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-rw-r--r--Alc/hrtf.cpp85
1 files changed, 60 insertions, 25 deletions
diff --git a/Alc/hrtf.cpp b/Alc/hrtf.cpp
index 96d5ec43..b6b5ce43 100644
--- a/Alc/hrtf.cpp
+++ b/Alc/hrtf.cpp
@@ -75,10 +75,12 @@ using namespace std::placeholders;
using HrtfHandlePtr = std::unique_ptr<HrtfHandle>;
-/* Current data set limits defined by the makehrtf utility. */
+/* Data set limits must be the same as or more flexible than those defined in
+ * the makehrtf utility.
+ */
#define MIN_IR_SIZE (8)
#define MAX_IR_SIZE (512)
-#define MOD_IR_SIZE (8)
+#define MOD_IR_SIZE (2)
#define MIN_FD_COUNT (1)
#define MAX_FD_COUNT (16)
@@ -300,9 +302,9 @@ void BuildBFormatHrtf(const HrtfEntry *Hrtf, DirectHrtfState *state, const ALsiz
static constexpr int OrderFromChan[MAX_AMBI_COEFFS]{
0, 1,1,1, 2,2,2,2,2, 3,3,3,3,3,3,3,
};
- /* Set this to true for dual-band HRTF processing. May require a higher
- * quality filter, or better calculation of the new IR length to deal with
- * the tail generated by the filter.
+ /* Set this to true for dual-band HRTF processing. May require better
+ * calculation of the new IR length to deal with the head and tail
+ * generated by the HF scaling.
*/
static constexpr bool DualBand{true};
@@ -315,7 +317,7 @@ void BuildBFormatHrtf(const HrtfEntry *Hrtf, DirectHrtfState *state, const ALsiz
std::bind(std::mem_fn(&HrtfEntry::Field::evCount), _2)))};
ALsizei min_delay{HRTF_HISTORY_LENGTH};
ALsizei max_delay{0};
- al::vector<ALsizei> idx(AmbiCount);
+ auto idx = al::vector<ALsizei>(AmbiCount);
auto calc_idxs = [Hrtf,ebase,&field,&max_delay,&min_delay](const AngularPoint &pt) noexcept -> ALsizei
{
/* Calculate elevation index. */
@@ -339,17 +341,23 @@ void BuildBFormatHrtf(const HrtfEntry *Hrtf, DirectHrtfState *state, const ALsiz
};
std::transform(AmbiPoints, AmbiPoints+AmbiCount, idx.begin(), calc_idxs);
+ /* For dual-band processing, add a 12-sample delay to compensate for the HF
+ * scale on the minimum-phase response.
+ */
+ static constexpr ALsizei base_delay{DualBand ? 12 : 0};
const ALdouble xover_norm{400.0 / Hrtf->sampleRate};
BandSplitterR<double> splitter;
+ SplitterAllpassR<double> allpass;
splitter.init(xover_norm);
+ allpass.init(xover_norm);
auto tmpres = al::vector<HrirArray<ALdouble>>(NumChannels);
- auto tmpfilt = al::vector<std::array<ALdouble,HRIR_LENGTH>>(3);
+ auto tmpfilt = al::vector<std::array<ALdouble,HRIR_LENGTH*4>>(3);
for(ALsizei c{0};c < AmbiCount;++c)
{
const ALfloat (*fir)[2]{&Hrtf->coeffs[idx[c] * Hrtf->irSize]};
- const ALsizei ldelay{Hrtf->delays[idx[c]][0] - min_delay};
- const ALsizei rdelay{Hrtf->delays[idx[c]][1] - min_delay};
+ const ALsizei ldelay{Hrtf->delays[idx[c]][0] - min_delay + base_delay};
+ const ALsizei rdelay{Hrtf->delays[idx[c]][1] - min_delay + base_delay};
if(!DualBand)
{
@@ -369,35 +377,62 @@ void BuildBFormatHrtf(const HrtfEntry *Hrtf, DirectHrtfState *state, const ALsiz
continue;
}
- /* Split the left HRIR into low and high frequency bands. */
- auto tmpfilt_iter = std::transform(fir, fir+Hrtf->irSize, tmpfilt[2].begin(),
- [](const ALfloat (&ir)[2]) noexcept { return ir[0]; });
- std::fill(tmpfilt_iter, tmpfilt[2].end(), 0.0);
+ /* For dual-band processing, the HRIR needs to be split into low and
+ * high frequency responses. The band-splitter alone creates frequency-
+ * dependent phase-shifts, which is not ideal. To counteract it,
+ * combine it with a backwards phase-shift.
