| /* |
| * Copyright (c) 2021, Alliance for Open Media. All rights reserved |
| * |
| * This source code is subject to the terms of the BSD 3-Clause Clear License |
| * and the Alliance for Open Media Patent License 1.0. If the BSD 3-Clause Clear |
| * License was not distributed with this source code in the LICENSE file, you |
| * can obtain it at aomedia.org/license/software-license/bsd-3-c-c/. If the |
| * Alliance for Open Media Patent License 1.0 was not distributed with this |
| * source code in the PATENTS file, you can obtain it at |
| * aomedia.org/license/patent-license/. |
| */ |
| |
| #include <assert.h> |
| #include <emmintrin.h> |
| #include <stdio.h> |
| |
| #include "aom_dsp/x86/synonyms.h" |
| #include "aom_dsp/x86/sum_squares_sse2.h" |
| #include "config/aom_dsp_rtcd.h" |
| |
| static INLINE __m128i xx_loadh_64(__m128i a, const void *b) { |
| const __m128d ad = _mm_castsi128_pd(a); |
| return _mm_castpd_si128(_mm_loadh_pd(ad, (double *)b)); |
| } |
| |
| static INLINE uint64_t xx_cvtsi128_si64(__m128i a) { |
| #if ARCH_X86_64 |
| return (uint64_t)_mm_cvtsi128_si64(a); |
| #else |
| { |
| uint64_t tmp; |
| _mm_storel_epi64((__m128i *)&tmp, a); |
| return tmp; |
| } |
| #endif |
| } |
| |
| static INLINE __m128i sum_squares_i16_4x4_sse2(const int16_t *src, int stride) { |
| const __m128i v_val_0_w = xx_loadl_64(src + 0 * stride); |
| const __m128i v_val_2_w = xx_loadl_64(src + 2 * stride); |
| const __m128i v_val_01_w = xx_loadh_64(v_val_0_w, src + 1 * stride); |
| const __m128i v_val_23_w = xx_loadh_64(v_val_2_w, src + 3 * stride); |
| const __m128i v_sq_01_d = _mm_madd_epi16(v_val_01_w, v_val_01_w); |
| const __m128i v_sq_23_d = _mm_madd_epi16(v_val_23_w, v_val_23_w); |
| |
| return _mm_add_epi32(v_sq_01_d, v_sq_23_d); |
| } |
| |
| uint64_t aom_sum_squares_2d_i16_4x4_sse2(const int16_t *src, int stride) { |
| const __m128i v_sum_0123_d = sum_squares_i16_4x4_sse2(src, stride); |
| __m128i v_sum_d = |
| _mm_add_epi32(v_sum_0123_d, _mm_srli_epi64(v_sum_0123_d, 32)); |
| v_sum_d = _mm_add_epi32(v_sum_d, _mm_srli_si128(v_sum_d, 8)); |
| return (uint64_t)_mm_cvtsi128_si32(v_sum_d); |
| } |
| |
| uint64_t aom_sum_sse_2d_i16_4x4_sse2(const int16_t *src, int stride, int *sum) { |
| const __m128i one_reg = _mm_set1_epi16(1); |
| const __m128i v_val_0_w = xx_loadl_64(src + 0 * stride); |
| const __m128i v_val_2_w = xx_loadl_64(src + 2 * stride); |
| __m128i v_val_01_w = xx_loadh_64(v_val_0_w, src + 1 * stride); |
| __m128i v_val_23_w = xx_loadh_64(v_val_2_w, src + 3 * stride); |
| |
| __m128i v_sum_0123_d = _mm_add_epi16(v_val_01_w, v_val_23_w); |
| v_sum_0123_d = _mm_madd_epi16(v_sum_0123_d, one_reg); |
| v_sum_0123_d = _mm_add_epi32(v_sum_0123_d, _mm_srli_si128(v_sum_0123_d, 8)); |
| v_sum_0123_d = _mm_add_epi32(v_sum_0123_d, _mm_srli_si128(v_sum_0123_d, 4)); |
| *sum = _mm_cvtsi128_si32(v_sum_0123_d); |
| |
| const __m128i v_sq_01_d = _mm_madd_epi16(v_val_01_w, v_val_01_w); |
