admin/SDL
1
0 Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

audiocvt: Replace divisions

Browse Source 
Division is expensive and the compiler can not replace it themselves.
Though we now we will be ok in terms of floating point edge behaviour.
This commit is contained in:
Joel Linn authored and Ryan C. Gordon committed 2021-07-24 15:39:17 -04:00
1 parent e1c3a25034
commit db56526f14
1 file changed
+15 -12
Download Patch File Download Diff File Expand all files Collapse all files
src/audio/SDL_audiocvt.c
+15 -12
View File
@@ -104,6 +104,7 @@ SDL_Convert51ToStereo(SDL_AudioCVT * cvt, SDL_AudioFormat format)
float *dst = (float *) cvt->buf;
const float *src = dst;
int i;
const float two_fifths = 1.0f / 2.5f;
LOG_DEBUG_CONVERT("5.1", "stereo");
SDL_assert(format == AUDIO_F32SYS);
@@ -111,8 +112,8 @@ SDL_Convert51ToStereo(SDL_AudioCVT * cvt, SDL_AudioFormat format)
/* SDL's 5.1 layout: FL+FR+FC+LFE+BL+BR */
for (i = cvt->len_cvt / (sizeof (float) * 6); i; --i, src += 6, dst += 2) {
const float front_center_distributed = src[2] * 0.5f;
dst[0] = (src[0] + front_center_distributed + src[4]) / 2.5f; /* left */
dst[1] = (src[1] + front_center_distributed + src[5]) / 2.5f; /* right */
dst[0] = (src[0] + front_center_distributed + src[4]) * two_fifths; /* left */
dst[1] = (src[1] + front_center_distributed + src[5]) * two_fifths; /* right */
}
cvt->len_cvt /= 3;
@@ -152,6 +153,7 @@ SDL_Convert71To51(SDL_AudioCVT * cvt, SDL_AudioFormat format)
float *dst = (float *) cvt->buf;
const float *src = dst;
int i;
const float two_thirds = 1.0f / 1.5f;
LOG_DEBUG_CONVERT("7.1", "5.1");
SDL_assert(format == AUDIO_F32SYS);
@@ -159,12 +161,12 @@ SDL_Convert71To51(SDL_AudioCVT * cvt, SDL_AudioFormat format)
for (i = cvt->len_cvt / (sizeof (float) * 8); i; --i, src += 8, dst += 6) {
const float surround_left_distributed = src[6] * 0.5f;
const float surround_right_distributed = src[7] * 0.5f;
dst[0] = (src[0] + surround_left_distributed) / 1.5f; /* FL */
dst[1] = (src[1] + surround_right_distributed) / 1.5f; /* FR */
dst[2] = src[2] / 1.5f; /* CC */
dst[3] = src[3] / 1.5f; /* LFE */
dst[4] = (src[4] + surround_left_distributed) / 1.5f; /* BL */
dst[5] = (src[5] + surround_right_distributed) / 1.5f; /* BR */
dst[0] = (src[0] + surround_left_distributed) * two_thirds; /* FL */
dst[1] = (src[1] + surround_right_distributed) * two_thirds; /* FR */
dst[2] = src[2] * two_thirds; /* CC */
dst[3] = src[3] * two_thirds; /* LFE */
dst[4] = (src[4] + surround_left_distributed) * two_thirds; /* BL */
dst[5] = (src[5] + surround_right_distributed) * two_thirds; /* BR */
}
cvt->len_cvt /= 8;
@@ -182,6 +184,7 @@ SDL_Convert51ToQuad(SDL_AudioCVT * cvt, SDL_AudioFormat format)
float *dst = (float *) cvt->buf;
const float *src = dst;
int i;
const float two_thirds = 1.0f / 1.5f;
LOG_DEBUG_CONVERT("5.1", "quad");
SDL_assert(format == AUDIO_F32SYS);
@@ -190,10 +193,10 @@ SDL_Convert51ToQuad(SDL_AudioCVT * cvt, SDL_AudioFormat format)
/* SDL's 5.1 layout: FL+FR+FC+LFE+BL+BR */
for (i = cvt->len_cvt / (sizeof (float) * 6); i; --i, src += 6, dst += 4) {
const float front_center_distributed = src[2] * 0.5f;
dst[0] = (src[0] + front_center_distributed) / 1.5f; /* FL */
dst[1] = (src[1] + front_center_distributed) / 1.5f; /* FR */
dst[2] = src[4] / 1.5f; /* BL */
dst[3] = src[5] / 1.5f; /* BR */
dst[0] = (src[0] + front_center_distributed) * two_thirds; /* FL */
dst[1] = (src[1] + front_center_distributed) * two_thirds; /* FR */
dst[2] = src[4] * two_thirds; /* BL */
dst[3] = src[5] * two_thirds; /* BR */
}
cvt->len_cvt /= 6;