The reverts both fa9ab9af7cb559ff9ecc1846f2996265bfbea1ec and
79604c3c0e0f3f71832a09348cc273a38882cc3e. As helpful as it was for the high
frequencies, the overall response's gain suffered.
Currently makehrtf only handles 24-bit output, not dual-ear, and only when
given the --experimental switch. Files produced this way will not be guaranteed
future compatibility. When the mhr format is also updated with multi-distance
measurements, the experimental switch can go away.
Some data sets are just too sparse, having noticeably few measurements to
properly handle slowly panning sources. Although not perfect, bilinearly
interpolating the HRIR measurements improves the positional accuracy.
This will make it easier to handle HRTF data sets that have separate left and
right ear responses. Will need an mhr version update to take advantage of that.
This improves fading between HRIRs as sources pan around. In particular, it
improves the issue with individual coefficients having various rounding errors
in the stepping values, as well as issues with interpolating delay values.
It does this by doing two mixing passes for each source. First using the last
coefficients that fade to silence, and then again using the new coefficients
that fade from silence. When added together, it creates a linear fade from one
to the other. Additionally, the gain is applied separately so the individual
coefficients don't step with rounding errors. Although this does increase CPU
cost since it's doing two mixes per source, each mix is a bit cheaper now since
the stepping is simplified to a single gain value, and the overall quality is
improved.
Unsigned 32-bit offsets actually have some potential overhead on 64-bit targets
for pointer/array accesses due to rules on integer wrapping. No idea how much
impact it has in practice, but it's nice to be correct about it.
This should improve positional quality for relatively low cost. Full HRTF
rendering still only uses first-order since the only use of the dry buffer
there is for first-order content (B-Format buffers, effects).
It's hard to tell which is ultimately better, although this way does make the
FOA output somewhat louder which will help when it's combined with direct HRTF
rendering.
