apps/codecs/demac/libdemac/entropy.c

   1 /*
   2
   3 libdemac - A Monkey's Audio decoder
   4
   5 $Id$
   6
   7 Copyright (C) Dave Chapman 2007
   8
   9 This program is free software; you can redistribute it and/or modify
  10 it under the terms of the GNU General Public License as published by
  11 the Free Software Foundation; either version 2 of the License, or
  12 (at your option) any later version.
  13
  14 This program is distributed in the hope that it will be useful,
  15 but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 GNU General Public License for more details.
  18
  19 You should have received a copy of the GNU General Public License
  20 along with this program; if not, write to the Free Software
  21 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110, USA
  22
  23 */
  24
  25 #include <inttypes.h>
  26 #include <string.h>
  27
  28 #include "parser.h"
  29 #include "entropy.h"
  30 #include "rangecoding.h"   /* Range-coding (static inline) functions */
  31 #include "demac_iram.h"
  32
  33 #define MODEL_ELEMENTS 64
  34
  35 /*
  36   The following counts arrays for use with the range decoder are
  37   hard-coded in the Monkey's Audio decoder.
  38 */
  39
  40 static const int counts_3970[65] ICONST_ATTR =
  41 {
  42         0,14824,28224,39348,47855,53994,58171,60926,
  43     62682,63786,64463,64878,65126,65276,65365,65419,
  44     65450,65469,65480,65487,65491,65493,65494,65495,
  45     65496,65497,65498,65499,65500,65501,65502,65503,
  46     65504,65505,65506,65507,65508,65509,65510,65511,
  47     65512,65513,65514,65515,65516,65517,65518,65519,
  48     65520,65521,65522,65523,65524,65525,65526,65527,
  49     65528,65529,65530,65531,65532,65533,65534,65535,
  50     65536
  51 };
  52
  53 /* counts_diff_3970[i] = counts_3970[i+1] - counts_3970[i] */
  54 static const int counts_diff_3970[64] ICONST_ATTR =
  55 {
  56     14824,13400,11124,8507,6139,4177,2755,1756,
  57     1104,677,415,248,150,89,54,31,
  58     19,11,7,4,2,1,1,1,
  59     1,1,1,1,1,1,1,1,
  60     1,1,1,1,1,1,1,1,
  61     1,1,1,1,1,1,1,1,
  62     1,1,1,1,1,1,1,1,
  63     1,1,1,1,1,1,1,1
  64 };
  65
  66 static const int counts_3980[65] ICONST_ATTR =
  67 {
  68         0,19578,36160,48417,56323,60899,63265,64435,
  69     64971,65232,65351,65416,65447,65466,65476,65482,
  70     65485,65488,65490,65491,65492,65493,65494,65495,
  71     65496,65497,65498,65499,65500,65501,65502,65503,
  72     65504,65505,65506,65507,65508,65509,65510,65511,
  73     65512,65513,65514,65515,65516,65517,65518,65519,
  74     65520,65521,65522,65523,65524,65525,65526,65527,
  75     65528,65529,65530,65531,65532,65533,65534,65535,
  76     65536
  77 };
  78
  79 /* counts_diff_3980[i] = counts_3980[i+1] - counts_3980[i] */
  80
  81 static const int counts_diff_3980[64] ICONST_ATTR =
  82 {
  83     19578,16582,12257,7906,4576,2366,1170,536,
  84     261,119,65,31,19,10,6,3,
  85     3,2,1,1,1,1,1,1,
  86     1,1,1,1,1,1,1,1,
  87     1,1,1,1,1,1,1,1,
  88     1,1,1,1,1,1,1,1,
  89     1,1,1,1,1,1,1,1,
  90     1,1,1,1,1,1,1,1
  91 };
  92
  93 /*
  94   range_get_symbol_* functions based on main decoding loop in simple_d.c from
  95   http://www.compressconsult.com/rangecoder/rngcod13.zip
  96   (c) Michael Schindler
  97 */
  98
  99 static inline int range_get_symbol_3980(void)
 100 {
 101     int symbol, cf;
 102
 103     cf = range_decode_culshift(16);
 104
