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CABAC 

note, this is just the CABAC (de)coder not complete h264-cabac support

Originally committed as revision 1915 to svn://svn.ffmpeg.org/ffmpeg/trunk
tags/v0.5
Michael Niedermayer 22 years ago
parent
8e7284ba91
commit
d592f67fb6
2 changed files with 411 additions and 0 deletions
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  1. +179
    -0
      libavcodec/cabac.c
  2. +232
    -0
      libavcodec/cabac.h

+ 179
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libavcodec/cabac.c View File

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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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/

/**
* @file cabac.c
* Context Adaptive Binary Arithmetic Coder.
*/

#include <string.h>

#include "common.h"
#include "cabac.h"

const uint8_t ff_h264_lps_range[64][4]= {
{128,176,208,240}, {128,167,197,227}, {128,158,187,216}, {123,150,178,205},
{116,142,169,195}, {111,135,160,185}, {105,128,152,175}, {100,122,144,166},
{ 95,116,137,158}, { 90,110,130,150}, { 85,104,123,142}, { 81, 99,117,135},
{ 77, 94,111,128}, { 73, 89,105,122}, { 69, 85,100,116}, { 66, 80, 95,110},
{ 62, 76, 90,104}, { 59, 72, 86, 99}, { 56, 69, 81, 94}, { 53, 65, 77, 89},
{ 51, 62, 73, 85}, { 48, 59, 69, 80}, { 46, 56, 66, 76}, { 43, 53, 63, 72},
{ 41, 50, 59, 69}, { 39, 48, 56, 65}, { 37, 45, 54, 62}, { 35, 43, 51, 59},
{ 33, 41, 48, 56}, { 32, 39, 46, 53}, { 30, 37, 43, 50}, { 29, 35, 41, 48},
{ 27, 33, 39, 45}, { 26, 31, 37, 43}, { 24, 30, 35, 41}, { 23, 28, 33, 39},
{ 22, 27, 32, 37}, { 21, 26, 30, 35}, { 20, 24, 29, 33}, { 19, 23, 27, 31},
{ 18, 22, 26, 30}, { 17, 21, 25, 28}, { 16, 20, 23, 27}, { 15, 19, 22, 25},
{ 14, 18, 21, 24}, { 14, 17, 20, 23}, { 13, 16, 19, 22}, { 12, 15, 18, 21},
{ 12, 14, 17, 20}, { 11, 14, 16, 19}, { 11, 13, 15, 18}, { 10, 12, 15, 17},
{ 10, 12, 14, 16}, { 9, 11, 13, 15}, { 9, 11, 12, 14}, { 8, 10, 12, 14},
{ 8, 9, 11, 13}, { 7, 9, 11, 12}, { 7, 9, 10, 12}, { 7, 8, 10, 11},
{ 6, 8, 9, 11}, { 6, 7, 9, 10}, { 6, 7, 8, 9}, { 2, 2, 2, 2},
};

const uint8_t ff_h264_mps_state[64]= {
1, 2, 3, 4, 5, 6, 7, 8,
9,10,11,12,13,14,15,16,
17,18,19,20,21,22,23,24,
25,26,27,28,29,30,31,32,
33,34,35,36,37,38,39,40,
41,42,43,44,45,46,47,48,
49,50,51,52,53,54,55,56,
57,58,59,60,61,62,62,63,
};

const uint8_t ff_h264_lps_state[64]= {
0, 0, 1, 2, 2, 4, 4, 5,
6, 7, 8, 9, 9,11,11,12,
13,13,15,15,16,16,18,18,
19,19,21,21,22,22,23,24,
24,25,26,26,27,27,28,29,
29,30,30,30,31,32,32,33,
33,33,34,34,35,35,35,36,
36,36,37,37,37,38,38,63,
};

/**
*
* @param buf_size size of buf in bits
*/
void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size){
init_put_bits(&c->pb, buf, buf_size, NULL, NULL);

c->low= 0;
c->range= 0x1FE;
c->outstanding_count= 0;
#ifdef STRICT_LIMITS
c->sym_count =0;
#endif
c->pb.bit_left++; //avoids firstBitFlag
}

/**
*
* @param buf_size size of buf in bits
*/
void ff_init_cabac_decoder(CABACContext *c, uint8_t *buf, int buf_size){
c->bytestream= buf;

c->low= *c->bytestream++;
c->low= (c->low<<9) + ((*c->bytestream++)<<1);
c->range= 0x1FE00;
c->bits_left= 7;
}

