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[2][10];
  38     unsigned int    *lpc_coef;          ///< LPC coefficients
  39     unsigned int    *lpc_coef_old;      ///< previous frame LPC coefficients
  40     unsigned int     lpc_refl_rms;
  41     unsigned int     lpc_refl_rms_old;
  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_coef     = ractx->lpc_tables[0];
  52     ractx->lpc_coef_old = ractx->lpc_tables[1];
  53
  54     return 0;
  55 }
  56
  57 /**
  58  * Evaluate sqrt(x << 24). x must fit in 20 bits. This value is evaluated in an
  59  * odd way to make the output identical to the binary decoder.
  60  */
  61 static int t_sqrt(unsigned int x)
  62 {
  63     int s = 0;
  64     while (x > 0xfff) {
  65         s++;
  66         x = x >> 2;
  67     }
  68
  69     return (ff_sqrt(x << 20) << s) << 2;
  70 }
  71
  72 /**
  73  * Evaluate the LPC filter coefficients from the reflection coefficients.
  74  * Does the inverse of the eval_refl() function.
  75  */
  76 static void eval_coefs(const int *refl, int *coefs)
  77 {
  78     int buffer[10];
  79     int *b1 = buffer;
  80     int *b2 = coefs;
  81     int x, y;
  82
  83     for (x=0; x < 10; x++) {
  84         b1[x] = refl[x] << 4;
  85
  86         for (y=0; y < x; y++)
  87             b1[y] = ((refl[x] * b2[x-y-1]) >> 12) + b2[y];
  88
  89         FFSWAP(int *, b1, b2);
  90     }
  91
  92     for (x=0; x < 10; x++)
  93         coefs[x] >>= 4;
  94 }
  95
  96 /* rotate block */
  97 static void rotate_block(const int16_t *source, int16_t *target, int offset)
  98 {
  99     int i=0, k=0;
 100     source += BUFFERSIZE - offset;
 101
 102     while (i<BLOCKSIZE) {
 103         target[i++] = source[k++];
 104
 105         if (k == offset)
 106             k = 0;
 107     }
 108 }
 109
 110 /* inverse root mean square */
 111 static int irms(const int16_t *data, int factor)
 112 {
 113     unsigned int i, sum = 0;
 114
 115     for (i=0; i < BLOCKSIZE; i++)
 116         sum += data[i] * data[i];
 117
 118     if (sum == 0)
 119         return 0; /* OOPS - division by zero */
 120
 121     return (0x20000000 / (t_sqrt(sum) >> 8)) * factor;
 122 }
 123
 124 /* multiply/add wavetable */
 125 static void add_wav(int n, int skip_first, int *m, const int16_t *s1,
 126                     const int8_t *s2, const int8_t *s3, int16_t *dest)
 127 {
 128     int i;
 129     int v[3];
 130
 131     v[0] = 0;
 132     for (i=!skip_first; i<3; i++)
 133         v[i] = (gain_val_tab[n][i] * m[i]) >> (gain_exp_tab[n][i] + 1);
 134
 135     for (i=0; i < BLOCKSIZE; i++)
 136         dest[i] = ((*(s1++))*v[0] + (*(s2++))*v[1] + (*(s3++))*v[2]) >> 12;
 137 }
 138
 139
 140 static void lpc_filter(const int16_t *lpc_coefs, const int16_t *adapt_coef,
 141                   void *out, int *statbuf, int len)
 142 {
 143     int x, i;
 144     uint16_t work[50];
 145     int16_t *ptr = work;
 146
 147     memcpy(work, statbuf,20);
 148     memcpy(work + 10, adapt_coef, len * 2);
 149
 150     for (i=0; i<len; i++) {
 151         int sum = 0;
 152         int new_val;
 153
 154         for(x=0; x<10; x++)
 155             sum += lpc_coefs[9-x] * ptr[x];
 156
 157         sum >>= 12;
 158
 159         new_val = ptr[10] - sum;
 160
 161         if (new_val < -32768 || new_val > 32767) {
 162             memset(out, 0, len * 2);
 163             memset(statbuf, 0, 20);
 164             return;
 165         }
 166
 167         ptr[10] = new_val;
 168         ptr++;
 169     }
 170
