1 /*
2 * Copyright (c) 2013 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
11 #include "vp9/common/vp9_common.h"
12 #include "vp9/common/vp9_entropy.h"
13
14 #include "vp9/encoder/vp9_cost.h"
15 #include "vp9/encoder/vp9_writer.h"
16
17 #define vp9_cost_upd256 ((int)(vp9_cost_one(upd) - vp9_cost_zero(upd)))
18
19 static int update_bits[255];
20
recenter_nonneg(int v,int m)21 static int recenter_nonneg(int v, int m) {
22 if (v > (m << 1))
23 return v;
24 else if (v >= m)
25 return ((v - m) << 1);
26 else
27 return ((m - v) << 1) - 1;
28 }
29
remap_prob(int v,int m)30 static int remap_prob(int v, int m) {
31 int i;
32 static const int map_table[MAX_PROB - 1] = {
33 // generated by:
34 // map_table[j] = split_index(j, MAX_PROB - 1, MODULUS_PARAM);
35 20, 21, 22, 23, 24, 25, 0, 26, 27, 28, 29, 30, 31, 32, 33,
36 34, 35, 36, 37, 1, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,
37 48, 49, 2, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61,
38 3, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 4, 74,
39 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 5, 86, 87, 88,
40 89, 90, 91, 92, 93, 94, 95, 96, 97, 6, 98, 99, 100, 101, 102,
41 103, 104, 105, 106, 107, 108, 109, 7, 110, 111, 112, 113, 114, 115, 116,
42 117, 118, 119, 120, 121, 8, 122, 123, 124, 125, 126, 127, 128, 129, 130,
43 131, 132, 133, 9, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144,
44 145, 10, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 11,
45 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 12, 170, 171,
46 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 13, 182, 183, 184, 185,
47 186, 187, 188, 189, 190, 191, 192, 193, 14, 194, 195, 196, 197, 198, 199,
48 200, 201, 202, 203, 204, 205, 15, 206, 207, 208, 209, 210, 211, 212, 213,
49 214, 215, 216, 217, 16, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227,
50 228, 229, 17, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241,
51 18, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 19,
52 };
53 v--;
54 m--;
55 if ((m << 1) <= MAX_PROB)
56 i = recenter_nonneg(v, m) - 1;
57 else
58 i = recenter_nonneg(MAX_PROB - 1 - v, MAX_PROB - 1 - m) - 1;
59
60 i = map_table[i];
61 return i;
62 }
63
count_term_subexp(int word)64 static int count_term_subexp(int word) {
65 if (word < 16)
66 return 5;
67 if (word < 32)
68 return 6;
69 if (word < 64)
70 return 8;
71 if (word < 129)
72 return 10;
73 return 11;
74 }
75
prob_diff_update_cost(vp9_prob newp,vp9_prob oldp)76 static int prob_diff_update_cost(vp9_prob newp, vp9_prob oldp) {
77 int delp = remap_prob(newp, oldp);
78 return update_bits[delp] * 256;
79 }
80
encode_uniform(vp9_writer * w,int v)81 static void encode_uniform(vp9_writer *w, int v) {
82 const int l = 8;
83 const int m = (1 << l) - 191;
84 if (v < m) {
85 vp9_write_literal(w, v, l - 1);
86 } else {
87 vp9_write_literal(w, m + ((v - m) >> 1), l - 1);
88 vp9_write_literal(w, (v - m) & 1, 1);
89 }
90 }
91
write_bit_gte(vp9_writer * w,int word,int test)92 static INLINE int write_bit_gte(vp9_writer *w, int word, int test) {
93 vp9_write_literal(w, word >= test, 1);
94 return word >= test;
95 }
96
encode_term_subexp(vp9_writer * w,int word)97 static void encode_term_subexp(vp9_writer *w, int word) {
98 if (!write_bit_gte(w, word, 16)) {
99 vp9_write_literal(w, word, 4);
100 } else if (!write_bit_gte(w, word, 32)) {
101 vp9_write_literal(w, word - 16, 4);
