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 "get_bits.h"
  27 #include "ra144.h"
  28 #include "celp_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[146+2];
  52 } RA144Context;
  53
  54 static av_cold 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     avctx->sample_fmt = SAMPLE_FMT_S16;
  62     return 0;
  63 }
  64
  65 /**
  66  * Evaluate sqrt(x << 24). x must fit in 20 bits. This value is evaluated in an
  67  * odd way to make the output identical to the binary decoder.
  68  */
  69 static int t_sqrt(unsigned int x)
  70 {
  71     int s = 2;
  72     while (x > 0xfff) {
  73         s++;
  74         x >>= 2;
  75     }
  76
  77     return ff_sqrt(x << 20) << s;
  78 }
  79
  80 /**
  81  * Evaluate the LPC filter coefficients from the reflection coefficients.
  82  * Does the inverse of the eval_refl() function.
  83  */
  84 static void eval_coefs(int *coefs, const int *refl)
  85 {
  86     int buffer[10];
  87     int *b1 = buffer;
  88     int *b2 = coefs;
  89     int i, j;
  90
  91     for (i=0; i < 10; i++) {
  92         b1[i] = refl[i] << 4;
  93
  94         for (j=0; j < i; j++)
  95             b1[j] = ((refl[i] * b2[i-j-1]) >> 12) + b2[j];
  96
  97         FFSWAP(int *, b1, b2);
  98     }
  99
 100     for (i=0; i < 10; i++)
 101         coefs[i] >>= 4;
 102 }
 103
 104 /**
 105  * Copy the last offset values of *source to *target. If those values are not
 106  * enough to fill the target buffer, fill it with another copy of those values.
 107  */
 108 static void copy_and_dup(int16_t *target, const int16_t *source, int offset)
 109 {
 110     source += BUFFERSIZE - offset;
 111
 112     memcpy(target, source, FFMIN(BLOCKSIZE, offset)*sizeof(*target));
 113     if (offset < BLOCKSIZE)
 114         memcpy(target + offset, source, (BLOCKSIZE - offset)*sizeof(*target));
 115 }
 116
 117 /** inverse root mean square */
 118 static int irms(const int16_t *data)
 119 {
 120     unsigned int i, sum = 0;
 121
 122     for (i=0; i < BLOCKSIZE; i++)
 123         sum += data[i] * data[i];
 124
 125     if (sum == 0)
 126         return 0; /* OOPS - division by zero */
 127
 128     return 0x20000000 / (t_sqrt(sum) >> 8);
 129 }
 130
 131 static void add_wav(int16_t *dest, int n, int skip_first, int *m,
 132                     const int16_t *s1, const int8_t *s2, const int8_t *s3)
 133 {
 134     int i;
 135     int v[3];
 136
 137     v[0] = 0;
 138     for (i=!skip_first; i<3; i++)
 139         v[i] = (gain_val_tab[n][i] * m[i]) >> gain_exp_tab[n];
 140
 141     if (v[0]) {
 142         for (i=0; i < BLOCKSIZE; i++)
 143             dest[i] = (s1[i]*v[0] + s2[i]*v[1] + s3[i]*v[2]) >> 12;
 144     } else {
 145         for (i=0; i < BLOCKSIZE; i++)
 146             dest[i] = (             s2[i]*v[1] + s3[i]*v[2]) >> 12;
 147     }
 148 }
 149
 150 static unsigned int rescale_rms(unsigned int rms, unsigned int energy)
 151 {
 152     return (rms * energy) >> 10;
 153 }
 154
 155 static unsigned int rms(const int *data)
 156 {
 157     int i;
 158     unsigned int res = 0x10000;
 159     int b = 10;
 160
 161     for (i=0; i < 10; i++) {
 162         res = (((0x1000000 - data[i]*data[i]) >> 12) * res) >> 12;
 163
 164         if (res == 0)
 165             return 0;
 166
 167         while (res <= 0x3fff) {
 168             b++;
 169             res <<= 2;
 170         }
 171     }
 172
 173     return t_sqrt(res) >> b;
 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, cba_idx? buffer_a: NULL,
 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
 209     if (ff_celp_lp_synthesis_filter(ractx->curr_sblock + 10, lpc_coefs,
 210                                     block, BLOCKSIZE, 10, 1, 0xfff))
 211         memset(ractx->curr_sblock, 0, 50*sizeof(*ractx->curr_sblock));
 212 }
 213
 214 static void int_to_int16(int16_t *out, const int *inp)
 215 {
 216     int i;
 217
 218     for (i=0; i < 30; i++)
 219         *out++ = *inp++;
 220 }
 221
 222 /**
 223  * Evaluate the reflection coefficients from the filter coefficients.
 224  * Does the inverse of the eval_coefs() function.
 225  *
 226  * @return 1 if one of the reflection coefficients is greater than
 227  *         4095, 0 if not.
