| /* |
| * Copyright (c) 2016, Alliance for Open Media. All rights reserved |
| * |
| * This source code is subject to the terms of the BSD 2 Clause License and |
| * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License |
| * was not distributed with this source code in the LICENSE file, you can |
| * obtain it at www.aomedia.org/license/software. 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 www.aomedia.org/license/patent. |
| */ |
| |
| #include <assert.h> |
| #include <stdlib.h> |
| |
| #include "config/aom_dsp_rtcd.h" |
| #include "aom_ports/mem.h" |
| |
| void aom_minmax_8x8_c(const uint8_t *s, int p, const uint8_t *d, int dp, |
| int *min, int *max) { |
| int i, j; |
| *min = 255; |
| *max = 0; |
| for (i = 0; i < 8; ++i, s += p, d += dp) { |
| for (j = 0; j < 8; ++j) { |
| int diff = abs(s[j] - d[j]); |
| *min = diff < *min ? diff : *min; |
| *max = diff > *max ? diff : *max; |
| } |
| } |
| } |
| |
| unsigned int aom_avg_4x4_c(const uint8_t *s, int p) { |
| int i, j; |
| int sum = 0; |
| for (i = 0; i < 4; ++i, s += p) |
| for (j = 0; j < 4; sum += s[j], ++j) { |
| } |
| |
| return (sum + 8) >> 4; |
| } |
| |
| unsigned int aom_avg_8x8_c(const uint8_t *s, int p) { |
| int i, j; |
| int sum = 0; |
| for (i = 0; i < 8; ++i, s += p) |
| for (j = 0; j < 8; sum += s[j], ++j) { |
| } |
| |
| return (sum + 32) >> 6; |
| } |
| |
| void aom_avg_8x8_quad_c(const uint8_t *s, int p, int x16_idx, int y16_idx, |
| int *avg) { |
| const uint8_t *s_tmp = s; |
| for (int k = 0; k < 4; k++) { |
| int sum = 0; |
| const int x8_idx = x16_idx + ((k & 1) << 3); |
| const int y8_idx = y16_idx + ((k >> 1) << 3); |
| s_tmp = (s + y8_idx * p + x8_idx); |
| for (int i = 0; i < 8; i++) { |
| for (int j = 0; j < 8; j++) { |
| sum += s_tmp[j]; |
| } |
| s_tmp += p; |
| } |
| avg[k] = (sum + 32) >> 6; |
| } |
| } |
| |
| #if CONFIG_AV1_HIGHBITDEPTH |
| unsigned int aom_highbd_avg_8x8_c(const uint8_t *s8, int p) { |
| int i, j; |
| int sum = 0; |
| const uint16_t *s = CONVERT_TO_SHORTPTR(s8); |
| for (i = 0; i < 8; ++i, s += p) |
| for (j = 0; j < 8; sum += s[j], ++j) { |
| } |
| |
| return (sum + 32) >> 6; |
| } |
| |
| unsigned int aom_highbd_avg_4x4_c(const uint8_t *s8, int p) { |
| int i, j; |
| int sum = 0; |
| const uint16_t *s = CONVERT_TO_SHORTPTR(s8); |
| for (i = 0; i < 4; ++i, s += p) |
| for (j = 0; j < 4; sum += s[j], ++j) { |
| } |
| |
| return (sum + 8) >> 4; |
| } |
| |
| void aom_highbd_minmax_8x8_c(const uint8_t *s8, int p, const uint8_t *d8, |
| int dp, int *min, int *max) { |
| int i, j; |
| const uint16_t *s = CONVERT_TO_SHORTPTR(s8); |
| const uint16_t *d = CONVERT_TO_SHORTPTR(d8); |
| *min = 255; |
| *max = 0; |
| for (i = 0; i < 8; ++i, s += p, d += dp) { |
| for (j = 0; j < 8; ++j) { |
| int diff = abs(s[j] - d[j]); |
| *min = diff < *min ? diff : *min; |
| *max = diff > *max ? diff : *max; |
| } |
| } |
| } |
| #endif // CONFIG_AV1_HIGHBITDEPTH |