 105     /* figure out the symbol inefficiently; a binary search would be much better */
 106     for (symbol = 0; counts_3980[symbol+1] <= cf; symbol++);
 107
 108     range_decode_update(counts_diff_3980[symbol],counts_3980[symbol]);
 109
 110     return symbol;
 111 }
 112
 113 static inline int range_get_symbol_3970(void)
 114 {
 115     int symbol, cf;
 116
 117     cf = range_decode_culshift(16);
 118
 119     /* figure out the symbol inefficiently; a binary search would be much better */
 120     for (symbol = 0; counts_3970[symbol+1] <= cf; symbol++);
 121
 122     range_decode_update(counts_diff_3970[symbol],counts_3970[symbol]);
 123
 124     return symbol;
 125 }
 126
 127 /* MAIN DECODING FUNCTIONS */
 128
 129 struct rice_t
 130 {
 131   uint32_t k;
 132   uint32_t ksum;
 133 };
 134
 135 static struct rice_t riceX IBSS_ATTR;
 136 static struct rice_t riceY IBSS_ATTR;
 137
 138 static inline void update_rice(struct rice_t* rice, int x)
 139 {
 140     rice->ksum += ((x + 1) / 2) - ((rice->ksum + 16) >> 5);
 141
 142     if (rice->k == 0) {
 143         rice->k = 1;
 144     } else {
 145         uint32_t lim = 1 << (rice->k + 4);
 146         if (rice->ksum < lim) {
 147             rice->k--;
 148         } else if (rice->ksum >= 2 * lim) {
 149             rice->k++;
 150         }
 151     }
 152 }
 153
 154 static inline int entropy_decode3980(struct rice_t* rice)
 155 {
 156     int base, x, pivot, overflow;
 157
 158     pivot = rice->ksum >> 5;
 159     if (pivot == 0) pivot=1;
 160
 161     overflow = range_get_symbol_3980();
 162
 163     if (overflow == (MODEL_ELEMENTS-1)) {
 164         overflow = range_decode_short() << 16;
 165         overflow |= range_decode_short();
 166     }
 167
 168     if (pivot >= 0x10000) {
 169         /* Codepath for 24-bit streams */
 170         int nbits, lo_bits, base_hi, base_lo;
 171
 172         /* Count the number of bits in pivot */
 173         nbits = 17; /* We know there must be at least 17 bits */
 174         while ((pivot >> nbits) > 0) { nbits++; }
 175
 176         /* base_lo is the low (nbits-16) bits of base
 177            base_hi is the high 16 bits of base
 178         */
 179         lo_bits = (nbits - 16);
 180
 181         base_hi = range_decode_culfreq((pivot >> lo_bits) + 1);
 182         range_decode_update(1, base_hi);
 183
 184         base_lo = range_decode_culshift(lo_bits);
 185         range_decode_update(1, base_lo);
 186
 187         base = (base_hi << lo_bits) + base_lo;
 188     } else {
 189         /* Codepath for 16-bit streams */
 190         base = range_decode_culfreq(pivot);
 191         range_decode_update(1, base);
 192     }
 193
 194     x = base + (overflow * pivot);
 195     update_rice(rice, x);
 196
 197     /* Convert to signed */
 198     if (x & 1)
 199         return (x >> 1) + 1;
 200     else
 201         return -(x >> 1);
 202 }
 203
 204
 205 static inline int entropy_decode3970(struct rice_t* rice)
 206 {
 207     int x, tmpk;
 208
 209     int overflow = range_get_symbol_3970();
 210
 211     if (overflow == (MODEL_ELEMENTS - 1)) {
 212         tmpk = range_decode_bits(5);
 213         overflow = 0;
 214     } else {
 215         tmpk = (rice->k < 1) ? 0 : rice->k - 1;
 216     }
 217
 218     if (tmpk <= 16) {
 219         x = range_decode_bits(tmpk);
 220     } else {
 221         x = range_decode_short();
 222         x |= (range_decode_bits(tmpk - 16) << 16);
 223     }
 224     x += (overflow << tmpk);
