libavcodec/mpegaudio.c

   1 /*
   2  * The simplest mpeg audio layer 2 encoder
   3  * Copyright (c) 2000 Gerard Lantau.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  18  */
  19 #include "avcodec.h"
  20 #include <math.h>
  21 #include "mpegaudio.h"
  22
  23 /* define it to use floats in quantization (I don't like floats !) */
  24 //#define USE_FLOATS
  25
  26 #define MPA_STEREO  0
  27 #define MPA_JSTEREO 1
  28 #define MPA_DUAL    2
  29 #define MPA_MONO    3
  30
  31 #include "mpegaudiotab.h"
  32
  33 int MPA_encode_init(AVCodecContext *avctx)
  34 {
  35     MpegAudioContext *s = avctx->priv_data;
  36     int freq = avctx->sample_rate;
  37     int bitrate = avctx->bit_rate;
  38     int channels = avctx->channels;
  39     int i, v, table, ch_bitrate;
  40     float a;
  41
  42     if (channels > 2)
  43         return -1;
  44     bitrate = bitrate / 1000;
  45     s->nb_channels = channels;
  46     s->freq = freq;
  47     s->bit_rate = bitrate * 1000;
  48     avctx->frame_size = MPA_FRAME_SIZE;
  49     avctx->key_frame = 1; /* always key frame */
  50
  51     /* encoding freq */
  52     s->lsf = 0;
  53     for(i=0;i<3;i++) {
  54         if (freq_tab[i] == freq)
  55             break;
  56         if ((freq_tab[i] / 2) == freq) {
  57             s->lsf = 1;
  58             break;
  59         }
  60     }
  61     if (i == 3)
  62         return -1;
  63     s->freq_index = i;
  64
  65     /* encoding bitrate & frequency */
  66     for(i=0;i<15;i++) {
  67         if (bitrate_tab[1-s->lsf][i] == bitrate)
  68             break;
  69     }
  70     if (i == 15)
  71         return -1;
  72     s->bitrate_index = i;
  73
  74     /* compute total header size & pad bit */
  75
  76     a = (float)(bitrate * 1000 * MPA_FRAME_SIZE) / (freq * 8.0);
  77     s->frame_size = ((int)a) * 8;
  78
  79     /* frame fractional size to compute padding */
  80     s->frame_frac = 0;
  81     s->frame_frac_incr = (int)((a - floor(a)) * 65536.0);
  82
  83     /* select the right allocation table */
  84     ch_bitrate = bitrate / s->nb_channels;
  85     if (!s->lsf) {
  86         if ((freq == 48000 && ch_bitrate >= 56) ||
  87             (ch_bitrate >= 56 && ch_bitrate <= 80))
  88             table = 0;
  89         else if (freq != 48000 && ch_bitrate >= 96)
  90             table = 1;
  91         else if (freq != 32000 && ch_bitrate <= 48)
  92             table = 2;
  93         else
  94             table = 3;
  95     } else {
  96         table = 4;
  97     }
  98     /* number of used subbands */
  99     s->sblimit = sblimit_table[table];
 100     s->alloc_table = alloc_tables[table];
 101
 102 #ifdef DEBUG
 103     printf("%d kb/s, %d Hz, frame_size=%d bits, table=%d, padincr=%x\n",
 104            bitrate, freq, s->frame_size, table, s->frame_frac_incr);
 105 #endif
 106
 107     for(i=0;i<s->nb_channels;i++)
 108         s->samples_offset[i] = 0;
 109
 110     for(i=0;i<512;i++) {
 111         float a = enwindow[i] * 32768.0 * 16.0;
 112         filter_bank[i] = (int)(a);
 113     }
 114     for(i=0;i<64;i++) {
 115         v = (int)(pow(2.0, (3 - i) / 3.0) * (1 << 20));
 116         if (v <= 0)
 117             v = 1;
 118         scale_factor_table[i] = v;
 119 #ifdef USE_FLOATS
 120         scale_factor_inv_table[i] = pow(2.0, -(3 - i) / 3.0) / (float)(1 << 20);
 121 #else
 122 #define P 15
 123         scale_factor_shift[i] = 21 - P - (i / 3);
 124         scale_factor_mult[i] = (1 << P) * pow(2.0, (i % 3) / 3.0);
 125 #endif
 126     }
 127     for(i=0;i<128;i++) {