| |
| void aom_pixel_scale_c(const int16_t *src_diff, ptrdiff_t src_stride, |
| int16_t *coeff, int log_scale, int h8, int w8) { |
| for (int idy = 0; idy < h8 * 8; ++idy) |
| for (int idx = 0; idx < w8 * 8; ++idx) |
| coeff[idy * (h8 * 8) + idx] = src_diff[idy * src_stride + idx] |
| << log_scale; |
| } |
| |
| static void hadamard_col4(const int16_t *src_diff, ptrdiff_t src_stride, |
| int16_t *coeff) { |
| int16_t b0 = (src_diff[0 * src_stride] + src_diff[1 * src_stride]) >> 1; |
| int16_t b1 = (src_diff[0 * src_stride] - src_diff[1 * src_stride]) >> 1; |
| int16_t b2 = (src_diff[2 * src_stride] + src_diff[3 * src_stride]) >> 1; |
| int16_t b3 = (src_diff[2 * src_stride] - src_diff[3 * src_stride]) >> 1; |
| |
| coeff[0] = b0 + b2; |
| coeff[1] = b1 + b3; |
| coeff[2] = b0 - b2; |
| coeff[3] = b1 - b3; |
| } |
| |
| void aom_hadamard_4x4_c(const int16_t *src_diff, ptrdiff_t src_stride, |
| tran_low_t *coeff) { |
| int idx; |
| int16_t buffer[16]; |
| int16_t buffer2[16]; |
| int16_t *tmp_buf = &buffer[0]; |
| for (idx = 0; idx < 4; ++idx) { |
| hadamard_col4(src_diff, src_stride, tmp_buf); // src_diff: 9 bit |
| // dynamic range [-255, 255] |
| tmp_buf += 4; |
| ++src_diff; |
| } |
| |
| tmp_buf = &buffer[0]; |
| for (idx = 0; idx < 4; ++idx) { |
| hadamard_col4(tmp_buf, 4, buffer2 + 4 * idx); // tmp_buf: 12 bit |
| // dynamic range [-2040, 2040] |
| // buffer2: 15 bit |
| // dynamic range [-16320, 16320] |
| ++tmp_buf; |
| } |
| |
| for (idx = 0; idx < 16; ++idx) coeff[idx] = (tran_low_t)buffer2[idx]; |
| } |
| |
| // src_diff: first pass, 9 bit, dynamic range [-255, 255] |
| // second pass, 12 bit, dynamic range [-2040, 2040] |
| static void hadamard_col8(const int16_t *src_diff, ptrdiff_t src_stride, |
| int16_t *coeff) { |
| int16_t b0 = src_diff[0 * src_stride] + src_diff[1 * src_stride]; |
| int16_t b1 = src_diff[0 * src_stride] - src_diff[1 * src_stride]; |
| int16_t b2 = src_diff[2 * src_stride] + src_diff[3 * src_stride]; |
| int16_t b3 = src_diff[2 * src_stride] - src_diff[3 * src_stride]; |
| int16_t b4 = src_diff[4 * src_stride] + src_diff[5 * src_stride]; |
| int16_t b5 = src_diff[4 * src_stride] - src_diff[5 * src_stride]; |
| int16_t b6 = src_diff[6 * src_stride] + src_diff[7 * src_stride]; |
| int16_t b7 = src_diff[6 * src_stride] - src_diff[7 * src_stride]; |
| |
| int16_t c0 = b0 + b2; |
| int16_t c1 = b1 + b3; |
| int16_t c2 = b0 - b2; |
| int16_t c3 = b1 - b3; |
| int16_t c4 = b4 + b6; |
| int16_t c5 = b5 + b7; |
| int16_t c6 = b4 - b6; |
| int16_t c7 = b5 - b7; |
| |
| coeff[0] = c0 + c4; |
| coeff[7] = c1 + c5; |
| coeff[3] = c2 + c6; |
| coeff[4] = c3 + c7; |
| coeff[2] = c0 - c4; |
| coeff[6] = c1 - c5; |
| coeff[1] = c2 - c6; |
| coeff[5] = c3 - c7; |
| } |
| |
| // The order of the output coeff of the hadamard is not important. For |
| // optimization purposes the final transpose may be skipped. |
