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

[Curt Sampson]

On Sun, 24 Aug 2003, smoerk wrote:

> there are different channel profiles for 5.1:
> L R C LFE Ls Rs (DVD)
> L R Ls Rs C LFE
> L C R Ls Rs LFE (Film)

I don't see why you need more than one of the above formats. It's not
like you can't decide to put the LFE channel into "input 3" or "input 5"
or whatever set of inputs your sending it to, depending on how that set
of inputs is configured.

> then we have ambisonics where we have 1st, 2nd and 3rd order (4, 9 and
> 16 channels), but then you can also have 2 dimensional ambisonics
> without heigt signal, which gives another 3 options, plus different UHJ
> encoded variants, etc.

Well, we already have the problem of being able to encode only a very
limited number of independent tracks in this field, too. Currently
the limit is 8, which does me no good when I want to FLAC-encode a
multi-track "master" from my studio, which can easily be 48 tracks or
more.

One option would be to add a code for "get 16 bit number of tracks from
end of header." (Don't laugh at 16 bits; I've got friends who have
produced pieces with more than 256 tracks.)

Given that, you might well just be able to add another code for
"ambisonic, get 8-bit number of tracks from end of header," and then use
the number of tracks to figure out the format.

    1	W		(kinda dumb way of doing monaural)
    2	UHJ		(stereo-compatable)
    3	WXY 		(first order without height)
    4	WXYZ		(first order with height)
    5	WXYUV		(second order without height)
    6	WXYUVW'		(second order without height, mixed 1st/2nd order data)
    9	WXYZRSTUV	(second order with height)
    10	WXYZRSTUVW'	(second order with height, mixed 1st/2nd order data)
    16	WXYZRSTUVKLMNOPQ (third order with height)

(There can be no third order without height, since the
coefficents of all of the third order equations have a height
component. Note that I am just blindly using the equations from
http://www.york.ac.uk/inst/mustech/3d_audio/secondor.html; one would
want to check this with someone really in the know before standardizing
on it.)

Or one might want to tweak it to have every channel always in the same
"slot," which is currently broken by the 2, 6 and 10 channel formats.

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