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 "demac_config.h"
  31
  32 #define MODEL_ELEMENTS 64
  33
  34 /*
  35   The following counts arrays for use with the range decoder are
  36   hard-coded in the Monkey's Audio decoder.
  37 */
  38
  39 static const int counts_3970[65] ICONST_ATTR =
  40 {
  41         0,14824,28224,39348,47855,53994,58171,60926,
  42     62682,63786,64463,64878,65126,65276,65365,65419,
  43     65450,65469,65480,65487,65491,65493,65494,65495,
  44     65496,65497,65498,65499,65500,65501,65502,65503,
  45     65504,65505,65506,65507,65508,65509,65510,65511,
  46     65512,65513,65514,65515,65516,65517,65518,65519,
  47     65520,65521,65522,65523,65524,65525,65526,65527,
  48     65528,65529,65530,65531,65532,65533,65534,65535,
  49     65536
  50 };
  51
  52 /* counts_diff_3970[i] = counts_3970[i+1] - counts_3970[i] */
  53 static const int counts_diff_3970[64] ICONST_ATTR =
  54 {
  55     14824,13400,11124,8507,6139,4177,2755,1756,
  56     1104,677,415,248,150,89,54,31,
  57     19,11,7,4,2,1,1,1,
  58     1,1,1,1,1,1,1,1,
  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 };
  64
  65 static const int counts_3980[65] ICONST_ATTR =
  66 {
  67         0,19578,36160,48417,56323,60899,63265,64435,
  68     64971,65232,65351,65416,65447,65466,65476,65482,
  69     65485,65488,65490,65491,65492,65493,65494,65495,
  70     65496,65497,65498,65499,65500,65501,65502,65503,
  71     65504,65505,65506,65507,65508,65509,65510,65511,
  72     65512,65513,65514,65515,65516,65517,65518,65519,
  73     65520,65521,65522,65523,65524,65525,65526,65527,
  74     65528,65529,65530,65531,65532,65533,65534,65535,
  75     65536
  76 };
  77
  78 /* counts_diff_3980[i] = counts_3980[i+1] - counts_3980[i] */
  79
  80 static const int counts_diff_3980[64] ICONST_ATTR =
  81 {
  82     19578,16582,12257,7906,4576,2366,1170,536,
  83     261,119,65,31,19,10,6,3,
  84     3,2,1,1,1,1,1,1,
  85     1,1,1,1,1,1,1,1,
  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 };
  91
  92 /*
  93
  94 Range decoder adapted from rangecod.c included in:
  95
  96   http://www.compressconsult.com/rangecoder/rngcod13.zip
  97
  98   rangecod.c     range encoding
  99
 100   (c) Michael Schindler
 101   1997, 1998, 1999, 2000
 102   http://www.compressconsult.com/
 103   michael@compressconsult.com
 104
 105   This program is free software; you can redistribute it and/or modify
 106   it under the terms of the GNU General Public License as published by
 107   the Free Software Foundation; either version 2 of the License, or
 108   (at your option) any later version.
 109
 110
 111 The encoding functions were removed, and functions turned into "static
 112 inline" functions. Some minor cosmetic changes were made (e.g. turning
 113 pre-processor symbols into upper-case, removing the rc parameter from
 114 each function (and the RNGC macro)).
 115
 116 */
 117
 118 /* BITSTREAM READING FUNCTIONS */
 119
 120 /* We deal with the input data one byte at a time - to ensure
 121    functionality on CPUs of any endianness regardless of any requirements
 122    for aligned reads.
