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ffmpeg/libavcodec/cabac.h

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/*
* H.26L/H.264/AVC/JVT/14496-10/... encoder/decoder
* Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
*/
/**
* @file cabac.h
* Context Adaptive Binary Arithmetic Coder.
*/
//#undef NDEBUG
#include <assert.h>
#define CABAC_BITS 8
#define CABAC_MASK ((1<<CABAC_BITS)-1)
typedef struct CABACContext{
int low;
int range;
int outstanding_count;
#ifdef STRICT_LIMITS
int symCount;
#endif
uint8_t lps_range[2*65][4]; ///< rangeTabLPS
uint8_t lps_state[2*64]; ///< transIdxLPS
uint8_t mps_state[2*64]; ///< transIdxMPS
const uint8_t *bytestream_start;
const uint8_t *bytestream;
const uint8_t *bytestream_end;
PutBitContext pb;
}CABACContext;
extern const uint8_t ff_h264_lps_range[64][4];
extern const uint8_t ff_h264_mps_state[64];
extern const uint8_t ff_h264_lps_state[64];
extern const uint8_t ff_h264_norm_shift[256];
void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size);
void ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size);
void ff_init_cabac_states(CABACContext *c, uint8_t const (*lps_range)[4],
uint8_t const *mps_state, uint8_t const *lps_state, int state_count);
static inline void put_cabac_bit(CABACContext *c, int b){
put_bits(&c->pb, 1, b);
for(;c->outstanding_count; c->outstanding_count--){
put_bits(&c->pb, 1, 1-b);
}
}
static inline void renorm_cabac_encoder(CABACContext *c){
while(c->range < 0x100){
//FIXME optimize
if(c->low<0x100){
put_cabac_bit(c, 0);
}else if(c->low<0x200){
c->outstanding_count++;
c->low -= 0x100;
}else{
put_cabac_bit(c, 1);
c->low -= 0x200;
}
c->range+= c->range;
c->low += c->low;
}
}
static inline void put_cabac(CABACContext *c, uint8_t * const state, int bit){
int RangeLPS= c->lps_range[*state][c->range>>6];
if(bit == ((*state)&1)){
c->range -= RangeLPS;
*state= c->mps_state[*state];
}else{
c->low += c->range - RangeLPS;
c->range = RangeLPS;
*state= c->lps_state[*state];
}
renorm_cabac_encoder(c);
#ifdef STRICT_LIMITS
c->symCount++;
#endif
}
static inline void put_cabac_static(CABACContext *c, int RangeLPS, int bit){
assert(c->range > RangeLPS);
if(!bit){
c->range -= RangeLPS;
}else{
c->low += c->range - RangeLPS;
c->range = RangeLPS;
}
renorm_cabac_encoder(c);
#ifdef STRICT_LIMITS
c->symCount++;
#endif
}
/**
* @param bit 0 -> write zero bit, !=0 write one bit
*/
static inline void put_cabac_bypass(CABACContext *c, int bit){
c->low += c->low;
if(bit){
c->low += c->range;
}
//FIXME optimize
if(c->low<0x200){
put_cabac_bit(c, 0);
}else if(c->low<0x400){
c->outstanding_count++;
c->low -= 0x200;
}else{
put_cabac_bit(c, 1);
c->low -= 0x400;
}
#ifdef STRICT_LIMITS
c->symCount++;
#endif
}
/**
*
* @return the number of bytes written
*/
static inline int put_cabac_terminate(CABACContext *c, int bit){
c->range -= 2;
if(!bit){
renorm_cabac_encoder(c);
}else{
c->low += c->range;
c->range= 2;
renorm_cabac_encoder(c);
assert(c->low <= 0x1FF);
put_cabac_bit(c, c->low>>9);
put_bits(&c->pb, 2, ((c->low>>7)&3)|1);
flush_put_bits(&c->pb); //FIXME FIXME FIXME XXX wrong
}
#ifdef STRICT_LIMITS
c->symCount++;
#endif
return (put_bits_count(&c->pb)+7)>>3;
}
/**
* put (truncated) unary binarization.
*/
static inline void put_cabac_u(CABACContext *c, uint8_t * state, int v, int max, int max_index, int truncated){
int i;
assert(v <= max);
#if 1
for(i=0; i<v; i++){
put_cabac(c, state, 1);
if(i < max_index) state++;
}
if(truncated==0 || v<max)
put_cabac(c, state, 0);
#else
if(v <= max_index){
for(i=0; i<v; i++){
put_cabac(c, state+i, 1);
}
if(truncated==0 || v<max)
put_cabac(c, state+i, 0);
}else{
for(i=0; i<=max_index; i++){
put_cabac(c, state+i, 1);
}
for(; i<v; i++){
put_cabac(c, state+max_index, 1);
}
if(truncated==0 || v<max)
put_cabac(c, state+max_index, 0);
}
#endif
}
/**
* put unary exp golomb k-th order binarization.
