4 in info header
> Unknown track header entry 0x55aa - ignoring
> (several)
> Unknown attachedfile ID 0x46ae
> Is there interest in this file? can one just cut 10mb off the start of a
>  mkv file and it still is useable? Original is nearly 100mb in size.
> I am much more interested in the dts problem though...

Yea i've reported this before. The matroska demuxer only fills in pts values, 
then lavf copies this value to dts if it's missing. Normally this should be 
done almost correctly if there exists a parser for the video that marks up B 
frames correctly, but that isn't always the case.

I tried to talk michael into not entering dts values at all if demuxer 
couldn't generate them, but got no interest in that.

I think was discussed in the thread that talks about matroska returns dts not 
pts for matroska files with avi compatibility mode.


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