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 subblocks within a block
  27 #define BLOCKSIZE       40      ///< subblock size in 16-bit words
  28 #define BUFFERSIZE      146     ///< the size of the adaptive codebook
  29
  30
  31 typedef struct {
  32     unsigned int     old_energy;        ///< previous frame energy
  33
  34     unsigned int     lpc_tables[2][10];
  35     unsigned int    *lpc_coef;          ///< LPC coefficients
  36     unsigned int    *lpc_coef_old;      ///< previous frame LPC coefficients
  37     unsigned int     lpc_refl_rms;
  38     unsigned int     lpc_refl_rms_old;
  39
  40     /** the current subblock padded by the last 10 values of the previous one*/
  41     int16_t curr_sblock[50];
  42
  43     /** adaptive codebook. Its size is two units bigger to avoid a
  44      *  buffer overflow */
  45     uint16_t adapt_cb[148];
  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)
 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);
 125 }
 126
 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] = (gain_val_tab[n][i] * m[i]) >> (gain_exp_tab[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  * LPC Filter. Each output value is predicted from the 10 previous computed
 143  * ones. It overwrites the input with the output.
 144  *
 145  * @param in the input of the filter. It should be an array of size len + 10.
 146  * The 10 first input values are used to evaluate the first filtered one.
 147  */
 148 static void lpc_filter(const int16_t *lpc_coefs, uint16_t *in, int len)
 149 {
 150     int x, i;
 151     int16_t *ptr = in;
 152
 153     for (i=0; i<len; i++) {
 154         int sum = 0;
 155         int new_val;
 156
 157         for(x=0; x<10; x++)
 158             sum += lpc_coefs[9-x] * ptr[x];
 159
 160         sum >>= 12;
 161
 162         new_val = ptr[10] - sum;
 163
 164         if (new_val < -32768 || new_val > 32767) {
 165             memset(in, 0, 100);
 166             return;
 167         }
 168
 169         ptr[10] = new_val;
 170         ptr++;
 171     }
 172 }
 173
 174 static unsigned int rescale_rms(unsigned int rms, unsigned int energy)
 175 {
 176     return (rms * energy) >> 10;
 177 }
 178
 179 static unsigned int rms(const int *data)
 180 {
 181     int x;
 182     unsigned int res = 0x10000;
 183     int b = 0;
 184
 185     for (x=0; x<10; x++) {
 186         res = (((0x1000000 - (*data) * (*data)) >> 12) * res) >> 12;
 187
 188         if (res == 0)
 189             return 0;
 190
 191         while (res <= 0x3fff) {
 192             b++;
 193             res <<= 2;
 194         }
 195         data++;
 196     }
 197
 198     res = t_sqrt(res);
 199
 200     res >>= (b + 10);
 201     return res;
 202 }
 203
 204 static void do_output_subblock(RA144Context *ractx,
 205                                const uint16_t  *lpc_coefs, int gval,
 206                                GetBitContext *gb)
 207 {
 208     uint16_t buffer_a[40];
 209     uint16_t *block;
 210     int cba_idx = get_bits(gb, 7); // index of the adaptive CB, 0 if none
 211     int gain    = get_bits(gb, 8);
 212     int cb1_idx = get_bits(gb, 7);
 213     int cb2_idx = get_bits(gb, 7);
 214     int m[3];
 215
 216     if (cba_idx) {
 217         cba_idx += BLOCKSIZE/2 - 1;
 218         copy_and_dup(ractx->adapt_cb, buffer_a, cba_idx);
 219         m[0] = (irms(buffer_a) * gval) >> 12;
 220     } else {
 221         m[0] = 0;
 222     }
 223
 224     m[1] = ((cb1_base[cb1_idx] >> 4) * gval) >> 8;
 225     m[2] = ((cb2_base[cb2_idx] >> 4) * gval) >> 8;
 226
 227     memmove(ractx->adapt_cb, ractx->adapt_cb + BLOCKSIZE,
 228             (BUFFERSIZE - BLOCKSIZE) * 2);
 229
 230     block = ractx->adapt_cb + BUFFERSIZE - BLOCKSIZE;
 231
 232     add_wav(gain, cba_idx, m, buffer_a, cb1_vects[cb1_idx], cb2_vects[cb2_idx],
 233             block);
 234
 235     memcpy(ractx->curr_sblock, ractx->curr_sblock + 40,
 236            10*sizeof(*ractx->curr_sblock));
 237     memcpy(ractx->curr_sblock + 10, block,
 238            BLOCKSIZE*sizeof(*ractx->curr_sblock));
 239
 240     lpc_filter(lpc_coefs, ractx->curr_sblock, BLOCKSIZE);
 241 }
 242
 243 static void int_to_int16(int16_t *out, const int *inp)
 244 {
 245     int i;
 246
 247     for (i=0; i<30; i++)
 248         *(out++) = *(inp++);
 249 }
 250
 251 /**
 252  * Evaluate the reflection coefficients from the filter coefficients.
 253  * Does the inverse of the eval_coefs() function.
 254  *
 255  * @return 1 if one of the reflection coefficients is of magnitude greater than
 256  *         4095, 0 if not.
