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). any idea how to implement it?
On Sat, 23 Aug 2003, Josh Coalson wrote:> --- smoerk <smoerk@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@cynic.net> +81 90 7737 2974 http://www.NetBSD.org Don't you know, in this new Dark Age, we're all light. --XTC
--- smoerk <smoerk@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. Josh __________________________________ Do you Yahoo!? Yahoo! SiteBuilder - Free, easy-to-use web site design software http://sitebuilder.yahoo.com
Josh Coalson wrote:> --- smoerk <smoerk@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 would write a proposal for this, but i don't think 4 bit is enough for all the different surround formats. for example in a ac3 encoder i can define any combination of left-right, center, surround and LFE channels. http://www.soundonsound.com/sos/nov01/images/surroundfig1dolbyblobs.l.gif 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) 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. how can we squeeze this in 4 bits?