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 /* * Copyright (c) 2014 The WebM project authors. All Rights Reserved. * * Use of this source code is governed by a BSD-style license * that can be found in the LICENSE file in the root of the source * tree. An additional intellectual property rights grant can be found * in the file PATENTS. All contributing project authors may * be found in the AUTHORS file in the root of the source tree. */ #include #include "vpx/vpx_integer.h" #include "vpx_ports/system_state.h" static int horizontal_filter(const uint8_t *s) { return (s - s[-2]) * 2 + (s[-1] - s) * 6; } static int vertical_filter(const uint8_t *s, int p) { return (s[p] - s[-2 * p]) * 2 + (s[-p] - s) * 6; } static int variance(int sum, int sum_squared, int size) { return sum_squared / size - (sum / size) * (sum / size); } // Calculate a blockiness level for a vertical block edge. // This function returns a new blockiness metric that's defined as // p0 p1 p2 p3 // q0 q1 q2 q3 // block edge -> // r0 r1 r2 r3 // s0 s1 s2 s3 // blockiness = p0*-2+q0*6+r0*-6+s0*2 + // p1*-2+q1*6+r1*-6+s1*2 + // p2*-2+q2*6+r2*-6+s2*2 + // p3*-2+q3*6+r3*-6+s3*2 ; // reconstructed_blockiness = abs(blockiness from reconstructed buffer - // blockiness from source buffer,0) // // I make the assumption that flat blocks are much more visible than high // contrast blocks. As such, I scale the result of the blockiness calc // by dividing the blockiness by the variance of the pixels on either side // of the edge as follows: // var_0 = (q0^2+q1^2+q2^2+q3^2) - ((q0 + q1 + q2 + q3) / 4 )^2 // var_1 = (r0^2+r1^2+r2^2+r3^2) - ((r0 + r1 + r2 + r3) / 4 )^2 // The returned blockiness is the scaled value // Reconstructed blockiness / ( 1 + var_0 + var_1 ) ; static int blockiness_vertical(const uint8_t *s, int sp, const uint8_t *r, int rp, int size) { int s_blockiness = 0; int r_blockiness = 0; int sum_0 = 0; int sum_sq_0 = 0; int sum_1 = 0; int sum_sq_1 = 0; int i; int var_0; int var_1; for (i = 0; i < size; ++i, s += sp, r += rp) { s_blockiness += horizontal_filter(s); r_blockiness += horizontal_filter(r); sum_0 += s; sum_sq_0 += s*s; sum_1 += s[-1]; sum_sq_1 += s[-1]*s[-1]; } var_0 = variance(sum_0, sum_sq_0, size); var_1 = variance(sum_1, sum_sq_1, size); r_blockiness = abs(r_blockiness); s_blockiness = abs(s_blockiness); if (r_blockiness > s_blockiness) return (r_blockiness - s_blockiness) / (1 + var_0 + var_1); else return 0; } // Calculate a blockiness level for a horizontal block edge // same as above. static int blockiness_horizontal(const uint8_t *s, int sp, const uint8_t *r, int rp, int size) { int s_blockiness = 0; int r_blockiness = 0; int sum_0 = 0; int sum_sq_0 = 0; int sum_1 = 0; int sum_sq_1 = 0; int i; int var_0; int var_1; for (i = 0; i < size; ++i, ++s, ++r) { s_blockiness += vertical_filter(s, sp); r_blockiness += vertical_filter(r, rp); sum_0 += s; sum_sq_0 += s * s; sum_1 += s[-sp]; sum_sq_1 += s[-sp] * s[-sp]; } var_0 = variance(sum_0, sum_sq_0, size); var_1 = variance(sum_1, sum_sq_1, size); r_blockiness = abs(r_blockiness); s_blockiness = abs(s_blockiness); if (r_blockiness > s_blockiness) return (r_blockiness - s_blockiness) / (1 + var_0 + var_1); else return 0; } // This function returns the blockiness for the entire frame currently by // looking at all borders in steps of 4. double vp9_get_blockiness(const uint8_t *img1, int img1_pitch, const uint8_t *img2, int img2_pitch, int width, int height) { double blockiness = 0; int i, j; vpx_clear_system_state(); for (i = 0; i < height; i += 4, img1 += img1_pitch * 4, img2 += img2_pitch * 4) { for (j = 0; j < width; j += 4) { if (i > 0 && i < height && j > 0 && j < width) { blockiness += blockiness_vertical(img1 + j, img1_pitch, img2 + j, img2_pitch, 4); blockiness += blockiness_horizontal(img1 + j, img1_pitch, img2 + j, img2_pitch, 4); } } } blockiness /= width * height / 16; return blockiness; }