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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 file is part of FFmpeg.
*
* FFmpeg 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 2.1 of the License, or (at your option) any later version.
*
* FFmpeg 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 FFmpeg; 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.
*/
#ifndef AVCODEC_CABAC_H
#define AVCODEC_CABAC_H
#include "bitstream.h"
//#undef NDEBUG
#include <assert.h>
#include "libavutil/x86_cpu.h"
#define CABAC_BITS 16
#define CABAC_MASK ((1<<CABAC_BITS)-1)
#define BRANCHLESS_CABAC_DECODER 1
//#define ARCH_X86_DISABLED 1
typedef struct CABACContext{
int low;
int range;
int outstanding_count;
#ifdef STRICT_LIMITS
int symCount;
#endif
const uint8_t *bytestream_start;
const uint8_t *bytestream;
const uint8_t *bytestream_end;
PutBitContext pb;
}CABACContext;
extern uint8_t ff_h264_mlps_state[4*64];
extern uint8_t ff_h264_lps_range[4*2*64]; ///< rangeTabLPS
extern uint8_t ff_h264_mps_state[2*64]; ///< transIdxMPS
extern uint8_t ff_h264_lps_state[2*64]; ///< transIdxLPS
extern const uint8_t ff_h264_norm_shift[512];
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);
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;
}
}
#ifdef TEST
static void put_cabac(CABACContext *c, uint8_t * const state, int bit){
int RangeLPS= ff_h264_lps_range[2*(c->range&0xC0) + *state];
if(bit == ((*state)&1)){
c->range -= RangeLPS;
*state= ff_h264_mps_state[*state];
}else{
c->low += c->range - RangeLPS;
c->range = RangeLPS;
*state= ff_h264_lps_state[*state];
}
renorm_cabac_encoder(c);
#ifdef STRICT_LIMITS
c->symCount++;
#endif
}
static 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 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 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 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 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= FFABS(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);
}
}
#endif /* TEST */
static void refill(CABACContext *c){
#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 ! ( defined(ARCH_X86) && defined(HAVE_7REGS) && defined(HAVE_EBX_AVAILABLE) && !defined(BROKEN_RELOCATIONS) )
static void refill2(CABACContext *c){
int i, x;
x= c->low ^ (c->low-1);
i= 7 - ff_h264_norm_shift[x>>(CABAC_BITS-1)];
x= -CABAC_MASK;
#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 < 0x100){
c->range+= c->range;
c->low+= c->low;
if(!(c->low & CABAC_MASK))
refill(c);
}
}
static inline void renorm_cabac_decoder_once(CABACContext *c){
#ifdef ARCH_X86_DISABLED
int temp;
#if 0
//P3:683 athlon:475
__asm__(
"lea -0x100(%0), %2 \n\t"
"shr $31, %2 \n\t" //FIXME 31->63 for x86-64
"shl %%cl, %0 \n\t"
"shl %%cl, %1 \n\t"
: "+r"(c->range), "+r"(c->low), "+c"(temp)
);
#elif 0
//P3:680 athlon:474
__asm__(
"cmp $0x100, %0 \n\t"
"setb %%cl \n\t" //FIXME 31->63 for x86-64
"shl %%cl, %0 \n\t"
"shl %%cl, %1 \n\t"
: "+r"(c->range), "+r"(c->low), "+c"(temp)
);
#elif 1
int temp2;
//P3:665 athlon:517
__asm__(
"lea -0x100(%0), %%eax \n\t"
"cltd \n\t"
"mov %0, %%eax \n\t"
"and %%edx, %0 \n\t"
