libavcodec/ac3enc_template.c

   1 /*
   2  * AC-3 encoder float/fixed template
   3  * Copyright (c) 2000 Fabrice Bellard
   4  * Copyright (c) 2006-2011 Justin Ruggles <justin.ruggles@gmail.com>
   5  * Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
   6  *
   7  * This file is part of FFmpeg.
   8  *
   9  * FFmpeg is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; either
  12  * version 2.1 of the License, or (at your option) any later version.
  13  *
  14  * FFmpeg is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with FFmpeg; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  */
  23
  24 /**
  25  * @file
  26  * AC-3 encoder float/fixed template
  27  */
  28
  29 #include "config_components.h"
  30
  31 #include <stdint.h>
  32
  33 #include "libavutil/attributes.h"
  34 #include "libavutil/avassert.h"
  35 #include "libavutil/mem_internal.h"
  36
  37 #include "audiodsp.h"
  38 #include "ac3enc.h"
  39 #include "eac3enc.h"
  40
  41 #if AC3ENC_FLOAT
  42 #define RENAME(element) element ## _float
  43 #else
  44 #define RENAME(element) element ## _fixed
  45 #endif
  46
  47 /*
  48  * Apply the MDCT to input samples to generate frequency coefficients.
  49  * This applies the KBD window and normalizes the input to reduce precision
  50  * loss due to fixed-point calculations.
  51  */
  52 static void apply_mdct(AC3EncodeContext *s, uint8_t * const *samples)
  53 {
  54     av_assert1(s->num_blocks > 0);
  55
  56     for (int ch = 0; ch < s->channels; ch++) {
  57         const SampleType *input_samples0 = (const SampleType*)s->planar_samples[ch];
  58         /* Reorder channels from native order to AC-3 order. */
  59         const SampleType *input_samples1 = (const SampleType*)samples[s->channel_map[ch]];
  60         int blk = 0;
  61
  62         do {
  63             AC3Block *block = &s->blocks[blk];
  64             SampleType *windowed_samples = s->RENAME(windowed_samples);
  65
  66             s->fdsp->vector_fmul(windowed_samples, input_samples0,
  67                                  s->RENAME(mdct_window), AC3_BLOCK_SIZE);
  68             s->fdsp->vector_fmul_reverse(windowed_samples + AC3_BLOCK_SIZE,
  69                                          input_samples1,
  70                                          s->RENAME(mdct_window), AC3_BLOCK_SIZE);
  71
  72             s->tx_fn(s->tx, block->mdct_coef[ch+1],
  73                      windowed_samples, sizeof(*windowed_samples));
  74             input_samples0  = input_samples1;
  75             input_samples1 += AC3_BLOCK_SIZE;
  76         } while (++blk < s->num_blocks);
  77
  78         /* Store last 256 samples of current frame */
  79         memcpy(s->planar_samples[ch], input_samples0,
  80                AC3_BLOCK_SIZE * sizeof(*input_samples0));
  81     }
  82 }
  83
  84
  85 /*
  86  * Calculate coupling channel and coupling coordinates.
  87  */
  88 static void apply_channel_coupling(AC3EncodeContext *s)
  89 {
  90     LOCAL_ALIGNED_32(CoefType, cpl_coords,      [AC3_MAX_BLOCKS], [AC3_MAX_CHANNELS][16]);
  91 #if AC3ENC_FLOAT
  92     LOCAL_ALIGNED_32(int32_t, fixed_cpl_coords, [AC3_MAX_BLOCKS], [AC3_MAX_CHANNELS][16]);
  93 #else
  94     int32_t (*fixed_cpl_coords)[AC3_MAX_CHANNELS][16] = cpl_coords;
  95 #endif
  96     int av_uninit(blk), ch, bnd, i, j;
  97     CoefSumType energy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][16] = {{{0}}};
  98     int cpl_start, num_cpl_coefs;
  99
 100     memset(cpl_coords,       0, AC3_MAX_BLOCKS * sizeof(*cpl_coords));
 101 #if AC3ENC_FLOAT
 102     memset(fixed_cpl_coords, 0, AC3_MAX_BLOCKS * sizeof(*cpl_coords));
 103 #endif
 104
 105     /* align start to 16-byte boundary. align length to multiple of 32.