 257  */
 258 static int eval_refl(const int16_t *coefs, int *refl, RA144Context *ractx)
 259 {
 260     int retval = 0;
 261     int b, c, i;
 262     unsigned int u;
 263     int buffer1[10];
 264     int buffer2[10];
 265     int *bp1 = buffer1;
 266     int *bp2 = buffer2;
 267
 268     for (i=0; i < 10; i++)
 269         buffer2[i] = coefs[i];
 270
 271     u = refl[9] = bp2[9];
 272
 273     if (u + 0x1000 > 0x1fff) {
 274         av_log(ractx, AV_LOG_ERROR, "Overflow. Broken sample?\n");
 275         return 1;
 276     }
 277
 278     for (c=8; c >= 0; c--) {
 279         if (u == 0x1000)
 280             u++;
 281
 282         if (u == 0xfffff000)
 283             u--;
 284
 285         b = 0x1000-((u * u) >> 12);
 286
 287         if (b == 0)
 288             b++;
 289
 290         for (u=0; u<=c; u++)
 291             bp1[u] = ((bp2[u] - ((refl[c+1] * bp2[c-u]) >> 12)) * (0x1000000 / b)) >> 12;
 292
 293         refl[c] = u = bp1[c];
 294
 295         if ((u + 0x1000) > 0x1fff)
 296             retval = 1;
 297
 298         FFSWAP(int *, bp1, bp2);
 299     }
 300     return retval;
 301 }
 302
 303 static int interp(RA144Context *ractx, int16_t *out, int block_num,
 304                   int copynew, int energy)
 305 {
 306     int work[10];
 307     int a = block_num + 1;
 308     int b = NBLOCKS - a;
 309     int x;
 310
 311     // Interpolate block coefficients from the this frame forth block and
 312     // last frame forth block
 313     for (x=0; x<30; x++)
 314         out[x] = (a * ractx->lpc_coef[x] + b * ractx->lpc_coef_old[x])>> 2;
 315
 316     if (eval_refl(out, work, ractx)) {
 317         // The interpolated coefficients are unstable, copy either new or old
 318         // coefficients
 319         if (copynew) {
 320             int_to_int16(out, ractx->lpc_coef);
 321             return rescale_rms(ractx->lpc_refl_rms, energy);
 322         } else {
 323             int_to_int16(out, ractx->lpc_coef_old);
 324             return rescale_rms(ractx->lpc_refl_rms_old, energy);
 325         }
 326     } else {
 327         return rescale_rms(rms(work), energy);
 328     }
 329 }
 330
 331 /* Uncompress one block (20 bytes -> 160*2 bytes) */
 332 static int ra144_decode_frame(AVCodecContext * avctx,
 333                               void *vdata, int *data_size,
 334                               const uint8_t * buf, int buf_size)
 335 {
 336     static const uint8_t sizes[10] = {6, 5, 5, 4, 4, 3, 3, 3, 3, 2};
 337     unsigned int refl_rms[4];    // RMS of the reflection coefficients
 338     uint16_t block_coefs[4][30]; // LPC coefficients of each sub-block
 339     unsigned int lpc_refl[10];   // LPC reflection coefficients of the frame
 340     int i, c;
 341     int16_t *data = vdata;
 342     unsigned int energy;
 343
 344     RA144Context *ractx = avctx->priv_data;
 345     GetBitContext gb;
 346
 347     if(buf_size < 20) {
 348         av_log(avctx, AV_LOG_ERROR,
 349                "Frame too small (%d bytes). Truncated file?\n", buf_size);
 350         *data_size = 0;
 351         return buf_size;
 352     }
 353     init_get_bits(&gb, buf, 20 * 8);
 354
 355     for (i=0; i<10; i++)
 356         // "<< 1"? Doesn't this make one value out of two of the table useless?
 357         lpc_refl[i] = lpc_refl_cb[i][get_bits(&gb, sizes[i]) << 1];
 358
 359     eval_coefs(lpc_refl, ractx->lpc_coef);
 360     ractx->lpc_refl_rms = rms(lpc_refl);
 361
 362     energy = energy_tab[get_bits(&gb, 5) << 1]; // Useless table entries?
 363
 364     refl_rms[0] = interp(ractx, block_coefs[0], 0, 0, ractx->old_energy);
 365     refl_rms[1] = interp(ractx, block_coefs[1], 1, energy > ractx->old_energy,
 366                     t_sqrt(energy*ractx->old_energy) >> 12);
 367     refl_rms[2] = interp(ractx, block_coefs[2], 2, 1, energy);
 368     refl_rms[3] = rescale_rms(ractx->lpc_refl_rms, energy);
 369
 370     int_to_int16(block_coefs[3], ractx->lpc_coef);
 371
 372     for (c=0; c<4; c++) {
 373         do_output_subblock(ractx, block_coefs[c], refl_rms[c], &gb);
 374
 375         for (i=0; i<BLOCKSIZE; i++)
 376             *data++ = av_clip_int16(ractx->curr_sblock[i + 10] << 2);
 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 AVCodec ra_144_decoder =
 389 {
 390     "real_144",
 391     CODEC_TYPE_AUDIO,
 392     CODEC_ID_RA_144,
 393     sizeof(RA144Context),
 394     ra144_decode_init,
 395     NULL,
 396     NULL,
 397     ra144_decode_frame,
 398     .long_name = NULL_IF_CONFIG_SMALL("RealAudio 1.0 (14.4K)"),
 399 };