"and %1, %%edx \n\t"
"add %%eax, %0 \n\t"
"add %%edx, %1 \n\t"
: "+r"(c->range), "+r"(c->low), "+a"(temp), "+d"(temp2)
);
#elif 0
int temp2;
//P3:673 athlon:509
__asm__(
"cmp $0x100, %0 \n\t"
"sbb %%edx, %%edx \n\t"
"mov %0, %%eax \n\t"
"and %%edx, %0 \n\t"
"and %1, %%edx \n\t"
"add %%eax, %0 \n\t"
"add %%edx, %1 \n\t"
: "+r"(c->range), "+r"(c->low), "+a"(temp), "+d"(temp2)
);
#else
int temp2;
//P3:677 athlon:511
__asm__(
"cmp $0x100, %0 \n\t"
"lea (%0, %0), %%eax \n\t"
"lea (%1, %1), %%edx \n\t"
"cmovb %%eax, %0 \n\t"
"cmovb %%edx, %1 \n\t"
: "+r"(c->range), "+r"(c->low), "+a"(temp), "+d"(temp2)
);
#endif
#else
//P3:675 athlon:476
int shift= (uint32_t)(c->range - 0x100)>>31;
c->range<<= shift;
c->low <<= shift;
#endif
if(!(c->low & CABAC_MASK))
refill(c);
}
static av_always_inline int get_cabac_inline(CABACContext *c, uint8_t * const state){
//FIXME gcc generates duplicate load/stores for c->low and c->range
#define LOW "0"
#define RANGE "4"
#ifdef ARCH_X86_64
#define BYTESTART "16"
#define BYTE "24"
#define BYTEEND "32"
#else
#define BYTESTART "12"
#define BYTE "16"
#define BYTEEND "20"
#endif
#if defined(ARCH_X86) && defined(HAVE_7REGS) && defined(HAVE_EBX_AVAILABLE) && !defined(BROKEN_RELOCATIONS)
int bit;
#ifndef BRANCHLESS_CABAC_DECODER
__asm__ volatile(
"movzbl (%1), %0 \n\t"
"movl "RANGE "(%2), %%ebx \n\t"
"movl "RANGE "(%2), %%edx \n\t"
"andl $0xC0, %%ebx \n\t"
"movzbl "MANGLE(ff_h264_lps_range)"(%0, %%ebx, 2), %%esi\n\t"
"movl "LOW "(%2), %%ebx \n\t"
//eax:state ebx:low, edx:range, esi:RangeLPS
"subl %%esi, %%edx \n\t"
"movl %%edx, %%ecx \n\t"
"shll $17, %%ecx \n\t"
"cmpl %%ecx, %%ebx \n\t"
" ja 1f \n\t"
#if 1
//athlon:4067 P3:4110
"lea -0x100(%%edx), %%ecx \n\t"
"shr $31, %%ecx \n\t"
"shl %%cl, %%edx \n\t"
"shl %%cl, %%ebx \n\t"
#else
//athlon:4057 P3:4130
"cmp $0x100, %%edx \n\t" //FIXME avoidable
"setb %%cl \n\t"
"shl %%cl, %%edx \n\t"
"shl %%cl, %%ebx \n\t"
#endif
"movzbl "MANGLE(ff_h264_mps_state)"(%0), %%ecx \n\t"
"movb %%cl, (%1) \n\t"
//eax:state ebx:low, edx:range, esi:RangeLPS
"test %%bx, %%bx \n\t"
" jnz 2f \n\t"
"mov "BYTE "(%2), %%"REG_S" \n\t"
"subl $0xFFFF, %%ebx \n\t"
"movzwl (%%"REG_S"), %%ecx \n\t"
"bswap %%ecx \n\t"
"shrl $15, %%ecx \n\t"
"add $2, %%"REG_S" \n\t"
"addl %%ecx, %%ebx \n\t"
"mov %%"REG_S", "BYTE "(%2) \n\t"
"jmp 2f \n\t"
"1: \n\t"
//eax:state ebx:low, edx:range, esi:RangeLPS
"subl %%ecx, %%ebx \n\t"
"movl %%esi, %%edx \n\t"
"movzbl " MANGLE(ff_h264_norm_shift) "(%%esi), %%ecx \n\t"
"shll %%cl, %%ebx \n\t"
"shll %%cl, %%edx \n\t"
"movzbl "MANGLE(ff_h264_lps_state)"(%0), %%ecx \n\t"
"movb %%cl, (%1) \n\t"
"add $1, %0 \n\t"
"test %%bx, %%bx \n\t"
" jnz 2f \n\t"
"mov "BYTE "(%2), %%"REG_c" \n\t"
"movzwl (%%"REG_c"), %%esi \n\t"
"bswap %%esi \n\t"
"shrl $15, %%esi \n\t"
"subl $0xFFFF, %%esi \n\t"
"add $2, %%"REG_c" \n\t"
"mov %%"REG_c", "BYTE "(%2) \n\t"
"leal -1(%%ebx), %%ecx \n\t"
"xorl %%ebx, %%ecx \n\t"
"shrl $15, %%ecx \n\t"
"movzbl " MANGLE(ff_h264_norm_shift) "(%%ecx), %%ecx \n\t"
"neg %%ecx \n\t"
"add $7, %%ecx \n\t"
"shll %%cl , %%esi \n\t"
"addl %%esi, %%ebx \n\t"
"2: \n\t"
"movl %%edx, "RANGE "(%2) \n\t"
