[Flac-dev] 2/0, 2/2 3/0, 3/2, 5.1, wxyz

[Curt Sampson]

On Sat, 23 Aug 2003, Josh Coalson wrote:

> --- smoerk <smoerk at gmx.de> wrote:
> > i didn't find anything about tagging flac files as surround files. i
> > think there should some possibility to tell the player how to play a
> > multi-channel file (how to map the different channels to the speakers
> > or if there some decode is needed, like for ambisonic files).
>
> it wouldn't be in the tags, it would be a specific channel
> assignment in the frame header:
>
> http://flac.sourceforge.net/format.html#frame_header
>
> there are currently none defined for >2 channels but there could be.

I've done a bit more research into what ambisonic is.

I'm not certain that this would be a good idea, but the four-channel
B-format ambisonic signal certainly maps very well to the channel
assignment header. The mid-side format is in fact the W and Y channels
of an ambisonic B-format recording; the additional X and Z channels are
just difference channels for the two other planes. In other words

    W	- omni-directional soundfield
    X	- difference of front/back
    Y	- difference of left/right
    Z	- difference of top/bottom

These are the first-order components of a sound field. The second order
components add five more channels, R, S, T, U and V, and can be seen
(along with the first order components) here:

    http://members.tripod.com/martin_leese/Ambisonic/harmonic.html

cjs
-- 
Curt Sampson  <cjs at cynic.net>   +81 90 7737 2974   http://www.NetBSD.org
    Don't you know, in this new Dark Age, we're all light.  --XTC