Ambisonic Channel Formats
Audio files associated with ambisonics are multi-channel files. The channels can though be of any number.
To allow transfer of files (or data streams) from one user to another, or from one software application to another, it is essential that there is agreement as to which channel is which.
There are basically three types of ambisonic files (and from hereon ‘files’ will be used to include datastreams, patch cables, and all). A-format is raw data from an ambisonic microphone. B-format is ambisonic material suitable for archiving and for exchange between users. G-format is decoded ambisonics, or ‘speaker feeds’.
Usage of A and G format is intended to be local, and thus the need for standardisation is less. It does though still exist, as different software applications should be able to ‘talk to each other’ with minimal configuration.
The principal need for standardisation is for B-format. A de facto standard already exists for files of up to third-order (16 channels in periphony, seven in pan to phony). As any new file format ought to countenance files of any order, then a channel order standard must do the same.
The present document proposes a standard for B-format and discusses approaches that are possible for the other two formats.