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[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     for (i=0; i < BLOCKSIZE; i++)
 142         dest[i] = (s1[i]*v[0] + s2[i]*v[1] + s3[i]*v[2]) >> 12;
 143 }
 144
 145 static unsigned int rescale_rms(unsigned int rms, unsigned int energy)
 146 {
 147     return (rms * energy) >> 10;
 148 }
 149
 150 static unsigned int rms(const int *data)
 151 {
 152     int i;
 153     unsigned int res = 0x10000;
 154     int b = 10;
 155
 156     for (i=0; i < 10; i++) {
 157         res = (((0x1000000 - data[i]*data[i]) >> 12) * res) >> 12;
 158
 159         if (res == 0)
 160             return 0;
 161
 162         while (res <= 0x3fff) {
 163             b++;
 164             res <<= 2;
 165         }
 166     }
 167
 168     return t_sqrt(res) >> b;
 169 }
 170
 171 static void do_output_subblock(RA144Context *ractx, const uint16_t  *lpc_coefs,
 172                                int gval, GetBitContext *gb)
 173 {
 174     uint16_t buffer_a[40];
 175     uint16_t *block;
 176     int cba_idx = get_bits(gb, 7); // index of the adaptive CB, 0 if none
 177     int gain    = get_bits(gb, 8);
 178     int cb1_idx = get_bits(gb, 7);
 179     int cb2_idx = get_bits(gb, 7);
 180     int m[3];
 181
 182     if (cba_idx) {
 183         cba_idx += BLOCKSIZE/2 - 1;
 184         copy_and_dup(buffer_a, ractx->adapt_cb, cba_idx);
 185         m[0] = (irms(buffer_a) * gval) >> 12;
 186     } else {
 187         m[0] = 0;
 188     }
 189
 190     m[1] = (cb1_base[cb1_idx] * gval) >> 8;
 191     m[2] = (cb2_base[cb2_idx] * gval) >> 8;
 192
 193     memmove(ractx->adapt_cb, ractx->adapt_cb + BLOCKSIZE,
 194             (BUFFERSIZE - BLOCKSIZE) * sizeof(*ractx->adapt_cb));
 195
 196     block = ractx->adapt_cb + BUFFERSIZE - BLOCKSIZE;
 197
 198     add_wav(block, gain, cba_idx, m, buffer_a,
 199             cb1_vects[cb1_idx], cb2_vects[cb2_idx]);
 200
 201     memcpy(ractx->curr_sblock, ractx->curr_sblock + 40,
 202            10*sizeof(*ractx->curr_sblock));
 203
 204     if (ff_acelp_lp_synthesis_filter(ractx->curr_sblock + 10, lpc_coefs,
 205                                      block, BLOCKSIZE, 10, 1, 0xfff))
 206         memset(ractx->curr_sblock, 0, 50*sizeof(*ractx->curr_sblock));
 207 }
 208
 209 static void int_to_int16(int16_t *out, const int *inp)
 210 {
 211     int i;
 212
 213     for (i=0; i < 30; i++)
 214         *out++ = *inp++;
 215 }
 216
 217 /**
 218  * Evaluate the reflection coefficients from the filter coefficients.
 219  * Does the inverse of the eval_coefs() function.
 220  *
 221  * @return 1 if one of the reflection coefficients is of magnitude greater than
 222  *         4095, 0 if not.
