libavcodec/ra144.c

   1 /*
   2  * Real Audio 1.0 (14.4K)
   3  *
   4  * Copyright (c) 2008 Vitor Sessak
   5  * Copyright (c) 2003 Nick Kurshev
   6  *     Based on public domain decoder at http://www.honeypot.net/audio
   7  *
   8  * This file is part of FFmpeg.
   9  *
  10  * FFmpeg is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU Lesser General Public
  12  * License as published by the Free Software Foundation; either
  13  * version 2.1 of the License, or (at your option) any later version.
  14  *
  15  * FFmpeg is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  18  * Lesser General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU Lesser General Public
  21  * License along with FFmpeg; if not, write to the Free Software
  22  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  23  */
  24
  25 #include "avcodec.h"
  26 #include "bitstream.h"
  27 #include "ra144.h"
  28 #include "acelp_filters.h"
  29
  30 #define NBLOCKS         4       ///< number of subblocks within a block
  31 #define BLOCKSIZE       40      ///< subblock size in 16-bit words
  32 #define BUFFERSIZE      146     ///< the size of the adaptive codebook
  33
  34
  35 typedef struct {
  36     unsigned int     old_energy;        ///< previous frame energy
  37
  38     unsigned int     lpc_tables[2][10];
  39
  40     /** LPC coefficients: lpc_coef[0] is the coefficients of the current frame
  41      *  and lpc_coef[1] of the previous one */
  42     unsigned int    *lpc_coef[2];
  43
  44     unsigned int     lpc_refl_rms[2];
  45
  46     /** the current subblock padded by the last 10 values of the previous one*/
  47     int16_t curr_sblock[50];
  48
  49     /** adaptive codebook. Its size is two units bigger to avoid a
  50      *  buffer overflow */
  51     uint16_t adapt_cb[148];
  52 } RA144Context;
  53
  54 static int ra144_decode_init(AVCodecContext * avctx)
  55 {
  56     RA144Context *ractx = avctx->priv_data;
  57
  58     ractx->lpc_coef[0] = ractx->lpc_tables[0];
  59     ractx->lpc_coef[1] = ractx->lpc_tables[1];
  60
  61     return 0;
  62 }
  63
  64 /**
  65  * Evaluate sqrt(x << 24). x must fit in 20 bits. This value is evaluated in an
  66  * odd way to make the output identical to the binary decoder.
  67  */
  68 static int t_sqrt(unsigned int x)
  69 {
  70     int s = 2;
  71     while (x > 0xfff) {
  72         s++;
  73         x = x >> 2;
  74     }
  75
  76     return ff_sqrt(x << 20) << s;
  77 }
  78
  79 /**
  80  * Evaluate the LPC filter coefficients from the reflection coefficients.
  81  * Does the inverse of the eval_refl() function.
  82  */
  83 static void eval_coefs(int *coefs, const int *refl)
  84 {
  85     int buffer[10];
  86     int *b1 = buffer;
  87     int *b2 = coefs;
  88     int x, y;
  89
  90     for (x=0; x < 10; x++) {
  91         b1[x] = refl[x] << 4;
  92
  93         for (y=0; y < x; y++)
  94             b1[y] = ((refl[x] * b2[x-y-1]) >> 12) + b2[y];
  95
  96         FFSWAP(int *, b1, b2);
  97     }
  98
  99     for (x=0; x < 10; x++)
 100         coefs[x] >>= 4;
 101 }
 102
 103 /**
 104  * Copy the last offset values of *source to *target. If those values are not
 105  * enough to fill the target buffer, fill it with another copy of those values.
