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fix some SSIM calculations

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* prevent 64bit overflow by controlling the 32b->64b conversions
  and preventively descaling by 8bit before the final multiply
* adjust the threshold constants C1 and C2 to de-emphasis the dark
  areas
* use a hat-like filter instead of box-filtering to avoid blockiness
  during averaging

SSIM distortion calc is actually *faster* now in SSE2, because of the
unrolling during the function rewrite.
The C-version is quite slower because still un-optimized.

Change-Id: I96e2715827f79d26faae354cc28c7406c6800c90
This commit is contained in:
Pascal Massimino
2016-10-04 07:10:27 +02:00
parent 51b71fd295
commit ba843a92e7
3 changed files with 103 additions and 77 deletions
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51
src/dsp/enc_sse2.c
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@ -1422,30 +1422,45 @@ static uint32_t HorizontalAdd32b(const __m128i* const m) {
return (uint32_t)_mm_cvtsi128_si32(c);
}
static const uint16_t kWeight[] = { 1, 2, 3, 4, 3, 2, 1, 0 };
#define ACCUMULATE_ROW(WEIGHT) do { \
/* compute row weight (Wx * Wy) */ \
const __m128i Wy = _mm_set1_epi16((WEIGHT)); \
const __m128i W = _mm_mullo_epi16(Wx, Wy); \
/* process 8 bytes at a time (7 bytes, actually) */ \
const __m128i a0 = _mm_loadl_epi64((const __m128i*)src1); \
const __m128i b0 = _mm_loadl_epi64((const __m128i*)src2); \
/* convert to 16b and multiply by weight */ \
const __m128i a1 = _mm_unpacklo_epi8(a0, zero); \
const __m128i b1 = _mm_unpacklo_epi8(b0, zero); \
const __m128i wa1 = _mm_mullo_epi16(a1, W); \
const __m128i wb1 = _mm_mullo_epi16(b1, W); \
/* accumulate */ \
xm = _mm_add_epi16(xm, wa1); \
ym = _mm_add_epi16(ym, wb1); \
xxm = _mm_add_epi32(xxm, _mm_madd_epi16(a1, wa1)); \
xym = _mm_add_epi32(xym, _mm_madd_epi16(a1, wb1)); \
yym = _mm_add_epi32(yym, _mm_madd_epi16(b1, wb1)); \
src1 += stride1; \
src2 += stride2; \
} while (0)
static double SSIMGet_SSE2(const uint8_t* src1, int stride1,
const uint8_t* src2, int stride2) {
VP8DistoStats stats;
int y;
const __m128i zero = _mm_setzero_si128();
__m128i xm = zero, ym = zero; // 16b accums
__m128i xm = zero, ym = zero; // 16b accums
__m128i xxm = zero, yym = zero, xym = zero; // 32b accum
const __m128i Wx = _mm_loadu_si128((const __m128i*)kWeight);
assert(2 * VP8_SSIM_KERNEL + 1 == 7);
for (y = 0; y <= 2 * VP8_SSIM_KERNEL; ++y, src1 += stride1, src2 += stride2) {
// process 8 bytes at a time (7 bytes, actually)
const __m128i a0 = _mm_loadl_epi64((const __m128i*)src1);
const __m128i b0 = _mm_loadl_epi64((const __m128i*)src2);
// convert 8b -> 16b
const __m128i a1 = _mm_unpacklo_epi8(a0, zero);
const __m128i b1 = _mm_unpacklo_epi8(b0, zero);
// zeroes the rightmost pixel we are not interested in:
const __m128i s1 = _mm_slli_si128(a1, 2);
const __m128i s2 = _mm_slli_si128(b1, 2);
xm = _mm_add_epi16(xm, s1);
ym = _mm_add_epi16(ym, s2);
xxm = _mm_add_epi32(xxm, _mm_madd_epi16(s1, s1));
xym = _mm_add_epi32(xym, _mm_madd_epi16(s1, s2));
yym = _mm_add_epi32(yym, _mm_madd_epi16(s2, s2));
}
ACCUMULATE_ROW(1);
ACCUMULATE_ROW(2);
ACCUMULATE_ROW(3);
ACCUMULATE_ROW(4);
ACCUMULATE_ROW(3);
ACCUMULATE_ROW(2);
ACCUMULATE_ROW(1);
stats.xm = HorizontalAdd16b(&xm);
stats.ym = HorizontalAdd16b(&ym);
stats.xxm = HorizontalAdd32b(&xxm);