 128         v = i - 64;
 129         if (v <= -3)
 130             v = 0;
 131         else if (v < 0)
 132             v = 1;
 133         else if (v == 0)
 134             v = 2;
 135         else if (v < 3)
 136             v = 3;
 137         else
 138             v = 4;
 139         scale_diff_table[i] = v;
 140     }
 141
 142     for(i=0;i<17;i++) {
 143         v = quant_bits[i];
 144         if (v < 0)
 145             v = -v;
 146         else
 147             v = v * 3;
 148         total_quant_bits[i] = 12 * v;
 149     }
 150
 151     return 0;
 152 }
 153
 154 /* 32 point floating point IDCT */
 155 static void idct32(int *out, int *tab, int sblimit, int left_shift)
 156 {
 157     int i, j;
 158     int *t, *t1, xr;
 159     const int *xp = costab32;
 160
 161     for(j=31;j>=3;j-=2) tab[j] += tab[j - 2];
 162
 163     t = tab + 30;
 164     t1 = tab + 2;
 165     do {
 166         t[0] += t[-4];
 167         t[1] += t[1 - 4];
 168         t -= 4;
 169     } while (t != t1);
 170
 171     t = tab + 28;
 172     t1 = tab + 4;
 173     do {
 174         t[0] += t[-8];
 175         t[1] += t[1-8];
 176         t[2] += t[2-8];
 177         t[3] += t[3-8];
 178         t -= 8;
 179     } while (t != t1);
 180
 181     t = tab;
 182     t1 = tab + 32;
 183     do {
 184         t[ 3] = -t[ 3];
 185         t[ 6] = -t[ 6];
 186
 187         t[11] = -t[11];
 188         t[12] = -t[12];
 189         t[13] = -t[13];
 190         t[15] = -t[15];
 191         t += 16;
 192     } while (t != t1);
 193
 194
 195     t = tab;
 196     t1 = tab + 8;
 197     do {
 198         int x1, x2, x3, x4;
 199
 200         x3 = MUL(t[16], FIX(SQRT2*0.5));
 201         x4 = t[0] - x3;
 202         x3 = t[0] + x3;
 203
 204         x2 = MUL(-(t[24] + t[8]), FIX(SQRT2*0.5));
 205         x1 = MUL((t[8] - x2), xp[0]);
 206         x2 = MUL((t[8] + x2), xp[1]);
 207
 208         t[ 0] = x3 + x1;
 209         t[ 8] = x4 - x2;
 210         t[16] = x4 + x2;
 211         t[24] = x3 - x1;
 212         t++;
 213     } while (t != t1);
 214
 215     xp += 2;
 216     t = tab;
 217     t1 = tab + 4;
 218     do {
 219         xr = MUL(t[28],xp[0]);
 220         t[28] = (t[0] - xr);
 221         t[0] = (t[0] + xr);
 222
 223         xr = MUL(t[4],xp[1]);
 224         t[ 4] = (t[24] - xr);
 225         t[24] = (t[24] + xr);
 226
 227         xr = MUL(t[20],xp[2]);
 228         t[20] = (t[8] - xr);
 229         t[ 8] = (t[8] + xr);
 230
 231         xr = MUL(t[12],xp[3]);
 232         t[12] = (t[16] - xr);
 233         t[16] = (t[16] + xr);
 234         t++;
 235     } while (t != t1);
 236     xp += 4;
 237
 238     for (i = 0; i < 4; i++) {
 239         xr = MUL(tab[30-i*4],xp[0]);
 240         tab[30-i*4] = (tab[i*4] - xr);
 241         tab[   i*4] = (tab[i*4] + xr);
 242
 243         xr = MUL(tab[ 2+i*4],xp[1]);
 244         tab[ 2+i*4] = (tab[28-i*4] - xr);
 245         tab[28-i*4] = (tab[28-i*4] + xr);
 246
 247         xr = MUL(tab[31-i*4],xp[0]);
 248         tab[31-i*4] = (tab[1+i*4] - xr);
 249         tab[ 1+i*4] = (tab[1+i*4] + xr);
 250
 251         xr = MUL(tab[ 3+i*4],xp[1]);
 252         tab[ 3+i*4] = (tab[29-i*4] - xr);
 253         tab[29-i*4] = (tab[29-i*4] + xr);
 254
 255         xp += 2;
 256     }
 257
 258     t = tab + 30;
 259     t1 = tab + 1;
 260     do {
 261         xr = MUL(t1[0], *xp);
 262         t1[0] = (t[0] - xr);
 263         t[0] = (t[0] + xr);
 264         t -= 2;
 265         t1 += 2;
 266         xp++;
 267     } while (t >= tab);
 268
 269     for(i=0;i<32;i++) {
 270         out[i] = tab[bitinv32[i]] << left_shift;
