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audio: Converting audio samples from int to float was using wrong equ…
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…ation.

Fixes Bugzilla #3775.
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@icculus
icculus committed Aug 29, 2017
1 parent 1067b52 commit a0cd7d6
Showing 1 changed file with 37 additions and 37 deletions.
74 changes: 37 additions & 37 deletions src/audio/SDL_audiotypecvt.c
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Expand Up @@ -60,9 +60,9 @@ SDL_AudioFilter SDL_Convert_F32_to_U16 = NULL;
SDL_AudioFilter SDL_Convert_F32_to_S32 = NULL;


#define DIVBY127 0.0078740157480315f
#define DIVBY32767 3.05185094759972e-05f
#define DIVBY2147483647 4.6566128752458e-10f
#define DIVBY128 0.0078125f
#define DIVBY32768 0.000030517578125f
#define DIVBY2147483648 0.00000000046566128730773926


#if NEED_SCALAR_CONVERTER_FALLBACKS
Expand All @@ -76,7 +76,7 @@ SDL_Convert_S8_to_F32_Scalar(SDL_AudioCVT *cvt, SDL_AudioFormat format)
LOG_DEBUG_CONVERT("AUDIO_S8", "AUDIO_F32");

for (i = cvt->len_cvt; i; --i, --src, --dst) {
*dst = (((float) *src) * DIVBY127);
*dst = ((float) *src) * DIVBY128;
}

cvt->len_cvt *= 4;
Expand All @@ -95,7 +95,7 @@ SDL_Convert_U8_to_F32_Scalar(SDL_AudioCVT *cvt, SDL_AudioFormat format)
LOG_DEBUG_CONVERT("AUDIO_U8", "AUDIO_F32");

for (i = cvt->len_cvt; i; --i, --src, --dst) {
*dst = ((((float) *src) * DIVBY127) - 1.0f);
*dst = (((float) *src) * DIVBY128) - 1.0f;
}

cvt->len_cvt *= 4;
Expand All @@ -114,7 +114,7 @@ SDL_Convert_S16_to_F32_Scalar(SDL_AudioCVT *cvt, SDL_AudioFormat format)
LOG_DEBUG_CONVERT("AUDIO_S16", "AUDIO_F32");

for (i = cvt->len_cvt / sizeof (Sint16); i; --i, --src, --dst) {
*dst = (((float) *src) * DIVBY32767);
*dst = ((float) *src) * DIVBY32768;
}

cvt->len_cvt *= 2;
Expand All @@ -133,7 +133,7 @@ SDL_Convert_U16_to_F32_Scalar(SDL_AudioCVT *cvt, SDL_AudioFormat format)
LOG_DEBUG_CONVERT("AUDIO_U16", "AUDIO_F32");

for (i = cvt->len_cvt / sizeof (Uint16); i; --i, --src, --dst) {
*dst = ((((float) *src) * DIVBY32767) - 1.0f);
*dst = (((float) *src) * DIVBY32768) - 1.0f;
}

cvt->len_cvt *= 2;
Expand All @@ -152,7 +152,7 @@ SDL_Convert_S32_to_F32_Scalar(SDL_AudioCVT *cvt, SDL_AudioFormat format)
LOG_DEBUG_CONVERT("AUDIO_S32", "AUDIO_F32");

for (i = cvt->len_cvt / sizeof (Sint32); i; --i, ++src, ++dst) {
*dst = (float) (((double) *src) * DIVBY2147483647);
*dst = (float) (((double) *src) * DIVBY2147483648);
}

if (cvt->filters[++cvt->filter_index]) {
Expand Down Expand Up @@ -268,7 +268,7 @@ SDL_Convert_S8_to_F32_SSE2(SDL_AudioCVT *cvt, SDL_AudioFormat format)

