libavcodec/ra144.c

   1 /*
   2  * Real Audio 1.0 (14.4K)
   3  * Copyright (c) 2003 the ffmpeg project
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #include "avcodec.h"
  23 #include "bitstream.h"
  24 #include "ra144.h"
  25
  26 #define NBLOCKS         4       /* number of segments within a block */
  27 #define BLOCKSIZE       40      /* (quarter) block size in 16-bit words (80 bytes) */
  28 #define HALFBLOCK       20      /* BLOCKSIZE/2 */
  29 #define BUFFERSIZE      146     /* for do_output */
  30
  31
  32 /* internal globals */
  33 typedef struct {
  34     unsigned int     old_energy;        ///< previous frame energy
  35
  36     /* the swapped buffers */
  37     unsigned int     lpc_tables[4][10];
  38     unsigned int    *lpc_refl;          ///< LPC reflection coefficients
  39     unsigned int    *lpc_coef;          ///< LPC coefficients
  40     unsigned int    *lpc_refl_old;      ///< previous frame LPC reflection coefs
  41     unsigned int    *lpc_coef_old;      ///< previous frame LPC coefficients
  42
  43     unsigned int buffer[5];
  44     uint16_t adapt_cb[148];             ///< adaptive codebook
  45 } RA144Context;
  46
  47 static int ra144_decode_init(AVCodecContext * avctx)
  48 {
  49     RA144Context *ractx = avctx->priv_data;
  50
  51     ractx->lpc_refl     = ractx->lpc_tables[0];
  52     ractx->lpc_coef     = ractx->lpc_tables[1];
  53     ractx->lpc_refl_old = ractx->lpc_tables[2];
  54     ractx->lpc_coef_old = ractx->lpc_tables[3];
  55
  56     return 0;
  57 }
  58
  59 /**
  60  * Evaluate sqrt(x << 24). x must fit in 20 bits. This value is evaluated in an
  61  * odd way to make the output identical to the binary decoder.
  62  */
  63 static int t_sqrt(unsigned int x)
  64 {
  65     int s = 0;
  66     while (x > 0xfff) {
  67         s++;
  68         x = x >> 2;
  69     }
  70
  71     return (ff_sqrt(x << 20) << s) << 2;
  72 }
  73
  74 /**
  75  * Evaluate the LPC filter coefficients from the reflection coefficients.
  76  * Does the inverse of the eval_refl() function.
  77  */
  78 static void eval_coefs(const int *refl, int *coefs)
  79 {
  80     int buffer[10];
  81     int *b1 = buffer;
  82     int *b2 = coefs;
  83     int x, y;
  84
  85     for (x=0; x < 10; x++) {
  86         b1[x] = refl[x] << 4;
  87
  88         for (y=0; y < x; y++)
  89             b1[y] = ((refl[x] * b2[x-y-1]) >> 12) + b2[y];
  90
  91         FFSWAP(int *, b1, b2);
  92     }
  93
  94     for (x=0; x < 10; x++)
  95         coefs[x] >>= 4;
  96 }
  97
  98 /* rotate block */
  99 static void rotate_block(const int16_t *source, int16_t *target, int offset)
 100 {
 101     int i=0, k=0;
 102     source += BUFFERSIZE - offset;
 103
 104     while (i<BLOCKSIZE) {
 105         target[i++] = source[k++];
 106
 107         if (k == offset)
 108             k = 0;
 109     }
 110 }
 111
 112 /* inverse root mean square */
 113 static int irms(const int16_t *data, int factor)
 114 {
 115     unsigned int i, sum = 0;
 116
 117     for (i=0; i < BLOCKSIZE; i++)
 118         sum += data[i] * data[i];
 119
 120     if (sum == 0)
 121         return 0; /* OOPS - division by zero */
 122
 123     return (0x20000000 / (t_sqrt(sum) >> 8)) * factor;
 124 }
 125
 126 /* multiply/add wavetable */
 127 static void add_wav(int n, int skip_first, int *m, const int16_t *s1,
 128                     const int8_t *s2, const int8_t *s3, int16_t *dest)
 129 {
 130     int i;
 131     int v[3];
 132
 133     v[0] = 0;
 134     for (i=!skip_first; i<3; i++)