+ */
+
+ /* Load the (left) HRIR backwards, into a temp buffer with padding. */
+ std::fill(tmpfilt[2].begin(), tmpfilt[2].end(), 0.0);
+ std::transform(fir, fir+Hrtf->irSize, tmpfilt[2].rbegin() + HRIR_LENGTH*3,
+ [](const ALfloat (&ir)[2]) noexcept -> ALdouble { return ir[0]; });
+
+ /* Apply the all-pass on the reversed signal and reverse the resulting
+ * sample array. This produces the forward response with a backwards
+ * phase-shift (+n degrees becomes -n degrees).
+ */
+ allpass.clear();
+ allpass.process(tmpfilt[2].data(), tmpfilt[2].size());
+ std::reverse(tmpfilt[2].begin(), tmpfilt[2].end());
+
+ /* Now apply the band-splitter. This applies the normal phase-shift,
+ * which cancels out with the backwards phase-shift to get the original
+ * phase on the split signal.
+ */
splitter.clear();
- splitter.process(tmpfilt[0].data(), tmpfilt[1].data(), tmpfilt[2].data(), HRIR_LENGTH);
+ splitter.process(tmpfilt[0].data(), tmpfilt[1].data(), tmpfilt[2].data(),
+ tmpfilt[2].size());
/* Apply left ear response with delay and HF scale. */
for(ALsizei i{0};i < NumChannels;++i)
{
const ALdouble mult{AmbiMatrix[c][i]};
const ALdouble hfgain{AmbiOrderHFGain[OrderFromChan[i]]};
- for(ALsizei lidx{ldelay},j{0};lidx < HRIR_LENGTH;++lidx,++j)
+ ALsizei j{HRIR_LENGTH*3 - ldelay};
+ for(ALsizei lidx{0};lidx < HRIR_LENGTH;++lidx,++j)
tmpres[i][lidx][0] += (tmpfilt[0][j]*hfgain + tmpfilt[1][j]) * mult;
}
- /* Split the right HRIR into low and high frequency bands. */
- tmpfilt_iter = std::transform(fir, fir+Hrtf->irSize, tmpfilt[2].begin(),
- [](const ALfloat (&ir)[2]) noexcept { return ir[1]; });
- std::fill(tmpfilt_iter, tmpfilt[2].end(), 0.0);
+ /* Now run the same process on the right HRIR. */
+ std::fill(tmpfilt[2].begin(), tmpfilt[2].end(), 0.0);
+ std::transform(fir, fir+Hrtf->irSize, tmpfilt[2].rbegin() + HRIR_LENGTH*3,
+ [](const ALfloat (&ir)[2]) noexcept -> ALdouble { return ir[1]; });
+
+ allpass.clear();
+ allpass.process(tmpfilt[2].data(), tmpfilt[2].size());
+ std::reverse(tmpfilt[2].begin(), tmpfilt[2].end());
+
splitter.clear();
- splitter.process(tmpfilt[0].data(), tmpfilt[1].data(), tmpfilt[2].data(), HRIR_LENGTH);
+ splitter.process(tmpfilt[0].data(), tmpfilt[1].data(), tmpfilt[2].data(),
+ tmpfilt[2].size());
- /* Apply right ear response with delay and HF scale. */
for(ALsizei i{0};i < NumChannels;++i)
{
const ALdouble mult{AmbiMatrix[c][i]};
const ALdouble hfgain{AmbiOrderHFGain[OrderFromChan[i]]};
- for(ALsizei ridx{rdelay},j{0};ridx < HRIR_LENGTH;++ridx,++j)
+ ALsizei j{HRIR_LENGTH*3 - rdelay};
+ for(ALsizei ridx{0};ridx < HRIR_LENGTH;++ridx,++j)
tmpres[i][ridx][1] += (tmpfilt[0][j]*hfgain + tmpfilt[1][j]) * mult;
}
}
@@ -414,10 +449,10 @@ void BuildBFormatHrtf(const HrtfEntry *Hrtf, DirectHrtfState *state, const ALsiz
tmpres.clear();
ALsizei max_length{HRIR_LENGTH};
- /* Increase the IR size by 2/3rds with dual-band processing to account for
- * the tail generated by the filter.
+ /* Increase the IR size by 24 samples with dual-band processing to account
+ * for the head and tail from the HF response scale.
*/
- const ALsizei irsize{DualBand ? mini(Hrtf->irSize*5/3, max_length) : Hrtf->irSize};
+ const ALsizei irsize{DualBand ? mini(Hrtf->irSize + base_delay*2, max_length) : Hrtf->irSize};
max_length = mini(max_delay-min_delay + irsize, max_length);
/* Round up to the next IR size multiple. */
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-01 03:57:35 +0000