 271     }
 272 }
 273
 274 static void filter(MpegAudioContext *s, int ch, short *samples, int incr)
 275 {
 276     short *p, *q;
 277     int sum, offset, i, j, norm, n;
 278     short tmp[64];
 279     int tmp1[32];
 280     int *out;
 281
 282     //    print_pow1(samples, 1152);
 283
 284     offset = s->samples_offset[ch];
 285     out = &s->sb_samples[ch][0][0][0];
 286     for(j=0;j<36;j++) {
 287         /* 32 samples at once */
 288         for(i=0;i<32;i++) {
 289             s->samples_buf[ch][offset + (31 - i)] = samples[0];
 290             samples += incr;
 291         }
 292
 293         /* filter */
 294         p = s->samples_buf[ch] + offset;
 295         q = filter_bank;
 296         /* maxsum = 23169 */
 297         for(i=0;i<64;i++) {
 298             sum = p[0*64] * q[0*64];
 299             sum += p[1*64] * q[1*64];
 300             sum += p[2*64] * q[2*64];
 301             sum += p[3*64] * q[3*64];
 302             sum += p[4*64] * q[4*64];
 303             sum += p[5*64] * q[5*64];
 304             sum += p[6*64] * q[6*64];
 305             sum += p[7*64] * q[7*64];
 306             tmp[i] = sum >> 14;
 307             p++;
 308             q++;
 309         }
 310         tmp1[0] = tmp[16];
 311         for( i=1; i<=16; i++ ) tmp1[i] = tmp[i+16]+tmp[16-i];
 312         for( i=17; i<=31; i++ ) tmp1[i] = tmp[i+16]-tmp[80-i];
 313
 314         /* integer IDCT 32 with normalization. XXX: There may be some
 315            overflow left */
 316         norm = 0;
 317         for(i=0;i<32;i++) {
 318             norm |= abs(tmp1[i]);
 319         }
 320         n = av_log2(norm) - 12;
 321         if (n > 0) {
 322             for(i=0;i<32;i++)
 323                 tmp1[i] >>= n;
 324         } else {
 325             n = 0;
 326         }
 327
 328         idct32(out, tmp1, s->sblimit, n);
 329
 330         /* advance of 32 samples */
 331         offset -= 32;
 332         out += 32;
 333         /* handle the wrap around */
 334         if (offset < 0) {
 335             memmove(s->samples_buf[ch] + SAMPLES_BUF_SIZE - (512 - 32),
 336                     s->samples_buf[ch], (512 - 32) * 2);
 337             offset = SAMPLES_BUF_SIZE - 512;
 338         }
 339     }
 340     s->samples_offset[ch] = offset;
 341
 342     //    print_pow(s->sb_samples, 1152);
 343 }
 344
 345 static void compute_scale_factors(unsigned char scale_code[SBLIMIT],
 346                                   unsigned char scale_factors[SBLIMIT][3],
 347                                   int sb_samples[3][12][SBLIMIT],
 348                                   int sblimit)
 349 {
 350     int *p, vmax, v, n, i, j, k, code;
 351     int index, d1, d2;
 352     unsigned char *sf = &scale_factors[0][0];
 353
 354     for(j=0;j<sblimit;j++) {
 355         for(i=0;i<3;i++) {
 356             /* find the max absolute value */
 357             p = &sb_samples[i][0][j];
 358             vmax = abs(*p);
 359             for(k=1;k<12;k++) {
 360                 p += SBLIMIT;
 361                 v = abs(*p);
 362                 if (v > vmax)
 363                     vmax = v;
 364             }
 365             /* compute the scale factor index using log 2 computations */
 366             if (vmax > 0) {
 367                 n = av_log2(vmax);
 368                 /* n is the position of the MSB of vmax. now
 369                    use at most 2 compares to find the index */
 370                 index = (21 - n) * 3 - 3;
 371                 if (index >= 0) {
 372                     while (vmax <= scale_factor_table[index+1])