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){
int i, j;
for(i=0; i<state_count; i++){
for(j=0; j<4; j++){ //FIXME check if this is worth the 1 shift we save
c->lps_range[2*i+0][j]=
c->lps_range[2*i+1][j]= lps_range[i][j];
}

c->mps_state[2*i+0]= 2*mps_state[i];
c->mps_state[2*i+1]= 2*mps_state[i]+1;

if(lps_state[i]){
c->lps_state[2*i+0]= 2*lps_state[i];
c->lps_state[2*i+1]= 2*lps_state[i]+1;
}else{
c->lps_state[2*i+0]= 1;
c->lps_state[2*i+1]= 0;
}
}
}

#if 0 //selftest
#define SIZE 10240
int main(){
CABACContext c;
uint8_t b[9*SIZE];
uint8_t bit[9*SIZE];
int i;
uint8_t state= 0;
ff_init_cabac_encoder(&c, b, SIZE);
ff_init_cabac_states(&c, ff_h264_lps_range, ff_h264_mps_state, ff_h264_lps_state, 64);
for(i=0; i<SIZE; i++){
bit[i]= (random()%7)&1;
}
for(i=0; i<SIZE; i++){
START_TIMER
put_cabac_bypass(&c, bit[i]);
STOP_TIMER("put_cabac_bypass")
}
for(i=0; i<SIZE; i++){
START_TIMER
put_cabac(&c, &state, bit[i]);
STOP_TIMER("put_cabac")
}

put_cabac_terminate(&c, 1);
ff_init_cabac_decoder(&c, b, SIZE);
state=0;
for(i=0; i<SIZE; i++){
START_TIMER
if( bit[i] != get_cabac_bypass(&c) )
printf("CABAC bypass failure at %d\n", i);
STOP_TIMER("get_cabac_bypass")
}
for(i=0; i<SIZE; i++){
START_TIMER
if( bit[i] != get_cabac(&c, &state) )
printf("CABAC failure at %d\n", i);
STOP_TIMER("get_cabac")
}
if(!get_cabac_terminate(&c))
printf("where's the Terminator?\n");
return 0;
}

#endif

+ 232
- 0
libavcodec/cabac.h View File

@@ -0,0 +1,232 @@
/*
* 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
/**
* @file cabac.h
* Context Adaptive Binary Arithmetic Coder.
*/


#undef NDEBUG
#include <assert.h>

typedef struct CABACContext{
int low;
int range;
int outstanding_count;
#ifdef STRICT_LIMITS
int symCount;
#endif
uint8_t lps_range[2*64][4]; ///< rangeTabLPS
uint8_t lps_state[2*64]; ///< transIdxLPS
uint8_t mps_state[2*64]; ///< transIdxMPS
uint8_t *bytestream;
int bits_left; ///<
PutBitContext pb;
}CABACContext;

const uint8_t ff_h264_lps_range[64][4];
const uint8_t ff_h264_mps_state[64];
const uint8_t ff_h264_lps_state[64];

void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size);
void ff_init_cabac_decoder(CABACContext *c, 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)&3];
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
}

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
}

static inline void 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
}

static inline void renorm_cabac_decoder(CABACContext *c){
while(c->range < 0x10000){
c->range+= c->range;
c->low+= c->low;
if(--c->bits_left == 0){
c->low+= *c->bytestream++;
c->bits_left= 8;
}
}
}

static inline int get_cabac(CABACContext *c, uint8_t * const state){
int RangeLPS= c->lps_range[*state][((c->range)>>14)&3]<<8;
int bit;
c->range -= RangeLPS;
if(c->low < c->range){
bit= (*state)&1;
*state= c->mps_state[*state];
}else{
bit= ((*state)&1)^1;
c->low -= c->range;
c->range = RangeLPS;
*state= c->lps_state[*state];
}
renorm_cabac_decoder(c);
return bit;
}

static inline int get_cabac_static(CABACContext *c, int RangeLPS){
int bit;
c->range -= RangeLPS;
if(c->low < c->range){
bit= 0;
}else{
bit= 1;
c->low -= c->range;
c->range = RangeLPS;
}
renorm_cabac_decoder(c);
return bit;
}

static inline int get_cabac_bypass(CABACContext *c){
c->low += c->low;

if(--c->bits_left == 0){
c->low+= *c->bytestream++;
c->bits_left= 8;
}
if(c->low < c->range){
return 0;
}else{
c->low -= c->range;
return 1;
}
}

static inline int get_cabac_terminate(CABACContext *c){
c->range -= 2<<8;
if(c->low < c->range){
renorm_cabac_decoder(c);
return 0;
}else{
return 1;
}
}


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