 223  */
 224 static int eval_refl(int *refl, const int16_t *coefs, RA144Context *ractx)
 225 {
 226     int b, i, j;
 227     int buffer1[10];
 228     int buffer2[10];
 229     int *bp1 = buffer1;
 230     int *bp2 = buffer2;
 231
 232     for (i=0; i < 10; i++)
 233         buffer2[i] = coefs[i];
 234
 235     refl[9] = bp2[9];
 236
 237     if ((unsigned) bp2[9] + 0x1000 > 0x1fff) {
 238         av_log(ractx, AV_LOG_ERROR, "Overflow. Broken sample?\n");
 239         return 1;
 240     }
 241
 242     for (i=8; i >= 0; i--) {
 243         b = 0x1000-((bp2[i+1] * bp2[i+1]) >> 12);
 244
 245         if (!b)
 246             b = -2;
 247
 248         for (j=0; j <= i; j++)
 249             bp1[j] = ((bp2[j] - ((refl[i+1] * bp2[i-j]) >> 12)) * (0x1000000 / b)) >> 12;
 250
 251         if ((unsigned) bp1[i] + 0x1000 > 0x1fff)
 252             return 1;
 253
 254         refl[i] = bp1[i];
 255
 256         FFSWAP(int *, bp1, bp2);
 257     }
 258     return 0;
 259 }
 260
 261 static int interp(RA144Context *ractx, int16_t *out, int a,
 262                   int copyold, int energy)
 263 {
 264     int work[10];
 265     int b = NBLOCKS - a;
 266     int i;
 267
 268     // Interpolate block coefficients from the this frame forth block and
 269     // last frame forth block
 270     for (i=0; i<30; i++)
 271         out[i] = (a * ractx->lpc_coef[0][i] + b * ractx->lpc_coef[1][i])>> 2;
 272
 273     if (eval_refl(work, out, ractx)) {
 274         // The interpolated coefficients are unstable, copy either new or old
 275         // coefficients
 276         int_to_int16(out, ractx->lpc_coef[copyold]);
 277         return rescale_rms(ractx->lpc_refl_rms[copyold], energy);
 278     } else {
 279         return rescale_rms(rms(work), energy);
 280     }
 281 }
 282
 283 /** Uncompress one block (20 bytes -> 160*2 bytes) */
 284 static int ra144_decode_frame(AVCodecContext * avctx, void *vdata,
 285                               int *data_size, const uint8_t *buf, int buf_size)
 286 {
 287     static const uint8_t sizes[10] = {6, 5, 5, 4, 4, 3, 3, 3, 3, 2};
 288     unsigned int refl_rms[4];    // RMS of the reflection coefficients
 289     uint16_t block_coefs[4][30]; // LPC coefficients of each sub-block
 290     unsigned int lpc_refl[10];   // LPC reflection coefficients of the frame
 291     int i, j;
 292     int16_t *data = vdata;
 293     unsigned int energy;
 294
 295     RA144Context *ractx = avctx->priv_data;
 296     GetBitContext gb;
 297
 298     if (*data_size < 2*160)
 299         return -1;
 300
 301     if(buf_size < 20) {
 302         av_log(avctx, AV_LOG_ERROR,
 303                "Frame too small (%d bytes). Truncated file?\n", buf_size);
 304         *data_size = 0;
 305         return buf_size;
 306     }
 307     init_get_bits(&gb, buf, 20 * 8);
 308
 309     for (i=0; i<10; i++)
 310         lpc_refl[i] = lpc_refl_cb[i][get_bits(&gb, sizes[i])];
 311
 312     eval_coefs(ractx->lpc_coef[0], lpc_refl);
 313     ractx->lpc_refl_rms[0] = rms(lpc_refl);
 314
 315     energy = energy_tab[get_bits(&gb, 5)];
 316
 317     refl_rms[0] = interp(ractx, block_coefs[0], 1, 1, ractx->old_energy);
 318     refl_rms[1] = interp(ractx, block_coefs[1], 2, energy <= ractx->old_energy,
 319                     t_sqrt(energy*ractx->old_energy) >> 12);
 320     refl_rms[2] = interp(ractx, block_coefs[2], 3, 0, energy);
 321     refl_rms[3] = rescale_rms(ractx->lpc_refl_rms[0], energy);
 322
 323     int_to_int16(block_coefs[3], ractx->lpc_coef[0]);
 324
 325     for (i=0; i < 4; i++) {
 326         do_output_subblock(ractx, block_coefs[i], refl_rms[i], &gb);
 327
 328         for (j=0; j < BLOCKSIZE; j++)
 329             *data++ = av_clip_int16(ractx->curr_sblock[j + 10] << 2);
 330     }
 331
 332     ractx->old_energy = energy;
 333     ractx->lpc_refl_rms[1] = ractx->lpc_refl_rms[0];
 334
 335     FFSWAP(unsigned int *, ractx->lpc_coef[0], ractx->lpc_coef[1]);
 336
 337     *data_size = 2*160;
 338     return 20;
 339 }
 340
 341 AVCodec ra_144_decoder =
 342 {
 343     "real_144",
 344     CODEC_TYPE_AUDIO,
 345     CODEC_ID_RA_144,
 346     sizeof(RA144Context),
 347     ra144_decode_init,
 348     NULL,
 349     NULL,
 350     ra144_decode_frame,
 351     .long_name = NULL_IF_CONFIG_SMALL("RealAudio 1.0 (14.4K)"),
 352 };