 373                         index++;
 374                 } else {
 375                     index = 0; /* very unlikely case of overflow */
 376                 }
 377             } else {
 378                 index = 63;
 379             }
 380
 381 #if 0
 382             printf("%2d:%d in=%x %x %d\n",
 383                    j, i, vmax, scale_factor_table[index], index);
 384 #endif
 385             /* store the scale factor */
 386             assert(index >=0 && index <= 63);
 387             sf[i] = index;
 388         }
 389
 390         /* compute the transmission factor : look if the scale factors
 391            are close enough to each other */
 392         d1 = scale_diff_table[sf[0] - sf[1] + 64];
 393         d2 = scale_diff_table[sf[1] - sf[2] + 64];
 394
 395         /* handle the 25 cases */
 396         switch(d1 * 5 + d2) {
 397         case 0*5+0:
 398         case 0*5+4:
 399         case 3*5+4:
 400         case 4*5+0:
 401         case 4*5+4:
 402             code = 0;
 403             break;
 404         case 0*5+1:
 405         case 0*5+2:
 406         case 4*5+1:
 407         case 4*5+2:
 408             code = 3;
 409             sf[2] = sf[1];
 410             break;
 411         case 0*5+3:
 412         case 4*5+3:
 413             code = 3;
 414             sf[1] = sf[2];
 415             break;
 416         case 1*5+0:
 417         case 1*5+4:
 418         case 2*5+4:
 419             code = 1;
 420             sf[1] = sf[0];
 421             break;
 422         case 1*5+1:
 423         case 1*5+2:
 424         case 2*5+0:
 425         case 2*5+1:
 426         case 2*5+2:
 427             code = 2;
 428             sf[1] = sf[2] = sf[0];
 429             break;
 430         case 2*5+3:
 431         case 3*5+3:
 432             code = 2;
 433             sf[0] = sf[1] = sf[2];
 434             break;
 435         case 3*5+0:
 436         case 3*5+1:
 437         case 3*5+2:
 438             code = 2;
 439             sf[0] = sf[2] = sf[1];
 440             break;
 441         case 1*5+3:
 442             code = 2;
 443             if (sf[0] > sf[2])
 444               sf[0] = sf[2];
 445             sf[1] = sf[2] = sf[0];
 446             break;
 447         default:
 448             abort();
 449         }
 450
 451 #if 0
 452         printf("%d: %2d %2d %2d %d %d -> %d\n", j,
 453                sf[0], sf[1], sf[2], d1, d2, code);
 454 #endif
 455         scale_code[j] = code;
 456         sf += 3;
 457     }
 458 }
 459
 460 /* The most important function : psycho acoustic module. In this
 461    encoder there is basically none, so this is the worst you can do,
 462    but also this is the simpler. */
 463 static void psycho_acoustic_model(MpegAudioContext *s, short smr[SBLIMIT])
 464 {
 465     int i;
 466
 467     for(i=0;i<s->sblimit;i++) {
 468         smr[i] = (int)(fixed_smr[i] * 10);
 469     }
 470 }
 471
 472
 473 #define SB_NOTALLOCATED  0
 474 #define SB_ALLOCATED     1
 475 #define SB_NOMORE        2
 476
 477 /* Try to maximize the smr while using a number of bits inferior to
 478    the frame size. I tried to make the code simpler, faster and
 479    smaller than other encoders :-) */
 480 static void compute_bit_allocation(MpegAudioContext *s,
 481                                    short smr1[MPA_MAX_CHANNELS][SBLIMIT],
 482                                    unsigned char bit_alloc[MPA_MAX_CHANNELS][SBLIMIT],
 483                                    int *padding)
 484 {
 485     int i, ch, b, max_smr, max_ch, max_sb, current_frame_size, max_frame_size;
