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 typedef struct {
  33     unsigned int     old_energy;        ///< previous frame energy
  34
  35     /* the swapped buffers */
  36     unsigned int     lpc_tables[2][10];
  37     unsigned int    *lpc_coef;          ///< LPC coefficients
  38     unsigned int    *lpc_coef_old;      ///< previous frame LPC coefficients
  39     unsigned int     lpc_refl_rms;
  40     unsigned int     lpc_refl_rms_old;
  41
  42     /** the current subblock padded by the last 10 values of the previous one*/
  43     int16_t curr_sblock[50];
  44
  45     uint16_t adapt_cb[148];             ///< adaptive codebook
  46 } RA144Context;
  47
  48 static int ra144_decode_init(AVCodecContext * avctx)
  49 {
  50     RA144Context *ractx = avctx->priv_data;
  51
  52     ractx->lpc_coef     = ractx->lpc_tables[0];
  53     ractx->lpc_coef_old = ractx->lpc_tables[1];
  54
  55     return 0;
  56 }
  57
  58 /**
  59  * Evaluate sqrt(x << 24). x must fit in 20 bits. This value is evaluated in an
  60  * odd way to make the output identical to the binary decoder.
  61  */
  62 static int t_sqrt(unsigned int x)
  63 {
  64     int s = 2;
  65     while (x > 0xfff) {
  66         s++;
  67         x = x >> 2;
  68     }
  69
  70     return ff_sqrt(x << 20) << s;
  71 }
  72
  73 /**
  74  * Evaluate the LPC filter coefficients from the reflection coefficients.
  75  * Does the inverse of the eval_refl() function.
  76  */
  77 static void eval_coefs(const int *refl, int *coefs)
  78 {
  79     int buffer[10];
  80     int *b1 = buffer;
  81     int *b2 = coefs;
  82     int x, y;
  83
  84     for (x=0; x < 10; x++) {
  85         b1[x] = refl[x] << 4;
  86
  87         for (y=0; y < x; y++)
  88             b1[y] = ((refl[x] * b2[x-y-1]) >> 12) + b2[y];
  89
  90         FFSWAP(int *, b1, b2);
  91     }
  92
  93     for (x=0; x < 10; x++)
  94         coefs[x] >>= 4;
  95 }
  96
  97 /**
  98  * Copy the last offset values of *source to *target. If those values are not
  99  * enough to fill the target buffer, fill it with another copy of those values.
 100  */
 101 static void copy_and_dup(const int16_t *source, int16_t *target, int offset)
 102 {
 103     source += BUFFERSIZE - offset;
 104
 105     if (offset > BLOCKSIZE) {
 106         memcpy(target, source, BLOCKSIZE*sizeof(*target));
 107     } else {
 108         memcpy(target, source, offset*sizeof(*target));
 109         memcpy(target + offset, source, (BLOCKSIZE - offset)*sizeof(*target));
 110     }
 111 }
 112
 113 /* inverse root mean square */
 114 static int irms(const int16_t *data, int factor)
 115 {
 116     unsigned int i, sum = 0;
 117
 118     for (i=0; i < BLOCKSIZE; i++)
 119         sum += data[i] * data[i];
 120
 121     if (sum == 0)
 122         return 0; /* OOPS - division by zero */
 123
 124     return (0x20000000 / (t_sqrt(sum) >> 8)) * factor;
 125 }
 126
 127 /* multiply/add wavetable */
 128 static void add_wav(int n, int skip_first, int *m, const int16_t *s1,
 129                     const int8_t *s2, const int8_t *s3, int16_t *dest)
 130 {
 131     int i;
 132     int v[3];
 133
 134     v[0] = 0;
 135     for (i=!skip_first; i<3; i++)
 136         v[i] = (gain_val_tab[n][i] * m[i]) >> (gain_exp_tab[n][i] + 1);
 137
 138     for (i=0; i < BLOCKSIZE; i++)
 139         dest[i] = ((*(s1++))*v[0] + (*(s2++))*v[1] + (*(s3++))*v[2]) >> 12;
 140 }
 141
 142 /**
 143  * LPC Filter. Each output value is predicted from the 10 previous computed
 144  * ones. It overwrites the input with the output.
