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
19static int update_bits[255];
20
21static 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
30static 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
64static 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
76static 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
81static 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
92static 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
97static 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
109void 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
114void vp9_compute_update_table() {
115  int i;
116  for (i = 0; i < 254; i++)
117    update_bits[i] = count_term_subexp(i);
118}
119
120int 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
141int 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
179void 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