[Matroska-devel] Opus in Matroksa Cont.

Ralph Giles giles at thaumas.net
Wed Apr 10 02:20:23 CEST 2013

On 13-03-27 4:22 PM, Frank Galligan wrote:
> Agreed. Unless someone has an objection I think we can consider pre-roll
> done.

Thanks for having another go at this. Pre-roll is certainly the easier
of the two. So it's an optional element in the TrackHeader, and players
which don't understand it will skip it and get playback wrong, but
implementations which have been updated can do the correct thing in general?

We should perhaps also say that for Opus a default value of 80ms should
be assumed.

Can you please update the draft spec on
https://wiki.xiph.org/MatroskaOpus with this part of the proposal?

Re units, time is fine for SeekPreRoll as far as Opus is concerned. The
value is a vague minimum.

For Pre-skip in Ogg we chose sample units deliberately. This controls
duration, in- and out- trimming and sync, where samples are exact.
Matroska generally can't represent sample-accurate durations, so maybe
that's less important for this spec. Still, unless you're also proposing
to remove the value from CodecPrivate, using the same units as the Ogg
header has some value for Opus.


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