*/
static inline void put_cabac_ueg(CABACContext *c, uint8_t * state, int v, int max, int is_signed, int k, int max_index){
int i;
if(v==0)
put_cabac(c, state, 0);
else{
const int sign= v < 0;
if(is_signed) v= ABS(v);
if(v<max){
for(i=0; i<v; i++){
put_cabac(c, state, 1);
if(i < max_index) state++;
}
put_cabac(c, state, 0);
}else{
int m= 1<<k;
for(i=0; i<max; i++){
put_cabac(c, state, 1);
if(i < max_index) state++;
}
v -= max;
while(v >= m){ //FIXME optimize
put_cabac_bypass(c, 1);
v-= m;
m+= m;
}
put_cabac_bypass(c, 0);
while(m>>=1){
put_cabac_bypass(c, v&m);
}
}
if(is_signed)
put_cabac_bypass(c, sign);
}
}
static void refill(CABACContext *c){
if(c->bytestream <= c->bytestream_end)
#if CABAC_BITS == 16
c->low+= ((c->bytestream[0]<<9) + (c->bytestream[1])<<1);
#else
c->low+= c->bytestream[0]<<1;
#endif
c->low -= CABAC_MASK;
c->bytestream+= CABAC_BITS/8;
}
#if 0 /* all use commented */
static void refill2(CABACContext *c){
int i, x;
x= c->low ^ (c->low-1);
i= 8 - ff_h264_norm_shift[x>>(CABAC_BITS+1)];
x= -CABAC_MASK;
if(c->bytestream < c->bytestream_end)
#if CABAC_BITS == 16
x+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
#else
x+= c->bytestream[0]<<1;
#endif
c->low += x<<i;
c->bytestream+= CABAC_BITS/8;
}
#endif
static inline void renorm_cabac_decoder(CABACContext *c){
while(c->range < (0x200 << CABAC_BITS)){
c->range+= c->range;
c->low+= c->low;
if(!(c->low & CABAC_MASK))
refill(c);
}
}
static inline void renorm_cabac_decoder_once(CABACContext *c){
int mask= (c->range - (0x200 << CABAC_BITS))>>31;
c->range+= c->range&mask;
c->low += c->low &mask;
if(!(c->low & CABAC_MASK))
refill(c);
}
static inline int get_cabac(CABACContext *c, uint8_t * const state){
int RangeLPS= c->lps_range[*state][c->range>>(CABAC_BITS+7)]<<(CABAC_BITS+1);
int bit, lps_mask attribute_unused;
c->range -= RangeLPS;
#if 1
if(c->low < c->range){
bit= (*state)&1;
*state= c->mps_state[*state];
renorm_cabac_decoder_once(c);
}else{
// int shift= ff_h264_norm_shift[RangeLPS>>17];
bit= ((*state)&1)^1;
c->low -= c->range;
*state= c->lps_state[*state];
c->range = RangeLPS;
renorm_cabac_decoder(c);
/* c->range = RangeLPS<<shift;
c->low <<= shift;
if(!(c->low & 0xFFFF)){
refill2(c);
}*/
}
#else
lps_mask= (c->range - c->low)>>31;
c->low -= c->range & lps_mask;
c->range += (RangeLPS - c->range) & lps_mask;
bit= ((*state)^lps_mask)&1;
*state= c->mps_state[(*state) - (128&lps_mask)];
lps_mask= ff_h264_norm_shift[c->range>>(CABAC_BITS+2)];
c->range<<= lps_mask;
c->low <<= lps_mask;
if(!(c->low & CABAC_MASK))
refill2(c);
#endif
return bit;
}
static inline int get_cabac_bypass(CABACContext *c){
c->low += c->low;
if(!(c->low & CABAC_MASK))
refill(c);
if(c->low < c->range){
return 0;
}else{
c->low -= c->range;
return 1;
}
}
/**
*
* @return the number of bytes read or 0 if no end
*/
static inline int get_cabac_terminate(CABACContext *c){
c->range -= 4<<CABAC_BITS;
if(c->low < c->range){
renorm_cabac_decoder_once(c);
return 0;
}else{
return c->bytestream - c->bytestream_start;
}
}
/**
* get (truncated) unnary binarization.
*/
static inline int get_cabac_u(CABACContext *c, uint8_t * state, int max, int max_index, int truncated){
int i;
for(i=0; i<max; i++){
if(get_cabac(c, state)==0)
return i;
if(i< max_index) state++;
}
return truncated ? max : -1;
}
/**
* get unary exp golomb k-th order binarization.
*/
static inline int get_cabac_ueg(CABACContext *c, uint8_t * state, int max, int is_signed, int k, int max_index){
int i, v;
int m= 1<<k;
if(get_cabac(c, state)==0)
return 0;
if(0 < max_index) state++;
for(i=1; i<max; i++){
if(get_cabac(c, state)==0){
if(is_signed && get_cabac_bypass(c)){
return -i;
}else
return i;
}
if(i < max_index) state++;
}
while(get_cabac_bypass(c)){
i+= m;
m+= m;
}
v=0;
while(m>>=1){
v+= v + get_cabac_bypass(c);
}
i += v;
if(is_signed && get_cabac_bypass(c)){
return -i;
}else
return i;
}
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