apps/codecs/libffmpegFLAC/golomb.h

   1 /*
   2  * exp golomb vlc stuff
   3  * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
   4  * Copyright (c) 2004 Alex Beregszaszi
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19  *
  20  */
  21
  22 #include <limits.h>
  23
  24 /* From libavutil/common.h */
  25 extern const uint8_t ff_log2_tab[256];
  26
  27 static inline int av_log2(unsigned int v)
  28 {
  29     int n;
  30
  31     n = 0;
  32     if (v & 0xffff0000) {
  33         v >>= 16;
  34         n += 16;
  35     }
  36     if (v & 0xff00) {
  37         v >>= 8;
  38         n += 8;
  39     }
  40     n += ff_log2_tab[v];
  41
  42     return n;
  43 }
  44
  45 /**
  46  * @file golomb.h
  47  * @brief
  48  *     exp golomb vlc stuff
  49  * @author Michael Niedermayer <michaelni@gmx.at> and Alex Beregszaszi
  50  */
  51
  52
  53 /**
  54  * read unsigned golomb rice code (jpegls).
  55  */
  56 static inline int get_ur_golomb_jpegls(GetBitContext *gb, int k, int limit, int esc_len){
  57     unsigned int buf;
  58     int log;
  59
  60     OPEN_READER(re, gb);
  61     UPDATE_CACHE(re, gb);
  62     buf=GET_CACHE(re, gb);
  63
  64     log= av_log2(buf);
  65
  66     if(log - k >= 32-MIN_CACHE_BITS+(MIN_CACHE_BITS==32) && 32-log < limit){
  67         buf >>= log - k;
  68         buf += (30-log)<<k;
  69         LAST_SKIP_BITS(re, gb, 32 + k - log);
  70         CLOSE_READER(re, gb);
  71
  72         return buf;
  73     }else{
  74         int i;
  75         for(i=0; SHOW_UBITS(re, gb, 1) == 0; i++){
  76             LAST_SKIP_BITS(re, gb, 1);
  77             UPDATE_CACHE(re, gb);
  78         }
  79         SKIP_BITS(re, gb, 1);
  80
  81         if(i < limit - 1){
  82             if(k){
  83                 buf = SHOW_UBITS(re, gb, k);
  84                 LAST_SKIP_BITS(re, gb, k);
  85             }else{
  86                 buf=0;
  87             }
  88
  89             CLOSE_READER(re, gb);
  90             return buf + (i<<k);
  91         }else if(i == limit - 1){
  92             buf = SHOW_UBITS(re, gb, esc_len);
  93             LAST_SKIP_BITS(re, gb, esc_len);
  94             CLOSE_READER(re, gb);
  95
  96             return buf + 1;
  97         }else
  98             return -1;
  99     }
 100 }
 101
 102 /**
 103  * read signed golomb rice code (flac).
 104  */
 105 static inline int get_sr_golomb_flac(GetBitContext *gb, int k, int limit, int esc_len){
 106     int v= get_ur_golomb_jpegls(gb, k, limit, esc_len);
 107     return (v>>1) ^ -(v&1);
 108 }
 109
 110 /**
 111  * read unsigned golomb rice code (shorten).
 112  */
 113 #define get_ur_golomb_shorten(gb, k) get_ur_golomb_jpegls(gb, k, INT_MAX, 0)
 114 /*
 115 static inline unsigned int get_ur_golomb_shorten(GetBitContext *gb, int k){
 116         return get_ur_golomb_jpegls(gb, k, INT_MAX, 0);
 117 }
 118 */
 119
 120 /**
 121  * read signed golomb rice code (shorten).
 122  */
 123 static inline int get_sr_golomb_shorten(GetBitContext* gb, int k)
 124 {
 125     int uvar = get_ur_golomb_jpegls(gb, k + 1, INT_MAX, 0);
 126     if (uvar & 1)
 127         return ~(uvar >> 1);
 128     else
 129         return uvar >> 1;
 130 }