 106  */
 107 static void copy_and_dup(int16_t *target, const int16_t *source, int offset)
 108 {
 109     source += BUFFERSIZE - offset;
 110
 111     if (offset > BLOCKSIZE) {
 112         memcpy(target, source, BLOCKSIZE*sizeof(*target));
 113     } else {
 114         memcpy(target, source, offset*sizeof(*target));
 115         memcpy(target + offset, source, (BLOCKSIZE - offset)*sizeof(*target));
 116     }
 117 }
 118
 119 /** inverse root mean square */
 120 static int irms(const int16_t *data)
 121 {
 122     unsigned int i, sum = 0;
 123
 124     for (i=0; i < BLOCKSIZE; i++)
 125         sum += data[i] * data[i];
 126
 127     if (sum == 0)
 128         return 0; /* OOPS - division by zero */
 129
 130     return 0x20000000 / (t_sqrt(sum) >> 8);
 131 }
 132
 133 static void add_wav(int16_t *dest, int n, int skip_first, int *m,
 134                     const int16_t *s1, const int8_t *s2, const int8_t *s3)
 135 {
 136     int i;
 137     int v[3];
 138
 139     v[0] = 0;
 140     for (i=!skip_first; i<3; i++)
 141         v[i] = (gain_val_tab[n][i] * m[i]) >> (gain_exp_tab[n][i] + 1);
 142
 143     for (i=0; i < BLOCKSIZE; i++)
 144         dest[i] = (s1[i]*v[0] + s2[i]*v[1] + s3[i]*v[2]) >> 12;
 145 }
 146
 147 static unsigned int rescale_rms(unsigned int rms, unsigned int energy)
 148 {
 149     return (rms * energy) >> 10;
 150 }
 151
 152 static unsigned int rms(const int *data)
 153 {
 154     int x;
 155     unsigned int res = 0x10000;
 156     int b = 0;
 157
 158     for (x=0; x<10; x++) {
 159         res = (((0x1000000 - data[x]*data[x]) >> 12) * res) >> 12;
 160
 161         if (res == 0)
 162             return 0;
 163
 164         while (res <= 0x3fff) {
 165             b++;
 166             res <<= 2;
 167         }
 168     }
 169
 170     res = t_sqrt(res);
 171
 172     res >>= (b + 10);
 173     return res;
 174 }
 175
 176 static void do_output_subblock(RA144Context *ractx, const uint16_t  *lpc_coefs,
 177                                int gval, GetBitContext *gb)
 178 {
 179     uint16_t buffer_a[40];
 180     uint16_t *block;
 181     int cba_idx = get_bits(gb, 7); // index of the adaptive CB, 0 if none
 182     int gain    = get_bits(gb, 8);
 183     int cb1_idx = get_bits(gb, 7);
 184     int cb2_idx = get_bits(gb, 7);
 185     int m[3];
 186
 187     if (cba_idx) {
 188         cba_idx += BLOCKSIZE/2 - 1;
 189         copy_and_dup(buffer_a, ractx->adapt_cb, cba_idx);
 190         m[0] = (irms(buffer_a) * gval) >> 12;
 191     } else {
 192         m[0] = 0;
 193     }
 194
 195     m[1] = (cb1_base[cb1_idx] * gval) >> 8;
 196     m[2] = (cb2_base[cb2_idx] * gval) >> 8;
 197
 198     memmove(ractx->adapt_cb, ractx->adapt_cb + BLOCKSIZE,
 199             (BUFFERSIZE - BLOCKSIZE) * sizeof(*ractx->adapt_cb));
 200
 201     block = ractx->adapt_cb + BUFFERSIZE - BLOCKSIZE;
 202
 203     add_wav(block, gain, cba_idx, m, buffer_a,
 204             cb1_vects[cb1_idx], cb2_vects[cb2_idx]);
 205
 206     memcpy(ractx->curr_sblock, ractx->curr_sblock + 40,
 207            10*sizeof(*ractx->curr_sblock));
 208     memcpy(ractx->curr_sblock + 10, block,
 209            BLOCKSIZE*sizeof(*ractx->curr_sblock));
 210
 211     if (ff_acelp_lp_synthesis_filter(
 212                                      ractx->curr_sblock + 10, lpc_coefs,
 213                                      ractx->curr_sblock + 10, BLOCKSIZE,
 214                                      10, 1, 0xfff)
 215         )
 216         memset(ractx->curr_sblock, 0, 50*sizeof(*ractx->curr_sblock));
 217 }
 218
 219 static void int_to_int16(int16_t *out, const int *inp)
 220 {
 221     int i;
 222
 223     for (i=0; i<30; i++)
 224         *(out++) = *(inp++);
 225 }
 226
 227 /**
 228  * Evaluate the reflection coefficients from the filter coefficients.
 229  * Does the inverse of the eval_coefs() function.
 230  *
 231  * @return 1 if one of the reflection coefficients is of magnitude greater than
 232  *         4095, 0 if not.