 486     int incr;
 487     short smr[MPA_MAX_CHANNELS][SBLIMIT];
 488     unsigned char subband_status[MPA_MAX_CHANNELS][SBLIMIT];
 489     const unsigned char *alloc;
 490
 491     memcpy(smr, smr1, s->nb_channels * sizeof(short) * SBLIMIT);
 492     memset(subband_status, SB_NOTALLOCATED, s->nb_channels * SBLIMIT);
 493     memset(bit_alloc, 0, s->nb_channels * SBLIMIT);
 494
 495     /* compute frame size and padding */
 496     max_frame_size = s->frame_size;
 497     s->frame_frac += s->frame_frac_incr;
 498     if (s->frame_frac >= 65536) {
 499         s->frame_frac -= 65536;
 500         s->do_padding = 1;
 501         max_frame_size += 8;
 502     } else {
 503         s->do_padding = 0;
 504     }
 505
 506     /* compute the header + bit alloc size */
 507     current_frame_size = 32;
 508     alloc = s->alloc_table;
 509     for(i=0;i<s->sblimit;i++) {
 510         incr = alloc[0];
 511         current_frame_size += incr * s->nb_channels;
 512         alloc += 1 << incr;
 513     }
 514     for(;;) {
 515         /* look for the subband with the largest signal to mask ratio */
 516         max_sb = -1;
 517         max_ch = -1;
 518         max_smr = 0x80000000;
 519         for(ch=0;ch<s->nb_channels;ch++) {
 520             for(i=0;i<s->sblimit;i++) {
 521                 if (smr[ch][i] > max_smr && subband_status[ch][i] != SB_NOMORE) {
 522                     max_smr = smr[ch][i];
 523                     max_sb = i;
 524                     max_ch = ch;
 525                 }
 526             }
 527         }
 528 #if 0
 529         printf("current=%d max=%d max_sb=%d alloc=%d\n",
 530                current_frame_size, max_frame_size, max_sb,
 531                bit_alloc[max_sb]);
 532 #endif
 533         if (max_sb < 0)
 534             break;
 535
 536         /* find alloc table entry (XXX: not optimal, should use
 537            pointer table) */
 538         alloc = s->alloc_table;
 539         for(i=0;i<max_sb;i++) {
 540             alloc += 1 << alloc[0];
 541         }
 542
 543         if (subband_status[max_ch][max_sb] == SB_NOTALLOCATED) {
 544             /* nothing was coded for this band: add the necessary bits */
 545             incr = 2 + nb_scale_factors[s->scale_code[max_ch][max_sb]] * 6;
 546             incr += total_quant_bits[alloc[1]];
 547         } else {
 548             /* increments bit allocation */
 549             b = bit_alloc[max_ch][max_sb];
 550             incr = total_quant_bits[alloc[b + 1]] -
 551                 total_quant_bits[alloc[b]];
 552         }
 553
 554         if (current_frame_size + incr <= max_frame_size) {
 555             /* can increase size */
 556             b = ++bit_alloc[max_ch][max_sb];
 557             current_frame_size += incr;
 558             /* decrease smr by the resolution we added */
 559             smr[max_ch][max_sb] = smr1[max_ch][max_sb] - quant_snr[alloc[b]];
 560             /* max allocation size reached ? */
 561             if (b == ((1 << alloc[0]) - 1))
 562                 subband_status[max_ch][max_sb] = SB_NOMORE;
 563             else
 564                 subband_status[max_ch][max_sb] = SB_ALLOCATED;
 565         } else {
 566             /* cannot increase the size of this subband */
 567             subband_status[max_ch][max_sb] = SB_NOMORE;
 568         }
 569     }
 570     *padding = max_frame_size - current_frame_size;
 571     assert(*padding >= 0);
 572
 573 #if 0
 574     for(i=0;i<s->sblimit;i++) {
 575         printf("%d ", bit_alloc[i]);
 576     }
 577     printf("\n");
 578 #endif
 579 }
 580
