libavcodec/cabac.c
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00001 /*
00002  * H.26L/H.264/AVC/JVT/14496-10/... encoder/decoder
00003  * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
00004  *
00005  * This file is part of Libav.
00006  *
00007  * Libav is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * Libav is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with Libav; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00027 #include <string.h>
00028 
00029 #include "libavutil/common.h"
00030 #include "get_bits.h"
00031 #include "cabac.h"
00032 #include "cabac_functions.h"
00033 
00034 static const uint8_t lps_range[64][4]= {
00035 {128,176,208,240}, {128,167,197,227}, {128,158,187,216}, {123,150,178,205},
00036 {116,142,169,195}, {111,135,160,185}, {105,128,152,175}, {100,122,144,166},
00037 { 95,116,137,158}, { 90,110,130,150}, { 85,104,123,142}, { 81, 99,117,135},
00038 { 77, 94,111,128}, { 73, 89,105,122}, { 69, 85,100,116}, { 66, 80, 95,110},
00039 { 62, 76, 90,104}, { 59, 72, 86, 99}, { 56, 69, 81, 94}, { 53, 65, 77, 89},
00040 { 51, 62, 73, 85}, { 48, 59, 69, 80}, { 46, 56, 66, 76}, { 43, 53, 63, 72},
00041 { 41, 50, 59, 69}, { 39, 48, 56, 65}, { 37, 45, 54, 62}, { 35, 43, 51, 59},
00042 { 33, 41, 48, 56}, { 32, 39, 46, 53}, { 30, 37, 43, 50}, { 29, 35, 41, 48},
00043 { 27, 33, 39, 45}, { 26, 31, 37, 43}, { 24, 30, 35, 41}, { 23, 28, 33, 39},
00044 { 22, 27, 32, 37}, { 21, 26, 30, 35}, { 20, 24, 29, 33}, { 19, 23, 27, 31},
00045 { 18, 22, 26, 30}, { 17, 21, 25, 28}, { 16, 20, 23, 27}, { 15, 19, 22, 25},
00046 { 14, 18, 21, 24}, { 14, 17, 20, 23}, { 13, 16, 19, 22}, { 12, 15, 18, 21},
00047 { 12, 14, 17, 20}, { 11, 14, 16, 19}, { 11, 13, 15, 18}, { 10, 12, 15, 17},
00048 { 10, 12, 14, 16}, {  9, 11, 13, 15}, {  9, 11, 12, 14}, {  8, 10, 12, 14},
00049 {  8,  9, 11, 13}, {  7,  9, 11, 12}, {  7,  9, 10, 12}, {  7,  8, 10, 11},
00050 {  6,  8,  9, 11}, {  6,  7,  9, 10}, {  6,  7,  8,  9}, {  2,  2,  2,  2},
00051 };
00052 
00053 uint8_t ff_h264_mlps_state[4*64];
00054 uint8_t ff_h264_lps_range[4*2*64];
00055 static uint8_t h264_mps_state[2 * 64];
00056 
00057 static const uint8_t mps_state[64]= {
00058   1, 2, 3, 4, 5, 6, 7, 8,
00059   9,10,11,12,13,14,15,16,
00060  17,18,19,20,21,22,23,24,
00061  25,26,27,28,29,30,31,32,
00062  33,34,35,36,37,38,39,40,
00063  41,42,43,44,45,46,47,48,
00064  49,50,51,52,53,54,55,56,
00065  57,58,59,60,61,62,62,63,
00066 };
00067 
00068 static const uint8_t lps_state[64]= {
00069   0, 0, 1, 2, 2, 4, 4, 5,
00070   6, 7, 8, 9, 9,11,11,12,
00071  13,13,15,15,16,16,18,18,
00072  19,19,21,21,22,22,23,24,
00073  24,25,26,26,27,27,28,29,
00074  29,30,30,30,31,32,32,33,
00075  33,33,34,34,35,35,35,36,
00076  36,36,37,37,37,38,38,63,
00077 };
00078 
00079 const uint8_t ff_h264_norm_shift[512]= {
00080  9,8,7,7,6,6,6,6,5,5,5,5,5,5,5,5,
00081  4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
00082  3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
00083  3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
00084  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
00085  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
00086  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
00087  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
00088  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
00089  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
00090  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
00091  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
00092  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
00093  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
00094  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
00095  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
00096  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
00097  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
00098  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
00099  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
00100 };
00101 
00106 void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size){
00107     init_put_bits(&c->pb, buf, buf_size);
00108 
00109     c->low= 0;
00110     c->range= 0x1FE;
00111     c->outstanding_count= 0;
00112     c->pb.bit_left++; //avoids firstBitFlag
00113 }
00114 
00119 void ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size){
00120     c->bytestream_start=
00121     c->bytestream= buf;
00122     c->bytestream_end= buf + buf_size;
00123 
00124 #if CABAC_BITS == 16
00125     c->low =  (*c->bytestream++)<<18;
00126     c->low+=  (*c->bytestream++)<<10;
00127 #else
00128     c->low =  (*c->bytestream++)<<10;
00129 #endif
00130     c->low+= ((*c->bytestream++)<<2) + 2;
00131     c->range= 0x1FE;
00132 }
00133 
