Ambisonic G-format Channel Ordering
Ambisonic decoders produce ‘speaker feeds’. Typically these are for local use (to be fed to a sound card). Even so, a standard order will minimise user configuration.
G-format files can also be made and distributed. This breaks the prime utility of ambisonics: an ambisonic file can be decoded to any speaker array. It has thought to be accepted that, at the moment, providing pre-decoded files suitable for simple (e.g. square, cube) arrays will appeal to some users.
The WAVE specification has the following speaker channels:
LF |
RF |
F |
'LFE' |
LB |
RB |
LoCF |
RoCF |
B |
L |
R |
U |
ULF |
UFC |
URF |
ULB |
UB |
URB |
Which (if one takes ‘LF’ to mean ‘DLF’, etc., where necessary …) would allow for square and cube rigs. It would also allow for bi-rectangular(?). It also allows for an octagon, and if one agreed which two feeds to ‘drop’ out of an octagon would allow for a hexagon.
Whilst not ideal, it is perhaps sufficient for what anyway ought to be a marginal use, for file interchange.
For speaker feeds for higher order arrays a standard is desirable, and probably ought to match any standard for higher order microphones (the problem of placing three dimensional positions in a linear order is after all the same).
It is intended to release the final standard under an appropriate licence (that allows use and copying, but which prohibits changes (that would confuse the result with the original) and requires attribution).For the moment these pages are copyright © 2008 Michael Chapman. All rights reserved.
