/src/aom/aom_dsp/binary_codes_writer.c
Line | Count | Source (jump to first uncovered line) |
1 | | /* |
2 | | * Copyright (c) 2017, 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 "aom_dsp/bitwriter.h" |
13 | | #include "aom_dsp/binary_codes_writer.h" |
14 | | #include "aom_dsp/recenter.h" |
15 | | #include "aom_ports/bitops.h" |
16 | | |
17 | | // Codes a symbol v in [-2^mag_bits, 2^mag_bits]. |
18 | | // mag_bits is number of bits for magnitude. The alphabet is of size |
19 | | // 2 * 2^mag_bits + 1, symmetric around 0, where one bit is used to |
20 | | // indicate 0 or non-zero, mag_bits bits are used to indicate magnitide |
21 | | // and 1 more bit for the sign if non-zero. |
22 | | void aom_write_primitive_symmetric(aom_writer *w, int16_t v, |
23 | 0 | unsigned int abs_bits) { |
24 | 0 | if (v == 0) { |
25 | 0 | aom_write_bit(w, 0); |
26 | 0 | } else { |
27 | 0 | const int x = abs(v); |
28 | 0 | const int s = v < 0; |
29 | 0 | aom_write_bit(w, 1); |
30 | 0 | aom_write_bit(w, s); |
31 | 0 | aom_write_literal(w, x - 1, abs_bits); |
32 | 0 | } |
33 | 0 | } |
34 | | |
35 | 0 | int aom_count_primitive_symmetric(int16_t v, unsigned int abs_bits) { |
36 | 0 | return (v == 0 ? 1 : abs_bits + 2); |
37 | 0 | } |
38 | | |
39 | | // Encodes a value v in [0, n-1] quasi-uniformly |
40 | 0 | void aom_write_primitive_quniform(aom_writer *w, uint16_t n, uint16_t v) { |
41 | 0 | if (n <= 1) return; |
42 | 0 | const int l = get_msb(n) + 1; |
43 | 0 | const int m = (1 << l) - n; |
44 | 0 | if (v < m) { |
45 | 0 | aom_write_literal(w, v, l - 1); |
46 | 0 | } else { |
47 | 0 | aom_write_literal(w, m + ((v - m) >> 1), l - 1); |
48 | 0 | aom_write_bit(w, (v - m) & 1); |
49 | 0 | } |
50 | 0 | } |
51 | | |
52 | 0 | int aom_count_primitive_quniform(uint16_t n, uint16_t v) { |
53 | 0 | if (n <= 1) return 0; |
54 | 0 | const int l = get_msb(n) + 1; |
55 | 0 | const int m = (1 << l) - n; |
56 | 0 | return v < m ? l - 1 : l; |
57 | 0 | } |
58 | | |
59 | | // Finite subexponential code that codes a symbol v in [0, n-1] with parameter k |
60 | | void aom_write_primitive_subexpfin(aom_writer *w, uint16_t n, uint16_t k, |
61 | 0 | uint16_t v) { |
62 | 0 | int i = 0; |
63 | 0 | int mk = 0; |
64 | 0 | while (1) { |
65 | 0 | int b = (i ? k + i - 1 : k); |
66 | 0 | int a = (1 << b); |
67 | 0 | if (n <= mk + 3 * a) { |
68 | 0 | aom_write_primitive_quniform(w, n - mk, v - mk); |
69 | 0 | break; |
70 | 0 | } else { |
71 | 0 | int t = (v >= mk + a); |
72 | 0 | aom_write_bit(w, t); |
73 | 0 | if (t) { |
74 | 0 | i = i + 1; |
75 | 0 | mk += a; |
76 | 0 | } else { |
77 | 0 | aom_write_literal(w, v - mk, b); |
78 | 0 | break; |
79 | 0 | } |
80 | 0 | } |
81 | 0 | } |
82 | 0 | } |
83 | | |
84 | 0 | int aom_count_primitive_subexpfin(uint16_t n, uint16_t k, uint16_t v) { |
85 | 0 | int count = 0; |
86 | 0 | int i = 0; |
87 | 0 | int mk = 0; |
88 | 0 | while (1) { |
89 | 0 | int b = (i ? k + i - 1 : k); |
90 | 0 | int a = (1 << b); |
91 | 0 | if (n <= mk + 3 * a) { |
92 | 0 | count += aom_count_primitive_quniform(n - mk, v - mk); |
93 | 0 | break; |
94 | 0 | } else { |
95 | 0 | int t = (v >= mk + a); |
96 | 0 | count++; |
97 | 0 | if (t) { |
98 | 0 | i = i + 1; |
99 | 0 | mk += a; |
100 | 0 | } else { |
101 | 0 | count += b; |
102 | 0 | break; |
103 | 0 | } |
104 | 0 | } |
105 | 0 | } |
106 | 0 | return count; |
107 | 0 | } |
108 | | |
109 | | // Finite subexponential code that codes a symbol v in [0, n-1] with parameter k |
110 | | // based on a reference ref also in [0, n-1]. |
111 | | // Recenters symbol around r first and then uses a finite subexponential code. |
112 | | void aom_write_primitive_refsubexpfin(aom_writer *w, uint16_t n, uint16_t k, |
113 | 0 | uint16_t ref, uint16_t v) { |
114 | 0 | aom_write_primitive_subexpfin(w, n, k, recenter_finite_nonneg(n, ref, v)); |
115 | 0 | } |
116 | | |
117 | | void aom_write_signed_primitive_refsubexpfin(aom_writer *w, uint16_t n, |
118 | | uint16_t k, int16_t ref, |
119 | 0 | int16_t v) { |
120 | 0 | ref += n - 1; |
121 | 0 | v += n - 1; |
122 | 0 | const uint16_t scaled_n = (n << 1) - 1; |
123 | 0 | aom_write_primitive_refsubexpfin(w, scaled_n, k, ref, v); |
124 | 0 | } |
125 | | |
126 | | int aom_count_primitive_refsubexpfin(uint16_t n, uint16_t k, uint16_t ref, |
127 | 0 | uint16_t v) { |
128 | 0 | return aom_count_primitive_subexpfin(n, k, recenter_finite_nonneg(n, ref, v)); |
129 | 0 | } |
130 | | |
131 | | int aom_count_signed_primitive_refsubexpfin(uint16_t n, uint16_t k, int16_t ref, |
132 | 0 | int16_t v) { |
133 | 0 | ref += n - 1; |
134 | 0 | v += n - 1; |
135 | 0 | const uint16_t scaled_n = (n << 1) - 1; |
136 | 0 | return aom_count_primitive_refsubexpfin(scaled_n, k, ref, v); |
137 | 0 | } |