00134 void ff_init_cabac_states(CABACContext *c){
00135     int i, j;
00136 
00137     for(i=0; i<64; i++){
00138         for(j=0; j<4; j++){ //FIXME check if this is worth the 1 shift we save
00139             ff_h264_lps_range[j*2*64+2*i+0]=
00140             ff_h264_lps_range[j*2*64+2*i+1]= lps_range[i][j];
00141         }
00142 
00143         ff_h264_mlps_state[128+2*i+0]=
00144         h264_mps_state[2 * i + 0] = 2 * mps_state[i] + 0;
00145         ff_h264_mlps_state[128+2*i+1]=
00146         h264_mps_state[2 * i + 1] = 2 * mps_state[i] + 1;
00147 
00148         if( i ){
00149             ff_h264_mlps_state[128-2*i-1]= 2*lps_state[i]+0;
00150             ff_h264_mlps_state[128-2*i-2]= 2*lps_state[i]+1;
00151         }else{
00152             ff_h264_mlps_state[128-2*i-1]= 1;
00153             ff_h264_mlps_state[128-2*i-2]= 0;
00154         }
00155     }
00156 }
00157 
00158 #ifdef TEST
00159 #define SIZE 10240
00160 
00161 #include "libavutil/lfg.h"
00162 #include "avcodec.h"
00163 #include "cabac.h"
00164 
00165 static inline void put_cabac_bit(CABACContext *c, int b){
00166     put_bits(&c->pb, 1, b);
00167     for(;c->outstanding_count; c->outstanding_count--){
00168         put_bits(&c->pb, 1, 1-b);
00169     }
00170 }
00171 
00172 static inline void renorm_cabac_encoder(CABACContext *c){
00173     while(c->range < 0x100){
00174         //FIXME optimize
00175         if(c->low<0x100){
00176             put_cabac_bit(c, 0);
00177         }else if(c->low<0x200){
00178             c->outstanding_count++;
00179             c->low -= 0x100;
00180         }else{
00181             put_cabac_bit(c, 1);
00182             c->low -= 0x200;
00183         }
00184 
00185         c->range+= c->range;
00186         c->low += c->low;
00187     }
00188 }
00189 
00190 static void put_cabac(CABACContext *c, uint8_t * const state, int bit){
00191     int RangeLPS= ff_h264_lps_range[2*(c->range&0xC0) + *state];
00192 
00193     if(bit == ((*state)&1)){
00194         c->range -= RangeLPS;
00195         *state    = h264_mps_state[*state];
00196     }else{
00197         c->low += c->range - RangeLPS;
00198         c->range = RangeLPS;
00199     }
00200 
00201     renorm_cabac_encoder(c);
00202 }
00203 
00207 static void put_cabac_bypass(CABACContext *c, int bit){
00208     c->low += c->low;
00209 
00210     if(bit){
00211         c->low += c->range;
00212     }
00213 //FIXME optimize
00214     if(c->low<0x200){
00215         put_cabac_bit(c, 0);
00216     }else if(c->low<0x400){
00217         c->outstanding_count++;
00218         c->low -= 0x200;
00219     }else{
00220         put_cabac_bit(c, 1);
00221         c->low -= 0x400;
00222     }
00223 }
00224 
00229 static int put_cabac_terminate(CABACContext *c, int bit){
00230     c->range -= 2;
00231 
00232     if(!bit){
00233         renorm_cabac_encoder(c);
00234     }else{
00235         c->low += c->range;
00236         c->range= 2;
00237 
00238         renorm_cabac_encoder(c);
00239 
00240         assert(c->low <= 0x1FF);
00241         put_cabac_bit(c, c->low>>9);
00242         put_bits(&c->pb, 2, ((c->low>>7)&3)|1);
00243 
00244         flush_put_bits(&c->pb); //FIXME FIXME FIXME XXX wrong
00245     }
00246 
00247     return (put_bits_count(&c->pb)+7)>>3;
00248 }
00249 
00250 int main(void){
00251     CABACContext c;
00252     uint8_t b[9*SIZE];
00253     uint8_t r[9*SIZE];
00254     int i;
00255     uint8_t state[10]= {0};
00256     AVLFG prng;
00257 
00258     av_lfg_init(&prng, 1);
00259     ff_init_cabac_encoder(&c, b, SIZE);
00260     ff_init_cabac_states(&c);
00261 
00262     for(i=0; i<SIZE; i++){
00263         r[i] = av_lfg_get(&prng) % 7;
00264     }
00265 
00266     for(i=0; i<SIZE; i++){
00267 START_TIMER
00268         put_cabac_bypass(&c, r[i]&1);
00269 STOP_TIMER("put_cabac_bypass")
00270     }
00271 
00272     for(i=0; i<SIZE; i++){
00273 START_TIMER
00274         put_cabac(&c, state, r[i]&1);
00275 STOP_TIMER("put_cabac")
00276     }
00277 
00278     put_cabac_terminate(&c, 1);
00279 
00280     ff_init_cabac_decoder(&c, b, SIZE);
00281 
00282     memset(state, 0, sizeof(state));
00283 
00284     for(i=0; i<SIZE; i++){
00285 START_TIMER
00286         if( (r[i]&1) != get_cabac_bypass(&c) )
00287             av_log(NULL, AV_LOG_ERROR, "CABAC bypass failure at %d\n", i);
00288 STOP_TIMER("get_cabac_bypass")
00289     }
00290 
00291     for(i=0; i<SIZE; i++){
00292 START_TIMER
00293         if( (r[i]&1) != get_cabac(&c, state) )
00294             av_log(NULL, AV_LOG_ERROR, "CABAC failure at %d\n", i);
00295 STOP_TIMER("get_cabac")
00296     }
00297     if(!get_cabac_terminate(&c))
00298         av_log(NULL, AV_LOG_ERROR, "where's the Terminator?\n");
00299 
00300     return 0;
00301 }
00302 
00303 #endif /* TEST */