[Matroska-devel] Opus audio codec

Moritz Bunkus moritz at bunkus.org
Thu Dec 15 09:12:45 CET 2011


Hey,

On Thu, Dec 15, 2011 at 01:24, Ralph Giles <giles at thaumas.net> wrote:

> I agree this is completely unnecessary in Matroska, but if we go this
> route I think we might as well keep it. The extra eight bytes aren't
> significant overhead and it's easier if the two encapsulations use
> exactly the same format. I mean, the number of channels and sample
> rate fields aren't necessary here either.

True enough, so let's just keep it.

> The Ogg encapsulation also has a second vorbis-style comment header
> with tag data. These are also redundant of course, but including both
> headers exactly as they are in Ogg would match what's done for vorbis,
> theora, and flac.

Well, Vorbis, Theora and FLAC are codecs that originated from Xiph and
were usually delivered in Ogg encapsulation. It's different with OPUS
if I understood that correctly -- it doesn't originate from the Xiph
organisation. What I don't like is having a comment header in
CodecPrivate as it circumvents Matroska's tagging system.

> More than eight channels doesn't have a defined ordering and should be
> treated like channel mapping 255.

Agreed.

Kind regards,
mo



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