Libav
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00001 /* 00002 * Range coder 00003 * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at> 00004 * 00005 * This file is part of FFmpeg. 00006 * 00007 * FFmpeg is free software; you can redistribute it and/or 00008 * modify it under the terms of the GNU Lesser General Public 00009 * License as published by the Free Software Foundation; either 00010 * version 2.1 of the License, or (at your option) any later version. 00011 * 00012 * FFmpeg is distributed in the hope that it will be useful, 00013 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00015 * Lesser General Public License for more details. 00016 * 00017 * You should have received a copy of the GNU Lesser General Public 00018 * License along with FFmpeg; if not, write to the Free Software 00019 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 00020 */ 00021 00034 #include <string.h> 00035 00036 #include "avcodec.h" 00037 #include "rangecoder.h" 00038 #include "bytestream.h" 00039 00040 00041 void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size){ 00042 c->bytestream_start= 00043 c->bytestream= buf; 00044 c->bytestream_end= buf + buf_size; 00045 00046 c->low= 0; 00047 c->range= 0xFF00; 00048 c->outstanding_count= 0; 00049 c->outstanding_byte= -1; 00050 } 00051 00052 void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size){ 00053 /* cast to avoid compiler warning */ 00054 ff_init_range_encoder(c, (uint8_t *) buf, buf_size); 00055 00056 c->low = bytestream_get_be16(&c->bytestream); 00057 } 00058 00059 void ff_build_rac_states(RangeCoder *c, int factor, int max_p){ 00060 const int64_t one= 1LL<<32; 00061 int64_t p; 00062 int last_p8, p8, i; 00063 00064 memset(c->zero_state, 0, sizeof(c->zero_state)); 00065 memset(c-> one_state, 0, sizeof(c-> one_state)); 00066 00067 last_p8= 0; 00068 p= one/2; 00069 for(i=0; i<128; i++){ 00070 p8= (256*p + one/2) >> 32; //FIXME try without the one 00071 if(p8 <= last_p8) p8= last_p8+1; 00072 if(last_p8 && last_p8<256 && p8<=max_p) 00073 c->one_state[last_p8]= p8; 00074 00075 p+= ((one-p)*factor + one/2) >> 32; 00076 last_p8= p8; 00077 } 00078 00079 for(i=256-max_p; i<=max_p; i++){ 00080 if(c->one_state[i]) 00081 continue; 00082 00083 p= (i*one + 128) >> 8; 00084 p+= ((one-p)*factor + one/2) >> 32; 00085 p8= (256*p + one/2) >> 32; //FIXME try without the one 00086 if(p8 <= i) p8= i+1; 00087 if(p8 > max_p) p8= max_p; 00088 c->one_state[ i]= p8; 00089 } 00090 00091 for(i=1; i<255; i++) 00092 c->zero_state[i]= 256-c->one_state[256-i]; 00093 } 00094 00099 int ff_rac_terminate(RangeCoder *c){ 00100 c->range=0xFF; 00101 c->low +=0xFF; 00102 renorm_encoder(c); 00103 c->range=0xFF; 00104 renorm_encoder(c); 00105 00106 assert(c->low == 0); 00107 assert(c->range >= 0x100); 00108 00109 return c->bytestream - c->bytestream_start; 00110 } 00111 00112 #ifdef TEST 00113 #define SIZE 10240 00114 00115 #include "libavutil/lfg.h" 00116 00117 int main(void){ 00118 RangeCoder c; 00119 uint8_t b[9*SIZE]; 00120 uint8_t r[9*SIZE]; 00121 int i; 00122 uint8_t state[10]= {0}; 00123 AVLFG prng; 00124 00125 av_lfg_init(&prng, 1); 00126 00127 ff_init_range_encoder(&c, b, SIZE); 00128 ff_build_rac_states(&c, 0.05*(1LL<<32), 128+64+32+16); 00129 00130 memset(state, 128, sizeof(state)); 00131 00132 for(i=0; i<SIZE; i++){ 00133 r[i] = av_lfg_get(&prng) % 7; 00134 } 00135 00136 for(i=0; i<SIZE; i++){ 00137 START_TIMER 00138 put_rac(&c, state, r[i]&1); 00139 STOP_TIMER("put_rac") 00140 } 00141 00142 ff_rac_terminate(&c); 00143 00144 ff_init_range_decoder(&c, b, SIZE); 00145 00146 memset(state, 128, sizeof(state)); 00147 00148 for(i=0; i<SIZE; i++){ 00149 START_TIMER 00150 if( (r[i]&1) != get_rac(&c, state) ) 00151 av_log(NULL, AV_LOG_DEBUG, "rac failure at %d\n", i); 00152 STOP_TIMER("get_rac") 00153 } 00154 00155 return 0; 00156 } 00157 #endif /* TEST */