1 /*
2 * Copyright (c) 2014 The WebM project authors. All Rights Reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10 #include <stdlib.h>
11
12 #include "vpx/vpx_integer.h"
13 #include "vpx_ports/system_state.h"
14
horizontal_filter(const uint8_t * s)15 static int horizontal_filter(const uint8_t *s) {
16 return (s[1] - s[-2]) * 2 + (s[-1] - s[0]) * 6;
17 }
18
vertical_filter(const uint8_t * s,int p)19 static int vertical_filter(const uint8_t *s, int p) {
20 return (s[p] - s[-2 * p]) * 2 + (s[-p] - s[0]) * 6;
21 }
22
variance(int sum,int sum_squared,int size)23 static int variance(int sum, int sum_squared, int size) {
24 return sum_squared / size - (sum / size) * (sum / size);
25 }
26 // Calculate a blockiness level for a vertical block edge.
27 // This function returns a new blockiness metric that's defined as
28
29 // p0 p1 p2 p3
30 // q0 q1 q2 q3
31 // block edge ->
32 // r0 r1 r2 r3
33 // s0 s1 s2 s3
34
35 // blockiness = p0*-2+q0*6+r0*-6+s0*2 +
36 // p1*-2+q1*6+r1*-6+s1*2 +
37 // p2*-2+q2*6+r2*-6+s2*2 +
38 // p3*-2+q3*6+r3*-6+s3*2 ;
39
40 // reconstructed_blockiness = abs(blockiness from reconstructed buffer -
41 // blockiness from source buffer,0)
42 //
43 // I make the assumption that flat blocks are much more visible than high
44 // contrast blocks. As such, I scale the result of the blockiness calc
45 // by dividing the blockiness by the variance of the pixels on either side
46 // of the edge as follows:
47 // var_0 = (q0^2+q1^2+q2^2+q3^2) - ((q0 + q1 + q2 + q3) / 4 )^2
48 // var_1 = (r0^2+r1^2+r2^2+r3^2) - ((r0 + r1 + r2 + r3) / 4 )^2
49 // The returned blockiness is the scaled value
50 // Reconstructed blockiness / ( 1 + var_0 + var_1 ) ;
blockiness_vertical(const uint8_t * s,int sp,const uint8_t * r,int rp,int size)51 static int blockiness_vertical(const uint8_t *s, int sp, const uint8_t *r,
52 int rp, int size) {
53 int s_blockiness = 0;
54 int r_blockiness = 0;
55 int sum_0 = 0;
56 int sum_sq_0 = 0;
57 int sum_1 = 0;
58 int sum_sq_1 = 0;
59 int i;
60 int var_0;
61 int var_1;
62 for (i = 0; i < size; ++i, s += sp, r += rp) {
63 s_blockiness += horizontal_filter(s);
64 r_blockiness += horizontal_filter(r);
65 sum_0 += s[0];
66 sum_sq_0 += s[0] * s[0];
67 sum_1 += s[-1];
68 sum_sq_1 += s[-1] * s[-1];
69 }
70 var_0 = variance(sum_0, sum_sq_0, size);
71 var_1 = variance(sum_1, sum_sq_1, size);
72 r_blockiness = abs(r_blockiness);
73 s_blockiness = abs(s_blockiness);
74
75 if (r_blockiness > s_blockiness)
76 return (r_blockiness - s_blockiness) / (1 + var_0 + var_1);
77 else
78 return 0;
79 }
80
81 // Calculate a blockiness level for a horizontal block edge
82 // same as above.
blockiness_horizontal(const uint8_t * s,int sp,const uint8_t * r,int rp,int size)83 static int blockiness_horizontal(const uint8_t *s, int sp, const uint8_t *r,
84 int rp, int size) {
85 int s_blockiness = 0;
86 int r_blockiness = 0;
87 int sum_0 = 0;
88 int sum_sq_0 = 0;
89 int sum_1 = 0;
90 int sum_sq_1 = 0;
91 int i;
92 int var_0;
93 int var_1;
94 for (i = 0; i < size; ++i, ++s, ++r) {
95 s_blockiness += vertical_filter(s, sp);
96 r_blockiness += vertical_filter(r, rp);
97 sum_0 += s[0];
98 sum_sq_0 += s[0] * s[0];
99 sum_1 += s[-sp];
100 sum_sq_1 += s[-sp] * s[-sp];
101 }
102 var_0 = variance(sum_0, sum_sq_0, size);
103 var_1 = variance(sum_1, sum_sq_1, size);
104 r_blockiness = abs(r_blockiness);
105 s_blockiness = abs(s_blockiness);
106
107 if (r_blockiness > s_blockiness)
108 return (r_blockiness - s_blockiness) / (1 + var_0 + var_1);
109 else
110 return 0;
111 }
112
113 // This function returns the blockiness for the entire frame currently by
114 // looking at all borders in steps of 4.
vp9_get_blockiness(const uint8_t * img1,int img1_pitch,const uint8_t * img2,int img2_pitch,int width,int height)115 double vp9_get_blockiness(const uint8_t *img1, int img1_pitch,
116 const uint8_t *img2, int img2_pitch, int width,
117 int height) {
118 double blockiness = 0;
119 int i, j;
120 vpx_clear_system_state();
121 for (i = 0; i < height;
122 i += 4, img1 += img1_pitch * 4, img2 += img2_pitch * 4) {
123 for (j = 0; j < width; j += 4) {
124 if (i > 0 && i < height && j > 0 && j < width) {
125 blockiness +=
126 blockiness_vertical(img1 + j, img1_pitch, img2 + j, img2_pitch, 4);
127 blockiness += blockiness_horizontal(img1 + j, img1_pitch, img2 + j,
128 img2_pitch, 4);
129 }
130 }
131 }
132 blockiness /= width * height / 16;
133 return blockiness;
134 }
135