 228  */
 229 static int eval_refl(int *refl, const int16_t *coefs, RA144Context *ractx)
 230 {
 231     int b, i, j;
 232     int buffer1[10];
 233     int buffer2[10];
 234     int *bp1 = buffer1;
 235     int *bp2 = buffer2;
 236
 237     for (i=0; i < 10; i++)
 238         buffer2[i] = coefs[i];
 239
 240     refl[9] = bp2[9];
 241
 242     if ((unsigned) bp2[9] + 0x1000 > 0x1fff) {
 243         av_log(ractx, AV_LOG_ERROR, "Overflow. Broken sample?\n");
 244         return 1;
 245     }
 246
 247     for (i=8; i >= 0; i--) {
 248         b = 0x1000-((bp2[i+1] * bp2[i+1]) >> 12);
 249
 250         if (!b)
 251             b = -2;
 252
 253         for (j=0; j <= i; j++)
 254             bp1[j] = ((bp2[j] - ((refl[i+1] * bp2[i-j]) >> 12)) * (0x1000000 / b)) >> 12;
 255
 256         if ((unsigned) bp1[i] + 0x1000 > 0x1fff)
 257             return 1;
 258
 259         refl[i] = bp1[i];
 260
 261         FFSWAP(int *, bp1, bp2);
 262     }
 263     return 0;
 264 }
 265
 266 static int interp(RA144Context *ractx, int16_t *out, int a,
 267                   int copyold, int energy)
 268 {
 269     int work[10];
 270     int b = NBLOCKS - a;
 271     int i;
 272
 273     // Interpolate block coefficients from the this frame's forth block and
 274     // last frame's forth block.
 275     for (i=0; i<30; i++)
 276         out[i] = (a * ractx->lpc_coef[0][i] + b * ractx->lpc_coef[1][i])>> 2;
 277
 278     if (eval_refl(work, out, ractx)) {
 279         // The interpolated coefficients are unstable, copy either new or old
 280         // coefficients.
 281         int_to_int16(out, ractx->lpc_coef[copyold]);
 282         return rescale_rms(ractx->lpc_refl_rms[copyold], energy);
 283     } else {
 284         return rescale_rms(rms(work), energy);
 285     }
 286 }
 287
 288 /** Uncompress one block (20 bytes -> 160*2 bytes). */
 289 static int ra144_decode_frame(AVCodecContext * avctx, void *vdata,
 290                               int *data_size, AVPacket *avpkt)
 291 {
 292     const uint8_t *buf = avpkt->data;
 293     int buf_size = avpkt->size;
 294     static const uint8_t sizes[10] = {6, 5, 5, 4, 4, 3, 3, 3, 3, 2};
 295     unsigned int refl_rms[4];    // RMS of the reflection coefficients
 296     uint16_t block_coefs[4][30]; // LPC coefficients of each sub-block
 297     unsigned int lpc_refl[10];   // LPC reflection coefficients of the frame
 298     int i, j;
 299     int16_t *data = vdata;
 300     unsigned int energy;
 301
 302     RA144Context *ractx = avctx->priv_data;
 303     GetBitContext gb;
 304
 305     if (*data_size < 2*160)
 306         return -1;
 307
 308     if(buf_size < 20) {
 309         av_log(avctx, AV_LOG_ERROR,
 310                "Frame too small (%d bytes). Truncated file?\n", buf_size);
 311         *data_size = 0;
 312         return buf_size;
 313     }
 314     init_get_bits(&gb, buf, 20 * 8);
 315
 316     for (i=0; i<10; i++)
 317         lpc_refl[i] = lpc_refl_cb[i][get_bits(&gb, sizes[i])];
 318
 319     eval_coefs(ractx->lpc_coef[0], lpc_refl);
 320     ractx->lpc_refl_rms[0] = rms(lpc_refl);
 321
 322     energy = energy_tab[get_bits(&gb, 5)];
 323
 324     refl_rms[0] = interp(ractx, block_coefs[0], 1, 1, ractx->old_energy);
 325     refl_rms[1] = interp(ractx, block_coefs[1], 2, energy <= ractx->old_energy,
 326                     t_sqrt(energy*ractx->old_energy) >> 12);
 327     refl_rms[2] = interp(ractx, block_coefs[2], 3, 0, energy);
 328     refl_rms[3] = rescale_rms(ractx->lpc_refl_rms[0], energy);
 329
 330     int_to_int16(block_coefs[3], ractx->lpc_coef[0]);
 331
 332     for (i=0; i < 4; i++) {
 333         do_output_subblock(ractx, block_coefs[i], refl_rms[i], &gb);
 334
 335         for (j=0; j < BLOCKSIZE; j++)
 336             *data++ = av_clip_int16(ractx->curr_sblock[j + 10] << 2);
 337     }
 338
 339     ractx->old_energy = energy;
 340     ractx->lpc_refl_rms[1] = ractx->lpc_refl_rms[0];
 341
 342     FFSWAP(unsigned int *, ractx->lpc_coef[0], ractx->lpc_coef[1]);
 343
 344     *data_size = 2*160;
 345     return 20;
 346 }
 347
 348 AVCodec ra_144_decoder =
 349 {
 350     "real_144",
 351     CODEC_TYPE_AUDIO,
 352     CODEC_ID_RA_144,
 353     sizeof(RA144Context),
 354     ra144_decode_init,
 355     NULL,
 356     NULL,
 357     ra144_decode_frame,
 358     .long_name = NULL_IF_CONFIG_SMALL("RealAudio 1.0 (14.4K)"),
 359 };