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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.
*/
//#undef NDEBUG
#include <assert.h>
#define CABAC_BITS 16
#define CABAC_MASK ((1<<CABAC_BITS)-1)
#define BRANCHLESS_CABAC_DECODER 1
#define CMOV_IS_FAST 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_lps_range[2*65][4]; ///< 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[128];
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;
}
}
static void put_cabac(CABACContext *c, uint8_t * const state, int bit){
int RangeLPS= ff_h264_lps_range[*state][c->range>>6];
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);
}
}
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;
}
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;
}
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){
#ifdef ARCH_X86_DISABLED
int temp;
#if 0
//P3:683 athlon:475
asm(
"lea -0x2000000(%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 $0x2000000, %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 -0x2000000(%0), %%eax \n\t"
"cdq \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 $0x2000000, %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 $0x2000000, %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 - (0x200 << CABAC_BITS))>>31;
c->range<<= shift;
c->low <<= shift;
#endif
if(!(c->low & CABAC_MASK))
refill(c);
}
static int get_cabac(CABACContext *c, uint8_t * const state){
//FIXME gcc generates duplicate load/stores for c->low and c->range
#ifdef ARCH_X86
int bit;
#define LOW "0"
#define RANGE "4"
#define BYTESTART "12"
#define BYTE "16"
#define BYTEEND "20"
#ifndef BRANCHLESS_CABAC_DECODER
asm volatile(
"movzbl (%1), %%eax \n\t"
"movl "RANGE "(%2), %%ebx \n\t"
"movl "RANGE "(%2), %%edx \n\t"
"shrl $23, %%ebx \n\t"
"movzbl "MANGLE(ff_h264_lps_range)"(%%ebx, %%eax, 4), %%esi\n\t"
"shll $17, %%esi \n\t"
"movl "LOW "(%2), %%ebx \n\t"
//eax:state ebx:low, edx:range, esi:RangeLPS
"subl %%esi, %%edx \n\t"
"cmpl %%edx, %%ebx \n\t"
" ja 1f \n\t"
#if 1
//athlon:4067 P3:4110
"lea -0x2000000(%%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 $0x2000000, %%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)"(%%eax), %%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"
"movl "BYTE "(%2), %%esi \n\t"
"subl $0xFFFF, %%ebx \n\t"
"movzwl (%%esi), %%ecx \n\t"
"bswap %%ecx \n\t"
"shrl $15, %%ecx \n\t"
"addl $2, %%esi \n\t"
"addl %%ecx, %%ebx \n\t"
"movl %%esi, "BYTE "(%2) \n\t"
"jmp 2f \n\t"
"1: \n\t"
//eax:state ebx:low, edx:range, esi:RangeLPS
"subl %%edx, %%ebx \n\t"
"movl %%esi, %%edx \n\t"
"shr $19, %%esi \n\t"
"movzbl "MANGLE(ff_h264_lps_state)"(%%eax), %%ecx \n\t"
"movb %%cl, (%1) \n\t"
"movzbl " MANGLE(ff_h264_norm_shift) "(%%esi), %%ecx \n\t"
"shll %%cl, %%ebx \n\t"
"shll %%cl, %%edx \n\t"
"addl $1, %%eax \n\t"
"test %%bx, %%bx \n\t"
" jnz 2f \n\t"
"movl "BYTE "(%2), %%ecx \n\t"
"movzwl (%%ecx), %%esi \n\t"
"bswap %%esi \n\t"
"shrl $15, %%esi \n\t"
"subl $0xFFFF, %%esi \n\t"
"addl $2, %%ecx \n\t"
"movl %%ecx, "BYTE "(%2) \n\t"
"leal -1(%%ebx), %%ecx \n\t"
"xorl %%ebx, %%ecx \n\t"
