[ogg-dev] Ambisonics in Ogg Vorbis

[Martin Leese]

On 2/28/07, Ivo Emanuel Gonçalves <justivo at gmail.com> wrote:

> On 2/28/07, Ralph Giles <giles at xiph.org> wrote:
> > Well, there are todo pages at wiki.xiph.org, but I meant more in the
> > community folklore sense. My point is a roadmap doesn't help much unless
> > there are people committed to making things happen. That's been the
> > problem with a lot of this stuff, and why it's been so nice to see the
> > ambisonics work happening.
>
> The situation on Ambisonics is tricky, because it depends on someone
> coding a whole API for the different Xiph projects AND Monty being
> available to apply whatever changes are need in Vorbis.

I have been giving some thought to how to
include Ambisonics in Ogg Vorbis.  There is a
question at the end, so please plough on.

As I understand it, all that is needed is some
machine parseable metadata to identify the
audio data as being Ambsionics.  The channel
coupling wont be optimal and the phase may
get a bit munged (Ambisonics is big on
low-frequency phase), but it will work.  And the
missing bits can then be worked on in Ghost
at peoples' leisure.

Now, Vorbis comments aren't intended for
machine parseable metadata, so the metadata
will need to go in the Ogg container as a
separate (chained) stream.  This scheme will
not only work for Ogg Vorbis, but for Ogg
<anything>.  There currently isn't a standard
for a metadata stream to go into Ogg, but
there is a draft standard at:
http://wiki.xiph.org/index.php/Metadata

According to this draft standard, all I need to
do is to invent some XML which includes the
required information, and we are away.

Now for the question; how much did I get wrong?

Many thanks,
Martin
-- 
Martin J Leese
E-mail: martin.leese at stanfordalumni.org
Web: http://members.tripod.com/martin_leese/