| const __m128i v_sq_23_d = _mm_madd_epi16(v_val_23_w, v_val_23_w); |
| __m128i v_sq_0123_d = _mm_add_epi32(v_sq_01_d, v_sq_23_d); |
| v_sq_0123_d = _mm_add_epi32(v_sq_0123_d, _mm_srli_si128(v_sq_0123_d, 8)); |
| v_sq_0123_d = _mm_add_epi32(v_sq_0123_d, _mm_srli_si128(v_sq_0123_d, 4)); |
| return (uint64_t)_mm_cvtsi128_si32(v_sq_0123_d); |
| } |
| |
| uint64_t aom_sum_squares_2d_i16_4xn_sse2(const int16_t *src, int stride, |
| int height) { |
| int r = 0; |
| __m128i v_acc_q = _mm_setzero_si128(); |
| do { |
| const __m128i v_acc_d = sum_squares_i16_4x4_sse2(src, stride); |
| v_acc_q = _mm_add_epi32(v_acc_q, v_acc_d); |
| src += stride << 2; |
| r += 4; |
| } while (r < height); |
| const __m128i v_zext_mask_q = xx_set1_64_from_32i(0xffffffff); |
| __m128i v_acc_64 = _mm_add_epi64(_mm_srli_epi64(v_acc_q, 32), |
| _mm_and_si128(v_acc_q, v_zext_mask_q)); |
| v_acc_64 = _mm_add_epi64(v_acc_64, _mm_srli_si128(v_acc_64, 8)); |
| return xx_cvtsi128_si64(v_acc_64); |
| } |
| |
| uint64_t aom_sum_sse_2d_i16_4xn_sse2(const int16_t *src, int stride, int height, |
| int *sum) { |
| int r = 0; |
| uint64_t sse = 0; |
| do { |
| int curr_sum = 0; |
| sse += aom_sum_sse_2d_i16_4x4_sse2(src, stride, &curr_sum); |
| *sum += curr_sum; |
| src += stride << 2; |
| r += 4; |
| } while (r < height); |
| return sse; |
| } |
| |
| #ifdef __GNUC__ |
| // This prevents GCC/Clang from inlining this function into |
| // aom_sum_squares_2d_i16_sse2, which in turn saves some stack |
| // maintenance instructions in the common case of 4x4. |
| __attribute__((noinline)) |
| #endif |
| uint64_t |
| aom_sum_squares_2d_i16_nxn_sse2(const int16_t *src, int stride, int width, |
| int height) { |
| int r = 0; |
| |
| const __m128i v_zext_mask_q = xx_set1_64_from_32i(0xffffffff); |
| __m128i v_acc_q = _mm_setzero_si128(); |
| |
| do { |
| __m128i v_acc_d = _mm_setzero_si128(); |
| int c = 0; |
| do { |
| const int16_t *b = src + c; |
| |
| const __m128i v_val_0_w = xx_load_128(b + 0 * stride); |
| const __m128i v_val_1_w = xx_load_128(b + 1 * stride); |
| const __m128i v_val_2_w = xx_load_128(b + 2 * stride); |
| const __m128i v_val_3_w = xx_load_128(b + 3 * stride); |
| |
| const __m128i v_sq_0_d = _mm_madd_epi16(v_val_0_w, v_val_0_w); |
| const __m128i v_sq_1_d = _mm_madd_epi16(v_val_1_w, v_val_1_w); |
| const __m128i v_sq_2_d = _mm_madd_epi16(v_val_2_w, v_val_2_w); |
| const __m128i v_sq_3_d = _mm_madd_epi16(v_val_3_w, v_val_3_w); |
| |
| const __m128i v_sum_01_d = _mm_add_epi32(v_sq_0_d, v_sq_1_d); |
| const __m128i v_sum_23_d = _mm_add_epi32(v_sq_2_d, v_sq_3_d); |
| |
| const __m128i v_sum_0123_d = _mm_add_epi32(v_sum_01_d, v_sum_23_d); |
| |
| v_acc_d = _mm_add_epi32(v_acc_d, v_sum_0123_d); |
| c += 8; |
| } while (c < width); |
| |
| v_acc_q = _mm_add_epi64(v_acc_q, _mm_and_si128(v_acc_d, v_zext_mask_q)); |
| v_acc_q = _mm_add_epi64(v_acc_q, _mm_srli_epi64(v_acc_d, 32)); |
| |
| src += 4 * stride; |
| r += 4; |