 123 */
 124
 125 static unsigned char* bytebuffer IBSS_ATTR;
 126 static int bytebufferoffset IBSS_ATTR;
 127
 128 static inline void skip_byte(void)
 129 {
 130     bytebufferoffset--;
 131     bytebuffer += bytebufferoffset & 4;
 132     bytebufferoffset &= 3;
 133 }
 134
 135 static inline int read_byte(void)
 136 {
 137     int ch = bytebuffer[bytebufferoffset];
 138
 139     skip_byte();
 140
 141     return ch;
 142 }
 143
 144 /* RANGE DECODING FUNCTIONS */
 145
 146 /* SIZE OF RANGE ENCODING CODE VALUES. */
 147
 148 #define CODE_BITS 32
 149 #define TOP_VALUE ((unsigned int)1 << (CODE_BITS-1))
 150 #define SHIFT_BITS (CODE_BITS - 9)
 151 #define EXTRA_BITS ((CODE_BITS-2) % 8 + 1)
 152 #define BOTTOM_VALUE (TOP_VALUE >> 8)
 153
 154 struct rangecoder_t
 155 {
 156     uint32_t low;        /* low end of interval */
 157     uint32_t range;      /* length of interval */
 158     uint32_t help;       /* bytes_to_follow resp. intermediate value */
 159     unsigned int buffer; /* buffer for input/output */
 160 };
 161
 162 static struct rangecoder_t rc IBSS_ATTR;
 163
 164 /* Start the decoder */
 165 static inline void range_start_decoding(void)
 166 {
 167     rc.buffer = read_byte();
 168     rc.low = rc.buffer >> (8 - EXTRA_BITS);
 169     rc.range = (uint32_t) 1 << EXTRA_BITS;
 170 }
 171
 172 static inline void range_dec_normalize(void)
 173 {
 174     while (rc.range <= BOTTOM_VALUE)
 175     {
 176         rc.buffer = (rc.buffer << 8) | read_byte();
 177         rc.low = (rc.low << 8) | ((rc.buffer >> 1) & 0xff);
 178         rc.range <<= 8;
 179     }
 180 }
 181
 182 /* Calculate culmulative frequency for next symbol. Does NO update!*/
 183 /* tot_f is the total frequency                              */
 184 /* or: totf is (code_value)1<<shift                                      */
 185 /* returns the culmulative frequency                         */
 186 static inline int range_decode_culfreq(int tot_f)
 187 {
 188     range_dec_normalize();
 189     rc.help = UDIV32(rc.range, tot_f);
 190     return UDIV32(rc.low, rc.help);
 191 }
 192
 193 static inline int range_decode_culshift(int shift)
 194 {
 195     range_dec_normalize();
 196     rc.help = rc.range >> shift;
 197     return UDIV32(rc.low, rc.help);
 198 }
 199
 200
 201 /* Update decoding state                                     */
 202 /* sy_f is the interval length (frequency of the symbol)     */
 203 /* lt_f is the lower end (frequency sum of < symbols)        */
 204 static inline void range_decode_update(int sy_f, int lt_f)
 205 {
 206     rc.low -= rc.help * lt_f;
 207     rc.range = rc.help * sy_f;
 208 }
 209
 210
 211 /* Decode a byte/short without modelling                     */
 212 static inline unsigned char decode_byte(void)
 213 {   int tmp = range_decode_culshift(8);
 214     range_decode_update( 1,tmp);
 215     return tmp;
 216 }
 217
 218 static inline int short range_decode_short(void)
 219 {   int tmp = range_decode_culshift(16);
 220     range_decode_update( 1,tmp);
 221     return tmp;
 222 }
 223
 224 /* Decode n bits (n <= 16) without modelling - based on range_decode_short */
 225 static inline int range_decode_bits(int n)
 226 {   int tmp = range_decode_culshift(n);
 227     range_decode_update( 1,tmp);
 228     return tmp;
 229 }
 230
 231
 232 /* Finish decoding                                           */
 233 static inline void range_done_decoding(void)
 234 {   range_dec_normalize();      /* normalize to use up all bytes */
 235 }
 236
 237 /*
 238   range_get_symbol_* functions based on main decoding loop in simple_d.c from
