diff options
Diffstat (limited to 'Alc/hrtf.c')
| -rw-r--r-- | Alc/hrtf.c | 102 |
1 files changed, 82 insertions, 20 deletions
@@ -39,34 +39,96 @@ static struct HRTF { #include "hrtf_tables.inc" }; -static ALuint CalcEvIndex(ALdouble ev) +// Calculate the elevation indices given the polar elevation in radians. +// This will return two indices between 0 and (evCount - 1) and an +// interpolation factor between 0.0 and 1.0. +static void CalcEvIndices (ALfloat ev, ALuint evidx [2], ALfloat * evmu) { - ev = (M_PI/2.0 + ev) * (evCount-1) / M_PI; - return (ALuint)(ev+0.5); + ev = (M_PI/2.0f + ev) * (evCount-1) / M_PI; + evidx[0] = (ALuint)ev; + evidx[1] = __min(evidx[0] + 1, evCount - 1); + *evmu = ev - evidx[0]; } -static ALuint CalcAzIndex(ALint evidx, ALdouble az) +// Calculate the azimuth indices given the polar azimuth in radians. This +// will return two indices between 0 and (azCount [ei] - 1) and an +// interpolation factor between 0.0 and 1.0. +static void CalcAzIndices (ALuint evidx, ALfloat az, ALuint azidx [2], ALfloat * azmu) { - az = (M_PI*2.0 + az) * azCount[evidx] / (M_PI*2.0); - return (ALuint)(az+0.5) % azCount[evidx]; + az = (M_PI*2.0f + az) * azCount[evidx] / (M_PI*2.0f); + azidx[0] = (ALuint)az % azCount[evidx]; + azidx[1] = (azidx[0] + 1) % azCount[evidx]; + *azmu = az - (ALuint)az; } -void GetHrtfCoeffs(ALfloat elevation, ALfloat angle, const ALshort **left, const ALshort **right, ALuint *ldelay, ALuint *rdelay) +// Calculates static HRIR coefficients and delays for the given polar +// elevation and azimuth in radians. Linear interpolation is used to +// increase the apparent resolution of the HRIR dataset. The coefficients +// are also normalized and attenuated by the specified gain. +void GetLerpedHrtfCoeffs(ALfloat elevation, ALfloat azimuth, ALfloat gain, ALfloat (*coeffs)[2], ALuint *delays) { - ALuint lidx, ridx; - ALuint evidx, azidx; - - evidx = CalcEvIndex(elevation); - azidx = CalcAzIndex(evidx, angle); - - lidx = evOffset[evidx] + azidx; - ridx = evOffset[evidx] + ((azCount[evidx]-azidx) % azCount[evidx]); - - *ldelay = Hrtf.delays[lidx]; - *rdelay = Hrtf.delays[ridx]; + ALuint evidx[2], azidx[2]; + ALfloat mu[3]; + ALuint lidx[4], ridx[4]; + ALuint i; + + // Claculate elevation indices and interpolation factor. + CalcEvIndices(elevation, evidx, &mu[2]); + + // Calculate azimuth indices and interpolation factor for the first + // elevation. + CalcAzIndices(evidx[0], azimuth, azidx, &mu[0]); + + // Calculate the first set of linear HRIR indices for left and right + // channels. + lidx[0] = evOffset[evidx[0]] + azidx[0]; + lidx[1] = evOffset[evidx[0]] + azidx[1]; + ridx[0] = evOffset[evidx[0]] + ((azCount[evidx[0]]-azidx[0]) % azCount[evidx[0]]); + ridx[1] = evOffset[evidx[0]] + ((azCount[evidx[0]]-azidx[1]) % azCount[evidx[0]]); + + // Calculate azimuth indices and interpolation factor for the second + // elevation. + CalcAzIndices (evidx[1], azimuth, azidx, &mu[1]); + + // Calculate the second set of linear HRIR indices for left and right + // channels. + lidx[2] = evOffset[evidx[1]] + azidx[0]; + lidx[3] = evOffset[evidx[1]] + azidx[1]; + ridx[2] = evOffset[evidx[1]] + ((azCount[evidx[1]]-azidx[0]) % azCount[evidx[1]]); + ridx[3] = evOffset[evidx[1]] + ((azCount[evidx[1]]-azidx[1]) % azCount[evidx[1]]); + + // Calculate the normalized and attenuated HRIR coefficients using linear + // interpolation when there is enough gain to warrant it. Zero the + // coefficients if gain is too low. + if(gain > 0.0001f) + { + ALdouble scale = gain * (1.0/32767.0); + for(i = 0;i < HRIR_LENGTH;i++) + { + coeffs[i][0] = lerp(lerp(Hrtf.coeffs[lidx[0]][i], Hrtf.coeffs[lidx[1]][i], mu[0]), + lerp(Hrtf.coeffs[lidx[2]][i], Hrtf.coeffs[lidx[3]][i], mu[1]), + mu[2]) * scale; + coeffs[i][1] = lerp(lerp(Hrtf.coeffs[ridx[0]][i], Hrtf.coeffs[ridx[1]][i], mu[0]), + lerp(Hrtf.coeffs[ridx[2]][i], Hrtf.coeffs[ridx[3]][i], mu[1]), + mu[2]) * scale; + } + } + else + { + for(i = 0;i < HRIR_LENGTH;i++) + { + coeffs[i][0] = 0.0f; + coeffs[i][1] = 0.0f; + } + } - *left = Hrtf.coeffs[lidx]; - *right = Hrtf.coeffs[ridx]; + // Calculate the HRIR delays using linear interpolation. + delays[0] = (ALuint)(lerp(lerp(Hrtf.delays[lidx[0]], Hrtf.delays[lidx[1]], mu[0]), + lerp(Hrtf.delays[lidx[2]], Hrtf.delays[lidx[3]], mu[1]), + mu[2]) + 0.5f); + delays[1] = (ALuint)(lerp(lerp(Hrtf.delays[ridx[0]], Hrtf.delays[ridx[1]], mu[0]), + lerp(Hrtf.delays[ridx[2]], Hrtf.delays[ridx[3]], mu[1]), + mu[2]) + 0.5f); } ALCboolean IsHrtfCompatible(ALCdevice *device) |