| } while (r < height); |
| |
| v_acc_q = _mm_add_epi64(v_acc_q, _mm_srli_si128(v_acc_q, 8)); |
| return xx_cvtsi128_si64(v_acc_q); |
| } |
| |
| #ifdef __GNUC__ |
| // This prevents GCC/Clang from inlining this function into |
| // aom_sum_sse_2d_i16_nxn_sse2, which in turn saves some stack |
| // maintenance instructions in the common case of 4x4. |
| __attribute__((noinline)) |
| #endif |
| uint64_t |
| aom_sum_sse_2d_i16_nxn_sse2(const int16_t *src, int stride, int width, |
| int height, int *sum) { |
| int r = 0; |
| uint64_t result; |
| const __m128i zero_reg = _mm_setzero_si128(); |
| const __m128i one_reg = _mm_set1_epi16(1); |
| |
| __m128i v_sse_total = zero_reg; |
| __m128i v_sum_total = zero_reg; |
| |
| do { |
| int c = 0; |
| __m128i v_sse_row = zero_reg; |
| do { |
| const int16_t *b = src + c; |
| |
| __m128i v_val_0_w = xx_load_128(b + 0 * stride); |
| __m128i v_val_1_w = xx_load_128(b + 1 * stride); |
| __m128i v_val_2_w = xx_load_128(b + 2 * stride); |
| __m128i v_val_3_w = xx_load_128(b + 3 * stride); |
| |
| const __m128i v_sq_0_d = _mm_madd_epi16(v_val_0_w, v_val_0_w); |
| const __m128i v_sq_1_d = _mm_madd_epi16(v_val_1_w, v_val_1_w); |
| const __m128i v_sq_2_d = _mm_madd_epi16(v_val_2_w, v_val_2_w); |
| const __m128i v_sq_3_d = _mm_madd_epi16(v_val_3_w, v_val_3_w); |
| const __m128i v_sq_01_d = _mm_add_epi32(v_sq_0_d, v_sq_1_d); |
| const __m128i v_sq_23_d = _mm_add_epi32(v_sq_2_d, v_sq_3_d); |
| const __m128i v_sq_0123_d = _mm_add_epi32(v_sq_01_d, v_sq_23_d); |
| v_sse_row = _mm_add_epi32(v_sse_row, v_sq_0123_d); |
| |
| const __m128i v_sum_01 = _mm_add_epi16(v_val_0_w, v_val_1_w); |
| const __m128i v_sum_23 = _mm_add_epi16(v_val_2_w, v_val_3_w); |
| __m128i v_sum_0123_d = _mm_add_epi16(v_sum_01, v_sum_23); |
| v_sum_0123_d = _mm_madd_epi16(v_sum_0123_d, one_reg); |
| v_sum_total = _mm_add_epi32(v_sum_total, v_sum_0123_d); |
| |
| c += 8; |
| } while (c < width); |
| |
| const __m128i v_sse_row_low = _mm_unpacklo_epi32(v_sse_row, zero_reg); |
| const __m128i v_sse_row_hi = _mm_unpackhi_epi32(v_sse_row, zero_reg); |
| v_sse_row = _mm_add_epi64(v_sse_row_low, v_sse_row_hi); |
| v_sse_total = _mm_add_epi64(v_sse_total, v_sse_row); |
| src += 4 * stride; |
| r += 4; |
| } while (r < height); |
| |
| v_sum_total = _mm_add_epi32(v_sum_total, _mm_srli_si128(v_sum_total, 8)); |
| v_sum_total = _mm_add_epi32(v_sum_total, _mm_srli_si128(v_sum_total, 4)); |
| *sum += _mm_cvtsi128_si32(v_sum_total); |
| |
| v_sse_total = _mm_add_epi64(v_sse_total, _mm_srli_si128(v_sse_total, 8)); |
| xx_storel_64(&result, v_sse_total); |
| return result; |
| } |
| |
| uint64_t aom_sum_squares_2d_i16_sse2(const int16_t *src, int stride, int width, |
| int height) { |
| // 4 elements per row only requires half an XMM register, so this |
| // must be a special case, but also note that over 75% of all calls |
| // are with size == 4, so it is also the common case. |
| if (LIKELY(width == 4 && height == 4)) { |
