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#include "vpx_dsp/bitwriter.h"
11
12#include "vp9/common/vp9_common.h"
13#include "vp9/common/vp9_entropy.h"
14#include "vp9/encoder/vp9_cost.h"
15#include "vp9/encoder/vp9_subexp.h"
16
17#define vp9_cost_upd256  ((int)(vp9_cost_one(upd) - vp9_cost_zero(upd)))
18
19static const int update_bits[255] = {
20   5,  5,  5,  5,  5,  5,  5,  5,  5,  5,  5,  5,  5,  5,  5,  5,
21   6,  6,  6,  6,  6,  6,  6,  6,  6,  6,  6,  6,  6,  6,  6,  6,
22   8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,
23   8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,
24  10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,
25  10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,
26  10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,
27  10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,
28  10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
29  11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
30  11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
31  11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
32  11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
33  11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
34  11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
35  11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,  0,
36};
37
38static int recenter_nonneg(int v, int m) {
39  if (v > (m << 1))
40    return v;
41  else if (v >= m)
42    return ((v - m) << 1);
43  else
44    return ((m - v) << 1) - 1;
45}
46
47static int remap_prob(int v, int m) {
48  int i;
49  static const int map_table[MAX_PROB - 1] = {
50    // generated by:
51    //   map_table[j] = split_index(j, MAX_PROB - 1, MODULUS_PARAM);
52     20,  21,  22,  23,  24,  25,   0,  26,  27,  28,  29,  30,  31,  32,  33,
53     34,  35,  36,  37,   1,  38,  39,  40,  41,  42,  43,  44,  45,  46,  47,
54     48,  49,   2,  50,  51,  52,  53,  54,  55,  56,  57,  58,  59,  60,  61,
55      3,  62,  63,  64,  65,  66,  67,  68,  69,  70,  71,  72,  73,   4,  74,
56     75,  76,  77,  78,  79,  80,  81,  82,  83,  84,  85,   5,  86,  87,  88,
57     89,  90,  91,  92,  93,  94,  95,  96,  97,   6,  98,  99, 100, 101, 102,
58    103, 104, 105, 106, 107, 108, 109,   7, 110, 111, 112, 113, 114, 115, 116,
59    117, 118, 119, 120, 121,   8, 122, 123, 124, 125, 126, 127, 128, 129, 130,
60    131, 132, 133,   9, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144,
61    145,  10, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157,  11,
62    158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169,  12, 170, 171,
63    172, 173, 174, 175, 176, 177, 178, 179, 180, 181,  13, 182, 183, 184, 185,
64    186, 187, 188, 189, 190, 191, 192, 193,  14, 194, 195, 196, 197, 198, 199,
65    200, 201, 202, 203, 204, 205,  15, 206, 207, 208, 209, 210, 211, 212, 213,
66    214, 215, 216, 217,  16, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227,
67    228, 229,  17, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241,
68     18, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253,  19,
69  };
70  v--;
71  m--;
72  if ((m << 1) <= MAX_PROB)
73    i = recenter_nonneg(v, m) - 1;
74  else
75    i = recenter_nonneg(MAX_PROB - 1 - v, MAX_PROB - 1 - m) - 1;
76
77  i = map_table[i];
78  return i;
79}
80
81static int prob_diff_update_cost(vpx_prob newp, vpx_prob oldp) {
82  int delp = remap_prob(newp, oldp);
83  return update_bits[delp] * 256;
84}
85
86static void encode_uniform(vpx_writer *w, int v) {
87  const int l = 8;
88  const int m = (1 << l) - 191;
89  if (v < m) {
90    vpx_write_literal(w, v, l - 1);
91  } else {
92    vpx_write_literal(w, m + ((v - m) >> 1), l - 1);