/* Get dst aligned to 16 bytes (since buffer is growing, we don't have to worry about overreading from src) */
for (i = cvt->len_cvt; i && (((size_t) (dst-15)) & 15); --i, --src, --dst) {
*dst = (((float) *src) * DIVBY127);
*dst = ((float) *src) * DIVBY128;
}

src -= 15; dst -= 15; /* adjust to read SSE blocks from the start. */
Expand All @@ -279,18 +279,18 @@ SDL_Convert_S8_to_F32_SSE2(SDL_AudioCVT *cvt, SDL_AudioFormat format)
/* Aligned! Do SSE blocks as long as we have 16 bytes available. */
const __m128i *mmsrc = (const __m128i *) src;
const __m128i zero = _mm_setzero_si128();
const __m128 divby127 = _mm_set1_ps(DIVBY127);
const __m128 divby128 = _mm_set1_ps(DIVBY128);
while (i >= 16) { /* 16 * 8-bit */
const __m128i bytes = _mm_load_si128(mmsrc); /* get 16 sint8 into an XMM register. */
/* treat as int16, shift left to clear every other sint16, then back right with sign-extend. Now sint16. */
const __m128i shorts1 = _mm_srai_epi16(_mm_slli_epi16(bytes, 8), 8);
/* right-shift-sign-extend gets us sint16 with the other set of values. */
const __m128i shorts2 = _mm_srai_epi16(bytes, 8);
/* unpack against zero to make these int32, shift to make them sign-extend, convert to float, multiply. Whew! */
const __m128 floats1 = _mm_mul_ps(_mm_cvtepi32_ps(_mm_srai_epi32(_mm_slli_epi32(_mm_unpacklo_epi16(shorts1, zero), 16), 16)), divby127);
const __m128 floats2 = _mm_mul_ps(_mm_cvtepi32_ps(_mm_srai_epi32(_mm_slli_epi32(_mm_unpacklo_epi16(shorts2, zero), 16), 16)), divby127);
const __m128 floats3 = _mm_mul_ps(_mm_cvtepi32_ps(_mm_srai_epi32(_mm_slli_epi32(_mm_unpackhi_epi16(shorts1, zero), 16), 16)), divby127);
const __m128 floats4 = _mm_mul_ps(_mm_cvtepi32_ps(_mm_srai_epi32(_mm_slli_epi32(_mm_unpackhi_epi16(shorts2, zero), 16), 16)), divby127);
const __m128 floats1 = _mm_mul_ps(_mm_cvtepi32_ps(_mm_srai_epi32(_mm_slli_epi32(_mm_unpacklo_epi16(shorts1, zero), 16), 16)), divby128);
const __m128 floats2 = _mm_mul_ps(_mm_cvtepi32_ps(_mm_srai_epi32(_mm_slli_epi32(_mm_unpacklo_epi16(shorts2, zero), 16), 16)), divby128);
const __m128 floats3 = _mm_mul_ps(_mm_cvtepi32_ps(_mm_srai_epi32(_mm_slli_epi32(_mm_unpackhi_epi16(shorts1, zero), 16), 16)), divby128);
const __m128 floats4 = _mm_mul_ps(_mm_cvtepi32_ps(_mm_srai_epi32(_mm_slli_epi32(_mm_unpackhi_epi16(shorts2, zero), 16), 16)), divby128);
/* Interleave back into correct order, store. */
_mm_store_ps(dst, _mm_unpacklo_ps(floats1, floats2));
_mm_store_ps(dst+4, _mm_unpackhi_ps(floats1, floats2));
Expand All @@ -306,7 +306,7 @@ SDL_Convert_S8_to_F32_SSE2(SDL_AudioCVT *cvt, SDL_AudioFormat format)

/* Finish off any leftovers with scalar operations. */
while (i) {
*dst = (((float) *src) * DIVBY127);
*dst = ((float) *src) * DIVBY128;
i--; src--; dst--;
}

Expand All @@ -327,7 +327,7 @@ SDL_Convert_U8_to_F32_SSE2(SDL_AudioCVT *cvt, SDL_AudioFormat format)