"movl %%ebx, "LOW "(%2) \n\t"
:"=&a"(bit) //FIXME this is fragile gcc either runs out of registers or miscompiles it (for example if "+a"(bit) or "+m"(*state) is used
:"r"(state), "r"(c)
: "%"REG_c, "%ebx", "%edx", "%"REG_S, "memory"
);
bit&=1;
#else /* BRANCHLESS_CABAC_DECODER */
#if defined HAVE_FAST_CMOV
#define BRANCHLESS_GET_CABAC_UPDATE(ret, cabac, statep, low, lowword, range, tmp, tmpbyte)\
"mov "tmp" , %%ecx \n\t"\
"shl $17 , "tmp" \n\t"\
"cmp "low" , "tmp" \n\t"\
"cmova %%ecx , "range" \n\t"\
"sbb %%ecx , %%ecx \n\t"\
"and %%ecx , "tmp" \n\t"\
"sub "tmp" , "low" \n\t"\
"xor %%ecx , "ret" \n\t"
#else /* HAVE_FAST_CMOV */
#define BRANCHLESS_GET_CABAC_UPDATE(ret, cabac, statep, low, lowword, range, tmp, tmpbyte)\
"mov "tmp" , %%ecx \n\t"\
"shl $17 , "tmp" \n\t"\
"sub "low" , "tmp" \n\t"\
"sar $31 , "tmp" \n\t" /*lps_mask*/\
"sub %%ecx , "range" \n\t" /*RangeLPS - range*/\
"and "tmp" , "range" \n\t" /*(RangeLPS - range)&lps_mask*/\
"add %%ecx , "range" \n\t" /*new range*/\
"shl $17 , %%ecx \n\t"\
"and "tmp" , %%ecx \n\t"\
"sub %%ecx , "low" \n\t"\
"xor "tmp" , "ret" \n\t"
#endif /* HAVE_FAST_CMOV */
#define BRANCHLESS_GET_CABAC(ret, cabac, statep, low, lowword, range, tmp, tmpbyte)\
"movzbl "statep" , "ret" \n\t"\
"mov "range" , "tmp" \n\t"\
"and $0xC0 , "range" \n\t"\
"movzbl "MANGLE(ff_h264_lps_range)"("ret", "range", 2), "range" \n\t"\
"sub "range" , "tmp" \n\t"\
BRANCHLESS_GET_CABAC_UPDATE(ret, cabac, statep, low, lowword, range, tmp, tmpbyte)\
"movzbl " MANGLE(ff_h264_norm_shift) "("range"), %%ecx \n\t"\
"shl %%cl , "range" \n\t"\
"movzbl "MANGLE(ff_h264_mlps_state)"+128("ret"), "tmp" \n\t"\
"mov "tmpbyte" , "statep" \n\t"\
"shl %%cl , "low" \n\t"\
"test "lowword" , "lowword" \n\t"\
" jnz 1f \n\t"\
"mov "BYTE"("cabac"), %%"REG_c" \n\t"\
"movzwl (%%"REG_c") , "tmp" \n\t"\
"bswap "tmp" \n\t"\
"shr $15 , "tmp" \n\t"\
"sub $0xFFFF , "tmp" \n\t"\
"add $2 , %%"REG_c" \n\t"\
"mov %%"REG_c" , "BYTE "("cabac") \n\t"\
"lea -1("low") , %%ecx \n\t"\
"xor "low" , %%ecx \n\t"\
"shr $15 , %%ecx \n\t"\
"movzbl " MANGLE(ff_h264_norm_shift) "(%%ecx), %%ecx \n\t"\
"neg %%ecx \n\t"\
"add $7 , %%ecx \n\t"\
"shl %%cl , "tmp" \n\t"\
"add "tmp" , "low" \n\t"\
"1: \n\t"
__asm__ volatile(
"movl "RANGE "(%2), %%esi \n\t"
"movl "LOW "(%2), %%ebx \n\t"
BRANCHLESS_GET_CABAC("%0", "%2", "(%1)", "%%ebx", "%%bx", "%%esi", "%%edx", "%%dl")
"movl %%esi, "RANGE "(%2) \n\t"
"movl %%ebx, "LOW "(%2) \n\t"
:"=&a"(bit)
:"r"(state), "r"(c)
: "%"REG_c, "%ebx", "%edx", "%esi", "memory"
);
bit&=1;
#endif /* BRANCHLESS_CABAC_DECODER */
#else /* defined(ARCH_X86) && defined(HAVE_7REGS) && defined(HAVE_EBX_AVAILABLE) && !defined(BROKEN_RELOCATIONS) */
int s = *state;
int RangeLPS= ff_h264_lps_range[2*(c->range&0xC0) + s];
int bit, lps_mask av_unused;
c->range -= RangeLPS;
#ifndef BRANCHLESS_CABAC_DECODER
if(c->low < (c->range<<(CABAC_BITS+1))){
bit= s&1;
*state= ff_h264_mps_state[s];
renorm_cabac_decoder_once(c);
}else{
bit= ff_h264_norm_shift[RangeLPS];
c->low -= (c->range<<(CABAC_BITS+1));
*state= ff_h264_lps_state[s];
c->range = RangeLPS<<bit;
c->low <<= bit;
bit= (s&1)^1;
if(!(c->low & CABAC_MASK)){