| void aom_hadamard_8x8_c(const int16_t *src_diff, ptrdiff_t src_stride, |
| tran_low_t *coeff) { |
| int idx; |
| int16_t buffer[64]; |
| int16_t buffer2[64]; |
| int16_t *tmp_buf = &buffer[0]; |
| for (idx = 0; idx < 8; ++idx) { |
| hadamard_col8(src_diff, src_stride, tmp_buf); // src_diff: 9 bit |
| // dynamic range [-255, 255] |
| tmp_buf += 8; |
| ++src_diff; |
| } |
| |
| tmp_buf = &buffer[0]; |
| for (idx = 0; idx < 8; ++idx) { |
| hadamard_col8(tmp_buf, 8, buffer2 + 8 * idx); // tmp_buf: 12 bit |
| // dynamic range [-2040, 2040] |
| // buffer2: 15 bit |
| // dynamic range [-16320, 16320] |
| ++tmp_buf; |
| } |
| |
| for (idx = 0; idx < 64; ++idx) coeff[idx] = (tran_low_t)buffer2[idx]; |
| } |
| |
| void aom_hadamard_lp_8x8_c(const int16_t *src_diff, ptrdiff_t src_stride, |
| int16_t *coeff) { |
| int16_t buffer[64]; |
| int16_t buffer2[64]; |
| int16_t *tmp_buf = &buffer[0]; |
| for (int idx = 0; idx < 8; ++idx) { |
| hadamard_col8(src_diff, src_stride, tmp_buf); // src_diff: 9 bit |
| // dynamic range [-255, 255] |
| tmp_buf += 8; |
| ++src_diff; |
| } |
| |
| tmp_buf = &buffer[0]; |
| for (int idx = 0; idx < 8; ++idx) { |
| hadamard_col8(tmp_buf, 8, buffer2 + 8 * idx); // tmp_buf: 12 bit |
| // dynamic range [-2040, 2040] |
| // buffer2: 15 bit |
| // dynamic range [-16320, 16320] |
| ++tmp_buf; |
| } |
| |
| for (int idx = 0; idx < 64; ++idx) coeff[idx] = buffer2[idx]; |
| } |
| |
| void aom_hadamard_8x8_dual_c(const int16_t *src_diff, ptrdiff_t src_stride, |
| int16_t *coeff) { |
| for (int i = 0; i < 2; i++) { |
| aom_hadamard_lp_8x8_c(src_diff + (i * 8), src_stride, |
| (int16_t *)coeff + (i * 64)); |
| } |
| } |
| |
| // In place 16x16 2D Hadamard transform |
| void aom_hadamard_16x16_c(const int16_t *src_diff, ptrdiff_t src_stride, |
| tran_low_t *coeff) { |
| int idx; |
| for (idx = 0; idx < 4; ++idx) { |
| // src_diff: 9 bit, dynamic range [-255, 255] |
| const int16_t *src_ptr = |
| src_diff + (idx >> 1) * 8 * src_stride + (idx & 0x01) * 8; |
| aom_hadamard_8x8_c(src_ptr, src_stride, coeff + idx * 64); |
| } |
| |
| // coeff: 15 bit, dynamic range [-16320, 16320] |
| for (idx = 0; idx < 64; ++idx) { |
| tran_low_t a0 = coeff[0]; |
| tran_low_t a1 = coeff[64]; |
| tran_low_t a2 = coeff[128]; |
| tran_low_t a3 = coeff[192]; |
| |
| tran_low_t b0 = (a0 + a1) >> 1; // (a0 + a1): 16 bit, [-32640, 32640] |
| tran_low_t b1 = (a0 - a1) >> 1; // b0-b3: 15 bit, dynamic range |
| tran_low_t b2 = (a2 + a3) >> 1; // [-16320, 16320] |
| tran_low_t b3 = (a2 - a3) >> 1; |
| |
| coeff[0] = b0 + b2; // 16 bit, [-32640, 32640] |
| coeff[64] = b1 + b3; |
| coeff[128] = b0 - b2; |
| coeff[192] = b1 - b3; |
| |
| ++coeff; |
| } |
| } |
| |
| void aom_hadamard_lp_16x16_c(const int16_t *src_diff, ptrdiff_t src_stride, |
| int16_t *coeff) { |
| for (int idx = 0; idx < 4; ++idx) { |
| // src_diff: 9 bit, dynamic range [-255, 255] |
| const int16_t *src_ptr = |