 171     memcpy(out, work+10, len * 2);
 172     memcpy(statbuf, work + 40, 20);
 173 }
 174
 175 static unsigned int rescale_rms(int rms, int energy)
 176 {
 177     return (rms * energy) >> 10;
 178 }
 179
 180 static unsigned int rms(const int *data)
 181 {
 182     int x;
 183     unsigned int res = 0x10000;
 184     int b = 0;
 185
 186     for (x=0; x<10; x++) {
 187         res = (((0x1000000 - (*data) * (*data)) >> 12) * res) >> 12;
 188
 189         if (res == 0)
 190             return 0;
 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     return res;
 204 }
 205
 206 /* do quarter-block output */
 207 static void do_output_subblock(RA144Context *ractx,
 208                                const uint16_t  *lpc_coefs, unsigned int gval,
 209                                int16_t *output_buffer, GetBitContext *gb)
 210 {
 211     uint16_t buffer_a[40];
 212     uint16_t *block;
 213     int cba_idx = get_bits(gb, 7); // index of the adaptive CB, 0 if none
 214     int gain    = get_bits(gb, 8);
 215     int cb1_idx = get_bits(gb, 7);
 216     int cb2_idx = get_bits(gb, 7);
 217     int m[3];
 218
 219     if (cba_idx) {
 220         cba_idx += HALFBLOCK - 1;
 221         rotate_block(ractx->adapt_cb, buffer_a, cba_idx);
 222         m[0] = irms(buffer_a, gval) >> 12;
 223     } else {
 224         m[0] = 0;
 225     }
 226
 227     m[1] = ((cb1_base[cb1_idx] >> 4) * gval) >> 8;
 228     m[2] = ((cb2_base[cb2_idx] >> 4) * gval) >> 8;
 229
 230     memmove(ractx->adapt_cb, ractx->adapt_cb + BLOCKSIZE,
 231             (BUFFERSIZE - BLOCKSIZE) * 2);
 232
 233     block = ractx->adapt_cb + BUFFERSIZE - BLOCKSIZE;
 234
 235     add_wav(gain, cba_idx, m, buffer_a, cb1_vects[cb1_idx], cb2_vects[cb2_idx],
 236             block);
 237
 238     lpc_filter(lpc_coefs, block, output_buffer, ractx->buffer, BLOCKSIZE);
 239 }
 240
 241 static void int_to_int16(int16_t *out, const int *inp)
 242 {
 243     int i;
 244
 245     for (i=0; i<30; i++)
 246         *(out++) = *(inp++);
 247 }
 248
 249 /**
 250  * Evaluate the reflection coefficients from the filter coefficients.
 251  * Does the inverse of the eval_coefs() function.
 252  *
 253  * @return 1 if one of the reflection coefficients is of magnitude greater than
 254  *         4095, 0 if not.
 255  */
 256 static int eval_refl(const int16_t *coefs, int *refl, RA144Context *ractx)
 257 {
 258     int retval = 0;
 259     int b, c, i;
 260     unsigned int u;
 261     int buffer1[10];
 262     int buffer2[10];
 263     int *bp1 = buffer1;
 264     int *bp2 = buffer2;
 265
 266     for (i=0; i < 10; i++)
 267         buffer2[i] = coefs[i];
 268
 269     u = refl[9] = bp2[9];
 270
 271     if (u + 0x1000 > 0x1fff) {
 272         av_log(ractx, AV_LOG_ERROR, "Overflow. Broken sample?\n");
 273         return 0;
 274     }
 275
 276     for (c=8; c >= 0; c--) {
 277         if (u == 0x1000)
 278             u++;
 279
 280         if (u == 0xfffff000)
 281             u--;
 282
 283         b = 0x1000-((u * u) >> 12);
 284
 285         if (b == 0)
 286             b++;
 287
 288         for (u=0; u<=c; u++)
 289             bp1[u] = ((bp2[u] - ((refl[c+1] * bp2[c-u]) >> 12)) * (0x1000000 / b)) >> 12;
 290
 291         refl[c] = u = bp1[c];
 292
 293         if ((u + 0x1000) > 0x1fff)
 294             retval = 1;
 295
 296         FFSWAP(int *, bp1, bp2);
 297     }
 298     return retval;
 299 }
 300
 301 static int interp(RA144Context *ractx, int16_t *out, int block_num,
 302                   int copynew, int energy)
