3 * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
5 * This file is part of FFmpeg.
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
27 * "Range encoding: an algorithm for removing redundancy from a digitised
29 * G. N. N. Martin Presented in March 1979 to the Video &
30 * Data Recording Conference,
31 * IBM UK Scientific Center held in Southampton July 24-27 1979."
39 #include "rangecoder.h"
42 void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size){
45 c->bytestream_end= buf + buf_size;
49 c->outstanding_count= 0;
50 c->outstanding_byte= -1;
53 void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size){
54 /* cast to avoid compiler warning */
55 ff_init_range_encoder(c, (uint8_t *) buf, buf_size);
57 c->low =(*c->bytestream++)<<8;
58 c->low+= *c->bytestream++;
61 void ff_build_rac_states(RangeCoder *c, int factor, int max_p){
62 const int64_t one= 1LL<<32;
66 memset(c->zero_state, 0, sizeof(c->zero_state));
67 memset(c-> one_state, 0, sizeof(c-> one_state));
74 p= (i*one + 128) >> 8;
77 p+= ((one-p)*factor + one/2) >> 32;
78 p8= (256*p + one/2) >> 32; //FIXME try without the one
79 if(p8 <= last_p8) p8= last_p8+1;
80 if(p8 > max_p) p8= max_p;
83 c->one_state[last_p8]= p8;
94 p8= (256*p + one/2) >> 32; //FIXME try without the one
95 if(p8 <= last_p8) p8= last_p8+1;
96 if(last_p8 && last_p8<256 && p8<=max_p)
97 c->one_state[last_p8]= p8;
99 p+= ((one-p)*factor + one/2) >> 32;
103 for(i=256-max_p; i<=max_p; i++){
107 p= (i*one + 128) >> 8;
108 p+= ((one-p)*factor + one/2) >> 32;
109 p8= (256*p + one/2) >> 32; //FIXME try without the one
111 if(p8 > max_p) p8= max_p;
112 c->one_state[ i]= p8;
116 c->zero_state[i]= 256-c->one_state[256-i];
119 av_log(NULL, AV_LOG_DEBUG, "%3d %3d\n", i, c->one_state[i]);
125 * @return the number of bytes written
127 int ff_rac_terminate(RangeCoder *c){
135 assert(c->range >= 0x100);
137 return c->bytestream - c->bytestream_start;
147 uint8_t state[10]= {0};
149 ff_init_range_encoder(&c, b, SIZE);
150 ff_build_rac_states(&c, 0.05*(1LL<<32), 128+64+32+16);
152 memset(state, 128, sizeof(state));
154 for(i=0; i<SIZE; i++){
159 for(i=0; i<SIZE; i++){
161 put_rac(&c, state, r[i]&1);
162 STOP_TIMER("put_rac")
165 ff_put_rac_terminate(&c);
167 ff_init_range_decoder(&c, b, SIZE);
169 memset(state, 128, sizeof(state));
171 for(i=0; i<SIZE; i++){
173 if( (r[i]&1) != get_rac(&c, state) )
174 av_log(NULL, AV_LOG_DEBUG, "rac failure at %d\n", i);
175 STOP_TIMER("get_rac")