 239   http://www.compressconsult.com/rangecoder/rngcod13.zip
 240   (c) Michael Schindler
 241 */
 242
 243 static inline int range_get_symbol_3980(void)
 244 {
 245     int symbol, cf;
 246
 247     cf = range_decode_culshift(16);
 248
 249     /* figure out the symbol inefficiently; a binary search would be much better */
 250     for (symbol = 0; counts_3980[symbol+1] <= cf; symbol++);
 251
 252     range_decode_update(counts_diff_3980[symbol],counts_3980[symbol]);
 253
 254     return symbol;
 255 }
 256
 257 static inline int range_get_symbol_3970(void)
 258 {
 259     int symbol, cf;
 260
 261     cf = range_decode_culshift(16);
 262
 263     /* figure out the symbol inefficiently; a binary search would be much better */
 264     for (symbol = 0; counts_3970[symbol+1] <= cf; symbol++);
 265
 266     range_decode_update(counts_diff_3970[symbol],counts_3970[symbol]);
 267
 268     return symbol;
 269 }
 270
 271 /* MAIN DECODING FUNCTIONS */
 272
 273 struct rice_t
 274 {
 275   uint32_t k;
 276   uint32_t ksum;
 277 };
 278
 279 static struct rice_t riceX IBSS_ATTR;
 280 static struct rice_t riceY IBSS_ATTR;
 281
 282 static inline void update_rice(struct rice_t* rice, int x)
 283 {
 284     rice->ksum += ((x + 1) / 2) - ((rice->ksum + 16) >> 5);
 285
 286     if (UNLIKELY(rice->k == 0)) {
 287         rice->k = 1;
 288     } else {
 289         uint32_t lim = 1 << (rice->k + 4);
 290         if (UNLIKELY(rice->ksum < lim)) {
 291             rice->k--;
 292         } else if (UNLIKELY(rice->ksum >= 2 * lim)) {
 293             rice->k++;
 294         }
 295     }
 296 }
 297
 298 static inline int entropy_decode3980(struct rice_t* rice)
 299 {
 300     int base, x, pivot, overflow;
 301
 302     pivot = rice->ksum >> 5;
 303     if (UNLIKELY(pivot == 0))
 304         pivot=1;
 305
 306     overflow = range_get_symbol_3980();
 307
 308     if (UNLIKELY(overflow == (MODEL_ELEMENTS-1))) {
 309         overflow = range_decode_short() << 16;
 310         overflow |= range_decode_short();
 311     }
 312
 313     if (pivot >= 0x10000) {
 314         /* Codepath for 24-bit streams */
 315         int nbits, lo_bits, base_hi, base_lo;
 316
 317         /* Count the number of bits in pivot */
 318         nbits = 17; /* We know there must be at least 17 bits */
 319         while ((pivot >> nbits) > 0) { nbits++; }
 320
 321         /* base_lo is the low (nbits-16) bits of base
 322            base_hi is the high 16 bits of base
 323         */
 324         lo_bits = (nbits - 16);
 325
 326         base_hi = range_decode_culfreq((pivot >> lo_bits) + 1);
 327         range_decode_update(1, base_hi);
 328
 329         base_lo = range_decode_culshift(lo_bits);
 330         range_decode_update(1, base_lo);
 331
 332         base = (base_hi << lo_bits) + base_lo;
 333     } else {
 334         /* Codepath for 16-bit streams */
 335         base = range_decode_culfreq(pivot);
 336         range_decode_update(1, base);
 337     }
 338
 339     x = base + (overflow * pivot);
 340     update_rice(rice, x);
 341
 342     /* Convert to signed */
 343     if (x & 1)
 344         return (x >> 1) + 1;
 345     else
 346         return -(x >> 1);
 347 }
 348
 349
 350 static inline int entropy_decode3970(struct rice_t* rice)
 351 {
 352     int x, tmpk;
 353
 354     int overflow = range_get_symbol_3970();
 355
 356     if (UNLIKELY(overflow == (MODEL_ELEMENTS - 1))) {
 357         tmpk = range_decode_bits(5);
 358         overflow = 0;
 359     } else {
 360         tmpk = (rice->k < 1) ? 0 : rice->k - 1;
 361     }
 362
 363     if (tmpk <= 16) {
 364         x = range_decode_bits(tmpk);
