This unfortunately doesn't fix the %z warnings for whatever reason, but it
should help guarantee correct function behavior by not relying on msvcrt's
stdio functions.
Be aware this requires proper header data (a WAVE_FORMAT_EXTENSIBLE format with
the proper integer or float B-Format sub-format GUID). A normal 4-channel wave
file will not be recognized, since it's indistinguishable from quadrophonic.
This can almost certainly be improved further, as less than half of the indices
really need their reversed bit-pattern calculated and elements swapped (any
symetrical bit pattern would just swap with itself, and indices whose reversed
bit-pattern has already been traversed is already swapped).
It may also prove beneficial to provide the base-2 log of the fft buffer size
(number of bits to represent the indices), as that could help make the reversal
more efficient with a known bit/loop count.
This avoids an inherent delay from the effect, at the cost of higher CPU use.
Having a customizable user-specified delay (with said user ensuring a properly
trimmed impulse response) could help alleviate the cost since once the delay
exceeds the segment size, the initial FIR filter could be skipped.
Rather than creating an effect-specific buffer that gets passed along as a
property, the buffer is set the effect state when the effect state is created,
the device is updated, or the buffer is changed. The buffer can only be set
while the effect slot isn't playing, so it won't be changed or updated while
the mixer is processing the effect state.
A newly-created effect slot is in an AL_INITIAL state, in which processing is
stopped but will automatically become AL_PLAYING after successfully setting an
AL_EFFECTSLOT_EFFECT value (including AL_EFFECT_NULL or 0). Calling Play[v] or
Stop[v] will set the effect slot to AL_PLAYING or AL_STOPPED respectively.
While stopped, the effect won't produce audio and will not be processed.
Chris Robinson