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

[smoerk]

Curt Sampson wrote:
> 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.

i agree, but then flac needs a parameter to map the channels when 
converting from wav to flac or flac to wav.

example:

i'm working on a dvd production and my 5.1 files are L-R-C-LFE-Ls-Rs and 
FLAC's format is L-C-R-Ls-Rs-LFE. when encoding and decoding FLAC have 
to change the channel order of the file.

but then we still have the possibility to use not all channels. think of

L-C-R
L-C-R-LFE
L-R-Ls-Rs
L-C-R-Surround
L-R-Surround
and more

this is only for 5.1.

i still think we need a more flexible approach than only defining 16 
different channel mappings.


>>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.

FLAC can only encode 8 tracks? Why?

> 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.)

only 5.1 encoded ambisonics is missing, i think it's called g-format. 
but i can ask in the sursound mailing list, if this options are sufficient.