 135         v[i] = (wavtable1[n][i] * m[i]) >> (wavtable2[n][i] + 1);
 136
 137     for (i=0; i < BLOCKSIZE; i++)
 138         dest[i] = ((*(s1++))*v[0] + (*(s2++))*v[1] + (*(s3++))*v[2]) >> 12;
 139 }
 140
 141
 142 static void final(const int16_t *i1, const int16_t *i2,
 143                   void *out, int *statbuf, int len)
 144 {
 145     int x, i;
 146     uint16_t work[50];
 147     int16_t *ptr = work;
 148
 149     memcpy(work, statbuf,20);
 150     memcpy(work + 10, i2, len * 2);
 151
 152     for (i=0; i<len; i++) {
 153         int sum = 0;
 154         int new_val;
 155
 156         for(x=0; x<10; x++)
 157             sum += i1[9-x] * ptr[x];
 158
 159         sum >>= 12;
 160
 161         new_val = ptr[10] - sum;
 162
 163         if (new_val < -32768 || new_val > 32767) {
 164             memset(out, 0, len * 2);
 165             memset(statbuf, 0, 20);
 166             return;
 167         }
 168
 169         ptr[10] = new_val;
 170         ptr++;
 171     }
 172
 173     memcpy(out, work+10, len * 2);
 174     memcpy(statbuf, work + 40, 20);
 175 }
 176
 177 static unsigned int rms(const int *data, int f)
 178 {
 179     int x;
 180     unsigned int res = 0x10000;
 181     int b = 0;
 182
 183     for (x=0; x<10; x++) {
 184         res = (((0x1000000 - (*data) * (*data)) >> 12) * res) >> 12;
 185
 186         if (res == 0)
 187             return 0;
 188
 189         if (res > 0x10000)
 190             return 0; /* We're screwed, might as well go out with a bang. :P */
 191
 192         while (res <= 0x3fff) {
 193             b++;
 194             res <<= 2;
 195         }
 196         data++;
 197     }
 198
 199     if (res > 0)
 200         res = t_sqrt(res);
 201
 202     res >>= (b + 10);
 203     res = (res * f) >> 10;
 204     return res;
 205 }
 206
 207 /* do quarter-block output */
 208 static void do_output_subblock(RA144Context *ractx,
 209                                const uint16_t  *lpc_coefs, unsigned int gval,
 210                                int16_t *output_buffer, GetBitContext *gb)
 211 {
 212     uint16_t buffer_a[40];
 213     uint16_t *block;
 214     int cba_idx = get_bits(gb, 7); // index of the adaptive CB, 0 if none
 215     int gain    = get_bits(gb, 8);
 216     int cb1_idx = get_bits(gb, 7);
 217     int cb2_idx = get_bits(gb, 7);
 218     int m[3];
 219
 220     if (cba_idx) {
 221         cba_idx += HALFBLOCK - 1;
 222         rotate_block(ractx->adapt_cb, buffer_a, cba_idx);
 223         m[0] = irms(buffer_a, gval) >> 12;
 224     } else {
 225         m[0] = 0;
 226     }
 227
 228     m[1] = ((ftable1[cb1_idx] >> 4) * gval) >> 8;
 229     m[2] = ((ftable2[cb2_idx] >> 4) * gval) >> 8;
 230
 231     memmove(ractx->adapt_cb, ractx->adapt_cb + BLOCKSIZE,
 232             (BUFFERSIZE - BLOCKSIZE) * 2);
 233
 234     block = ractx->adapt_cb + BUFFERSIZE - BLOCKSIZE;
 235
 236     add_wav(gain, cba_idx, m, buffer_a, etable1[cb1_idx], etable2[cb2_idx],
 237             block);
 238
 239     final(lpc_coefs, block, output_buffer, ractx->buffer, BLOCKSIZE);
 240 }
 241
 242 static void int_to_int16(int16_t *decsp, const int *inp)
 243 {
 244     int i;
 245
 246     for (i=0; i<30; i++)
 247         *(decsp++) = *(inp++);
 248 }
 249
 250 /**
 251  * Evaluate the reflection coefficients from the filter coefficients.
 252  * Does the inverse of the eval_coefs() function.
 253  *
 254  * @return 1 if one of the reflection coefficients is of magnitude greater than
 255  *         4095, 0 if not.
