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