| src_diff + (idx >> 1) * 8 * src_stride + (idx & 0x01) * 8; |
| aom_hadamard_lp_8x8_c(src_ptr, src_stride, coeff + idx * 64); |
| } |
| |
| for (int idx = 0; idx < 64; ++idx) { |
| int16_t a0 = coeff[0]; |
| int16_t a1 = coeff[64]; |
| int16_t a2 = coeff[128]; |
| int16_t a3 = coeff[192]; |
| |
| int16_t b0 = (a0 + a1) >> 1; // (a0 + a1): 16 bit, [-32640, 32640] |
| int16_t b1 = (a0 - a1) >> 1; // b0-b3: 15 bit, dynamic range |
| int16_t b2 = (a2 + a3) >> 1; // [-16320, 16320] |
| int16_t b3 = (a2 - a3) >> 1; |
| |
| coeff[0] = b0 + b2; // 16 bit, [-32640, 32640] |
| coeff[64] = b1 + b3; |
| coeff[128] = b0 - b2; |
| coeff[192] = b1 - b3; |
| |
| ++coeff; |
| } |
| } |
| |
| void aom_hadamard_32x32_c(const int16_t *src_diff, ptrdiff_t src_stride, |
| tran_low_t *coeff) { |
| int idx; |
| for (idx = 0; idx < 4; ++idx) { |
| // src_diff: 9 bit, dynamic range [-255, 255] |
| const int16_t *src_ptr = |
| src_diff + (idx >> 1) * 16 * src_stride + (idx & 0x01) * 16; |
| aom_hadamard_16x16_c(src_ptr, src_stride, coeff + idx * 256); |
| } |
| |
| // coeff: 15 bit, dynamic range [-16320, 16320] |
| for (idx = 0; idx < 256; ++idx) { |
| tran_low_t a0 = coeff[0]; |
| tran_low_t a1 = coeff[256]; |
| tran_low_t a2 = coeff[512]; |
| tran_low_t a3 = coeff[768]; |
| |
| tran_low_t b0 = (a0 + a1) >> 2; // (a0 + a1): 16 bit, [-32640, 32640] |
| tran_low_t b1 = (a0 - a1) >> 2; // b0-b3: 15 bit, dynamic range |
| tran_low_t b2 = (a2 + a3) >> 2; // [-16320, 16320] |
| tran_low_t b3 = (a2 - a3) >> 2; |
| |
| coeff[0] = b0 + b2; // 16 bit, [-32640, 32640] |
| coeff[256] = b1 + b3; |
| coeff[512] = b0 - b2; |
| coeff[768] = b1 - b3; |
| |
| ++coeff; |
| } |
| } |
| |
| #if CONFIG_AV1_HIGHBITDEPTH |
| static void hadamard_highbd_col8_first_pass(const int16_t *src_diff, |
| ptrdiff_t src_stride, |
| int16_t *coeff) { |
| int16_t b0 = src_diff[0 * src_stride] + src_diff[1 * src_stride]; |
| int16_t b1 = src_diff[0 * src_stride] - src_diff[1 * src_stride]; |
| int16_t b2 = src_diff[2 * src_stride] + src_diff[3 * src_stride]; |
| int16_t b3 = src_diff[2 * src_stride] - src_diff[3 * src_stride]; |
| int16_t b4 = src_diff[4 * src_stride] + src_diff[5 * src_stride]; |
| int16_t b5 = src_diff[4 * src_stride] - src_diff[5 * src_stride]; |
| int16_t b6 = src_diff[6 * src_stride] + src_diff[7 * src_stride]; |
| int16_t b7 = src_diff[6 * src_stride] - src_diff[7 * src_stride]; |
| |
| int16_t c0 = b0 + b2; |
| int16_t c1 = b1 + b3; |
| int16_t c2 = b0 - b2; |
| int16_t c3 = b1 - b3; |
| int16_t c4 = b4 + b6; |
| int16_t c5 = b5 + b7; |
| int16_t c6 = b4 - b6; |
| int16_t c7 = b5 - b7; |
| |
| coeff[0] = c0 + c4; |
| coeff[7] = c1 + c5; |
| coeff[3] = c2 + c6; |
| coeff[4] = c3 + c7; |
| coeff[2] = c0 - c4; |
| coeff[6] = c1 - c5; |
| coeff[1] = c2 - c6; |
| coeff[5] = c3 - c7; |
| } |
| |
| // src_diff: 16 bit, dynamic range [-32760, 32760] |
| // coeff: 19 bit |
| static void hadamard_highbd_col8_second_pass(const int16_t *src_diff, |
