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audiocvt: 5.1 to Stereo conversion utilizing SSE

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Joel Linn 2021-06-10 17:22:39 +02:00 committed by Ryan C. Gordon
parent db56526f14
commit 638befc1a9
1 changed files with 77 additions and 1 deletions
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78
src/audio/SDL_audiocvt.c
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@ -35,6 +35,10 @@
#define DEBUG_AUDIOSTREAM 0
#ifdef __SSE__
#define HAVE_SSE_INTRINSICS 1
#endif
#ifdef __SSE3__
#define HAVE_SSE3_INTRINSICS 1
#endif
@ -97,6 +101,66 @@ SDL_ConvertStereoToMono(SDL_AudioCVT * cvt, SDL_AudioFormat format)
}
#if HAVE_SSE_INTRINSICS
/* Convert from 5.1 to stereo. Average left and right, distribute center, discard LFE. */
static void SDLCALL
SDL_Convert51ToStereo_SSE(SDL_AudioCVT * cvt, SDL_AudioFormat format)
{
float *dst = (float *) cvt->buf;
const float *src = dst;
int i = cvt->len_cvt / (sizeof (float) * 6);
const float two_fifths_f = 1.0f / 2.5f;
const __m128 two_fifths_v = _mm_set1_ps(two_fifths_f);
const __m128 half = _mm_set1_ps(0.5f);
LOG_DEBUG_CONVERT("5.1", "stereo (using SSE)");
SDL_assert(format == AUDIO_F32SYS);
/* SDL's 5.1 layout: FL+FR+FC+LFE+BL+BR */
/* Just use unaligned load/stores, if the memory at runtime is */
/* aligned it'll be just as fast on modern processors */
while (i >= 2) {
/* Two 5.1 samples (12 floats) fit nicely in three 128bit */
/* registers. Using shuffles they can be rearranged so that */
/* the conversion math can be vectorized. */
__m128 in0 = _mm_loadu_ps(src); /* 0FL 0FR 0FC 0LF */
__m128 in1 = _mm_loadu_ps(src + 4); /* 0BL 0BR 1FL 1FR */
__m128 in2 = _mm_loadu_ps(src + 8); /* 1FC 1LF 1BL 1BR */
/* 0FC 0FC 1FC 1FC */
__m128 fc_distributed = _mm_mul_ps(half, _mm_shuffle_ps(in0, in2, _MM_SHUFFLE(0, 0, 2, 2)));
/* 0FL 0FR 1BL 1BR */
__m128 blended = _mm_shuffle_ps(in0, in2, _MM_SHUFFLE(3, 2, 1, 0));
/* 0FL 0FR 1BL 1BR */
/* + 0BL 0BR 1FL 1FR */
/* = 0L 0R 1L 1R */
__m128 out = _mm_add_ps(blended, in1);
out = _mm_add_ps(out, fc_distributed);
out = _mm_mul_ps(out, two_fifths_v);
_mm_storeu_ps(dst, out);
i -= 2; src += 12; dst += 4;
}
/* Finish off any leftovers with scalar operations. */
while (i) {
const float front_center_distributed = src[2] * 0.5f;
dst[0] = (src[0] + front_center_distributed + src[4]) * two_fifths_f; /* left */
dst[1] = (src[1] + front_center_distributed + src[5]) * two_fifths_f; /* right */
i--; src += 6; dst+=2;
}
cvt->len_cvt /= 3;
if (cvt->filters[++cvt->filter_index]) {
cvt->filters[cvt->filter_index] (cvt, format);
}
}
#endif
/* Convert from 5.1 to stereo. Average left and right, distribute center, discard LFE. */
static void SDLCALL
SDL_Convert51ToStereo(SDL_AudioCVT * cvt, SDL_AudioFormat format)
@ -1020,7 +1084,19 @@ SDL_BuildAudioCVT(SDL_AudioCVT * cvt,
}
/* [7.1 ->] 5.1 -> Stereo [-> Mono] */
if ((src_channels == 6) && (dst_channels <= 2)) {
if (SDL_AddAudioCVTFilter(cvt, SDL_Convert51ToStereo) < 0) {
SDL_AudioFilter filter = NULL;
#if HAVE_SSE_INTRINSICS
if (SDL_HasSSE()) {
filter = SDL_Convert51ToStereo_SSE;
}
#endif
if (!filter) {
filter = SDL_Convert51ToStereo;
}
if (SDL_AddAudioCVTFilter(cvt, filter) < 0) {
return -1;
}
src_channels = 2;