 256  */
 257 static int eval_refl(const int16_t *coefs, int *refl)
 258 {
 259     int retval = 0;
 260     int b, c, i;
 261     unsigned int u;
 262     int buffer1[10];
 263     int buffer2[10];
 264     int *bp1 = buffer1;
 265     int *bp2 = buffer2;
 266
 267     for (i=0; i < 10; i++)
 268         buffer2[i] = coefs[i];
 269
 270     u = refl[9] = bp2[9];
 271
 272     if (u + 0x1000 > 0x1fff)
 273         return 0; /* We're screwed, might as well go out with a bang. :P */
 274
 275     for (c=8; c >= 0; c--) {
 276         if (u == 0x1000)
 277             u++;
 278
 279         if (u == 0xfffff000)
 280             u--;
 281
 282         b = 0x1000-((u * u) >> 12);
 283
 284         if (b == 0)
 285             b++;
 286
 287         for (u=0; u<=c; u++)
 288             bp1[u] = ((bp2[u] - ((refl[c+1] * bp2[c-u]) >> 12)) * (0x1000000 / b)) >> 12;
 289
 290         refl[c] = u = bp1[c];
 291
 292         if ((u + 0x1000) > 0x1fff)
 293             retval = 1;
 294
 295         FFSWAP(int *, bp1, bp2);
 296     }
 297     return retval;
 298 }
 299
 300 static int interp(RA144Context *ractx, int16_t *decsp, int block_num,
 301                 int copynew, int energy)
 302 {
 303     int work[10];
 304     int a = block_num + 1;
 305     int b = NBLOCKS - a;
 306     int x;
 307
 308     // Interpolate block coefficients from the this frame forth block and
 309     // last frame forth block
 310     for (x=0; x<30; x++)
 311         decsp[x] = (a * ractx->lpc_coef[x] + b * ractx->lpc_coef_old[x])>> 2;
 312
 313     if (eval_refl(decsp, work)) {
 314         // The interpolated coefficients are unstable, copy either new or old
 315         // coefficients
 316         if (copynew) {
 317             int_to_int16(decsp, ractx->lpc_coef);
 318             return rms(ractx->lpc_refl, energy);
 319         } else {
 320             int_to_int16(decsp, ractx->lpc_coef_old);
 321             return rms(ractx->lpc_refl_old, energy);
 322         }
 323     } else {
 324         return rms(work, energy);
 325     }
 326 }
 327
 328 /* Uncompress one block (20 bytes -> 160*2 bytes) */
 329 static int ra144_decode_frame(AVCodecContext * avctx,
 330                               void *vdata, int *data_size,
 331                               const uint8_t * buf, int buf_size)
 332 {
 333     static const uint8_t sizes[10] = {6, 5, 5, 4, 4, 3, 3, 3, 3, 2};
 334     unsigned int refl_rms[4];  // RMS of the reflection coefficients
 335     uint16_t block_coefs[4][30]; // LPC coefficients of each sub-block
 336     int i, c;
 337     int16_t *data = vdata;
 338     unsigned int energy;
 339
 340     RA144Context *ractx = avctx->priv_data;
 341     GetBitContext gb;
 342
 343     if(buf_size < 20) {
 344         av_log(avctx, AV_LOG_ERROR,
 345                "Frame too small (%d bytes). Truncated file?\n", buf_size);
 346         return buf_size;
 347     }
 348     init_get_bits(&gb, buf, 20 * 8);
 349
 350     for (i=0; i<10; i++)
 351         // "<< 1"? Doesn't this make one value out of two of the table useless?
 352         ractx->lpc_refl[i] = decodetable[i][get_bits(&gb, sizes[i]) << 1];
 353
 354     eval_coefs(ractx->lpc_refl, ractx->lpc_coef);
 355
 356     energy = decodeval[get_bits(&gb, 5) << 1]; // Useless table entries?
 357
 358     refl_rms[0] = interp(ractx, block_coefs[0], 0, 0, ractx->old_energy);
 359     refl_rms[1] = interp(ractx, block_coefs[1], 1, energy > ractx->old_energy,
 360                     t_sqrt(energy*ractx->old_energy) >> 12);
 361     refl_rms[2] = interp(ractx, block_coefs[2], 2, 1, energy);
 362     refl_rms[3] = rms(ractx->lpc_refl, energy);
 363
 364     int_to_int16(block_coefs[3], ractx->lpc_coef);
 365
 366     /* do output */
 367     for (c=0; c<4; c++) {
 368         do_output_subblock(ractx, block_coefs[c], refl_rms[c], data, &gb);
 369
 370         for (i=0; i<BLOCKSIZE; i++) {
 371             *data = av_clip_int16(*data << 2);
 372             data++;
 373         }
 374     }
 375
 376     ractx->old_energy = energy;
 377
 378     FFSWAP(unsigned int *, ractx->lpc_refl_old, ractx->lpc_refl);
 379     FFSWAP(unsigned int *, ractx->lpc_coef_old, ractx->lpc_coef);
 380
 381     *data_size = 2*160;
 382     return 20;
 383 }
 384
 385
 386 AVCodec ra_144_decoder =
 387 {
 388     "real_144",
 389     CODEC_TYPE_AUDIO,
 390     CODEC_ID_RA_144,
 391     sizeof(RA144Context),
 392     ra144_decode_init,
 393     NULL,
 394     NULL,
 395     ra144_decode_frame,
 396     .long_name = "RealAudio 1.0 (14.4K)",
 397 };