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Invert the inner ResampleAudio loops to avoid doing unnecessary work

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Brick
2023-08-21 13:23:38 +01:00
committed by Ryan C. Gordon
parent 88123a5109
commit 72d9d53def
1 changed files with 24 additions and 25 deletions
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45
src/audio/SDL_audiocvt.c
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@@ -91,35 +91,34 @@ static void ResampleAudio(const int chans, const float *lpadding, const float *r
SDL_assert(srcindex >= -1);
SDL_assert(srcindex < inframes);
const float interpolation1 = (float)srcfraction * 0x1p-32f;
const int filterindex1 = (int)(srcfraction >> (32 - RESAMPLER_BITS_PER_ZERO_CROSSING)) * RESAMPLER_ZERO_CROSSINGS;
const int filterindex = (int)(srcfraction >> (32 - RESAMPLER_BITS_PER_ZERO_CROSSING)) * RESAMPLER_ZERO_CROSSINGS;
const float interpolation1 = (float)srcfraction * 0x1p-32f;
const float interpolation2 = 1.0f - interpolation1;
const int filterindex2 = RESAMPLER_FILTER_SIZE - RESAMPLER_ZERO_CROSSINGS - filterindex1;
for (chan = 0; chan < chans; ++chan) {
dst[chan] = 0.0f;
}
for (j = 0; j < RESAMPLER_ZERO_CROSSINGS; j++) {
const int filt_ind1 = filterindex + j;
const int filt_ind2 = RESAMPLER_FILTER_SIZE - 1 - filt_ind1;
const float scale1 = ResamplerFilter[filt_ind1] + (interpolation1 * ResamplerFilterDifference[filt_ind1]);
const float scale2 = ResamplerFilter[filt_ind2] + (interpolation2 * ResamplerFilterDifference[filt_ind2]);
const int srcframe1 = srcindex - j;
const int srcframe2 = srcframe1 + RESAMPLER_ZERO_CROSSINGS;
const float* inputs1 = (srcframe1 < 0) ? &lpadding[(paddinglen + srcframe1) * chans] : &inbuf[srcframe1 * chans];
const float* inputs2 = (srcframe2 >= inframes) ? &rpadding[(srcframe2 - inframes) * chans] : &inbuf[srcframe2 * chans];
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; j < RESAMPLER_ZERO_CROSSINGS; j++) {
const int filt_ind = filterindex1 + j;
const int srcframe = srcindex - j;
/* !!! FIXME: we can bubble this conditional out of here by doing a pre loop. */
const float insample = (srcframe < 0) ? lpadding[((paddinglen + srcframe) * chans) + chan] : inbuf[(srcframe * chans) + chan];
outsample += (float) (insample * (ResamplerFilter[filt_ind] + (interpolation1 * ResamplerFilterDifference[filt_ind])));
dst[chan] += (inputs1[chan] * scale1) + (inputs2[chan] * scale2);
}
}
// Do the right wing!
for (j = 0; j < RESAMPLER_ZERO_CROSSINGS; j++) {
const int filt_ind = filterindex2 + j;
const int srcframe = srcindex + 1 + j;
// !!! FIXME: we can bubble this conditional out of here by doing a post loop.
const float insample = (srcframe >= inframes) ? rpadding[((srcframe - inframes) * chans) + chan] : inbuf[(srcframe * chans) + chan];
outsample += (float) (insample * (ResamplerFilter[filt_ind] + (interpolation2 * ResamplerFilterDifference[filt_ind])));
}
*(dst++) = outsample;
}
dst += chan;
}
*resample_offset = srcpos - ((Sint64)inframes << 32);