 106         note: coupling start bin % 4 will always be 1 */
 107     cpl_start     = s->start_freq[CPL_CH] - 1;
 108     num_cpl_coefs = FFALIGN(s->num_cpl_subbands * 12 + 1, 32);
 109     cpl_start     = FFMIN(256, cpl_start + num_cpl_coefs) - num_cpl_coefs;
 110
 111     /* calculate coupling channel from fbw channels */
 112     for (blk = 0; blk < s->num_blocks; blk++) {
 113         AC3Block *block = &s->blocks[blk];
 114         CoefType *cpl_coef = &block->mdct_coef[CPL_CH][cpl_start];
 115         if (!block->cpl_in_use)
 116             continue;
 117         memset(cpl_coef, 0, num_cpl_coefs * sizeof(*cpl_coef));
 118         for (ch = 1; ch <= s->fbw_channels; ch++) {
 119             CoefType *ch_coef = &block->mdct_coef[ch][cpl_start];
 120             if (!block->channel_in_cpl[ch])
 121                 continue;
 122             for (i = 0; i < num_cpl_coefs; i++)
 123                 cpl_coef[i] += ch_coef[i];
 124         }
 125
 126         /* coefficients must be clipped in order to be encoded */
 127         clip_coefficients(&s->adsp, cpl_coef, num_cpl_coefs);
 128     }
 129
 130     /* calculate energy in each band in coupling channel and each fbw channel */
 131     /* TODO: possibly use SIMD to speed up energy calculation */
 132     bnd = 0;
 133     i = s->start_freq[CPL_CH];
 134     while (i < s->cpl_end_freq) {
 135         int band_size = s->cpl_band_sizes[bnd];
 136         for (ch = CPL_CH; ch <= s->fbw_channels; ch++) {
 137             for (blk = 0; blk < s->num_blocks; blk++) {
 138                 AC3Block *block = &s->blocks[blk];
 139                 if (!block->cpl_in_use || (ch > CPL_CH && !block->channel_in_cpl[ch]))
 140                     continue;
 141                 for (j = 0; j < band_size; j++) {
 142                     CoefType v = block->mdct_coef[ch][i+j];
 143                     MAC_COEF(energy[blk][ch][bnd], v, v);
 144                 }
 145             }
 146         }
 147         i += band_size;
 148         bnd++;
 149     }
 150
 151     /* calculate coupling coordinates for all blocks for all channels */
 152     for (blk = 0; blk < s->num_blocks; blk++) {
 153         AC3Block *block  = &s->blocks[blk];
 154         if (!block->cpl_in_use)
 155             continue;
 156         for (ch = 1; ch <= s->fbw_channels; ch++) {
 157             if (!block->channel_in_cpl[ch])
 158                 continue;
 159             for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
 160                 cpl_coords[blk][ch][bnd] = calc_cpl_coord(energy[blk][ch][bnd],
 161                                                           energy[blk][CPL_CH][bnd]);
 162             }
 163         }
 164     }
 165
 166     /* determine which blocks to send new coupling coordinates for */
 167     for (blk = 0; blk < s->num_blocks; blk++) {
 168         AC3Block *block  = &s->blocks[blk];
 169         AC3Block *block0 = blk ? &s->blocks[blk-1] : NULL;
 170
 171         memset(block->new_cpl_coords, 0, sizeof(block->new_cpl_coords));
 172
 173         if (block->cpl_in_use) {
 174             /* send new coordinates if this is the first block, if previous
 175              * block did not use coupling but this block does, the channels
 176              * using coupling has changed from the previous block, or the
 177              * coordinate difference from the last block for any channel is
 178              * greater than a threshold value. */
 179             if (blk == 0 || !block0->cpl_in_use) {
 180                 for (ch = 1; ch <= s->fbw_channels; ch++)
 181                     block->new_cpl_coords[ch] = 1;
 182             } else {
 183                 for (ch = 1; ch <= s->fbw_channels; ch++) {