/* Get dst aligned to 16 bytes (since buffer is growing, we don't have to worry about overreading from src) */
for (i = cvt->len_cvt; i && (((size_t) (dst-15)) & 15); --i, --src, --dst) {
*dst = ((((float) *src) * DIVBY127) - 1.0f);
*dst = (((float) *src) * DIVBY128) - 1.0f;
}

src -= 15; dst -= 15; /* adjust to read SSE blocks from the start. */
Expand All @@ -338,7 +338,7 @@ SDL_Convert_U8_to_F32_SSE2(SDL_AudioCVT *cvt, SDL_AudioFormat format)
/* Aligned! Do SSE blocks as long as we have 16 bytes available. */
const __m128i *mmsrc = (const __m128i *) src;
const __m128i zero = _mm_setzero_si128();
const __m128 divby127 = _mm_set1_ps(DIVBY127);
const __m128 divby128 = _mm_set1_ps(DIVBY128);
const __m128 minus1 = _mm_set1_ps(-1.0f);
while (i >= 16) { /* 16 * 8-bit */
const __m128i bytes = _mm_load_si128(mmsrc); /* get 16 uint8 into an XMM register. */
Expand All @@ -348,10 +348,10 @@ SDL_Convert_U8_to_F32_SSE2(SDL_AudioCVT *cvt, SDL_AudioFormat format)
const __m128i shorts2 = _mm_srli_epi16(bytes, 8);
/* unpack against zero to make these int32, convert to float, multiply, add. Whew! */
/* Note that AVX2 can do floating point multiply+add in one instruction, fwiw. SSE2 cannot. */
const __m128 floats1 = _mm_add_ps(_mm_mul_ps(_mm_cvtepi32_ps(_mm_unpacklo_epi16(shorts1, zero)), divby127), minus1);
const __m128 floats2 = _mm_add_ps(_mm_mul_ps(_mm_cvtepi32_ps(_mm_unpacklo_epi16(shorts2, zero)), divby127), minus1);
const __m128 floats3 = _mm_add_ps(_mm_mul_ps(_mm_cvtepi32_ps(_mm_unpackhi_epi16(shorts1, zero)), divby127), minus1);
const __m128 floats4 = _mm_add_ps(_mm_mul_ps(_mm_cvtepi32_ps(_mm_unpackhi_epi16(shorts2, zero)), divby127), minus1);
const __m128 floats1 = _mm_add_ps(_mm_mul_ps(_mm_cvtepi32_ps(_mm_unpacklo_epi16(shorts1, zero)), divby128), minus1);
const __m128 floats2 = _mm_add_ps(_mm_mul_ps(_mm_cvtepi32_ps(_mm_unpacklo_epi16(shorts2, zero)), divby128), minus1);
const __m128 floats3 = _mm_add_ps(_mm_mul_ps(_mm_cvtepi32_ps(_mm_unpackhi_epi16(shorts1, zero)), divby128), minus1);
const __m128 floats4 = _mm_add_ps(_mm_mul_ps(_mm_cvtepi32_ps(_mm_unpackhi_epi16(shorts2, zero)), divby128), minus1);
/* Interleave back into correct order, store. */
_mm_store_ps(dst, _mm_unpacklo_ps(floats1, floats2));
_mm_store_ps(dst+4, _mm_unpackhi_ps(floats1, floats2));
Expand All @@ -367,7 +367,7 @@ SDL_Convert_U8_to_F32_SSE2(SDL_AudioCVT *cvt, SDL_AudioFormat format)

/* Finish off any leftovers with scalar operations. */
while (i) {
*dst = ((((float) *src) * DIVBY127) - 1.0f);
*dst = (((float) *src) * DIVBY128) - 1.0f;
i--; src--; dst--;
}

Expand All @@ -388,7 +388,7 @@ SDL_Convert_S16_to_F32_SSE2(SDL_AudioCVT *cvt, SDL_AudioFormat format)

