1 /*
2 * Copyright (c) 2016, Alliance for Open Media. All rights reserved.
3 *
4 * This source code is subject to the terms of the BSD 2 Clause License and
5 * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
6 * was not distributed with this source code in the LICENSE file, you can
7 * obtain it at www.aomedia.org/license/software. If the Alliance for Open
8 * Media Patent License 1.0 was not distributed with this source code in the
9 * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
10 */
11
12 #include "av1/encoder/blockiness.h"
13
14 #include <stdint.h>
15 #include <stdlib.h>
16
horizontal_filter(const uint8_t * s)17 static int horizontal_filter(const uint8_t *s) {
18 return (s[1] - s[-2]) * 2 + (s[-1] - s[0]) * 6;
19 }
20
vertical_filter(const uint8_t * s,int p)21 static int vertical_filter(const uint8_t *s, int p) {
22 return (s[p] - s[-2 * p]) * 2 + (s[-p] - s[0]) * 6;
23 }
24
variance(int sum,int sum_squared,int size)25 static int variance(int sum, int sum_squared, int size) {
26 return sum_squared / size - (sum / size) * (sum / size);
27 }
28 // Calculate a blockiness level for a vertical block edge.
29 // This function returns a new blockiness metric that's defined as
30
31 // p0 p1 p2 p3
32 // q0 q1 q2 q3
33 // block edge ->
34 // r0 r1 r2 r3
35 // s0 s1 s2 s3
36
37 // blockiness = p0*-2+q0*6+r0*-6+s0*2 +
38 // p1*-2+q1*6+r1*-6+s1*2 +
39 // p2*-2+q2*6+r2*-6+s2*2 +
40 // p3*-2+q3*6+r3*-6+s3*2 ;
41
42 // reconstructed_blockiness = abs(blockiness from reconstructed buffer -
43 // blockiness from source buffer,0)
44 //
45 // I make the assumption that flat blocks are much more visible than high
46 // contrast blocks. As such, I scale the result of the blockiness calc
47 // by dividing the blockiness by the variance of the pixels on either side
48 // of the edge as follows:
49 // var_0 = (q0^2+q1^2+q2^2+q3^2) - ((q0 + q1 + q2 + q3) / 4 )^2
50 // var_1 = (r0^2+r1^2+r2^2+r3^2) - ((r0 + r1 + r2 + r3) / 4 )^2
51 // The returned blockiness is the scaled value
52 // Reconstructed blockiness / ( 1 + var_0 + var_1 ) ;
blockiness_vertical(const uint8_t * s,int sp,const uint8_t * r,int rp,int size)53 static int blockiness_vertical(const uint8_t *s, int sp, const uint8_t *r,
54 int rp, int size) {
55 int s_blockiness = 0;
56 int r_blockiness = 0;
57 int sum_0 = 0;
58 int sum_sq_0 = 0;
59 int sum_1 = 0;
60 int sum_sq_1 = 0;
61 int i;
62 int var_0;
63 int var_1;
64 for (i = 0; i < size; ++i, s += sp, r += rp) {
65 s_blockiness += horizontal_filter(s);
66 r_blockiness += horizontal_filter(r);
67 sum_0 += s[0];
68 sum_sq_0 += s[0] * s[0];
69 sum_1 += s[-1];
70 sum_sq_1 += s[-1] * s[-1];
71 }
72 var_0 = variance(sum_0, sum_sq_0, size);
73 var_1 = variance(sum_1, sum_sq_1, size);
74 r_blockiness = abs(r_blockiness);
75 s_blockiness = abs(s_blockiness);
76
77 if (r_blockiness > s_blockiness)
78 return (r_blockiness - s_blockiness) / (1 + var_0 + var_1);
79 else
80 return 0;
81 }
82
83 // Calculate a blockiness level for a horizontal block edge
84 // same as above.
blockiness_horizontal(const uint8_t * s,int sp,const uint8_t * r,int rp,int size)85 static int blockiness_horizontal(const uint8_t *s, int sp, const uint8_t *r,
86 int rp, int size) {
87 int s_blockiness = 0;
88 int r_blockiness = 0;
89 int sum_0 = 0;
90 int sum_sq_0 = 0;
91 int sum_1 = 0;
92 int sum_sq_1 = 0;
93 int i;
94 int var_0;
95 int var_1;
96 for (i = 0; i < size; ++i, ++s, ++r) {
97 s_blockiness += vertical_filter(s, sp);
98 r_blockiness += vertical_filter(r, rp);
99 sum_0 += s[0];
100 sum_sq_0 += s[0] * s[0];
101 sum_1 += s[-sp];
102 sum_sq_1 += s[-sp] * s[-sp];
103 }
104 var_0 = variance(sum_0, sum_sq_0, size);
105 var_1 = variance(sum_1, sum_sq_1, size);
106 r_blockiness = abs(r_blockiness);
107 s_blockiness = abs(s_blockiness);
108
109 if (r_blockiness > s_blockiness)
110 return (r_blockiness - s_blockiness) / (1 + var_0 + var_1);
111 else
112 return 0;
113 }
114
115 // This function returns the blockiness for the entire frame currently by
116 // looking at all borders in steps of 4.
av1_get_blockiness(const unsigned char * img1,int img1_pitch,const unsigned char * img2,int img2_pitch,int width,int height)117 double av1_get_blockiness(const unsigned char *img1, int img1_pitch,
118 const unsigned char *img2, int img2_pitch, int width,
119 int height) {
120 double blockiness = 0;
121 int i, j;
122 for (i = 0; i < height;
123 i += 4, img1 += img1_pitch * 4, img2 += img2_pitch * 4) {
124 for (j = 0; j < width; j += 4) {
125 if (i > 0 && i < height && j > 0 && j < width) {
126 blockiness +=
127 blockiness_vertical(img1 + j, img1_pitch, img2 + j, img2_pitch, 4);
128 blockiness += blockiness_horizontal(img1 + j, img1_pitch, img2 + j,
129 img2_pitch, 4);
130 }
131 }
132 }
133 blockiness /= width * height / 16;
134 return blockiness;
135 }
136