"shrl $17, %%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 misscompiles it (for example if "+a"(bit) or "+m"(*state) is used
:"r"(state), "r"(c)
: "%ecx", "%ebx", "%edx", "%esi"
);
bit&=1;
#else /* BRANCHLESS_CABAC_DECODER */
asm volatile(
"movzbl (%1), %%eax \n\t"
"movl "RANGE "(%2), %%ebx \n\t"
"movl "RANGE "(%2), %%edx \n\t"
"shrl $23, %%ebx \n\t"
"movzbl "MANGLE(ff_h264_lps_range)"(%%ebx, %%eax, 4), %%esi\n\t"
"shll $17, %%esi \n\t"
"movl "LOW "(%2), %%ebx \n\t"
//eax:state ebx:low, edx:range, esi:RangeLPS
"subl %%esi, %%edx \n\t"
#ifdef CMOV_IS_FAST //FIXME actually define this somewhere
"cmpl %%ebx, %%edx \n\t"
"cmova %%edx, %%esi \n\t"
"sbbl %%ecx, %%ecx \n\t"
"andl %%ecx, %%edx \n\t"
"subl %%edx, %%ebx \n\t"
"xorl %%ecx, %%eax \n\t"
#else /* CMOV_IS_FAST */
"movl %%edx, %%ecx \n\t"
"subl %%ebx, %%edx \n\t"
"sarl $31, %%edx \n\t" //lps_mask
"subl %%ecx, %%esi \n\t" //RangeLPS - range
"andl %%edx, %%esi \n\t" //(RangeLPS - range)&lps_mask
"addl %%ecx, %%esi \n\t" //new range
"andl %%edx, %%ecx \n\t"
"subl %%ecx, %%ebx \n\t"
"xorl %%edx, %%eax \n\t"
#endif /* CMOV_IS_FAST */
//eax:state ebx:low edx:mask esi:range
"movzbl "MANGLE(ff_h264_mps_state)"(%%eax), %%ecx \n\t"
"movb %%cl, (%1) \n\t"
"movl %%esi, %%edx \n\t"
//eax:bit ebx:low edx:range esi:range
"shr $19, %%esi \n\t"
"movzbl " MANGLE(ff_h264_norm_shift) "(%%esi), %%ecx \n\t"
"shll %%cl, %%edx \n\t"
"movl %%edx, "RANGE "(%2) \n\t"
"shll %%cl, %%ebx \n\t"
"movl %%ebx, "LOW "(%2) \n\t"
"test %%bx, %%bx \n\t"
" jnz 1f \n\t"
"movl "BYTE "(%2), %%ecx \n\t"
"movzwl (%%ecx), %%esi \n\t"
"bswap %%esi \n\t"
"shrl $15, %%esi \n\t"
"subl $0xFFFF, %%esi \n\t"
"addl $2, %%ecx \n\t"
"movl %%ecx, "BYTE "(%2) \n\t"
"leal -1(%%ebx), %%ecx \n\t"
"xorl %%ebx, %%ecx \n\t"
"shrl $17, %%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"
"movl %%ebx, "LOW "(%2) \n\t"
"1: \n\t"
:"=&a"(bit)
:"r"(state), "r"(c)
: "%ecx", "%ebx", "%edx", "%esi"
);
bit&=1;
#endif /* BRANCHLESS_CABAC_DECODER */
#else /* ARCH_X86 */
int s = *state;
int RangeLPS= ff_h264_lps_range[s][c->range>>(CABAC_BITS+7)]<<(CABAC_BITS+1);
int bit, lps_mask attribute_unused;
c->range -= RangeLPS;
#ifndef BRANCHLESS_CABAC_DECODER
if(c->low < c->range){
bit= s&1;
*state= ff_h264_mps_state[s];
renorm_cabac_decoder_once(c);
}else{
bit= ff_h264_norm_shift[RangeLPS>>19];
c->low -= c->range;
*state= ff_h264_lps_state[s];
c->range = RangeLPS<<bit;
c->low <<= bit;
bit= (s&1)^1;
if(!(c->low & 0xFFFF)){
refill2(c);
}
}
#else /* BRANCHLESS_CABAC_DECODER */
lps_mask= (c->range - c->low)>>31;
c->low -= c->range & lps_mask;
c->range += (RangeLPS - c->range) & lps_mask;
s^=lps_mask;
*state= ff_h264_mps_state[s];
bit= s&1;
lps_mask= ff_h264_norm_shift[c->range>>(CABAC_BITS+3)];
c->range<<= lps_mask;
c->low <<= lps_mask;
if(!(c->low & CABAC_MASK))
refill2(c);
#endif /* BRANCHLESS_CABAC_DECODER */
#endif /* ARCH_X86 */
return bit;
}
static 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 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 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;
}