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FFmpeg/libavcodec/cabac.c

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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 Libav.
*
* Libav 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.
*
* Libav 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 Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file
* Context Adaptive Binary Arithmetic Coder.
*/
#include <string.h>
#include "libavutil/common.h"
#include "get_bits.h"
#include "cabac.h"
static const uint8_t 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},
};
uint8_t ff_h264_mlps_state[4*64];
uint8_t ff_h264_lps_range[4*2*64];
uint8_t ff_h264_lps_state[2*64];
uint8_t ff_h264_mps_state[2*64];
static const uint8_t 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,
};
static const uint8_t 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,
};
const uint8_t ff_h264_norm_shift[512]= {
9,8,7,7,6,6,6,6,5,5,5,5,5,5,5,5,
4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
};
/**
*
* @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);
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, const uint8_t *buf, int buf_size){
c->bytestream_start=
c->bytestream= buf;
c->bytestream_end= buf + buf_size;
#if CABAC_BITS == 16
c->low = (*c->bytestream++)<<18;
c->low+= (*c->bytestream++)<<10;
#else
c->low = (*c->bytestream++)<<10;
#endif
c->low+= ((*c->bytestream++)<<2) + 2;
c->range= 0x1FE;
}
void ff_init_cabac_states(CABACContext *c){
int i, j;
for(i=0; i<64; i++){
for(j=0; j<4; j++){ //FIXME check if this is worth the 1 shift we save
ff_h264_lps_range[j*2*64+2*i+0]=
ff_h264_lps_range[j*2*64+2*i+1]= lps_range[i][j];
}
ff_h264_mlps_state[128+2*i+0]=
ff_h264_mps_state[2*i+0]= 2*mps_state[i]+0;
ff_h264_mlps_state[128+2*i+1]=
ff_h264_mps_state[2*i+1]= 2*mps_state[i]+1;
if( i ){
ff_h264_mlps_state[128-2*i-1]= 2*lps_state[i]+0;
ff_h264_mlps_state[128-2*i-2]= 2*lps_state[i]+1;
}else{
ff_h264_mlps_state[128-2*i-1]= 1;
ff_h264_mlps_state[128-2*i-2]= 0;
}
}
}
#ifdef TEST
#define SIZE 10240
#include "libavutil/lfg.h"
#include "avcodec.h"
#include "cabac.h"
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
}
/**
* @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);
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);
}
/**
* 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);
}
}
int main(void){
CABACContext c;
uint8_t b[9*SIZE];
uint8_t r[9*SIZE];
int i;
uint8_t state[10]= {0};
AVLFG prng;
av_lfg_init(&prng, 1);
ff_init_cabac_encoder(&c, b, SIZE);
ff_init_cabac_states(&c);
for(i=0; i<SIZE; i++){
r[i] = av_lfg_get(&prng) % 7;
}
for(i=0; i<SIZE; i++){
START_TIMER
put_cabac_bypass(&c, r[i]&1);
STOP_TIMER("put_cabac_bypass")
}
for(i=0; i<SIZE; i++){
START_TIMER
put_cabac(&c, state, r[i]&1);
STOP_TIMER("put_cabac")
}
for(i=0; i<SIZE; i++){
START_TIMER
put_cabac_u(&c, state, r[i], 6, 3, i&1);
STOP_TIMER("put_cabac_u")
}
for(i=0; i<SIZE; i++){
START_TIMER
put_cabac_ueg(&c, state, r[i], 3, 0, 1, 2);
STOP_TIMER("put_cabac_ueg")
}
put_cabac_terminate(&c, 1);
ff_init_cabac_decoder(&c, b, SIZE);
memset(state, 0, sizeof(state));
for(i=0; i<SIZE; i++){
START_TIMER
if( (r[i]&1) != get_cabac_bypass(&c) )
av_log(NULL, AV_LOG_ERROR, "CABAC bypass failure at %d\n", i);
STOP_TIMER("get_cabac_bypass")
}
for(i=0; i<SIZE; i++){
START_TIMER
if( (r[i]&1) != get_cabac(&c, state) )
av_log(NULL, AV_LOG_ERROR, "CABAC failure at %d\n", i);
STOP_TIMER("get_cabac")
}
#if 0
for(i=0; i<SIZE; i++){
START_TIMER
if( r[i] != get_cabac_u(&c, state, (i&1) ? 6 : 7, 3, i&1) )
av_log(NULL, AV_LOG_ERROR, "CABAC unary (truncated) binarization failure at %d\n", i);
STOP_TIMER("get_cabac_u")
}
for(i=0; i<SIZE; i++){
START_TIMER
if( r[i] != get_cabac_ueg(&c, state, 3, 0, 1, 2))
av_log(NULL, AV_LOG_ERROR, "CABAC unary (truncated) binarization failure at %d\n", i);
STOP_TIMER("get_cabac_ueg")
}
#endif
if(!get_cabac_terminate(&c))
av_log(NULL, AV_LOG_ERROR, "where's the Terminator?\n");
return 0;
}
#endif /* TEST */
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