It's not available as an AL buffer format (yet) since I'm not sure how to
expose it. Internally it seems fine as a separate channel configuration, but
because OpenAL combines the channel configuration and sample type, a flag may
work better there.
a.k.a. Stereo Enhance. A common feature of UHJ decoders to take a plain
stereo signal and generate a B-Format signal with variable width control,
widening (or narrowing) the soundfield while maintaining a sharp central
image.
Classic B-Format uses scaling factors W=1, X=sqrt(2), Y=sqrt(2), and Z=sqrt(2),
which is +3dB louder than FuMa. The base factors are designed assuming classic
scaling, so encoding a 0dBFS FuMa signal without accounting for this would
result in the UHJ signal peaking at about -3dBFS. Similarly, decoding UHJ to
FuMa B-Format would be +3dB louder than intended.
So encoding needs to implicitly boost the signal by +3dB, and decoding needs to
attenuate by -3dB.
For real this time. The non-all-passed signal needs a one-sample delay over the
all-passed signal. Because of the way the all-pass FIR filter is structured,
it wouldn't otherwise use the last buffered sample, allowing it to be shifted
forward in time by one sample.
Also, remove a couple unnecessary buffers.
Chris Robinson