 145  *
 146  * @param in the input of the filter. It should be an array of size len + 10.
 147  * The 10 first input values are used to evaluate the first filtered one.
 148  */
 149 static void lpc_filter(const int16_t *lpc_coefs, uint16_t *in, int len)
 150 {
 151     int x, i;
 152     int16_t *ptr = in;
 153
 154     for (i=0; i<len; i++) {
 155         int sum = 0;
 156         int new_val;
 157
 158         for(x=0; x<10; x++)
 159             sum += lpc_coefs[9-x] * ptr[x];
 160
 161         sum >>= 12;
 162
 163         new_val = ptr[10] - sum;
 164
 165         if (new_val < -32768 || new_val > 32767) {
 166             memset(in, 0, 100);
 167             return;
 168         }
 169
 170         ptr[10] = new_val;
 171         ptr++;
 172     }
 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                                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         copy_and_dup(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     memcpy(ractx->curr_sblock, ractx->curr_sblock + 40,
 239            10*sizeof(*ractx->curr_sblock));
 240     memcpy(ractx->curr_sblock + 10, block,
 241            BLOCKSIZE*sizeof(*ractx->curr_sblock));
 242
 243     lpc_filter(lpc_coefs, ractx->curr_sblock, BLOCKSIZE);
 244 }
 245
 246 static void int_to_int16(int16_t *out, const int *inp)
 247 {
 248     int i;
 249
 250     for (i=0; i<30; i++)
 251         *(out++) = *(inp++);
 252 }
 253
 254 /**
 255  * Evaluate the reflection coefficients from the filter coefficients.
 256  * Does the inverse of the eval_coefs() function.
 257  *
 258  * @return 1 if one of the reflection coefficients is of magnitude greater than
 259  *         4095, 0 if not.
 260  */
 261 static int eval_refl(const int16_t *coefs, int *refl, RA144Context *ractx)
 262 {
 263     int retval = 0;
 264     int b, c, i;
 265     unsigned int u;
 266     int buffer1[10];
 267     int buffer2[10];
 268     int *bp1 = buffer1;
 269     int *bp2 = buffer2;
 270
 271     for (i=0; i < 10; i++)
 272         buffer2[i] = coefs[i];
 273
 274     u = refl[9] = bp2[9];
 275
 276     if (u + 0x1000 > 0x1fff) {
 277         av_log(ractx, AV_LOG_ERROR, "Overflow. Broken sample?\n");
 278         return 0;
 279     }
 280
 281     for (c=8; c >= 0; c--) {
 282         if (u == 0x1000)
 283             u++;
 284
 285         if (u == 0xfffff000)
 286             u--;
 287
 288         b = 0x1000-((u * u) >> 12);
 289
 290         if (b == 0)
 291             b++;
 292
 293         for (u=0; u<=c; u++)
 294             bp1[u] = ((bp2[u] - ((refl[c+1] * bp2[c-u]) >> 12)) * (0x1000000 / b)) >> 12;
 295
 296         refl[c] = u = bp1[c];
 297
 298         if ((u + 0x1000) > 0x1fff)
 299             retval = 1;
 300
 301         FFSWAP(int *, bp1, bp2);
 302     }
 303     return retval;
 304 }
 305
 306 static int interp(RA144Context *ractx, int16_t *out, int block_num,
 307                   int copynew, int energy)
 308 {
 309     int work[10];
 310     int a = block_num + 1;
 311     int b = NBLOCKS - a;
 312     int x;
 313
 314     // Interpolate block coefficients from the this frame forth block and
 315     // last frame forth block
 316     for (x=0; x<30; x++)
