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Optimized ResampleAudio, with special cases for 1 and 2 channels

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This would also benefit from some SIMD, since it's just a bunch of multiply-adds
This commit is contained in:
Brick 2023-08-23 18:31:15 +01:00 • committed by Ryan C. Gordon
parent fba6e1e3d3
commit b74ee86b1d
1 changed files with 62 additions and 15 deletions
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77
src/audio/SDL_audiocvt.c
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@ -82,12 +82,66 @@ static int GetHistoryBufferSampleFrames(const int required_resampler_frames)
#define RESAMPLER_FILTER_INTERP_BITS (32 - RESAMPLER_BITS_PER_ZERO_CROSSING)
#define RESAMPLER_FILTER_INTERP_RANGE (1 << RESAMPLER_FILTER_INTERP_BITS)
#define RESAMPLER_SAMPLES_PER_FRAME (RESAMPLER_ZERO_CROSSINGS * 2)
// TODO: Add SIMD-accelerated versions
static void ResampleFrame(const float* src, float* dst, const float* filter, const int chans)
{
int i, chan;
if (chans == 2) {
float v0 = 0.0f;
float v1 = 0.0f;
for (i = 0; i < RESAMPLER_SAMPLES_PER_FRAME; i++) {
const float scale = filter[i];
v0 += src[i * 2 + 0] * scale;
v1 += src[i * 2 + 1] * scale;
}
dst[0] = v0;
dst[1] = v1;
return;
}
if (chans == 1) {
float v0 = 0.0f;
for (i = 0; i < RESAMPLER_SAMPLES_PER_FRAME; i++) {
v0 += src[i] * filter[i];
}
dst[0] = v0;
return;
}
// Try and give the compiler a hint about how many channels there are
if (chans < 1 || chans > 8) {
SDL_assert(!"Invalid channel count");
return;
}
// Calculate the result in-place
for (chan = 0; chan < chans; ++chan) {
dst[chan] = 0.0f;
}
for (i = 0; i < RESAMPLER_SAMPLES_PER_FRAME; i++) {
const float* inputs = &src[i * chans];
const float scale = filter[i];
for (chan = 0; chan < chans; chan++) {
dst[chan] += inputs[chan] * scale;
}
}
}
static void ResampleAudio(const int chans, const float *inbuf, const int inframes, float *outbuf, const int outframes,
const Sint64 resample_rate, Sint64* resample_offset)
{
SDL_assert(resample_rate > 0);
float *dst = outbuf;
int i, j, chan;
int i, j;
Sint64 srcpos = *resample_offset;
@ -103,29 +157,22 @@ static void ResampleAudio(const int chans, const float *inbuf, const int inframe
const float interpolation1 = (float)(srcfraction & (RESAMPLER_FILTER_INTERP_RANGE - 1)) * (1.0f / RESAMPLER_FILTER_INTERP_RANGE);
const float interpolation2 = 1.0f - interpolation1;
for (chan = 0; chan < chans; ++chan) {
dst[chan] = 0.0f;
}
float filter[RESAMPLER_SAMPLES_PER_FRAME];
for (j = 0; j < RESAMPLER_ZERO_CROSSINGS; j++) {
const int filt_ind1 = filterindex + j;
const int filt_ind1 = filterindex + (RESAMPLER_ZERO_CROSSINGS - 1) - j;
const int filt_ind2 = (RESAMPLER_FILTER_SIZE - 1) - filt_ind1;
const float scale1 = (ResamplerFilter[filt_ind1] * interpolation2) + (ResamplerFilter[filt_ind1 + RESAMPLER_ZERO_CROSSINGS] * interpolation1);
const float scale2 = (ResamplerFilter[filt_ind2] * interpolation1) + (ResamplerFilter[filt_ind2 + RESAMPLER_ZERO_CROSSINGS] * interpolation2);
const int srcframe1 = srcindex - j;
const int srcframe2 = srcframe1 + RESAMPLER_ZERO_CROSSINGS;
const float* inputs1 = &inbuf[srcframe1 * chans];
const float* inputs2 = &inbuf[srcframe2 * chans];
for (chan = 0; chan < chans; chan++) {
dst[chan] += (inputs1[chan] * scale1) + (inputs2[chan] * scale2);
}
filter[j] = scale1;
filter[j + RESAMPLER_ZERO_CROSSINGS] = scale2;
}
dst += chan;
const float* src = &inbuf[(srcindex - (RESAMPLER_ZERO_CROSSINGS - 1)) * chans];
ResampleFrame(src, dst, filter, chans);
dst += chans;
}
*resample_offset = srcpos - ((Sint64)inframes << 32);