 184                     if (!block->channel_in_cpl[ch])
 185                         continue;
 186                     if (!block0->channel_in_cpl[ch]) {
 187                         block->new_cpl_coords[ch] = 1;
 188                     } else {
 189                         CoefSumType coord_diff = 0;
 190                         for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
 191                             coord_diff += FFABS(cpl_coords[blk-1][ch][bnd] -
 192                                                 cpl_coords[blk  ][ch][bnd]);
 193                         }
 194                         coord_diff /= s->num_cpl_bands;
 195                         if (coord_diff > NEW_CPL_COORD_THRESHOLD)
 196                             block->new_cpl_coords[ch] = 1;
 197                     }
 198                 }
 199             }
 200         }
 201     }
 202
 203     av_assert1(s->fbw_channels > 0);
 204
 205     /* calculate final coupling coordinates, taking into account reusing of
 206        coordinates in successive blocks */
 207     for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
 208         blk = 0;
 209         while (blk < s->num_blocks) {
 210             int av_uninit(blk1);
 211             AC3Block *block  = &s->blocks[blk];
 212
 213             if (!block->cpl_in_use) {
 214                 blk++;
 215                 continue;
 216             }
 217
 218             for (ch = 1; ch <= s->fbw_channels; ch++) {
 219                 CoefSumType energy_ch, energy_cpl;
 220                 if (!block->channel_in_cpl[ch])
 221                     continue;
 222                 energy_cpl = energy[blk][CPL_CH][bnd];
 223                 energy_ch = energy[blk][ch][bnd];
 224                 blk1 = blk+1;
 225                 while (blk1 < s->num_blocks && !s->blocks[blk1].new_cpl_coords[ch]) {
 226                     if (s->blocks[blk1].cpl_in_use) {
 227                         energy_cpl += energy[blk1][CPL_CH][bnd];
 228                         energy_ch += energy[blk1][ch][bnd];
 229                     }
 230                     blk1++;
 231                 }
 232                 cpl_coords[blk][ch][bnd] = calc_cpl_coord(energy_ch, energy_cpl);
 233             }
 234             blk = blk1;
 235         }
 236     }
 237
 238     /* calculate exponents/mantissas for coupling coordinates */
 239     for (blk = 0; blk < s->num_blocks; blk++) {
 240         AC3Block *block = &s->blocks[blk];
 241         if (!block->cpl_in_use)
 242             continue;
 243
 244 #if AC3ENC_FLOAT
 245         s->ac3dsp.float_to_fixed24(fixed_cpl_coords[blk][1],
 246                                    cpl_coords[blk][1],
 247                                    s->fbw_channels * 16);
 248 #endif
 249         s->ac3dsp.extract_exponents(block->cpl_coord_exp[1],
 250                                     fixed_cpl_coords[blk][1],
 251                                     s->fbw_channels * 16);
 252
 253         for (ch = 1; ch <= s->fbw_channels; ch++) {
 254             int bnd, min_exp, max_exp, master_exp;
 255
 256             if (!block->new_cpl_coords[ch])
 257                 continue;
 258
 259             /* determine master exponent */
 260             min_exp = max_exp = block->cpl_coord_exp[ch][0];
 261             for (bnd = 1; bnd < s->num_cpl_bands; bnd++) {
 262                 int exp = block->cpl_coord_exp[ch][bnd];
 263                 min_exp = FFMIN(exp, min_exp);
 264                 max_exp = FFMAX(exp, max_exp);
 265             }
 266             master_exp = ((max_exp - 15) + 2) / 3;
 267             master_exp = FFMAX(master_exp, 0);
