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1 /*
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2 * H.26L/H.264/AVC/JVT/14496-10/... encoder/decoder
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3 * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
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4 *
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5 * This file is part of FFmpeg.
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6 *
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7 * FFmpeg is free software; you can redistribute it and/or
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8 * modify it under the terms of the GNU Lesser General Public
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9 * License as published by the Free Software Foundation; either
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10 * version 2.1 of the License, or (at your option) any later version.
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11 *
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12 * FFmpeg is distributed in the hope that it will be useful,
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13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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15 * Lesser General Public License for more details.
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16 *
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17 * You should have received a copy of the GNU Lesser General Public
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18 * License along with FFmpeg; if not, write to the Free Software
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19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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20 */
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21
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22 /**
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23 * @file
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24 * Context Adaptive Binary Arithmetic Coder.
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25 */
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26
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27 #include <string.h>
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28
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29 #include "libavutil/common.h"
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30 #include "libavutil/timer.h"
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31 #include "get_bits.h"
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32 #include "cabac.h"
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33 #include "cabac_functions.h"
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34
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35 #include "cabac_tablegen.h"
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36
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37 /**
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38 *
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39 * @param buf_size size of buf in bits
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40 */
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41 void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size){
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42 init_put_bits(&c->pb, buf, buf_size);
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43
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44 c->low= 0;
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45 c->range= 0x1FE;
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46 c->outstanding_count= 0;
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47 c->pb.bit_left++; //avoids firstBitFlag
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48 }
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49
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50 /**
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51 *
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52 * @param buf_size size of buf in bits
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53 */
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54 void ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size){
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55 c->bytestream_start=
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56 c->bytestream= buf;
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57 c->bytestream_end= buf + buf_size;
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58
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59 #if CABAC_BITS == 16
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60 c->low = (*c->bytestream++)<<18;
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61 c->low+= (*c->bytestream++)<<10;
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62 #else
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63 c->low = (*c->bytestream++)<<10;
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64 #endif
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65 c->low+= ((*c->bytestream++)<<2) + 2;
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66 c->range= 0x1FE;
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67 }
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68
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69 void ff_init_cabac_states(void)
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70 {
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71 static int initialized = 0;
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72
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73 if (initialized)
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74 return;
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75
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76 cabac_tableinit();
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77
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78 initialized = 1;
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79 }
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80
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81 #ifdef TEST
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82 #define SIZE 10240
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83
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84 #include "libavutil/lfg.h"
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85 #include "avcodec.h"
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86
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87 static inline void put_cabac_bit(CABACContext *c, int b){
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88 put_bits(&c->pb, 1, b);
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89 for(;c->outstanding_count; c->outstanding_count--){
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90 put_bits(&c->pb, 1, 1-b);
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91 }
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92 }
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93
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94 static inline void renorm_cabac_encoder(CABACContext *c){
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95 while(c->range < 0x100){
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96 //FIXME optimize
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97 if(c->low<0x100){
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98 put_cabac_bit(c, 0);
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99 }else if(c->low<0x200){
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100 c->outstanding_count++;
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101 c->low -= 0x100;
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102 }else{
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103 put_cabac_bit(c, 1);
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104 c->low -= 0x200;
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105 }
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106
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107 c->range+= c->range;
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108 c->low += c->low;
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109 }
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110 }
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111
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112 static void put_cabac(CABACContext *c, uint8_t * const state, int bit){
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113 int RangeLPS= ff_h264_lps_range[2*(c->range&0xC0) + *state];
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114
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115 if(bit == ((*state)&1)){
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116 c->range -= RangeLPS;
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117 *state = ff_h264_mlps_state[128 + *state];
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118 }else{
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119 c->low += c->range - RangeLPS;
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120 c->range = RangeLPS;
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121 *state= ff_h264_mlps_state[127 - *state];
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122 }
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123
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124 renorm_cabac_encoder(c);
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125 }
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126
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127 /**
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128 * @param bit 0 -> write zero bit, !=0 write one bit
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129 */
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130 static void put_cabac_bypass(CABACContext *c, int bit){
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131 c->low += c->low;
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132
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133 if(bit){
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134 c->low += c->range;
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135 }
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136 //FIXME optimize
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137 if(c->low<0x200){
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138 put_cabac_bit(c, 0);
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139 }else if(c->low<0x400){
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140 c->outstanding_count++;
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141 c->low -= 0x200;
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142 }else{
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143 put_cabac_bit(c, 1);
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144 c->low -= 0x400;
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145 }
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146 }
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147
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148 /**
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149 *
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150 * @return the number of bytes written
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151 */
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152 static int put_cabac_terminate(CABACContext *c, int bit){
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153 c->range -= 2;
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154
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155 if(!bit){
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156 renorm_cabac_encoder(c);
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157 }else{
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158 c->low += c->range;
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159 c->range= 2;
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160
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161 renorm_cabac_encoder(c);
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162
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163 av_assert0(c->low <= 0x1FF);
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164 put_cabac_bit(c, c->low>>9);
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165 put_bits(&c->pb, 2, ((c->low>>7)&3)|1);
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166
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167 flush_put_bits(&c->pb); //FIXME FIXME FIXME XXX wrong
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168 }
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169
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170 return (put_bits_count(&c->pb)+7)>>3;
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171 }
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172
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173 int main(void){
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174 CABACContext c;
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175 uint8_t b[9*SIZE];
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176 uint8_t r[9*SIZE];
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177 int i;
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178 uint8_t state[10]= {0};
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179 AVLFG prng;
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180
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181 av_lfg_init(&prng, 1);
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182 ff_init_cabac_encoder(&c, b, SIZE);
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183 ff_init_cabac_states();
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184
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185 for(i=0; i<SIZE; i++){
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186 if(2*i<SIZE) r[i] = av_lfg_get(&prng) % 7;
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187 else r[i] = (i>>8)&1;
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188 }
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189
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190 for(i=0; i<SIZE; i++){
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191 START_TIMER
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192 put_cabac_bypass(&c, r[i]&1);
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193 STOP_TIMER("put_cabac_bypass")
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194 }
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195
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196 for(i=0; i<SIZE; i++){
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197 START_TIMER
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198 put_cabac(&c, state, r[i]&1);
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199 STOP_TIMER("put_cabac")
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200 }
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201
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202 put_cabac_terminate(&c, 1);
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203
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204 ff_init_cabac_decoder(&c, b, SIZE);
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205
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206 memset(state, 0, sizeof(state));
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207
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208 for(i=0; i<SIZE; i++){
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209 START_TIMER
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210 if( (r[i]&1) != get_cabac_bypass(&c) )
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211 av_log(NULL, AV_LOG_ERROR, "CABAC bypass failure at %d\n", i);
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212 STOP_TIMER("get_cabac_bypass")
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213 }
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214
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215 for(i=0; i<SIZE; i++){
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216 START_TIMER
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217 if( (r[i]&1) != get_cabac_noinline(&c, state) )
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218 av_log(NULL, AV_LOG_ERROR, "CABAC failure at %d\n", i);
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219 STOP_TIMER("get_cabac")
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220 }
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221 if(!get_cabac_terminate(&c))
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222 av_log(NULL, AV_LOG_ERROR, "where's the Terminator?\n");
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223
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224 return 0;
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225 }
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226
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227 #endif /* TEST */
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