ffmpeg / libavcodec / cabac.h @ 5509bffa
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/*
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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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 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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#define CABAC_BITS 8 |
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#define CABAC_MASK ((1<<CABAC_BITS)-1) |
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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*65][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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const uint8_t *bytestream_end;
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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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extern const uint8_t ff_h264_norm_shift[256]; |
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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]; |
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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 void refill(CABACContext *c){ |
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if(c->bytestream <= c->bytestream_end)
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#if CABAC_BITS == 16 |
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c->low+= ((c->bytestream[0]<<9) + (c->bytestream[1])<<1); |
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#else
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c->low+= c->bytestream[0]<<1; |
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#endif
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c->low -= CABAC_MASK; |
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c->bytestream+= CABAC_BITS/8;
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} |
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#if 0 /* all use commented */
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static void refill2(CABACContext *c){
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int i, x;
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x= c->low ^ (c->low-1);
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i= 8 - ff_h264_norm_shift[x>>(CABAC_BITS+1)];
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x= -CABAC_MASK;
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if(c->bytestream < c->bytestream_end)
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#if CABAC_BITS == 16
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x+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
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#else
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x+= c->bytestream[0]<<1; |
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#endif
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c->low += x<<i; |
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c->bytestream+= CABAC_BITS/8;
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} |
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#endif
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static inline void renorm_cabac_decoder(CABACContext *c){ |
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while(c->range < (0x200 << CABAC_BITS)){ |
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c->range+= c->range; |
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c->low+= c->low; |
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if(!(c->low & CABAC_MASK))
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refill(c); |
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} |
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} |
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static inline void renorm_cabac_decoder_once(CABACContext *c){ |
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int mask= (c->range - (0x200 << CABAC_BITS))>>31; |
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c->range+= c->range&mask; |
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c->low += c->low &mask; |
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if(!(c->low & CABAC_MASK))
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refill(c); |
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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>>(CABAC_BITS+7)]<<(CABAC_BITS+1); |
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int bit, lps_mask attribute_unused;
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c->range -= RangeLPS; |
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#if 1 |
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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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renorm_cabac_decoder_once(c); |
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}else{
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// int shift= ff_h264_norm_shift[RangeLPS>>17];
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bit= ((*state)&1)^1; |
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c->low -= c->range; |
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*state= c->lps_state[*state]; |
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c->range = RangeLPS; |
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renorm_cabac_decoder(c); |
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/* c->range = RangeLPS<<shift;
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c->low <<= shift;
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if(!(c->low & 0xFFFF)){
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refill2(c);
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}*/
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} |
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#else
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lps_mask= (c->range - c->low)>>31;
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c->low -= c->range & lps_mask; |
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c->range += (RangeLPS - c->range) & lps_mask; |
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bit= ((*state)^lps_mask)&1;
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*state= c->mps_state[(*state) - (128&lps_mask)];
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lps_mask= ff_h264_norm_shift[c->range>>(CABAC_BITS+2)];
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c->range<<= lps_mask; |
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c->low <<= lps_mask; |
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if(!(c->low & CABAC_MASK))
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refill2(c); |
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#endif
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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->low & CABAC_MASK))
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refill(c); |
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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 -= 4<<CABAC_BITS;
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if(c->low < c->range){
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renorm_cabac_decoder_once(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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} |