quicktime/ffmpeg/libavcodec/rangecoder.c

   1 /*
   2  * Range coder
   3  * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the License, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this library; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18  *
  19  */
  20
  21 /**
  22  * @file rangecoder.c
  23  * Range coder.
  24  * based upon
  25  *    "Range encoding: an algorithm for removing redundancy from a digitised
  26  *                     message.
  27  *     G. N. N. Martin                  Presented in March 1979 to the Video &
  28  *                                      Data Recording Conference,
  29  *     IBM UK Scientific Center         held in Southampton July 24-27 1979."
  30  *
  31  */
  32
  33 #include <string.h>
  34
  35 #include "avcodec.h"
  36 #include "common.h"
  37 #include "rangecoder.h"
  38
  39
  40 void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size){
  41     c->bytestream_start=
  42     c->bytestream= buf;
  43     c->bytestream_end= buf + buf_size;
  44
  45     c->low= 0;
  46     c->range= 0xFF00;
  47     c->outstanding_count= 0;
  48     c->outstanding_byte= -1;
  49 }
  50
  51 void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size){
  52     ff_init_range_encoder(c, buf, buf_size);
  53
  54     c->low =(*c->bytestream++)<<8;
  55     c->low+= *c->bytestream++;
  56 }
  57
  58 void ff_build_rac_states(RangeCoder *c, int factor, int max_p){
  59     const int64_t one= 1LL<<32;
  60     int64_t p;
  61     int last_p8, p8, i;
  62
  63     memset(c->zero_state, 0, sizeof(c->zero_state));
  64     memset(c-> one_state, 0, sizeof(c-> one_state));
  65
  66 #if 0
  67     for(i=1; i<256; i++){
  68         if(c->one_state[i])
  69             continue;
  70
  71         p= (i*one + 128) >> 8;
  72         last_p8= i;
  73         for(;;){
  74             p+= ((one-p)*factor + one/2) >> 32;
  75             p8= (256*p + one/2) >> 32; //FIXME try without the one
  76             if(p8 <= last_p8) p8= last_p8+1;
  77             if(p8 > max_p) p8= max_p;
  78             if(p8 < last_p8)
  79                 break;
  80             c->one_state[last_p8]=     p8;
  81             if(p8 == last_p8)
  82                 break;
  83             last_p8= p8;
  84         }
  85     }
  86 #endif
  87 #if 1
  88     last_p8= 0;
  89     p= one/2;
  90     for(i=0; i<128; i++){
  91         p8= (256*p + one/2) >> 32; //FIXME try without the one
  92         if(p8 <= last_p8) p8= last_p8+1;
  93         if(last_p8 && last_p8<256 && p8<=max_p)
  94             c->one_state[last_p8]= p8;
  95
  96         p+= ((one-p)*factor + one/2) >> 32;
  97         last_p8= p8;
  98     }
  99 #endif
 100     for(i=256-max_p; i<=max_p; i++){
 101         if(c->one_state[i])
 102             continue;
 103
 104         p= (i*one + 128) >> 8;
 105         p+= ((one-p)*factor + one/2) >> 32;
 106         p8= (256*p + one/2) >> 32; //FIXME try without the one
 107         if(p8 <= i) p8= i+1;
 108         if(p8 > max_p) p8= max_p;
 109         c->one_state[    i]=     p8;
 110     }
 111
 112     for(i=0; i<256; i++)
 113         c->zero_state[i]= 256-c->one_state[256-i];
 114 #if 0
 115     for(i=0; i<256; i++)
 116         av_log(NULL, AV_LOG_DEBUG, "%3d %3d\n", i, c->one_state[i]);
 117 #endif
 118 }
 119
 120 /**
 121  *
 122  * @return the number of bytes written
 123  */
 124 int ff_rac_terminate(RangeCoder *c){
 125     c->range=0xFF;
 126     c->low +=0xFF;
 127     renorm_encoder(c);
 128     c->range=0xFF;
 129     renorm_encoder(c);
 130
 131     assert(c->low   == 0);
 132     assert(c->range >= 0x100);
 133
 134     return c->bytestream - c->bytestream_start;
 135 }
 136
 137 #if 0 //selftest
 138 #define SIZE 10240
 139 int main(){
 140     RangeCoder c;
 141     uint8_t b[9*SIZE];
 142     uint8_t r[9*SIZE];
 143     int i;
 144     uint8_t state[10]= {0};
 145
 146     ff_init_range_encoder(&c, b, SIZE);
 147     ff_build_rac_states(&c, 0.05*(1LL<<32), 128+64+32+16);
 148
 149     memset(state, 128, sizeof(state));
 150
 151     for(i=0; i<SIZE; i++){
 152         r[i]= random()%7;
 153     }
 154
 155
 156     for(i=0; i<SIZE; i++){
 157 START_TIMER
 158         put_rac(&c, state, r[i]&1);
 159 STOP_TIMER("put_rac")
 160     }
 161
 162     ff_put_rac_terminate(&c);
 163
 164     ff_init_range_decoder(&c, b, SIZE);
 165
 166     memset(state, 128, sizeof(state));
 167
 168     for(i=0; i<SIZE; i++){
 169 START_TIMER
 170         if( (r[i]&1) != get_rac(&c, state) )
 171             av_log(NULL, AV_LOG_DEBUG, "rac failure at %d\n", i);
 172 STOP_TIMER("get_rac")
 173     }
 174
 175     return 0;
 176 }
 177
 178 #endif