 233  */
 234 static int eval_refl(int *refl, const int16_t *coefs, RA144Context *ractx)
 235 {
 236     int retval = 0;
 237     int b, c, i;
 238     unsigned int u;
 239     int buffer1[10];
 240     int buffer2[10];
 241     int *bp1 = buffer1;
 242     int *bp2 = buffer2;
 243
 244     for (i=0; i < 10; i++)
 245         buffer2[i] = coefs[i];
 246
 247     u = refl[9] = bp2[9];
 248
 249     if (u + 0x1000 > 0x1fff) {
 250         av_log(ractx, AV_LOG_ERROR, "Overflow. Broken sample?\n");
 251         return 1;
 252     }
 253
 254     for (c=8; c >= 0; c--) {
 255         if (u == 0x1000)
 256             u++;
 257
 258         if (u == 0xfffff000)
 259             u--;
 260
 261         b = 0x1000-((u * u) >> 12);
 262
 263         if (b == 0)
 264             b++;
 265
 266         for (u=0; u<=c; u++)
 267             bp1[u] = ((bp2[u] - ((refl[c+1] * bp2[c-u]) >> 12)) * (0x1000000 / b)) >> 12;
 268
 269         refl[c] = u = bp1[c];
 270
 271         if ((u + 0x1000) > 0x1fff)
 272             retval = 1;
 273
 274         FFSWAP(int *, bp1, bp2);
 275     }
 276     return retval;
 277 }
 278
 279 static int interp(RA144Context *ractx, int16_t *out, int block_num,
 280                   int copyold, int energy)
 281 {
 282     int work[10];
 283     int a = block_num + 1;
 284     int b = NBLOCKS - a;
 285     int x;
 286
 287     // Interpolate block coefficients from the this frame forth block and
 288     // last frame forth block
 289     for (x=0; x<30; x++)
 290         out[x] = (a * ractx->lpc_coef[0][x] + b * ractx->lpc_coef[1][x])>> 2;
 291
 292     if (eval_refl(work, out, ractx)) {
 293         // The interpolated coefficients are unstable, copy either new or old
 294         // coefficients
 295         int_to_int16(out, ractx->lpc_coef[copyold]);
 296         return rescale_rms(ractx->lpc_refl_rms[copyold], energy);
 297     } else {
 298         return rescale_rms(rms(work), energy);
 299     }
 300 }
 301
 302 /** Uncompress one block (20 bytes -> 160*2 bytes) */
 303 static int ra144_decode_frame(AVCodecContext * avctx, void *vdata,
 304                               int *data_size, const uint8_t *buf, int buf_size)
 305 {
 306     static const uint8_t sizes[10] = {6, 5, 5, 4, 4, 3, 3, 3, 3, 2};
 307     unsigned int refl_rms[4];    // RMS of the reflection coefficients
 308     uint16_t block_coefs[4][30]; // LPC coefficients of each sub-block
 309     unsigned int lpc_refl[10];   // LPC reflection coefficients of the frame
 310     int i, c;
 311     int16_t *data = vdata;
 312     unsigned int energy;
 313
 314     RA144Context *ractx = avctx->priv_data;
 315     GetBitContext gb;
 316
 317     if(buf_size < 20) {
 318         av_log(avctx, AV_LOG_ERROR,
 319                "Frame too small (%d bytes). Truncated file?\n", buf_size);
 320         *data_size = 0;
 321         return buf_size;
 322     }
 323     init_get_bits(&gb, buf, 20 * 8);
 324
 325     for (i=0; i<10; i++)
 326         lpc_refl[i] = lpc_refl_cb[i][get_bits(&gb, sizes[i])];
 327
 328     eval_coefs(ractx->lpc_coef[0], lpc_refl);
 329     ractx->lpc_refl_rms[0] = rms(lpc_refl);
 330
 331     energy = energy_tab[get_bits(&gb, 5)];
 332
 333     refl_rms[0] = interp(ractx, block_coefs[0], 0, 1, ractx->old_energy);
 334     refl_rms[1] = interp(ractx, block_coefs[1], 1, energy <= ractx->old_energy,
 335                     t_sqrt(energy*ractx->old_energy) >> 12);
 336     refl_rms[2] = interp(ractx, block_coefs[2], 2, 0, energy);
 337     refl_rms[3] = rescale_rms(ractx->lpc_refl_rms[0], energy);
 338
 339     int_to_int16(block_coefs[3], ractx->lpc_coef[0]);
 340
 341     for (c=0; c<4; c++) {
 342         do_output_subblock(ractx, block_coefs[c], refl_rms[c], &gb);
 343
 344         for (i=0; i<BLOCKSIZE; i++)
 345             *data++ = av_clip_int16(ractx->curr_sblock[i + 10] << 2);
 346     }
 347
 348     ractx->old_energy = energy;
 349     ractx->lpc_refl_rms[1] = ractx->lpc_refl_rms[0];
 350
 351     FFSWAP(unsigned int *, ractx->lpc_coef[0], ractx->lpc_coef[1]);
 352
 353     *data_size = 2*160;
 354     return 20;
 355 }
 356
 357 AVCodec ra_144_decoder =
 358 {
 359     "real_144",
 360     CODEC_TYPE_AUDIO,
 361     CODEC_ID_RA_144,
 362     sizeof(RA144Context),
 363     ra144_decode_init,
 364     NULL,
 365     NULL,
 366     ra144_decode_frame,
 367     .long_name = NULL_IF_CONFIG_SMALL("RealAudio 1.0 (14.4K)"),
 368 };