 365     } else {
 366         x = range_decode_short();
 367         x |= (range_decode_bits(tmpk - 16) << 16);
 368     }
 369     x += (overflow << tmpk);
 370
 371     update_rice(rice, x);
 372
 373     /* Convert to signed */
 374     if (x & 1)
 375         return (x >> 1) + 1;
 376     else
 377         return -(x >> 1);
 378 }
 379
 380 void init_entropy_decoder(struct ape_ctx_t* ape_ctx,
 381                           unsigned char* inbuffer, int* firstbyte,
 382                           int* bytesconsumed)
 383 {
 384     bytebuffer = inbuffer;
 385     bytebufferoffset = *firstbyte;
 386
 387     /* Read the CRC */
 388     ape_ctx->CRC = read_byte();
 389     ape_ctx->CRC = (ape_ctx->CRC << 8) | read_byte();
 390     ape_ctx->CRC = (ape_ctx->CRC << 8) | read_byte();
 391     ape_ctx->CRC = (ape_ctx->CRC << 8) | read_byte();
 392
 393     /* Read the frame flags if they exist */
 394     ape_ctx->frameflags = 0;
 395     if ((ape_ctx->fileversion > 3820) && (ape_ctx->CRC & 0x80000000)) {
 396         ape_ctx->CRC &= ~0x80000000;
 397
 398         ape_ctx->frameflags = read_byte();
 399         ape_ctx->frameflags = (ape_ctx->frameflags << 8) | read_byte();
 400         ape_ctx->frameflags = (ape_ctx->frameflags << 8) | read_byte();
 401         ape_ctx->frameflags = (ape_ctx->frameflags << 8) | read_byte();
 402     }
 403     /* Keep a count of the blocks decoded in this frame */
 404     ape_ctx->blocksdecoded = 0;
 405
 406     /* Initialise the rice structs */
 407     riceX.k = 10;
 408     riceX.ksum = (1 << riceX.k) * 16;
 409     riceY.k = 10;
 410     riceY.ksum = (1 << riceY.k) * 16;
 411
 412     /* The first 8 bits of input are ignored. */
 413     skip_byte();
 414
 415     range_start_decoding();
 416
 417     /* Return the new state of the buffer */
 418     *bytesconsumed = (intptr_t)bytebuffer - (intptr_t)inbuffer;
 419     *firstbyte = bytebufferoffset;
 420 }
 421
 422 int ICODE_ATTR_DEMAC entropy_decode(struct ape_ctx_t* ape_ctx,
 423                                     unsigned char* inbuffer, int* firstbyte,
 424                                     int* bytesconsumed,
 425                                     int32_t* decoded0, int32_t* decoded1,
 426                                     int blockstodecode)
 427 {
 428     bytebuffer = inbuffer;
 429     bytebufferoffset = *firstbyte;
 430
 431     ape_ctx->blocksdecoded += blockstodecode;
 432
 433     if (ape_ctx->frameflags & APE_FRAMECODE_STEREO_SILENCE) {
 434         /* We are pure silence, just memset the output buffer. */
 435         memset(decoded0, 0, blockstodecode * sizeof(int32_t));
 436         memset(decoded1, 0, blockstodecode * sizeof(int32_t));
 437     } else {
 438         if (ape_ctx->fileversion > 3970) {
 439             while (LIKELY(blockstodecode--)) {
 440                 *(decoded0++) = entropy_decode3980(&riceY);
 441                 if (decoded1 != NULL)
 442                     *(decoded1++) = entropy_decode3980(&riceX);
 443             }
 444         } else {
 445             while (LIKELY(blockstodecode--)) {
 446                 *(decoded0++) = entropy_decode3970(&riceY);
 447                 if (decoded1 != NULL)
 448                     *(decoded1++) = entropy_decode3970(&riceX);
 449             }
 450         }
 451     }
 452
 453     if (ape_ctx->blocksdecoded == ape_ctx->currentframeblocks)
 454     {
 455         range_done_decoding();
 456     }
 457
 458     /* Return the new state of the buffer */
 459     *bytesconsumed = bytebuffer - inbuffer;
 460     *firstbyte = bytebufferoffset;
 461
 462     return(0);
 463 }