| ptrdiff_t src_stride, |
| int32_t *coeff) { |
| int32_t b0 = src_diff[0 * src_stride] + src_diff[1 * src_stride]; |
| int32_t b1 = src_diff[0 * src_stride] - src_diff[1 * src_stride]; |
| int32_t b2 = src_diff[2 * src_stride] + src_diff[3 * src_stride]; |
| int32_t b3 = src_diff[2 * src_stride] - src_diff[3 * src_stride]; |
| int32_t b4 = src_diff[4 * src_stride] + src_diff[5 * src_stride]; |
| int32_t b5 = src_diff[4 * src_stride] - src_diff[5 * src_stride]; |
| int32_t b6 = src_diff[6 * src_stride] + src_diff[7 * src_stride]; |
| int32_t b7 = src_diff[6 * src_stride] - src_diff[7 * src_stride]; |
| |
| int32_t c0 = b0 + b2; |
| int32_t c1 = b1 + b3; |
| int32_t c2 = b0 - b2; |
| int32_t c3 = b1 - b3; |
| int32_t c4 = b4 + b6; |
| int32_t c5 = b5 + b7; |
| int32_t c6 = b4 - b6; |
| int32_t c7 = b5 - b7; |
| |
| coeff[0] = c0 + c4; |
| coeff[7] = c1 + c5; |
| coeff[3] = c2 + c6; |
| coeff[4] = c3 + c7; |
| coeff[2] = c0 - c4; |
| coeff[6] = c1 - c5; |
| coeff[1] = c2 - c6; |
| coeff[5] = c3 - c7; |
| } |
| |
| // The order of the output coeff of the hadamard is not important. For |
| // optimization purposes the final transpose may be skipped. |
| void aom_highbd_hadamard_8x8_c(const int16_t *src_diff, ptrdiff_t src_stride, |
| tran_low_t *coeff) { |
| int idx; |
| int16_t buffer[64]; |
| int32_t buffer2[64]; |
| int16_t *tmp_buf = &buffer[0]; |
| for (idx = 0; idx < 8; ++idx) { |
| // src_diff: 13 bit |
| // buffer: 16 bit, dynamic range [-32760, 32760] |
| hadamard_highbd_col8_first_pass(src_diff, src_stride, tmp_buf); |
| tmp_buf += 8; |
| ++src_diff; |
| } |
| |
| tmp_buf = &buffer[0]; |
| for (idx = 0; idx < 8; ++idx) { |
| // buffer: 16 bit |
| // buffer2: 19 bit, dynamic range [-262080, 262080] |
| hadamard_highbd_col8_second_pass(tmp_buf, 8, buffer2 + 8 * idx); |
| ++tmp_buf; |
| } |
| |
| for (idx = 0; idx < 64; ++idx) coeff[idx] = (tran_low_t)buffer2[idx]; |
| } |
| |
| // In place 16x16 2D Hadamard transform |
| void aom_highbd_hadamard_16x16_c(const int16_t *src_diff, ptrdiff_t src_stride, |
| tran_low_t *coeff) { |
| int idx; |
| for (idx = 0; idx < 4; ++idx) { |
| // src_diff: 13 bit, dynamic range [-4095, 4095] |
| const int16_t *src_ptr = |
| src_diff + (idx >> 1) * 8 * src_stride + (idx & 0x01) * 8; |
| aom_highbd_hadamard_8x8_c(src_ptr, src_stride, coeff + idx * 64); |
| } |
| |
| // coeff: 19 bit, dynamic range [-262080, 262080] |
| for (idx = 0; idx < 64; ++idx) { |
| tran_low_t a0 = coeff[0]; |
| tran_low_t a1 = coeff[64]; |
| tran_low_t a2 = coeff[128]; |
| tran_low_t a3 = coeff[192]; |
| |
| tran_low_t b0 = (a0 + a1) >> 1; |
| tran_low_t b1 = (a0 - a1) >> 1; |
| tran_low_t b2 = (a2 + a3) >> 1; |
| tran_low_t b3 = (a2 - a3) >> 1; |
| |
| // new coeff dynamic range: 20 bit |
| coeff[0] = b0 + b2; |
| coeff[64] = b1 + b3; |
| coeff[128] = b0 - b2; |
| coeff[192] = b1 - b3; |
| |
| ++coeff; |
| } |
| } |
| |