93    vpx_write_literal(w, (v - m) & 1, 1);
94  }
95}
96
97static INLINE int write_bit_gte(vpx_writer *w, int word, int test) {
98  vpx_write_literal(w, word >= test, 1);
99  return word >= test;
100}
101
102static void encode_term_subexp(vpx_writer *w, int word) {
103  if (!write_bit_gte(w, word, 16)) {
104    vpx_write_literal(w, word, 4);
105  } else if (!write_bit_gte(w, word, 32)) {
106    vpx_write_literal(w, word - 16, 4);
107  } else if (!write_bit_gte(w, word, 64)) {
108    vpx_write_literal(w, word - 32, 5);
109  } else {
110    encode_uniform(w, word - 64);
111  }
112}
113
114void vp9_write_prob_diff_update(vpx_writer *w, vpx_prob newp, vpx_prob oldp) {
115  const int delp = remap_prob(newp, oldp);
116  encode_term_subexp(w, delp);
117}
118
119int vp9_prob_diff_update_savings_search(const unsigned int *ct,
120                                        vpx_prob oldp, vpx_prob *bestp,
121                                        vpx_prob upd) {
122  const int old_b = cost_branch256(ct, oldp);
123  int bestsavings = 0;
124  vpx_prob newp, bestnewp = oldp;
125  const int step = *bestp > oldp ? -1 : 1;
126
127  for (newp = *bestp; newp != oldp; newp += step) {
128    const int new_b = cost_branch256(ct, newp);
129    const int update_b = prob_diff_update_cost(newp, oldp) + vp9_cost_upd256;
130    const int savings = old_b - new_b - update_b;
131    if (savings > bestsavings) {
132      bestsavings = savings;
133      bestnewp = newp;
134    }
135  }
136  *bestp = bestnewp;
137  return bestsavings;
138}
139
140int vp9_prob_diff_update_savings_search_model(const unsigned int *ct,
141                                              const vpx_prob *oldp,
142                                              vpx_prob *bestp,
143                                              vpx_prob upd,
144                                              int stepsize) {
145  int i, old_b, new_b, update_b, savings, bestsavings, step;
146  int newp;
147  vpx_prob bestnewp, newplist[ENTROPY_NODES], oldplist[ENTROPY_NODES];
148  vp9_model_to_full_probs(oldp, oldplist);
149  memcpy(newplist, oldp, sizeof(vpx_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  if (*bestp > oldp[PIVOT_NODE]) {
158    step = -stepsize;
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  } else {
176    step = stepsize;
177    for (newp = *bestp; newp < oldp[PIVOT_NODE]; newp += step) {
178      if (newp < 1 || newp > 255)
179        continue;
180      newplist[PIVOT_NODE] = newp;
181      vp9_model_to_full_probs(newplist, newplist);
182      for (i = UNCONSTRAINED_NODES, new_b = 0; i < ENTROPY_NODES; ++i)
183        new_b += cost_branch256(ct + 2 * i, newplist[i]);
184      new_b += cost_branch256(ct + 2 * PIVOT_NODE, newplist[PIVOT_NODE]);
185      update_b = prob_diff_update_cost(newp, oldp[PIVOT_NODE]) +
186          vp9_cost_upd256;
187      savings = old_b - new_b - update_b;
188      if (savings > bestsavings) {
189        bestsavings = savings;
190        bestnewp = newp;
191      }
192    }
193  }
194
195  *bestp = bestnewp;
196  return bestsavings;
197}
198
199void vp9_cond_prob_diff_update(vpx_writer *w, vpx_prob *oldp,
200                               const unsigned int ct[2]) {
201  const vpx_prob upd = DIFF_UPDATE_PROB;
202  vpx_prob newp = get_binary_prob(ct[0], ct[1]);
203  const int savings = vp9_prob_diff_update_savings_search(ct, *oldp, &newp,
204                                                          upd);
205  assert(newp >= 1);
206  if (savings > 0) {
207    vpx_write(w, 1, upd);
208    vp9_write_prob_diff_update(w, newp, *oldp);
209    *oldp = newp;
210  } else {
211    vpx_write(w, 0, upd);
212  }
213}
214