 317         out[x] = (a * ractx->lpc_coef[x] + b * ractx->lpc_coef_old[x])>> 2;
 318
 319     if (eval_refl(out, work, ractx)) {
 320         // The interpolated coefficients are unstable, copy either new or old
 321         // coefficients
 322         if (copynew) {
 323             int_to_int16(out, ractx->lpc_coef);
 324             return rescale_rms(ractx->lpc_refl_rms, energy);
 325         } else {
 326             int_to_int16(out, ractx->lpc_coef_old);
 327             return rescale_rms(ractx->lpc_refl_rms_old, energy);
 328         }
 329     } else {
 330         return rescale_rms(rms(work), energy);
 331     }
 332 }
 333
 334 /* Uncompress one block (20 bytes -> 160*2 bytes) */
 335 static int ra144_decode_frame(AVCodecContext * avctx,
 336                               void *vdata, int *data_size,
 337                               const uint8_t * buf, int buf_size)
 338 {
 339     static const uint8_t sizes[10] = {6, 5, 5, 4, 4, 3, 3, 3, 3, 2};
 340     unsigned int refl_rms[4];    // RMS of the reflection coefficients
 341     uint16_t block_coefs[4][30]; // LPC coefficients of each sub-block
 342     unsigned int lpc_refl[10];   // LPC reflection coefficients of the frame
 343     int i, c;
 344     int16_t *data = vdata;
 345     unsigned int energy;
 346
 347     RA144Context *ractx = avctx->priv_data;
 348     GetBitContext gb;
 349
 350     if(buf_size < 20) {
 351         av_log(avctx, AV_LOG_ERROR,
 352                "Frame too small (%d bytes). Truncated file?\n", buf_size);
 353         *data_size = 0;
 354         return buf_size;
 355     }
 356     init_get_bits(&gb, buf, 20 * 8);
 357
 358     for (i=0; i<10; i++)
 359         // "<< 1"? Doesn't this make one value out of two of the table useless?
 360         lpc_refl[i] = lpc_refl_cb[i][get_bits(&gb, sizes[i]) << 1];
 361
 362     eval_coefs(lpc_refl, ractx->lpc_coef);
 363     ractx->lpc_refl_rms = rms(lpc_refl);
 364
 365     energy = energy_tab[get_bits(&gb, 5) << 1]; // Useless table entries?
 366
 367     refl_rms[0] = interp(ractx, block_coefs[0], 0, 0, ractx->old_energy);
 368     refl_rms[1] = interp(ractx, block_coefs[1], 1, energy > ractx->old_energy,
 369                     t_sqrt(energy*ractx->old_energy) >> 12);
 370     refl_rms[2] = interp(ractx, block_coefs[2], 2, 1, energy);
 371     refl_rms[3] = rescale_rms(ractx->lpc_refl_rms, energy);
 372
 373     int_to_int16(block_coefs[3], ractx->lpc_coef);
 374
 375     /* do output */
 376     for (c=0; c<4; c++) {
 377         do_output_subblock(ractx, block_coefs[c], refl_rms[c], &gb);
 378
 379         for (i=0; i<BLOCKSIZE; i++)
 380             *data++ = av_clip_int16(ractx->curr_sblock[i + 10] << 2);
 381     }
 382
 383     ractx->old_energy = energy;
 384     ractx->lpc_refl_rms_old = ractx->lpc_refl_rms;
 385
 386     FFSWAP(unsigned int *, ractx->lpc_coef_old, ractx->lpc_coef);
 387
 388     *data_size = 2*160;
 389     return 20;
 390 }
 391
 392 AVCodec ra_144_decoder =
 393 {
 394     "real_144",
 395     CODEC_TYPE_AUDIO,
 396     CODEC_ID_RA_144,
 397     sizeof(RA144Context),
 398     ra144_decode_init,
 399     NULL,
 400     NULL,
 401     ra144_decode_frame,
 402     .long_name = NULL_IF_CONFIG_SMALL("RealAudio 1.0 (14.4K)"),
 403 };