diff options
Diffstat (limited to 'Alc/ALu.c')
| -rw-r--r-- | Alc/ALu.c | 74 |
1 files changed, 74 insertions, 0 deletions
@@ -173,6 +173,78 @@ static inline aluVector aluMatrixVector(const aluMatrix *mtx, const aluVector *v } +/* Prepares the interpolator for a given rate (determined by increment). A + * result of AL_FALSE indicates that the filter output will completely cut + * the input signal. + * + * With a bit of work, and a trade of memory for CPU cost, this could be + * modified for use with an interpolated increment for buttery-smooth pitch + * changes. + */ +static ALboolean BsincPrepare(const ALuint increment, BsincState *state) +{ + static const ALfloat scaleBase = 0.1510579f, scaleRange = 1.177937f; + static const ALuint m[BSINC_SCALE_COUNT] = { 24, 24, 24, 24, 24, 24, 24, 20, 20, 20, 16, 16, 16, 12, 12, 12 }; + static const ALuint to[4][BSINC_SCALE_COUNT] = { + { 0, 24, 408, 792, 1176, 1560, 1944, 2328, 2648, 2968, 3288, 3544, 3800, 4056, 4248, 4440 }, + { 4632, 5016, 5400, 5784, 6168, 6552, 6936, 7320, 7640, 7960, 8280, 8536, 8792, 9048, 9240, 0 }, + { 0, 9432, 9816, 10200, 10584, 10968, 11352, 11736, 12056, 12376, 12696, 12952, 13208, 13464, 13656, 13848 }, + { 14040, 14424, 14808, 15192, 15576, 15960, 16344, 16728, 17048, 17368, 17688, 17944, 18200, 18456, 18648, 0 } + }; + static const ALuint tm[2][BSINC_SCALE_COUNT] = { + { 0, 24, 24, 24, 24, 24, 24, 20, 20, 20, 16, 16, 16, 12, 12, 12 }, + { 24, 24, 24, 24, 24, 24, 24, 20, 20, 20, 16, 16, 16, 12, 12, 0 } + }; + ALfloat sf; + ALuint si, pi; + ALboolean uncut = AL_TRUE; + + if(increment > FRACTIONONE) + { + sf = (ALfloat)FRACTIONONE / increment; + if(sf < scaleBase) + { + /* Signal has been completely cut. The return result can be used + * to skip the filter (and output zeros) as an optimization. + */ + sf = 0.0f; + si = 0; + uncut = AL_FALSE; + } + else + { + sf = (BSINC_SCALE_COUNT - 1) * (sf - scaleBase) * scaleRange; + si = fastf2u(sf); + /* The interpolation factor is fit to this diagonally-symmetric + * curve to reduce the transition ripple caused by interpolating + * different scales of the sinc function. + */ + sf = 1.0f - cosf(asinf(sf - si)); + } + } + else + { + sf = 0.0f; + si = BSINC_SCALE_COUNT - 1; + } + + state->sf = sf; + state->m = m[si]; + state->l = -(ALint)((m[si] / 2) - 1); + /* The CPU cost of this table re-mapping could be traded for the memory + * cost of a complete table map (1024 elements large). + */ + for(pi = 0;pi < BSINC_PHASE_COUNT;pi++) + { + state->coeffs[pi].filter = &bsincTab[to[0][si] + tm[0][si]*pi]; + state->coeffs[pi].scDelta = &bsincTab[to[1][si] + tm[1][si]*pi]; + state->coeffs[pi].phDelta = &bsincTab[to[2][si] + tm[0][si]*pi]; + state->coeffs[pi].spDelta = &bsincTab[to[3][si] + tm[1][si]*pi]; + } + return uncut; +} + + /* Calculates the fade time from the changes in gain and listener to source * angle between updates. The result is a the time, in seconds, for the * transition to complete. @@ -413,6 +485,7 @@ ALvoid CalcNonAttnSourceParams(ALvoice *voice, const ALsource *ALSource, const A voice->Step = MAX_PITCH<<FRACTIONBITS; else voice->Step = maxi(fastf2i(Pitch*FRACTIONONE + 0.5f), 1); + BsincPrepare(voice->Step, &voice->SincState); Channels = ALBuffer->FmtChannels; break; @@ -1023,6 +1096,7 @@ ALvoid CalcSourceParams(ALvoice *voice, const ALsource *ALSource, const ALCconte voice->Step = MAX_PITCH<<FRACTIONBITS; else voice->Step = maxi(fastf2i(Pitch*FRACTIONONE + 0.5f), 1); + BsincPrepare(voice->Step, &voice->SincState); break; } |