 225
 226     update_rice(rice, x);
 227
 228     /* Convert to signed */
 229     if (x & 1)
 230         return (x >> 1) + 1;
 231     else
 232         return -(x >> 1);
 233 }
 234
 235 void init_entropy_decoder(struct ape_ctx_t* ape_ctx,
 236                           unsigned char* inbuffer, int* firstbyte,
 237                           int* bytesconsumed)
 238 {
 239     bytebuffer = inbuffer;
 240     bytebufferoffset = *firstbyte;
 241
 242     /* Read the CRC */
 243     ape_ctx->CRC = read_byte();
 244     ape_ctx->CRC = (ape_ctx->CRC << 8) | read_byte();
 245     ape_ctx->CRC = (ape_ctx->CRC << 8) | read_byte();
 246     ape_ctx->CRC = (ape_ctx->CRC << 8) | read_byte();
 247
 248     /* Read the frame flags if they exist */
 249     ape_ctx->frameflags = 0;
 250     if ((ape_ctx->fileversion > 3820) && (ape_ctx->CRC & 0x80000000)) {
 251         ape_ctx->CRC &= ~0x80000000;
 252
 253         ape_ctx->frameflags = read_byte();
 254         ape_ctx->frameflags = (ape_ctx->frameflags << 8) | read_byte();
 255         ape_ctx->frameflags = (ape_ctx->frameflags << 8) | read_byte();
 256         ape_ctx->frameflags = (ape_ctx->frameflags << 8) | read_byte();
 257     }
 258     /* Keep a count of the blocks decoded in this frame */
 259     ape_ctx->blocksdecoded = 0;
 260
 261     /* Initialise the rice structs */
 262     riceX.k = 10;
 263     riceX.ksum = (1 << riceX.k) * 16;
 264     riceY.k = 10;
 265     riceY.ksum = (1 << riceY.k) * 16;
 266
 267     /* The first 8 bits of input are ignored. */
 268     skip_byte();
 269
 270     range_start_decoding();
 271
 272     /* Return the new state of the buffer */
 273     *bytesconsumed = (intptr_t)bytebuffer - (intptr_t)inbuffer;
 274     *firstbyte = bytebufferoffset;
 275 }
 276
 277 int ICODE_ATTR_DEMAC entropy_decode(struct ape_ctx_t* ape_ctx,
 278                                     unsigned char* inbuffer, int* firstbyte,
 279                                     int* bytesconsumed,
 280                                     int32_t* decoded0, int32_t* decoded1,
 281                                     int blockstodecode)
 282 {
 283     bytebuffer = inbuffer;
 284     bytebufferoffset = *firstbyte;
 285
 286     ape_ctx->blocksdecoded += blockstodecode;
 287
 288     if (ape_ctx->frameflags & APE_FRAMECODE_STEREO_SILENCE) {
 289         /* We are pure silence, just memset the output buffer. */
 290         memset(decoded0, 0, blockstodecode * sizeof(int32_t));
 291         memset(decoded1, 0, blockstodecode * sizeof(int32_t));
 292     } else {
 293         if (ape_ctx->fileversion > 3970) {
 294             while (blockstodecode--) {
 295                 *(decoded0++) = entropy_decode3980(&riceY);
 296                 if (decoded1 != NULL)
 297                     *(decoded1++) = entropy_decode3980(&riceX);
 298             }
 299         } else {
 300             while (blockstodecode--) {
 301                 *(decoded0++) = entropy_decode3970(&riceY);
 302                 if (decoded1 != NULL)
 303                     *(decoded1++) = entropy_decode3970(&riceX);
 304             }
 305         }
 306     }
 307
 308     if (ape_ctx->blocksdecoded == ape_ctx->currentframeblocks)
 309     {
 310         range_done_decoding();
 311     }
 312
 313     /* Return the new state of the buffer */
 314     *bytesconsumed = bytebuffer - inbuffer;
 315     *firstbyte = bytebufferoffset;
 316
 317     return(0);
 318 }