cabac.c

Go to the documentation of this file.

/*
 * 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
 */
 
#include "libavcodec/cabac.c"
 
#define SIZE 10240
 
#include "libavutil/lfg.h"
#include "libavcodec/avcodec.h"
 
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[2*(c->range&0xC0) + *state];
 
    if(bit == ((*state)&1)){
        c->range -= RangeLPS;
        *state    = ff_h264_mlps_state[128 + *state];
    }else{
        c->low += c->range - RangeLPS;
        c->range = RangeLPS;
        *state= ff_h264_mlps_state[127 - *state];
    }
 
    renorm_cabac_encoder(c);
}
 
/**
 * @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;
    }
}
 
/**
 *
 * @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);
 
        av_assert0(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
    }
 
    return (put_bits_count(&c->pb)+7)>>3;
}
 
int main(void){
    CABACContext c;
    uint8_t b[9*SIZE];
    uint8_t r[9*SIZE];
    int i, ret = 0;
    uint8_t state[10]= {0};
    AVLFG prng;
 
    av_lfg_init(&prng, 1);
    ff_init_cabac_encoder(&c, b, SIZE);
 
    for(i=0; i<SIZE; i++){
        if(2*i<SIZE) r[i] = av_lfg_get(&prng) % 7;
        else         r[i] = (i>>8)&1;
    }
 
    for(i=0; i<SIZE; i++){
        put_cabac_bypass(&c, r[i]&1);
    }
 
    for(i=0; i<SIZE; i++){
        put_cabac(&c, state, r[i]&1);
    }
 
    i= put_cabac_terminate(&c, 1);
    b[i++] = av_lfg_get(&prng);
    b[i  ] = av_lfg_get(&prng);
 
    ff_init_cabac_decoder(&c, b, SIZE);
 
    memset(state, 0, sizeof(state));
 
    for(i=0; i<SIZE; i++){
        if( (r[i]&1) != get_cabac_bypass(&c) ) {
            av_log(NULL, AV_LOG_ERROR, "CABAC bypass failure at %d\n", i);
            ret = 1;
        }
    }
 
    for(i=0; i<SIZE; i++){
        if( (r[i]&1) != get_cabac_noinline(&c, state) ) {
            av_log(NULL, AV_LOG_ERROR, "CABAC failure at %d\n", i);
            ret = 1;
        }
    }
    if(!get_cabac_terminate(&c)) {
        av_log(NULL, AV_LOG_ERROR, "where's the Terminator?\n");
        ret = 1;
    }
 
    return ret;
}