 581 /*
 582  * Output the mpeg audio layer 2 frame. Note how the code is small
 583  * compared to other encoders :-)
 584  */
 585 static void encode_frame(MpegAudioContext *s,
 586                          unsigned char bit_alloc[MPA_MAX_CHANNELS][SBLIMIT],
 587                          int padding)
 588 {
 589     int i, j, k, l, bit_alloc_bits, b, ch;
 590     unsigned char *sf;
 591     int q[3];
 592     PutBitContext *p = &s->pb;
 593
 594     /* header */
 595
 596     put_bits(p, 12, 0xfff);
 597     put_bits(p, 1, 1 - s->lsf); /* 1 = mpeg1 ID, 0 = mpeg2 lsf ID */
 598     put_bits(p, 2, 4-2);  /* layer 2 */
 599     put_bits(p, 1, 1); /* no error protection */
 600     put_bits(p, 4, s->bitrate_index);
 601     put_bits(p, 2, s->freq_index);
 602     put_bits(p, 1, s->do_padding); /* use padding */
 603     put_bits(p, 1, 0);             /* private_bit */
 604     put_bits(p, 2, s->nb_channels == 2 ? MPA_STEREO : MPA_MONO);
 605     put_bits(p, 2, 0); /* mode_ext */
 606     put_bits(p, 1, 0); /* no copyright */
 607     put_bits(p, 1, 1); /* original */
 608     put_bits(p, 2, 0); /* no emphasis */
 609
 610     /* bit allocation */
 611     j = 0;
 612     for(i=0;i<s->sblimit;i++) {
 613         bit_alloc_bits = s->alloc_table[j];
 614         for(ch=0;ch<s->nb_channels;ch++) {
 615             put_bits(p, bit_alloc_bits, bit_alloc[ch][i]);
 616         }
 617         j += 1 << bit_alloc_bits;
 618     }
 619
 620     /* scale codes */
 621     for(i=0;i<s->sblimit;i++) {
 622         for(ch=0;ch<s->nb_channels;ch++) {
 623             if (bit_alloc[ch][i])
 624                 put_bits(p, 2, s->scale_code[ch][i]);
 625         }
 626     }
 627
 628     /* scale factors */
 629     for(i=0;i<s->sblimit;i++) {
 630         for(ch=0;ch<s->nb_channels;ch++) {
 631             if (bit_alloc[ch][i]) {
 632                 sf = &s->scale_factors[ch][i][0];
 633                 switch(s->scale_code[ch][i]) {
 634                 case 0:
 635                     put_bits(p, 6, sf[0]);
 636                     put_bits(p, 6, sf[1]);
 637                     put_bits(p, 6, sf[2]);
 638                     break;
 639                 case 3:
 640                 case 1:
 641                     put_bits(p, 6, sf[0]);
 642                     put_bits(p, 6, sf[2]);
 643                     break;
 644                 case 2:
 645                     put_bits(p, 6, sf[0]);
 646                     break;
 647                 }
 648             }
 649         }
 650     }
 651
 652     /* quantization & write sub band samples */
 653
 654     for(k=0;k<3;k++) {
 655         for(l=0;l<12;l+=3) {
 656             j = 0;
 657             for(i=0;i<s->sblimit;i++) {
 658                 bit_alloc_bits = s->alloc_table[j];
 659                 for(ch=0;ch<s->nb_channels;ch++) {
 660                     b = bit_alloc[ch][i];
 661                     if (b) {
 662                         int qindex, steps, m, sample, bits;
 663                         /* we encode 3 sub band samples of the same sub band at a time */
 664                         qindex = s->alloc_table[j+b];
 665                         steps = quant_steps[qindex];
 666                         for(m=0;m<3;m++) {
 667                             sample = s->sb_samples[ch][k][l + m][i];
 668                             /* divide by scale factor */
 669 #ifdef USE_FLOATS
 670                             {
 671                                 float a;
 672                                 a = (float)sample * scale_factor_inv_table[s->scale_factors[ch][i][k]];
