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Improved ResampleAudio

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* filterindex2 was off-by-one
* Generate ResamplerFilter using doubles
* Transpose ResamplerFilter to improve access patterns
This commit is contained in:
Brick
2023-08-19 20:12:40 +01:00
committed by Ryan C. Gordon
parent cdaa19869d
commit b9541b9eab
4 changed files with 1065 additions and 1066 deletions
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2057
src/audio/SDL_audio_resampler_filter.h
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12
src/audio/SDL_audiocvt.c
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@@ -95,16 +95,16 @@ static void ResampleAudio(const int chans, const int inrate, const int outrate,
* = mod(i * inrate, outrate) / outrate */
const int srcfraction = (int)(srcpos % outrate);
const float interpolation1 = ((float)srcfraction) / ((float)outrate);
const int filterindex1 = ((Sint32)srcfraction) * RESAMPLER_SAMPLES_PER_ZERO_CROSSING / outrate;
const int filterindex1 = (((Sint32)srcfraction) * RESAMPLER_SAMPLES_PER_ZERO_CROSSING / outrate) * RESAMPLER_ZERO_CROSSINGS;
const float interpolation2 = 1.0f - interpolation1;
const int filterindex2 = ((Sint32)(outrate - srcfraction)) * RESAMPLER_SAMPLES_PER_ZERO_CROSSING / outrate;
const int filterindex2 = RESAMPLER_FILTER_SIZE - filterindex1 - RESAMPLER_ZERO_CROSSINGS;
for (chan = 0; chan < chans; chan++) {
float outsample = 0.0f;
// do this twice to calculate the sample, once for the "left wing" and then same for the right.
for (j = 0; (filterindex1 + (j * RESAMPLER_SAMPLES_PER_ZERO_CROSSING)) < RESAMPLER_FILTER_SIZE; j++) {
const int filt_ind = filterindex1 + j * RESAMPLER_SAMPLES_PER_ZERO_CROSSING;
for (j = 0; j < RESAMPLER_ZERO_CROSSINGS; j++) {
const int filt_ind = j + filterindex1;
const int srcframe = srcindex - j;
SDL_assert(paddinglen + srcframe >= 0);
/* !!! FIXME: we can bubble this conditional out of here by doing a pre loop. */
@@ -113,8 +113,8 @@ static void ResampleAudio(const int chans, const int inrate, const int outrate,
}
// Do the right wing!
for (j = 0; (filterindex2 + (j * RESAMPLER_SAMPLES_PER_ZERO_CROSSING)) < RESAMPLER_FILTER_SIZE; j++) {
const int filt_ind = filterindex2 + j * RESAMPLER_SAMPLES_PER_ZERO_CROSSING;
for (j = 0; j < RESAMPLER_ZERO_CROSSINGS; j++) {
const int filt_ind = j + filterindex2;
const int srcframe = srcindex + 1 + j;
SDL_assert(srcframe - inframes < paddinglen);
// !!! FIXME: we can bubble this conditional out of here by doing a post loop.