Commit dad07f960b59caa413d84acedea2e17668cf09de
2017-01-23T16:45:50
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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diff --git a/src/audio/SDL_audiocvt.c b/src/audio/SDL_audiocvt.c
index 1787917..09ea91b 100644
--- a/src/audio/SDL_audiocvt.c
+++ b/src/audio/SDL_audiocvt.c
@@ -249,49 +249,115 @@ SDL_ResampleAudioSimple(const int chans, const double rate_incr,
SDL_assert((dest_samples * framelen) <= outbuflen);
SDL_assert((inbuflen % framelen) == 0);
- if (rate_incr > 1.0) {
+ if (rate_incr > 1.0) { /* upsample */
float *target = (outbuf + chans);
- const float *earlier_sample = &inbuf[finalpos];
- float final_sample[8];
dst = outbuf + (dest_samples * chans);
idx = (double) total;
- /* save this off so we can correctly maintain state between runs. */
- SDL_memcpy(final_sample, &inbuf[finalpos], framelen);
-
- while (dst > target) {
- const int pos = ((int) idx) * chans;
- const float *src = &inbuf[pos];
- SDL_assert(pos >= 0.0);
- for (i = chans - 1; i >= 0; i--) {
+ if (chans == 1) {
+ const float final_sample = inbuf[finalpos];
+ float earlier_sample = inbuf[finalpos];
+ while (dst > target) {
+ const int pos = ((int) idx) * chans;
+ const float *src = &inbuf[pos];
const float val = *(--src);
- *(--dst) = (val + earlier_sample[i]) * 0.5f;
+ SDL_assert(pos >= 0.0);
+ *(--dst) = (val + earlier_sample) * 0.5f;
+ earlier_sample = val;
+ idx -= src_incr;
}
- earlier_sample = src;
- idx -= src_incr;
+ /* do last sample, interpolated against previous run's state. */
+ *(--dst) = (inbuf[0] + last_sample[0]) * 0.5f;
+ *last_sample = final_sample;
+ } else if (chans == 2) {
+ const float final_sample2 = inbuf[finalpos+1];
+ const float final_sample1 = inbuf[finalpos];
+ float earlier_sample2 = inbuf[finalpos];
+ float earlier_sample1 = inbuf[finalpos-1];
+ while (dst > target) {
+ const int pos = ((int) idx) * chans;
+ const float *src = &inbuf[pos];
+ const float val2 = *(--src);
+ const float val1 = *(--src);
+ SDL_assert(pos >= 0.0);
+ *(--dst) = (val2 + earlier_sample2) * 0.5f;
+ *(--dst) = (val1 + earlier_sample1) * 0.5f;
+ earlier_sample2 = val2;
+ earlier_sample1 = val1;
+ idx -= src_incr;
+ }
+ /* do last sample, interpolated against previous run's state. */
+ *(--dst) = (inbuf[1] + last_sample[1]) * 0.5f;
+ *(--dst) = (inbuf[0] + last_sample[0]) * 0.5f;
+ last_sample[1] = final_sample2;
+ last_sample[0] = final_sample1;
+ } else {
+ const float *earlier_sample = &inbuf[finalpos];
+ float final_sample[8];
+ SDL_memcpy(final_sample, &inbuf[finalpos], framelen);
+ while (dst > target) {
+ const int pos = ((int) idx) * chans;
+ const float *src = &inbuf[pos];
+ SDL_assert(pos >= 0.0);
+ for (i = chans - 1; i >= 0; i--) {
+ const float val = *(--src);
+ *(--dst) = (val + earlier_sample[i]) * 0.5f;
+ }
+ earlier_sample = src;
+ idx -= src_incr;
+ }
+ /* do last sample, interpolated against previous run's state. */
+ for (i = chans - 1; i >= 0; i--) {
+ const float val = inbuf[i];
+ *(--dst) = (val + last_sample[i]) * 0.5f;
+ }
+ SDL_memcpy(last_sample, final_sample, framelen);
}
- /* do last sample, interpolated against previous run's state. */
- for (i = chans - 1; i >= 0; i--) {
- const float val = inbuf[i];
- *(--dst) = (val + last_sample[i]) * 0.5f;
- }
- SDL_memcpy(last_sample, final_sample, framelen);
dst = (outbuf + (dest_samples * chans)) - 1;
- } else {
+ } else { /* downsample */
float *target = (outbuf + (dest_samples * chans));
dst = outbuf;
idx = 0.0;
- while (dst < target) {
- const int pos = ((int) idx) * chans;
- const float *src = &inbuf[pos];
- SDL_assert(pos <= finalpos);
- for (i = 0; i < chans; i++) {
- const float val = *(src++);
- *(dst++) = (val + last_sample[i]) * 0.5f;
- last_sample[i] = val;
+ if (chans == 1) {
+ float last = *last_sample;
+ while (dst < target) {
+ const int pos = ((int) idx) * chans;
+ const float val = inbuf[pos];
+ SDL_assert(pos <= finalpos);
+ *(dst++) = (val + last) * 0.5f;
+ last = val;
+ idx += src_incr;
+ }
+ *last_sample = last;
+ } else if (chans == 2) {
+ float last1 = last_sample[0];
+ float last2 = last_sample[1];
+ while (dst < target) {
+ const int pos = ((int) idx) * chans;
+ const float val1 = inbuf[pos];
+ const float val2 = inbuf[pos+1];
+ SDL_assert(pos <= finalpos);
+ *(dst++) = (val1 + last1) * 0.5f;
+ *(dst++) = (val2 + last2) * 0.5f;
+ last1 = val1;
+ last2 = val2;
+ idx += src_incr;
+ }
+ last_sample[0] = last1;
+ last_sample[1] = last2;
+ } else {
+ while (dst < target) {
+ const int pos = ((int) idx) * chans;
+ const float *src = &inbuf[pos];
+ SDL_assert(pos <= finalpos);
+ for (i = 0; i < chans; i++) {
+ const float val = *(src++);
+ *(dst++) = (val + last_sample[i]) * 0.5f;
+ last_sample[i] = val;
+ }
+ idx += src_incr;
}
- idx += src_incr;
}
}