 268             while (min_exp < master_exp * 3)
 269                 master_exp--;
 270             for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
 271                 block->cpl_coord_exp[ch][bnd] = av_clip(block->cpl_coord_exp[ch][bnd] -
 272                                                         master_exp * 3, 0, 15);
 273             }
 274             block->cpl_master_exp[ch] = master_exp;
 275
 276             /* quantize mantissas */
 277             for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
 278                 int cpl_exp  = block->cpl_coord_exp[ch][bnd];
 279                 int cpl_mant = (fixed_cpl_coords[blk][ch][bnd] << (5 + cpl_exp + master_exp * 3)) >> 24;
 280                 if (cpl_exp == 15)
 281                     cpl_mant >>= 1;
 282                 else
 283                     cpl_mant -= 16;
 284
 285                 block->cpl_coord_mant[ch][bnd] = cpl_mant;
 286             }
 287         }
 288     }
 289
 290     if (AC3ENC_FLOAT && CONFIG_EAC3_ENCODER && s->eac3)
 291         ff_eac3_set_cpl_states(s);
 292 }
 293
 294
 295 /*
 296  * Determine rematrixing flags for each block and band.
 297  */
 298 static void compute_rematrixing_strategy(AC3EncodeContext *s)
 299 {
 300     int nb_coefs;
 301     int blk, bnd;
 302     AC3Block *block, *block0 = NULL;
 303
 304     if (s->channel_mode != AC3_CHMODE_STEREO)
 305         return;
 306
 307     for (blk = 0; blk < s->num_blocks; blk++) {
 308         block = &s->blocks[blk];
 309         block->new_rematrixing_strategy = !blk;
 310
 311         block->num_rematrixing_bands = 4;
 312         if (block->cpl_in_use) {
 313             block->num_rematrixing_bands -= (s->start_freq[CPL_CH] <= 61);
 314             block->num_rematrixing_bands -= (s->start_freq[CPL_CH] == 37);
 315             if (blk && block->num_rematrixing_bands != block0->num_rematrixing_bands)
 316                 block->new_rematrixing_strategy = 1;
 317         }
 318         nb_coefs = FFMIN(block->end_freq[1], block->end_freq[2]);
 319
 320         if (!s->rematrixing_enabled) {
 321             block0 = block;
 322             continue;
 323         }
 324
 325         for (bnd = 0; bnd < block->num_rematrixing_bands; bnd++) {
 326             /* calculate sum of squared coeffs for one band in one block */
 327             int start = ff_ac3_rematrix_band_tab[bnd];
 328             int end   = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]);
 329             CoefSumType sum[4];
 330             sum_square_butterfly(s, sum, block->mdct_coef[1] + start,
 331                                  block->mdct_coef[2] + start, end - start);
 332
 333             /* compare sums to determine if rematrixing will be used for this band */
 334             if (FFMIN(sum[2], sum[3]) < FFMIN(sum[0], sum[1]))
 335                 block->rematrixing_flags[bnd] = 1;
 336             else
 337                 block->rematrixing_flags[bnd] = 0;
 338
 339             /* determine if new rematrixing flags will be sent */
 340             if (blk &&
 341                 block->rematrixing_flags[bnd] != block0->rematrixing_flags[bnd]) {
 342                 block->new_rematrixing_strategy = 1;
 343             }
 344         }
 345         block0 = block;
 346     }
 347 }
 348
 349
 350 static void encode_frame(AC3EncodeContext *s, uint8_t * const *samples)
 351 {
 352     apply_mdct(s, samples);
 353
 354     s->cpl_on = s->cpl_enabled;
 355     ff_ac3_compute_coupling_strategy(s);
 356
 357     if (s->cpl_on)
 358         apply_channel_coupling(s);
 359
 360     compute_rematrixing_strategy(s);
 361
 362 #if AC3ENC_FLOAT
 363     scale_coefficients(s);
 364 #endif
 365 }