[Vorbis-dev] Mapping = 1 Ambisonic Vorbis flag

Oliver Oli oliver.oli+0815 at gmail.com
Fri Sep 12 11:49:01 PDT 2008

On Fri, Sep 12, 2008 at 7:24 PM, Richard Furse
<rf015d9821 at blueyonder.co.uk> wrote:
> Are we saying that something like the excellent OggPCM stuff would be
> difficult to implement in Vorbis? This does seem a shame...
> That aside, the suggestion below is nicely simple and directly
> backwards-compatible, give or take the unusual ordering for the mixed/full
> channel cases and the extensions to higher order.

we can use any other ordering, it's just a continuation of the
sequence Gerzon started with W XYZ.

> Some possible tweaks:
> Furse/Malham encoding is only defined to third order, and at higher order I
> guess it isn't going to be the standard as it makes more sense to redefine
> in a general way from the spherical harmonics - using the FuMa components
> here for the lower orders only is entirely possible but ugly. The problem
> with redefining now is that we'd lose direct backwards-compatibility and
> we'd need to herd the cats long enough to agree which formulation and
> normalisation to use; I think this will scare some folk and I'm probably
> going to regret mentioning it ;-)

Better break it now, than later.

I don't have much clue about HOA. What are the specific problems in
defining a higher order standard? Is there more than defining ordering
and weightings? Sorry if that is a dumb question, I started
understanding higher order Ambisonics a little bit, when I started
rotating 3d models of spherical harmonics on my computer... I have no
idea how the math works.

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