mirror of
https://git.ffmpeg.org/ffmpeg.git
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382 lines
8.7 KiB
C
382 lines
8.7 KiB
C
/*
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* H.26L/H.264/AVC/JVT/14496-10/... encoder/decoder
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* Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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*/
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/**
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* @file cabac.h
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* Context Adaptive Binary Arithmetic Coder.
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*/
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#undef NDEBUG
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#include <assert.h>
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typedef struct CABACContext{
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int low;
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int range;
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int outstanding_count;
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#ifdef STRICT_LIMITS
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int symCount;
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#endif
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uint8_t lps_range[2*64][4]; ///< rangeTabLPS
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uint8_t lps_state[2*64]; ///< transIdxLPS
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uint8_t mps_state[2*64]; ///< transIdxMPS
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const uint8_t *bytestream_start;
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const uint8_t *bytestream;
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int bits_left; ///<
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PutBitContext pb;
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}CABACContext;
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extern const uint8_t ff_h264_lps_range[64][4];
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extern const uint8_t ff_h264_mps_state[64];
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extern const uint8_t ff_h264_lps_state[64];
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void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size);
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void ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size);
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void ff_init_cabac_states(CABACContext *c, uint8_t const (*lps_range)[4],
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uint8_t const *mps_state, uint8_t const *lps_state, int state_count);
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static inline void put_cabac_bit(CABACContext *c, int b){
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put_bits(&c->pb, 1, b);
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for(;c->outstanding_count; c->outstanding_count--){
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put_bits(&c->pb, 1, 1-b);
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}
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}
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static inline void renorm_cabac_encoder(CABACContext *c){
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while(c->range < 0x100){
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//FIXME optimize
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if(c->low<0x100){
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put_cabac_bit(c, 0);
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}else if(c->low<0x200){
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c->outstanding_count++;
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c->low -= 0x100;
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}else{
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put_cabac_bit(c, 1);
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c->low -= 0x200;
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}
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c->range+= c->range;
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c->low += c->low;
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}
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}
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static inline void put_cabac(CABACContext *c, uint8_t * const state, int bit){
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int RangeLPS= c->lps_range[*state][((c->range)>>6)&3];
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if(bit == ((*state)&1)){
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c->range -= RangeLPS;
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*state= c->mps_state[*state];
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}else{
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c->low += c->range - RangeLPS;
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c->range = RangeLPS;
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*state= c->lps_state[*state];
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}
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renorm_cabac_encoder(c);
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#ifdef STRICT_LIMITS
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c->symCount++;
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#endif
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}
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static inline void put_cabac_static(CABACContext *c, int RangeLPS, int bit){
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assert(c->range > RangeLPS);
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if(!bit){
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c->range -= RangeLPS;
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}else{
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c->low += c->range - RangeLPS;
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c->range = RangeLPS;
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}
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renorm_cabac_encoder(c);
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#ifdef STRICT_LIMITS
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c->symCount++;
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#endif
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}
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/**
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* @param bit 0 -> write zero bit, !=0 write one bit
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*/
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static inline void put_cabac_bypass(CABACContext *c, int bit){
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c->low += c->low;
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if(bit){
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c->low += c->range;
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}
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//FIXME optimize
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if(c->low<0x200){
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put_cabac_bit(c, 0);
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}else if(c->low<0x400){
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c->outstanding_count++;
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c->low -= 0x200;
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}else{
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put_cabac_bit(c, 1);
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c->low -= 0x400;
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}
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#ifdef STRICT_LIMITS
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c->symCount++;
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#endif
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}
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/**
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*
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* @return the number of bytes written
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*/
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static inline int put_cabac_terminate(CABACContext *c, int bit){
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c->range -= 2;
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if(!bit){
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renorm_cabac_encoder(c);
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}else{
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c->low += c->range;
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c->range= 2;
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renorm_cabac_encoder(c);
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assert(c->low <= 0x1FF);
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put_cabac_bit(c, c->low>>9);
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put_bits(&c->pb, 2, ((c->low>>7)&3)|1);
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flush_put_bits(&c->pb); //FIXME FIXME FIXME XXX wrong
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}
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#ifdef STRICT_LIMITS
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c->symCount++;
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#endif
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return (put_bits_count(&c->pb)+7)>>3;
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}
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/**
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* put (truncated) unary binarization.