 673                                 q[m] = (int)((a + 1.0) * steps * 0.5);
 674                             }
 675 #else
 676                             {
 677                                 int q1, e, shift, mult;
 678                                 e = s->scale_factors[ch][i][k];
 679                                 shift = scale_factor_shift[e];
 680                                 mult = scale_factor_mult[e];
 681
 682                                 /* normalize to P bits */
 683                                 if (shift < 0)
 684                                     q1 = sample << (-shift);
 685                                 else
 686                                     q1 = sample >> shift;
 687                                 q1 = (q1 * mult) >> P;
 688                                 q[m] = ((q1 + (1 << P)) * steps) >> (P + 1);
 689                             }
 690 #endif
 691                             if (q[m] >= steps)
 692                                 q[m] = steps - 1;
 693                             assert(q[m] >= 0 && q[m] < steps);
 694                         }
 695                         bits = quant_bits[qindex];
 696                         if (bits < 0) {
 697                             /* group the 3 values to save bits */
 698                             put_bits(p, -bits,
 699                                      q[0] + steps * (q[1] + steps * q[2]));
 700 #if 0
 701                             printf("%d: gr1 %d\n",
 702                                    i, q[0] + steps * (q[1] + steps * q[2]));
 703 #endif
 704                         } else {
 705 #if 0
 706                             printf("%d: gr3 %d %d %d\n",
 707                                    i, q[0], q[1], q[2]);
 708 #endif
 709                             put_bits(p, bits, q[0]);
 710                             put_bits(p, bits, q[1]);
 711                             put_bits(p, bits, q[2]);
 712                         }
 713                     }
 714                 }
 715                 /* next subband in alloc table */
 716                 j += 1 << bit_alloc_bits;
 717             }
 718         }
 719     }
 720
 721     /* padding */
 722     for(i=0;i<padding;i++)
 723         put_bits(p, 1, 0);
 724
 725     /* flush */
 726     flush_put_bits(p);
 727 }
 728
 729 int MPA_encode_frame(AVCodecContext *avctx,
 730                      unsigned char *frame, int buf_size, void *data)
 731 {
 732     MpegAudioContext *s = avctx->priv_data;
 733     short *samples = data;
 734     short smr[MPA_MAX_CHANNELS][SBLIMIT];
 735     unsigned char bit_alloc[MPA_MAX_CHANNELS][SBLIMIT];
 736     int padding, i;
 737
 738     for(i=0;i<s->nb_channels;i++) {
 739         filter(s, i, samples + i, s->nb_channels);
 740     }
 741
 742     for(i=0;i<s->nb_channels;i++) {
 743         compute_scale_factors(s->scale_code[i], s->scale_factors[i],
 744                               s->sb_samples[i], s->sblimit);
 745     }
 746     for(i=0;i<s->nb_channels;i++) {
 747         psycho_acoustic_model(s, smr[i]);
 748     }
 749     compute_bit_allocation(s, smr, bit_alloc, &padding);
 750
 751     init_put_bits(&s->pb, frame, MPA_MAX_CODED_FRAME_SIZE, NULL, NULL);
 752
 753     encode_frame(s, bit_alloc, padding);
 754
 755     s->nb_samples += MPA_FRAME_SIZE;
 756     return s->pb.buf_ptr - s->pb.buf;
 757 }
 758
 759
 760 AVCodec mp2_encoder = {
 761     "mp2",
 762     CODEC_TYPE_AUDIO,
 763     CODEC_ID_MP2,
 764     sizeof(MpegAudioContext),
 765     MPA_encode_init,
 766     MPA_encode_frame,
 767     NULL,
 768 };