| return aom_sum_squares_2d_i16_4x4_sse2(src, stride); |
| } else if (LIKELY(width == 4 && (height & 3) == 0)) { |
| return aom_sum_squares_2d_i16_4xn_sse2(src, stride, height); |
| } else if (LIKELY((width & 7) == 0 && (height & 3) == 0)) { |
| // Generic case |
| return aom_sum_squares_2d_i16_nxn_sse2(src, stride, width, height); |
| } else { |
| return aom_sum_squares_2d_i16_c(src, stride, width, height); |
| } |
| } |
| |
| uint64_t aom_sum_sse_2d_i16_sse2(const int16_t *src, int src_stride, int width, |
| int height, int *sum) { |
| if (LIKELY(width == 4 && height == 4)) { |
| return aom_sum_sse_2d_i16_4x4_sse2(src, src_stride, sum); |
| } else if (LIKELY(width == 4 && (height & 3) == 0)) { |
| return aom_sum_sse_2d_i16_4xn_sse2(src, src_stride, height, sum); |
| } else if (LIKELY((width & 7) == 0 && (height & 3) == 0)) { |
| // Generic case |
| return aom_sum_sse_2d_i16_nxn_sse2(src, src_stride, width, height, sum); |
| } else { |
| return aom_sum_sse_2d_i16_c(src, src_stride, width, height, sum); |
| } |
| } |
| |
| ////////////////////////////////////////////////////////////////////////////// |
| // 1D version |
| ////////////////////////////////////////////////////////////////////////////// |
| |
| static uint64_t aom_sum_squares_i16_64n_sse2(const int16_t *src, uint32_t n) { |
| const __m128i v_zext_mask_q = xx_set1_64_from_32i(0xffffffff); |
| __m128i v_acc0_q = _mm_setzero_si128(); |
| __m128i v_acc1_q = _mm_setzero_si128(); |
| |
| const int16_t *const end = src + n; |
| |
| assert(n % 64 == 0); |
| |
| while (src < end) { |
| const __m128i v_val_0_w = xx_load_128(src); |
| const __m128i v_val_1_w = xx_load_128(src + 8); |
| const __m128i v_val_2_w = xx_load_128(src + 16); |
| const __m128i v_val_3_w = xx_load_128(src + 24); |
| const __m128i v_val_4_w = xx_load_128(src + 32); |
| const __m128i v_val_5_w = xx_load_128(src + 40); |
| const __m128i v_val_6_w = xx_load_128(src + 48); |
| const __m128i v_val_7_w = xx_load_128(src + 56); |
| |
| const __m128i v_sq_0_d = _mm_madd_epi16(v_val_0_w, v_val_0_w); |
| const __m128i v_sq_1_d = _mm_madd_epi16(v_val_1_w, v_val_1_w); |
| const __m128i v_sq_2_d = _mm_madd_epi16(v_val_2_w, v_val_2_w); |
| const __m128i v_sq_3_d = _mm_madd_epi16(v_val_3_w, v_val_3_w); |
| const __m128i v_sq_4_d = _mm_madd_epi16(v_val_4_w, v_val_4_w); |
| const __m128i v_sq_5_d = _mm_madd_epi16(v_val_5_w, v_val_5_w); |
| const __m128i v_sq_6_d = _mm_madd_epi16(v_val_6_w, v_val_6_w); |
| const __m128i v_sq_7_d = _mm_madd_epi16(v_val_7_w, v_val_7_w); |
| |
| const __m128i v_sum_01_d = _mm_add_epi32(v_sq_0_d, v_sq_1_d); |
| const __m128i v_sum_23_d = _mm_add_epi32(v_sq_2_d, v_sq_3_d); |
| const __m128i v_sum_45_d = _mm_add_epi32(v_sq_4_d, v_sq_5_d); |
| const __m128i v_sum_67_d = _mm_add_epi32(v_sq_6_d, v_sq_7_d); |
| |
| const __m128i v_sum_0123_d = _mm_add_epi32(v_sum_01_d, v_sum_23_d); |
| const __m128i v_sum_4567_d = _mm_add_epi32(v_sum_45_d, v_sum_67_d); |
| |