| void aom_highbd_hadamard_32x32_c(const int16_t *src_diff, ptrdiff_t src_stride, |
| tran_low_t *coeff) { |
| int idx; |
| for (idx = 0; idx < 4; ++idx) { |
| // src_diff: 13 bit, dynamic range [-4095, 4095] |
| const int16_t *src_ptr = |
| src_diff + (idx >> 1) * 16 * src_stride + (idx & 0x01) * 16; |
| aom_highbd_hadamard_16x16_c(src_ptr, src_stride, coeff + idx * 256); |
| } |
| |
| // coeff: 20 bit |
| for (idx = 0; idx < 256; ++idx) { |
| tran_low_t a0 = coeff[0]; |
| tran_low_t a1 = coeff[256]; |
| tran_low_t a2 = coeff[512]; |
| tran_low_t a3 = coeff[768]; |
| |
| tran_low_t b0 = (a0 + a1) >> 2; |
| tran_low_t b1 = (a0 - a1) >> 2; |
| tran_low_t b2 = (a2 + a3) >> 2; |
| tran_low_t b3 = (a2 - a3) >> 2; |
| |
| // new coeff dynamic range: 20 bit |
| coeff[0] = b0 + b2; |
| coeff[256] = b1 + b3; |
| coeff[512] = b0 - b2; |
| coeff[768] = b1 - b3; |
| |
| ++coeff; |
| } |
| } |
| #endif // CONFIG_AV1_HIGHBITDEPTH |
| |
| // coeff: 16 bits, dynamic range [-32640, 32640]. |
| // length: value range {16, 64, 256, 1024}. |
| int aom_satd_c(const tran_low_t *coeff, int length) { |
| int i; |
| int satd = 0; |
| for (i = 0; i < length; ++i) satd += abs(coeff[i]); |
| |
| // satd: 26 bits, dynamic range [-32640 * 1024, 32640 * 1024] |
| return satd; |
| } |
| |
| int aom_satd_lp_c(const int16_t *coeff, int length) { |
| int satd = 0; |
| for (int i = 0; i < length; ++i) satd += abs(coeff[i]); |
| |
| // satd: 26 bits, dynamic range [-32640 * 1024, 32640 * 1024] |
| return satd; |
| } |
| |
| // Integer projection onto row vectors. |
| // height: value range {16, 32, 64, 128}. |
| void aom_int_pro_row_c(int16_t hbuf[16], const uint8_t *ref, |
| const int ref_stride, const int height) { |
| int idx; |
| const int norm_factor = height >> 1; |
| assert(height >= 2); |
| for (idx = 0; idx < 16; ++idx) { |
| int i; |
| hbuf[idx] = 0; |
| // hbuf[idx]: 14 bit, dynamic range [0, 32640]. |
| for (i = 0; i < height; ++i) hbuf[idx] += ref[i * ref_stride]; |
| // hbuf[idx]: 9 bit, dynamic range [0, 1020]. |
| hbuf[idx] /= norm_factor; |
| ++ref; |
| } |
| } |
| |
| // width: value range {16, 32, 64, 128}. |
| int16_t aom_int_pro_col_c(const uint8_t *ref, const int width) { |
| int idx; |
| int16_t sum = 0; |
| // sum: 14 bit, dynamic range [0, 32640] |
| for (idx = 0; idx < width; ++idx) sum += ref[idx]; |
| return sum; |
| } |
| |
| // ref: [0 - 510] |
| // src: [0 - 510] |
| // bwl: {2, 3, 4, 5} |
| int aom_vector_var_c(const int16_t *ref, const int16_t *src, const int bwl) { |
| int i; |
| int width = 4 << bwl; |
| int sse = 0, mean = 0, var; |
| |
| for (i = 0; i < width; ++i) { |
| int diff = ref[i] - src[i]; // diff: dynamic range [-510, 510], 10 bits. |
| mean += diff; // mean: dynamic range 16 bits. |
| sse += diff * diff; // sse: dynamic range 26 bits. |
| } |
| |
| // (mean * mean): dynamic range 31 bits. |
| var = sse - ((mean * mean) >> (bwl + 2)); |
| return var; |
| } |