/* Get dst aligned to 16 bytes (since buffer is growing, we don't have to worry about overreading from src) */
for (i = cvt->len_cvt / sizeof (Sint16); i && (((size_t) (dst-7)) & 15); --i, --src, --dst) {
*dst = (((float) *src) * DIVBY32767);
*dst = ((float) *src) * DIVBY32768;
}

src -= 7; dst -= 7; /* adjust to read SSE blocks from the start. */
Expand All @@ -397,16 +397,16 @@ SDL_Convert_S16_to_F32_SSE2(SDL_AudioCVT *cvt, SDL_AudioFormat format)
/* Make sure src is aligned too. */
if ((((size_t) src) & 15) == 0) {
/* Aligned! Do SSE blocks as long as we have 16 bytes available. */
const __m128 divby32767 = _mm_set1_ps(DIVBY32767);
const __m128 divby32768 = _mm_set1_ps(DIVBY32768);
while (i >= 8) { /* 8 * 16-bit */
const __m128i ints = _mm_load_si128((__m128i const *) src); /* get 8 sint16 into an XMM register. */
/* treat as int32, shift left to clear every other sint16, then back right with sign-extend. Now sint32. */
const __m128i a = _mm_srai_epi32(_mm_slli_epi32(ints, 16), 16);
/* right-shift-sign-extend gets us sint32 with the other set of values. */
const __m128i b = _mm_srai_epi32(ints, 16);
/* Interleave these back into the right order, convert to float, multiply, store. */
_mm_store_ps(dst, _mm_mul_ps(_mm_cvtepi32_ps(_mm_unpacklo_epi32(a, b)), divby32767));
_mm_store_ps(dst+4, _mm_mul_ps(_mm_cvtepi32_ps(_mm_unpackhi_epi32(a, b)), divby32767));
_mm_store_ps(dst, _mm_mul_ps(_mm_cvtepi32_ps(_mm_unpacklo_epi32(a, b)), divby32768));
_mm_store_ps(dst+4, _mm_mul_ps(_mm_cvtepi32_ps(_mm_unpackhi_epi32(a, b)), divby32768));
i -= 8; src -= 8; dst -= 8;
}
}
Expand All @@ -415,7 +415,7 @@ SDL_Convert_S16_to_F32_SSE2(SDL_AudioCVT *cvt, SDL_AudioFormat format)

/* Finish off any leftovers with scalar operations. */
while (i) {
*dst = (((float) *src) * DIVBY32767);
*dst = ((float) *src) * DIVBY32768;
i--; src--; dst--;
}

Expand All @@ -436,7 +436,7 @@ SDL_Convert_U16_to_F32_SSE2(SDL_AudioCVT *cvt, SDL_AudioFormat format)

/* Get dst aligned to 16 bytes (since buffer is growing, we don't have to worry about overreading from src) */
for (i = cvt->len_cvt / sizeof (Sint16); i && (((size_t) (dst-7)) & 15); --i, --src, --dst) {
*dst = ((((float) *src) * DIVBY32767) - 1.0f);
*dst = (((float) *src) * DIVBY32768) - 1.0f;
}