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*/
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static inline void put_cabac_u(CABACContext *c, uint8_t * state, int v, int max, int max_index, int truncated){
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int i;
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assert(v <= max);
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#if 1
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for(i=0; i<v; i++){
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put_cabac(c, state, 1);
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if(i < max_index) state++;
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}
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if(truncated==0 || v<max)
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put_cabac(c, state, 0);
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#else
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if(v <= max_index){
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for(i=0; i<v; i++){
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put_cabac(c, state+i, 1);
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}
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if(truncated==0 || v<max)
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put_cabac(c, state+i, 0);
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}else{
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for(i=0; i<=max_index; i++){
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put_cabac(c, state+i, 1);
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}
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for(; i<v; i++){
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put_cabac(c, state+max_index, 1);
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}
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if(truncated==0 || v<max)
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put_cabac(c, state+max_index, 0);
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}
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#endif
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}
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/**
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* put unary exp golomb k-th order binarization.
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*/
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static inline void put_cabac_ueg(CABACContext *c, uint8_t * state, int v, int max, int is_signed, int k, int max_index){
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int i;
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if(v==0)
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put_cabac(c, state, 0);
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else{
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const int sign= v < 0;
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if(is_signed) v= ABS(v);
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if(v<max){
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for(i=0; i<v; i++){
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put_cabac(c, state, 1);
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if(i < max_index) state++;
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}
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put_cabac(c, state, 0);
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}else{
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int m= 1<<k;
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for(i=0; i<max; i++){
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put_cabac(c, state, 1);
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if(i < max_index) state++;
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}
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v -= max;
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while(v >= m){ //FIXME optimize
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put_cabac_bypass(c, 1);
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v-= m;
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m+= m;
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}
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put_cabac_bypass(c, 0);
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while(m>>=1){
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put_cabac_bypass(c, v&m);
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}
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}
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if(is_signed)
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put_cabac_bypass(c, sign);
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}
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}
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static inline void renorm_cabac_decoder(CABACContext *c){
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while(c->range < 0x10000){
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c->range+= c->range;
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c->low+= c->low;
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if(--c->bits_left == 0){
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c->low+= *c->bytestream++;
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c->bits_left= 8;
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}
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}
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}
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static inline int get_cabac(CABACContext *c, uint8_t * const state){
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int RangeLPS= c->lps_range[*state][((c->range)>>14)&3]<<8;
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int bit;
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c->range -= RangeLPS;
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if(c->low < c->range){
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bit= (*state)&1;
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*state= c->mps_state[*state];
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}else{
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bit= ((*state)&1)^1;
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c->low -= c->range;
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c->range = RangeLPS;
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*state= c->lps_state[*state];
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}
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renorm_cabac_decoder(c);
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return bit;
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}
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static inline int get_cabac_static(CABACContext *c, int RangeLPS){
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int bit;
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c->range -= RangeLPS;
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if(c->low < c->range){
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bit= 0;
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}else{
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bit= 1;
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c->low -= c->range;
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c->range = RangeLPS;
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}
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renorm_cabac_decoder(c);
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return bit;
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}
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static inline int get_cabac_bypass(CABACContext *c){
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c->low += c->low;
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if(--c->bits_left == 0){
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c->low+= *c->bytestream++;
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c->bits_left= 8;
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}
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if(c->low < c->range){
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return 0;
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}else{
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c->low -= c->range;
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return 1;
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}
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}
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/**
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*
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* @return the number of bytes read or 0 if no end
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*/
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static inline int get_cabac_terminate(CABACContext *c){
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c->range -= 2<<8;
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if(c->low < c->range){
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renorm_cabac_decoder(c);
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return 0;
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}else{
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return c->bytestream - c->bytestream_start;
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}
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}
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/**
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* get (truncated) unnary binarization.
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*/
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static inline int get_cabac_u(CABACContext *c, uint8_t * state, int max, int max_index, int truncated){
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int i;
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for(i=0; i<max; i++){
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if(get_cabac(c, state)==0)
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return i;
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if(i< max_index) state++;
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}
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return truncated ? max : -1;
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}
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/**
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* get unary exp golomb k-th order binarization.
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*/
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static inline int get_cabac_ueg(CABACContext *c, uint8_t * state, int max, int is_signed, int k, int max_index){
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int i, v;
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int m= 1<<k;
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if(get_cabac(c, state)==0)
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return 0;
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if(0 < max_index) state++;
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for(i=1; i<max; i++){
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if(get_cabac(c, state)==0){
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if(is_signed && get_cabac_bypass(c)){
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return -i;
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}else
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return i;
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}
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if(i < max_index) state++;
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}
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while(get_cabac_bypass(c)){
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i+= m;
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m+= m;
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}
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v=0;
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while(m>>=1){
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v+= v + get_cabac_bypass(c);
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}
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i += v;
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if(is_signed && get_cabac_bypass(c)){
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return -i;
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}else
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return i;
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}
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