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https://github.com/Relintai/sdl2_frt.git
synced 2024-12-20 22:16:49 +01:00
audio: Resampler now special-cases stereo and mono processing.
Turns out that iterating from 0 to channels-1 was a serious performance hit! These cases now tend to match or beat the original audio resampler's speed!
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@ -249,49 +249,115 @@ SDL_ResampleAudioSimple(const int chans, const double rate_incr,
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SDL_assert((dest_samples * framelen) <= outbuflen);
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SDL_assert((inbuflen % framelen) == 0);
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if (rate_incr > 1.0) {
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if (rate_incr > 1.0) { /* upsample */
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float *target = (outbuf + chans);
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const float *earlier_sample = &inbuf[finalpos];
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float final_sample[8];
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dst = outbuf + (dest_samples * chans);
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idx = (double) total;
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/* save this off so we can correctly maintain state between runs. */
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SDL_memcpy(final_sample, &inbuf[finalpos], framelen);
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while (dst > target) {
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const int pos = ((int) idx) * chans;
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const float *src = &inbuf[pos];
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SDL_assert(pos >= 0.0);
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for (i = chans - 1; i >= 0; i--) {
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if (chans == 1) {
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const float final_sample = inbuf[finalpos];
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float earlier_sample = inbuf[finalpos];
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while (dst > target) {
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const int pos = ((int) idx) * chans;
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const float *src = &inbuf[pos];
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const float val = *(--src);
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*(--dst) = (val + earlier_sample[i]) * 0.5f;
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SDL_assert(pos >= 0.0);
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*(--dst) = (val + earlier_sample) * 0.5f;
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earlier_sample = val;
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idx -= src_incr;
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}
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earlier_sample = src;
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idx -= src_incr;
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/* do last sample, interpolated against previous run's state. */
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*(--dst) = (inbuf[0] + last_sample[0]) * 0.5f;
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*last_sample = final_sample;
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} else if (chans == 2) {
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const float final_sample2 = inbuf[finalpos+1];
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const float final_sample1 = inbuf[finalpos];
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float earlier_sample2 = inbuf[finalpos];
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float earlier_sample1 = inbuf[finalpos-1];
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while (dst > target) {
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const int pos = ((int) idx) * chans;
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const float *src = &inbuf[pos];
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const float val2 = *(--src);
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const float val1 = *(--src);
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SDL_assert(pos >= 0.0);
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*(--dst) = (val2 + earlier_sample2) * 0.5f;
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*(--dst) = (val1 + earlier_sample1) * 0.5f;
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earlier_sample2 = val2;
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earlier_sample1 = val1;
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idx -= src_incr;
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}
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/* do last sample, interpolated against previous run's state. */
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*(--dst) = (inbuf[1] + last_sample[1]) * 0.5f;
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*(--dst) = (inbuf[0] + last_sample[0]) * 0.5f;
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last_sample[1] = final_sample2;
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last_sample[0] = final_sample1;
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} else {
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const float *earlier_sample = &inbuf[finalpos];
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float final_sample[8];
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SDL_memcpy(final_sample, &inbuf[finalpos], framelen);
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while (dst > target) {
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const int pos = ((int) idx) * chans;
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const float *src = &inbuf[pos];
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SDL_assert(pos >= 0.0);
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for (i = chans - 1; i >= 0; i--) {
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const float val = *(--src);
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*(--dst) = (val + earlier_sample[i]) * 0.5f;
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}
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earlier_sample = src;
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idx -= src_incr;
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}
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/* do last sample, interpolated against previous run's state. */
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for (i = chans - 1; i >= 0; i--) {
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const float val = inbuf[i];
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*(--dst) = (val + last_sample[i]) * 0.5f;
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}
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SDL_memcpy(last_sample, final_sample, framelen);
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}
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/* do last sample, interpolated against previous run's state. */
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for (i = chans - 1; i >= 0; i--) {
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const float val = inbuf[i];
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*(--dst) = (val + last_sample[i]) * 0.5f;
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}
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SDL_memcpy(last_sample, final_sample, framelen);
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dst = (outbuf + (dest_samples * chans)) - 1;
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} else {
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} else { /* downsample */
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float *target = (outbuf + (dest_samples * chans));
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dst = outbuf;
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idx = 0.0;
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while (dst < target) {
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const int pos = ((int) idx) * chans;
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const float *src = &inbuf[pos];
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SDL_assert(pos <= finalpos);
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for (i = 0; i < chans; i++) {
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const float val = *(src++);
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*(dst++) = (val + last_sample[i]) * 0.5f;
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last_sample[i] = val;
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if (chans == 1) {
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float last = *last_sample;
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while (dst < target) {
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const int pos = ((int) idx) * chans;
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const float val = inbuf[pos];
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SDL_assert(pos <= finalpos);
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*(dst++) = (val + last) * 0.5f;
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last = val;
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idx += src_incr;
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}
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*last_sample = last;
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} else if (chans == 2) {
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float last1 = last_sample[0];
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float last2 = last_sample[1];
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while (dst < target) {
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const int pos = ((int) idx) * chans;
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const float val1 = inbuf[pos];
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const float val2 = inbuf[pos+1];
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SDL_assert(pos <= finalpos);
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*(dst++) = (val1 + last1) * 0.5f;
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*(dst++) = (val2 + last2) * 0.5f;
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last1 = val1;
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last2 = val2;
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idx += src_incr;
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}
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last_sample[0] = last1;
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last_sample[1] = last2;
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} else {
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while (dst < target) {
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const int pos = ((int) idx) * chans;
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const float *src = &inbuf[pos];
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SDL_assert(pos <= finalpos);
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for (i = 0; i < chans; i++) {
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const float val = *(src++);
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*(dst++) = (val + last_sample[i]) * 0.5f;
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last_sample[i] = val;
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}
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idx += src_incr;
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}
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idx += src_incr;
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}
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}
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