From e13c6bca207d5a7659fca03a9576bcab6ea7728e Mon Sep 17 00:00:00 2001 From: Chris Robinson Date: Wed, 17 Aug 2016 05:34:09 -0700 Subject: Only use the cube points for generating the ambisonic HRTF coefficients Using all the HRIRs seems to have problems with volume balancing, due in part to HRTF data sets not having uniform enough measurements for a simple decoder matrix to work (and generating a proper one that would work better is not that easy). This still maintains the benefits of decoding ambisonics directly to HRTF, namely that it only needs to filter the 4 ambisonic channels and can use more optimized HRTF filtering methods on those channels. It can also be improved further with frequency-dependent processing baked into the generated coefficients, incurring no extra run-time cost for it. --- Alc/hrtf.c | 128 ++++++++++++++++++++++++++++++++++--------------------------- 1 file changed, 72 insertions(+), 56 deletions(-) (limited to 'Alc') diff --git a/Alc/hrtf.c b/Alc/hrtf.c index ed99554c..46d814d9 100644 --- a/Alc/hrtf.c +++ b/Alc/hrtf.c @@ -174,76 +174,92 @@ void GetLerpedHrtfCoeffs(const struct Hrtf *Hrtf, ALfloat elevation, ALfloat azi ALuint BuildBFormatHrtf(const struct Hrtf *Hrtf, ALfloat (*coeffs)[HRIR_LENGTH][2], ALuint NumChannels) { - ALuint total_hrirs = 0; + static const struct { + ALfloat elevation; + ALfloat azimuth; + } CubePoints[8] = { + { DEG2RAD( 35.0f), DEG2RAD( -45.0f) }, + { DEG2RAD( 35.0f), DEG2RAD( 45.0f) }, + { DEG2RAD( 35.0f), DEG2RAD(-135.0f) }, + { DEG2RAD( 35.0f), DEG2RAD( 135.0f) }, + { DEG2RAD(-35.0f), DEG2RAD( -45.0f) }, + { DEG2RAD(-35.0f), DEG2RAD( 45.0f) }, + { DEG2RAD(-35.0f), DEG2RAD(-135.0f) }, + { DEG2RAD(-35.0f), DEG2RAD( 135.0f) }, + }; + static const ALfloat CubeMatrix[8][MAX_AMBI_COEFFS] = { + { 0.25f, 0.14425f, 0.14425f, 0.14425f }, + { 0.25f, -0.14425f, 0.14425f, 0.14425f }, + { 0.25f, 0.14425f, 0.14425f, -0.14425f }, + { 0.25f, -0.14425f, 0.14425f, -0.14425f }, + { 0.25f, 0.14425f, -0.14425f, 0.14425f }, + { 0.25f, -0.14425f, -0.14425f, 0.14425f }, + { 0.25f, 0.14425f, -0.14425f, -0.14425f }, + { 0.25f, -0.14425f, -0.14425f, -0.14425f }, + }; + ALuint lidx[8], ridx[8]; + ALuint min_delay = HRTF_HISTORY_LENGTH; ALuint max_length = 0; - ALuint eidx, aidx, i, j; - ALfloat scale; + ALuint i, j, c; assert(NumChannels == 4); - for(eidx = 0;eidx < Hrtf->evCount;++eidx) + for(c = 0;c < 8;c++) { - const ALfloat elev = (ALfloat)eidx/(ALfloat)(Hrtf->evCount-1)*F_PI - F_PI_2; - const ALuint evoffset = Hrtf->evOffset[eidx]; - const ALuint azcount = Hrtf->azCount[eidx]; + ALuint evidx[2]; + ALuint evoffset; + ALuint azidx[2]; + ALuint azcount; + ALfloat mu; - for(aidx = 0;aidx < azcount;++aidx) - { - ALfloat ambcoeffs[4]; - const ALshort *fir; - ALuint length, delay; - ALuint lidx, ridx; - ALfloat x, y, z; - ALfloat azi; - - lidx = evoffset + aidx; - ridx = evoffset + ((azcount - aidx) % azcount); - - azi = (ALfloat)aidx/(ALfloat)azcount * -F_TAU; - x = cosf(azi) * cosf(elev); - y = sinf(azi) * cosf(elev); - z = sinf(elev); - - ambcoeffs[0] = 1.0f; - ambcoeffs[1] = y / 1.732050808f; - ambcoeffs[2] = z / 1.732050808f; - ambcoeffs[3] = x / 1.732050808f; - - /* Apply left ear response */ - delay = Hrtf->delays[lidx]; - fir = &Hrtf->coeffs[lidx * Hrtf->irSize]; - length = minu(delay + Hrtf->irSize, HRIR_LENGTH); - for(i = 0;i < NumChannels;++i) - { - for(j = delay;j < length;++j) - coeffs[i][j][0] += fir[j-delay]/32767.0f * ambcoeffs[i]; - } - max_length = maxu(max_length, length); + /* Calculate elevation index. */ + CalcEvIndices(Hrtf->evCount, CubePoints[c].elevation, evidx, &mu); + if(mu >= 0.5f) evidx[0] = evidx[1]; - /* Apply right ear response */ - delay = Hrtf->delays[ridx]; - fir = &Hrtf->coeffs[ridx * Hrtf->irSize]; - length = minu(delay + Hrtf->irSize, HRIR_LENGTH); - for(i = 0;i < NumChannels;++i) - { - for(j = delay;j < length;++j) - coeffs[i][j][1] += fir[j-delay]/32767.0f * ambcoeffs[i]; - } - max_length = maxu(max_length, length); + azcount = Hrtf->azCount[evidx[0]]; + evoffset = Hrtf->evOffset[evidx[0]]; - total_hrirs++; - } + /* Calculate azimuth index for this elevation. */ + CalcAzIndices(azcount, CubePoints[c].azimuth, azidx, &mu); + if(mu >= 0.5f) azidx[0] = azidx[1]; + + /* Calculate indices for left and right channels. */ + lidx[c] = evoffset + azidx[0]; + ridx[c] = evoffset + ((azcount-azidx[0]) % azcount); + + min_delay = minu(min_delay, minu(Hrtf->delays[lidx[c]], Hrtf->delays[ridx[c]])); } - scale = (ALfloat)total_hrirs; - for(i = 0;i < NumChannels;++i) + for(c = 0;c < 8;c++) { - for(j = 0;j < max_length;++j) + const ALshort *fir; + ALuint length; + ALuint delay; + + fir = &Hrtf->coeffs[lidx[c] * Hrtf->irSize]; + delay = Hrtf->delays[lidx[c]] - min_delay; + length = minu(delay + Hrtf->irSize, HRIR_LENGTH); + for(i = 0;i < NumChannels;++i) + { + ALuint k = 0; + for(j = delay;j < length;++j) + coeffs[i][j][0] += fir[k++]/32767.0f * CubeMatrix[c][i]; + } + max_length = maxu(max_length, length); + + fir = &Hrtf->coeffs[ridx[c] * Hrtf->irSize]; + delay = Hrtf->delays[ridx[c]] - min_delay; + length = minu(delay + Hrtf->irSize, HRIR_LENGTH); + for(i = 0;i < NumChannels;++i) { - coeffs[i][j][0] /= scale; - coeffs[i][j][1] /= scale; + ALuint k = 0; + for(j = delay;j < length;++j) + coeffs[i][j][1] += fir[k++]/32767.0f * CubeMatrix[c][i]; } + max_length = maxu(max_length, length); } + TRACE("Skipped min delay: %u, new combined length: %u\n", min_delay, max_length); + return max_length; } -- cgit v1.2.3