src -= 7; dst -= 7; /* adjust to read SSE blocks from the start. */
Expand All @@ -445,7 +445,7 @@ SDL_Convert_U16_to_F32_SSE2(SDL_AudioCVT *cvt, SDL_AudioFormat format)
/* Make sure src is aligned too. */
if ((((size_t) src) & 15) == 0) {
/* Aligned! Do SSE blocks as long as we have 16 bytes available. */
const __m128 divby32767 = _mm_set1_ps(DIVBY32767);
const __m128 divby32768 = _mm_set1_ps(DIVBY32768);
const __m128 minus1 = _mm_set1_ps(1.0f);
while (i >= 8) { /* 8 * 16-bit */
const __m128i ints = _mm_load_si128((__m128i const *) src); /* get 8 sint16 into an XMM register. */
Expand All @@ -454,8 +454,8 @@ SDL_Convert_U16_to_F32_SSE2(SDL_AudioCVT *cvt, SDL_AudioFormat format)
/* right-shift-sign-extend gets us sint32 with the other set of values. */
const __m128i b = _mm_srli_epi32(ints, 16);
/* Interleave these back into the right order, convert to float, multiply, store. */
_mm_store_ps(dst, _mm_add_ps(_mm_mul_ps(_mm_cvtepi32_ps(_mm_unpacklo_epi32(a, b)), divby32767), minus1));
_mm_store_ps(dst+4, _mm_add_ps(_mm_mul_ps(_mm_cvtepi32_ps(_mm_unpackhi_epi32(a, b)), divby32767), minus1));
_mm_store_ps(dst, _mm_add_ps(_mm_mul_ps(_mm_cvtepi32_ps(_mm_unpacklo_epi32(a, b)), divby32768), minus1));
_mm_store_ps(dst+4, _mm_add_ps(_mm_mul_ps(_mm_cvtepi32_ps(_mm_unpackhi_epi32(a, b)), divby32768), minus1));
i -= 8; src -= 8; dst -= 8;
}
}
Expand All @@ -464,7 +464,7 @@ SDL_Convert_U16_to_F32_SSE2(SDL_AudioCVT *cvt, SDL_AudioFormat format)

/* Finish off any leftovers with scalar operations. */
while (i) {
*dst = ((((float) *src) * DIVBY32767) - 1.0f);
*dst = (((float) *src) * DIVBY32768) - 1.0f;
i--; src--; dst--;
}

Expand All @@ -485,21 +485,21 @@ SDL_Convert_S32_to_F32_SSE2(SDL_AudioCVT *cvt, SDL_AudioFormat format)

/* Get dst aligned to 16 bytes */
for (i = cvt->len_cvt / sizeof (Sint32); i && (((size_t) dst) & 15); --i, ++src, ++dst) {
*dst = (float) (((double) *src) * DIVBY2147483647);
*dst = (float) (((double) *src) * DIVBY2147483648);
}

SDL_assert(!i || ((((size_t) dst) & 15) == 0));
SDL_assert(!i || ((((size_t) src) & 15) == 0));

{
/* Aligned! Do SSE blocks as long as we have 16 bytes available. */
const __m128d divby2147483647 = _mm_set1_pd(DIVBY2147483647);
const __m128d divby2147483648 = _mm_set1_pd(DIVBY2147483648);
const __m128i *mmsrc = (const __m128i *) src;
while (i >= 4) { /* 4 * sint32 */
const __m128i ints = _mm_load_si128(mmsrc);
/* bitshift the whole register over, so _mm_cvtepi32_pd can read the top ints in the bottom of the vector. */
const __m128d doubles1 = _mm_mul_pd(_mm_cvtepi32_pd(_mm_srli_si128(ints, 8)), divby2147483647);
const __m128d doubles2 = _mm_mul_pd(_mm_cvtepi32_pd(ints), divby2147483647);
const __m128d doubles1 = _mm_mul_pd(_mm_cvtepi32_pd(_mm_srli_si128(ints, 8)), divby2147483648);
const __m128d doubles2 = _mm_mul_pd(_mm_cvtepi32_pd(ints), divby2147483648);
/* convert to float32, bitshift/or to get these into a vector to store. */
_mm_store_ps(dst, _mm_castsi128_ps(_mm_or_si128(_mm_slli_si128(_mm_castps_si128(_mm_cvtpd_ps(doubles1)), 8), _mm_castps_si128(_mm_cvtpd_ps(doubles2)))));
i -= 4; mmsrc++; dst += 4;
Expand All @@ -509,7 +509,7 @@ SDL_Convert_S32_to_F32_SSE2(SDL_AudioCVT *cvt, SDL_AudioFormat format)

/* Finish off any leftovers with scalar operations. */
while (i) {
*dst = (float) (((double) *src) * DIVBY2147483647);
*dst = (float) (((double) *src) * DIVBY2147483648);
i--; src++; dst++;
}

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