refill2(c);
}
}
#else /* BRANCHLESS_CABAC_DECODER */
lps_mask= ((c->range<<(CABAC_BITS+1)) - c->low)>>31;
c->low -= (c->range<<(CABAC_BITS+1)) & lps_mask;
c->range += (RangeLPS - c->range) & lps_mask;
s^=lps_mask;
*state= (ff_h264_mlps_state+128)[s];
bit= s&1;
lps_mask= ff_h264_norm_shift[c->range];
c->range<<= lps_mask;
c->low <<= lps_mask;
if(!(c->low & CABAC_MASK))
refill2(c);
#endif /* BRANCHLESS_CABAC_DECODER */
#endif /* defined(ARCH_X86) && defined(HAVE_7REGS) && defined(HAVE_EBX_AVAILABLE) && !defined(BROKEN_RELOCATIONS) */
return bit;
}
static int av_noinline av_unused get_cabac_noinline(CABACContext *c, uint8_t * const state){
return get_cabac_inline(c,state);
}
static int av_unused get_cabac(CABACContext *c, uint8_t * const state){
return get_cabac_inline(c,state);
}
static int av_unused get_cabac_bypass(CABACContext *c){
#if 0 //not faster
int bit;
__asm__ volatile(
"movl "RANGE "(%1), %%ebx \n\t"
"movl "LOW "(%1), %%eax \n\t"
"shl $17, %%ebx \n\t"
"add %%eax, %%eax \n\t"
"sub %%ebx, %%eax \n\t"
"cltd \n\t"
"and %%edx, %%ebx \n\t"
"add %%ebx, %%eax \n\t"
"test %%ax, %%ax \n\t"
" jnz 1f \n\t"
"movl "BYTE "(%1), %%"REG_b" \n\t"
"subl $0xFFFF, %%eax \n\t"
"movzwl (%%"REG_b"), %%ecx \n\t"
"bswap %%ecx \n\t"
"shrl $15, %%ecx \n\t"
"addl $2, %%"REG_b" \n\t"
"addl %%ecx, %%eax \n\t"
"movl %%"REG_b", "BYTE "(%1) \n\t"
"1: \n\t"
"movl %%eax, "LOW "(%1) \n\t"
:"=&d"(bit)
:"r"(c)
: "%eax", "%"REG_b, "%ecx", "memory"
);
return bit+1;
#else
int range;
c->low += c->low;
if(!(c->low & CABAC_MASK))
refill(c);
range= c->range<<(CABAC_BITS+1);
if(c->low < range){
return 0;
}else{
c->low -= range;
return 1;
}
#endif
}
static av_always_inline int get_cabac_bypass_sign(CABACContext *c, int val){
#if defined(ARCH_X86) && !(defined(PIC) && defined(__GNUC__))
__asm__ volatile(
"movl "RANGE "(%1), %%ebx \n\t"
"movl "LOW "(%1), %%eax \n\t"
"shl $17, %%ebx \n\t"
"add %%eax, %%eax \n\t"
"sub %%ebx, %%eax \n\t"
"cltd \n\t"
"and %%edx, %%ebx \n\t"
"add %%ebx, %%eax \n\t"
"xor %%edx, %%ecx \n\t"
"sub %%edx, %%ecx \n\t"
"test %%ax, %%ax \n\t"
" jnz 1f \n\t"
"mov "BYTE "(%1), %%"REG_b" \n\t"
"subl $0xFFFF, %%eax \n\t"
"movzwl (%%"REG_b"), %%edx \n\t"
"bswap %%edx \n\t"
"shrl $15, %%edx \n\t"
"add $2, %%"REG_b" \n\t"
"addl %%edx, %%eax \n\t"
"mov %%"REG_b", "BYTE "(%1) \n\t"
"1: \n\t"
"movl %%eax, "LOW "(%1) \n\t"
:"+c"(val)
:"r"(c)
: "%eax", "%"REG_b, "%edx", "memory"
);
return val;
#else
int range, mask;
c->low += c->low;
if(!(c->low & CABAC_MASK))
refill(c);
range= c->range<<(CABAC_BITS+1);
c->low -= range;
mask= c->low >> 31;
range &= mask;
c->low += range;
return (val^mask)-mask;
#endif
}
/**
*
* @return the number of bytes read or 0 if no end
*/
static int av_unused get_cabac_terminate(CABACContext *c){
c->range -= 2;
if(c->low < c->range<<(CABAC_BITS+1)){
renorm_cabac_decoder_once(c);
return 0;
}else{
return c->bytestream - c->bytestream_start;
}
}
#if 0
/**
* Get (truncated) unary binarization.
*/
static 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 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;
}
#endif /* 0 */
#endif /* AVCODEC_CABAC_H */