| const __m128i v_sum_d = _mm_add_epi32(v_sum_0123_d, v_sum_4567_d); |
| |
| v_acc0_q = _mm_add_epi64(v_acc0_q, _mm_and_si128(v_sum_d, v_zext_mask_q)); |
| v_acc1_q = _mm_add_epi64(v_acc1_q, _mm_srli_epi64(v_sum_d, 32)); |
| |
| src += 64; |
| } |
| |
| v_acc0_q = _mm_add_epi64(v_acc0_q, v_acc1_q); |
| v_acc0_q = _mm_add_epi64(v_acc0_q, _mm_srli_si128(v_acc0_q, 8)); |
| return xx_cvtsi128_si64(v_acc0_q); |
| } |
| |
| uint64_t aom_sum_squares_i16_sse2(const int16_t *src, uint32_t n) { |
| if (n % 64 == 0) { |
| return aom_sum_squares_i16_64n_sse2(src, n); |
| } else if (n > 64) { |
| int k = n & ~(64 - 1); |
| return aom_sum_squares_i16_64n_sse2(src, k) + |
| aom_sum_squares_i16_c(src + k, n - k); |
| } else { |
| return aom_sum_squares_i16_c(src, n); |
| } |
| } |
| |
| // Accumulate sum of 16-bit elements in the vector |
| static AOM_INLINE int32_t mm_accumulate_epi16(__m128i vec_a) { |
| __m128i vtmp = _mm_srli_si128(vec_a, 8); |
| vec_a = _mm_add_epi16(vec_a, vtmp); |
| vtmp = _mm_srli_si128(vec_a, 4); |
| vec_a = _mm_add_epi16(vec_a, vtmp); |
| vtmp = _mm_srli_si128(vec_a, 2); |
| vec_a = _mm_add_epi16(vec_a, vtmp); |
| return _mm_extract_epi16(vec_a, 0); |
| } |
| |
| // Accumulate sum of 32-bit elements in the vector |
| static AOM_INLINE int32_t mm_accumulate_epi32(__m128i vec_a) { |
| __m128i vtmp = _mm_srli_si128(vec_a, 8); |
| vec_a = _mm_add_epi32(vec_a, vtmp); |
| vtmp = _mm_srli_si128(vec_a, 4); |
| vec_a = _mm_add_epi32(vec_a, vtmp); |
| return _mm_cvtsi128_si32(vec_a); |
| } |
| |
| uint64_t aom_var_2d_u8_sse2(uint8_t *src, int src_stride, int width, |
| int height) { |
| uint8_t *srcp; |
| uint64_t s = 0, ss = 0; |
| __m128i vzero = _mm_setzero_si128(); |
| __m128i v_acc_sum = vzero; |
| __m128i v_acc_sqs = vzero; |
| int i, j; |
| |
| // Process 16 elements in a row |
| for (i = 0; i < width - 15; i += 16) { |
| srcp = src + i; |
| // Process 8 columns at a time |
| for (j = 0; j < height - 7; j += 8) { |
| __m128i vsrc[8]; |
| for (int k = 0; k < 8; k++) { |
| vsrc[k] = _mm_loadu_si128((__m128i *)srcp); |
| srcp += src_stride; |
| } |
| for (int k = 0; k < 8; k++) { |
| __m128i vsrc0 = _mm_unpacklo_epi8(vsrc[k], vzero); |
| __m128i vsrc1 = _mm_unpackhi_epi8(vsrc[k], vzero); |
| v_acc_sum = _mm_add_epi16(v_acc_sum, vsrc0); |
| v_acc_sum = _mm_add_epi16(v_acc_sum, vsrc1); |
| |
| __m128i vsqs0 = _mm_madd_epi16(vsrc0, vsrc0); |
| __m128i vsqs1 = _mm_madd_epi16(vsrc1, vsrc1); |
| v_acc_sqs = _mm_add_epi32(v_acc_sqs, vsqs0); |
| v_acc_sqs = _mm_add_epi32(v_acc_sqs, vsqs1); |
| } |
| |
| // Update total sum and clear the vectors |
| s += mm_accumulate_epi16(v_acc_sum); |
| ss += mm_accumulate_epi32(v_acc_sqs); |
| v_acc_sum = vzero; |
| v_acc_sqs = vzero; |
| } |
| |
| // Process remaining rows (height not a multiple of 8) |
| for (; j < height; j++) { |
| __m128i vsrc = _mm_loadu_si128((__m128i *)srcp); |
| __m128i vsrc0 = _mm_unpacklo_epi8(vsrc, vzero); |