 303 {
 304     int work[10];
 305     int a = block_num + 1;
 306     int b = NBLOCKS - a;
 307     int x;
 308
 309     // Interpolate block coefficients from the this frame forth block and
 310     // last frame forth block
 311     for (x=0; x<30; x++)
 312         out[x] = (a * ractx->lpc_coef[x] + b * ractx->lpc_coef_old[x])>> 2;
 313
 314     if (eval_refl(out, work, ractx)) {
 315         // The interpolated coefficients are unstable, copy either new or old
 316         // coefficients
 317         if (copynew) {
 318             int_to_int16(out, ractx->lpc_coef);
 319             return rescale_rms(ractx->lpc_refl_rms, energy);
 320         } else {
 321             int_to_int16(out, ractx->lpc_coef_old);
 322             return rescale_rms(ractx->lpc_refl_rms_old, energy);
 323         }
 324     } else {
 325         return rescale_rms(rms(work), energy);
 326     }
 327 }
 328
 329 /* Uncompress one block (20 bytes -> 160*2 bytes) */
 330 static int ra144_decode_frame(AVCodecContext * avctx,
 331                               void *vdata, int *data_size,
 332                               const uint8_t * buf, int buf_size)
 333 {
 334     static const uint8_t sizes[10] = {6, 5, 5, 4, 4, 3, 3, 3, 3, 2};
 335     unsigned int refl_rms[4];  // RMS of the reflection coefficients
 336     uint16_t block_coefs[4][30]; // LPC coefficients of each sub-block
 337     unsigned int lpc_refl[10];   // LPC reflection coefficients of the frame
 338     int i, c;
 339     int16_t *data = vdata;
 340     unsigned int energy;
 341
 342     RA144Context *ractx = avctx->priv_data;
 343     GetBitContext gb;
 344
 345     if(buf_size < 20) {
 346         av_log(avctx, AV_LOG_ERROR,
 347                "Frame too small (%d bytes). Truncated file?\n", buf_size);
 348         return buf_size;
 349     }
 350     init_get_bits(&gb, buf, 20 * 8);
 351
 352     for (i=0; i<10; i++)
 353         // "<< 1"? Doesn't this make one value out of two of the table useless?
 354         lpc_refl[i] = lpc_refl_cb[i][get_bits(&gb, sizes[i]) << 1];
 355
 356     eval_coefs(lpc_refl, ractx->lpc_coef);
 357     ractx->lpc_refl_rms = rms(lpc_refl);
 358
 359     energy = energy_tab[get_bits(&gb, 5) << 1]; // Useless table entries?
 360
 361     refl_rms[0] = interp(ractx, block_coefs[0], 0, 0, ractx->old_energy);
 362     refl_rms[1] = interp(ractx, block_coefs[1], 1, energy > ractx->old_energy,
 363                     t_sqrt(energy*ractx->old_energy) >> 12);
 364     refl_rms[2] = interp(ractx, block_coefs[2], 2, 1, energy);
 365     refl_rms[3] = rescale_rms(ractx->lpc_refl_rms, energy);
 366
 367     int_to_int16(block_coefs[3], ractx->lpc_coef);
 368
 369     /* do output */
 370     for (c=0; c<4; c++) {
 371         do_output_subblock(ractx, block_coefs[c], refl_rms[c], data, &gb);
 372
 373         for (i=0; i<BLOCKSIZE; i++) {
 374             *data = av_clip_int16(*data << 2);
 375             data++;
 376         }
 377     }
 378
 379     ractx->old_energy = energy;
 380     ractx->lpc_refl_rms_old = ractx->lpc_refl_rms;
 381
 382     FFSWAP(unsigned int *, ractx->lpc_coef_old, ractx->lpc_coef);
 383
 384     *data_size = 2*160;
 385     return 20;
 386 }
 387
 388
 389 AVCodec ra_144_decoder =
 390 {
 391     "real_144",
 392     CODEC_TYPE_AUDIO,
 393     CODEC_ID_RA_144,
 394     sizeof(RA144Context),
 395     ra144_decode_init,
 396     NULL,
 397     NULL,
 398     ra144_decode_frame,
 399     .long_name = NULL_IF_CONFIG_SMALL("RealAudio 1.0 (14.4K)"),
 400 };