[FFmpeg-devel] Matroska shortcomings / DTS (was: GoC 2008 and H264 SVC decoder)

Nicolas George nicolas.george
Mon Mar 31 14:56:42 CEST 2008

Le duodi 12 germinal, an CCXVI, Nico Sabbi a ?crit?:
> search Steve Lhomme's posts: he even went as far as
> denying that all the mess needed to disentangle different
> codecs in mkv is a serious problem

This man writes rather a lot on the mailing list, I was not able to find the
particular thread you are referring to yet. For the moment, I have found the
following criticisms:

- CPU overhead and implementation complexity;

- muxing overhead, and more specifically muxing overhead compared to NUT for
  very low bitrates;

- timestamps accuracy problems.

Richard Felker summarised it that way (2004-04-03 04:08:32 GMT):

# Anyway feel free to correct me if I'm wrong, but I think my complaint
# about Matroska from the beginning wasn't that it was _worse_ than
# existing formats, but rather that it was not sufficiently better, and
# that adopting it would discourage people from adopting a really good
# format (NUT) in the future.

(My opinion is that the main thing that discourage people from adopting NUT
is that the name is not globally unique on Google; and secondarily, that the
official homepage looks so much like vaporware.)

> for all codecs, not only for H264, but H264 also has B-pyramid
> that require a massive frame reordering.

In that case, would it be correct to say it that way: DTS could have been
implemented as a sequence number rather than a timestamp, but it was
convenient to make it somewhat similar to PTS?

Thus a definition: DTS is the latest instant a frame must be fed to the
decoder if it is to be decoded and ready at its PTS.

> There's a nice and long thread in nut-devel (search broadcast)
> that discusses the importance of DTS, PTS and PCR in a multiplex

I found this one:
which is quite instructive.

Thanks for your help.


  Nicolas George
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