| __m128i vsrc1 = _mm_unpackhi_epi8(vsrc, vzero); |
| v_acc_sum = _mm_add_epi16(v_acc_sum, vsrc0); |
| v_acc_sum = _mm_add_epi16(v_acc_sum, vsrc1); |
| |
| __m128i vsqs0 = _mm_madd_epi16(vsrc0, vsrc0); |
| __m128i vsqs1 = _mm_madd_epi16(vsrc1, vsrc1); |
| v_acc_sqs = _mm_add_epi32(v_acc_sqs, vsqs0); |
| v_acc_sqs = _mm_add_epi32(v_acc_sqs, vsqs1); |
| |
| srcp += src_stride; |
| } |
| |
| // Update total sum and clear the vectors |
| s += mm_accumulate_epi16(v_acc_sum); |
| ss += mm_accumulate_epi32(v_acc_sqs); |
| v_acc_sum = vzero; |
| v_acc_sqs = vzero; |
| } |
| |
| // Process the remaining area using C |
| srcp = src; |
| for (int k = 0; k < height; k++) { |
| for (int m = i; m < width; m++) { |
| uint8_t val = srcp[m]; |
| s += val; |
| ss += val * val; |
| } |
| srcp += src_stride; |
| } |
| return (ss - s * s / (width * height)); |
| } |
| |
| uint64_t aom_var_2d_u16_sse2(uint8_t *src, int src_stride, int width, |
| int height) { |
| uint16_t *srcp1 = CONVERT_TO_SHORTPTR(src), *srcp; |
| uint64_t s = 0, ss = 0; |
| __m128i vzero = _mm_setzero_si128(); |
| __m128i v_acc_sum = vzero; |
| __m128i v_acc_sqs = vzero; |
| int i, j; |
| |
| // Process 8 elements in a row |
| for (i = 0; i < width - 8; i += 8) { |
| srcp = srcp1 + i; |
| // Process 8 columns at a time |
| for (j = 0; j < height - 8; j += 8) { |
| __m128i vsrc[8]; |
| for (int k = 0; k < 8; k++) { |
| vsrc[k] = _mm_loadu_si128((__m128i *)srcp); |
| srcp += src_stride; |
| } |
| for (int k = 0; k < 8; k++) { |
| __m128i vsrc0 = _mm_unpacklo_epi16(vsrc[k], vzero); |
| __m128i vsrc1 = _mm_unpackhi_epi16(vsrc[k], vzero); |
| v_acc_sum = _mm_add_epi32(vsrc0, v_acc_sum); |
| v_acc_sum = _mm_add_epi32(vsrc1, v_acc_sum); |
| |
| __m128i vsqs0 = _mm_madd_epi16(vsrc[k], vsrc[k]); |
| v_acc_sqs = _mm_add_epi32(v_acc_sqs, vsqs0); |
| } |
| |
| // Update total sum and clear the vectors |
| s += mm_accumulate_epi32(v_acc_sum); |
| ss += mm_accumulate_epi32(v_acc_sqs); |
| v_acc_sum = vzero; |
| v_acc_sqs = vzero; |
| } |
| |
| // Process remaining rows (height not a multiple of 8) |
| for (; j < height; j++) { |
| __m128i vsrc = _mm_loadu_si128((__m128i *)srcp); |
| __m128i vsrc0 = _mm_unpacklo_epi16(vsrc, vzero); |
| __m128i vsrc1 = _mm_unpackhi_epi16(vsrc, vzero); |
| v_acc_sum = _mm_add_epi32(vsrc0, v_acc_sum); |
| v_acc_sum = _mm_add_epi32(vsrc1, v_acc_sum); |
| |
| __m128i vsqs0 = _mm_madd_epi16(vsrc, vsrc); |
| v_acc_sqs = _mm_add_epi32(v_acc_sqs, vsqs0); |
| srcp += src_stride; |
| } |
| |
| // Update total sum and clear the vectors |
| s += mm_accumulate_epi32(v_acc_sum); |
| ss += mm_accumulate_epi32(v_acc_sqs); |
| v_acc_sum = vzero; |
| v_acc_sqs = vzero; |
| } |
| |
| // Process the remaining area using C |
| srcp = srcp1; |
| for (int k = 0; k < height; k++) { |
| for (int m = i; m < width; m++) { |
| uint16_t val = srcp[m]; |
| s += val; |
| ss += val * val; |
| } |
| srcp += src_stride; |
| } |
| return (ss - s * s / (width * height)); |
| } |