[Matroska-devel] Opus in Matroksa Cont.

Steve Lhomme slhomme at matroska.org
Fri May 24 17:38:19 CEST 2013


It's possible to make this work so that in the end the SimpleBlock is
unchanged. The same block value *must* give the same timecode (rounding
excluded) when using either system on the same file.

Currently we use TimecodeScale * TrackTimecodeScale * (Cluster Timecode
Count + Block Timecode Count)
The new system would be the same except the scales are expressed in
fractions. It's possible to arrange the 2 fractions to match the one in
float. I just looked at the specs and the only scaled values are all
depending on tracks. It would be a problem if Chapter timecodes or other
things would need to be scaled, but it's not the case.

We may need to de-deprecate the TrackTimecodeScale if we want to really
have tracks with different clock scales. It was deprecated because never
used, but not because it didn't make sense. Another reason is because it
was a float. And forced floating point values on all timecodes. The problem
we may have is that new files using it may not play correctly on older
players if the element wasn't used, which is very likely as it was rarely
written and most likely 1.0f.

Maybe muxers should only allow a non 1.0f TrackTimecodeScale when a newer
Matroska version (4) is forced ? And for the EBMLReadVersion to 4 as well.

By the way, when/if we update the specs, Timecode should be renamed to
Timestamp on new elements and descriptions...
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