102 } else if (!write_bit_gte(w, word, 64)) {
103 vp9_write_literal(w, word - 32, 5);
104 } else {
105 encode_uniform(w, word - 64);
106 }
107 }
108
vp9_write_prob_diff_update(vp9_writer * w,vp9_prob newp,vp9_prob oldp)109 void vp9_write_prob_diff_update(vp9_writer *w, vp9_prob newp, vp9_prob oldp) {
110 const int delp = remap_prob(newp, oldp);
111 encode_term_subexp(w, delp);
112 }
113
vp9_compute_update_table()114 void vp9_compute_update_table() {
115 int i;
116 for (i = 0; i < 254; i++)
117 update_bits[i] = count_term_subexp(i);
118 }
119
vp9_prob_diff_update_savings_search(const unsigned int * ct,vp9_prob oldp,vp9_prob * bestp,vp9_prob upd)120 int vp9_prob_diff_update_savings_search(const unsigned int *ct,
121 vp9_prob oldp, vp9_prob *bestp,
122 vp9_prob upd) {
123 const int old_b = cost_branch256(ct, oldp);
124 int bestsavings = 0;
125 vp9_prob newp, bestnewp = oldp;
126 const int step = *bestp > oldp ? -1 : 1;
127
128 for (newp = *bestp; newp != oldp; newp += step) {
129 const int new_b = cost_branch256(ct, newp);
130 const int update_b = prob_diff_update_cost(newp, oldp) + vp9_cost_upd256;
131 const int savings = old_b - new_b - update_b;
132 if (savings > bestsavings) {
133 bestsavings = savings;
134 bestnewp = newp;
135 }
136 }
137 *bestp = bestnewp;
138 return bestsavings;
139 }
140
vp9_prob_diff_update_savings_search_model(const unsigned int * ct,const vp9_prob * oldp,vp9_prob * bestp,vp9_prob upd)141 int vp9_prob_diff_update_savings_search_model(const unsigned int *ct,
142 const vp9_prob *oldp,
143 vp9_prob *bestp,
144 vp9_prob upd) {
145 int i, old_b, new_b, update_b, savings, bestsavings, step;
146 int newp;
147 vp9_prob bestnewp, newplist[ENTROPY_NODES], oldplist[ENTROPY_NODES];
148 vp9_model_to_full_probs(oldp, oldplist);
149 vpx_memcpy(newplist, oldp, sizeof(vp9_prob) * UNCONSTRAINED_NODES);
150 for (i = UNCONSTRAINED_NODES, old_b = 0; i < ENTROPY_NODES; ++i)
151 old_b += cost_branch256(ct + 2 * i, oldplist[i]);
152 old_b += cost_branch256(ct + 2 * PIVOT_NODE, oldplist[PIVOT_NODE]);
153
154 bestsavings = 0;
155 bestnewp = oldp[PIVOT_NODE];
156
157 step = (*bestp > oldp[PIVOT_NODE] ? -1 : 1);
158
159 for (newp = *bestp; newp != oldp[PIVOT_NODE]; newp += step) {
160 if (newp < 1 || newp > 255)
161 continue;
162 newplist[PIVOT_NODE] = newp;
163 vp9_model_to_full_probs(newplist, newplist);
164 for (i = UNCONSTRAINED_NODES, new_b = 0; i < ENTROPY_NODES; ++i)
165 new_b += cost_branch256(ct + 2 * i, newplist[i]);
166 new_b += cost_branch256(ct + 2 * PIVOT_NODE, newplist[PIVOT_NODE]);
167 update_b = prob_diff_update_cost(newp, oldp[PIVOT_NODE]) +
168 vp9_cost_upd256;
169 savings = old_b - new_b - update_b;
170 if (savings > bestsavings) {
171 bestsavings = savings;
172 bestnewp = newp;
173 }
174 }
175 *bestp = bestnewp;
176 return bestsavings;
177 }
178
vp9_cond_prob_diff_update(vp9_writer * w,vp9_prob * oldp,const unsigned int ct[2])179 void vp9_cond_prob_diff_update(vp9_writer *w, vp9_prob *oldp,
180 const unsigned int ct[2]) {
181 const vp9_prob upd = DIFF_UPDATE_PROB;
182 vp9_prob newp = get_binary_prob(ct[0], ct[1]);
183 const int savings = vp9_prob_diff_update_savings_search(ct, *oldp, &newp,
184 upd);
185 assert(newp >= 1);
186 if (savings > 0) {
187 vp9_write(w, 1, upd);
188 vp9_write_prob_diff_update(w, newp, *oldp);
189 *oldp = newp;
190 } else {
191 vp9_write(w, 0, upd);
192 }
193 }
194