Opus: add support for Ambisonic mixing matrices
Add support for libopus >=1.3.0 projection decoder & mixing matrices. Opus Ambisonic channel_mapping == 3 being now default for opusenc < 16 channels.
samples/A-codecs/Opus/Ambisonic/Z0e0ea5cfcbcb96d34283.opus
Edited by François Cartegnie