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- /*
- * Range coder
- * Copyright (c) 2004 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 rangecoder.c
- * Range coder.
- * based upon
- * "Range encoding: an algorithm for removing redundancy from a digitised
- * message.
- * G. N. N. Martin Presented in March 1979 to the Video &
- * Data Recording Conference,
- * IBM UK Scientific Center held in Southampton July 24-27 1979."
- *
- */
- #include <string.h>
- #include "avcodec.h"
- #include "common.h"
- #include "rangecoder.h"
- void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size){
- c->bytestream_start=
- c->bytestream= buf;
- c->bytestream_end= buf + buf_size;
- c->low= 0;
- c->range= 0xFF00;
- c->outstanding_count= 0;
- c->outstanding_byte= -1;
- }
- void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size){
- /* cast to avoid compiler warning */
- ff_init_range_encoder(c, (uint8_t *) buf, buf_size);
- c->low =(*c->bytestream++)<<8;
- c->low+= *c->bytestream++;
- }
- void ff_build_rac_states(RangeCoder *c, int factor, int max_p){
- const int64_t one= 1LL<<32;
- int64_t p;
- int last_p8, p8, i;
- memset(c->zero_state, 0, sizeof(c->zero_state));
- memset(c-> one_state, 0, sizeof(c-> one_state));
- last_p8= 0;
- p= one/2;
- for(i=0; i<128; i++){
- p8= (256*p + one/2) >> 32; //FIXME try without the one
- if(p8 <= last_p8) p8= last_p8+1;
- if(last_p8 && last_p8<256 && p8<=max_p)
- c->one_state[last_p8]= p8;
- p+= ((one-p)*factor + one/2) >> 32;
- last_p8= p8;
- }
- for(i=256-max_p; i<=max_p; i++){
- if(c->one_state[i])
- continue;
- p= (i*one + 128) >> 8;
- p+= ((one-p)*factor + one/2) >> 32;
- p8= (256*p + one/2) >> 32; //FIXME try without the one
- if(p8 <= i) p8= i+1;
- if(p8 > max_p) p8= max_p;
- c->one_state[ i]= p8;
- }
- for(i=1; i<255; i++)
- c->zero_state[i]= 256-c->one_state[256-i];
- }
- /**
- *
- * @return the number of bytes written
- */
- int ff_rac_terminate(RangeCoder *c){
- c->range=0xFF;
- c->low +=0xFF;
- renorm_encoder(c);
- c->range=0xFF;
- renorm_encoder(c);
- assert(c->low == 0);
- assert(c->range >= 0x100);
- return c->bytestream - c->bytestream_start;
- }
- #if 0 //selftest
- #define SIZE 10240
- int main(){
- RangeCoder c;
- uint8_t b[9*SIZE];
- uint8_t r[9*SIZE];
- int i;
- uint8_t state[10]= {0};
- ff_init_range_encoder(&c, b, SIZE);
- ff_build_rac_states(&c, 0.05*(1LL<<32), 128+64+32+16);
- memset(state, 128, sizeof(state));
- for(i=0; i<SIZE; i++){
- r[i]= random()%7;
- }
- for(i=0; i<SIZE; i++){
- START_TIMER
- put_rac(&c, state, r[i]&1);
- STOP_TIMER("put_rac")
- }
- ff_put_rac_terminate(&c);
- ff_init_range_decoder(&c, b, SIZE);
- memset(state, 128, sizeof(state));
- for(i=0; i<SIZE; i++){
- START_TIMER
- if( (r[i]&1) != get_rac(&c, state) )
- av_log(NULL, AV_LOG_DEBUG, "rac failure at %d\n", i);
- STOP_TIMER("get_rac")
- }
- return 0;
- }
- #endif
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