hvirtual/quicktime/libavcodec/mpegaudio.c

   1 /*
   2  * The simplest mpeg audio layer 2 encoder
   3  * Copyright (c) 2000, 2001 Fabrice Bellard.
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the License, or (at your option) any later version.
   9  *
  10  * This library 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 GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this library; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18  */
  19 #include "avcodec.h"
  20 #include "mpegaudio.h"
  21
  22 /* currently, cannot change these constants (need to modify
  23    quantization stage) */
  24 #define FRAC_BITS 15
  25 #define WFRAC_BITS  14
  26 #define MUL(a,b) (((INT64)(a) * (INT64)(b)) >> FRAC_BITS)
  27 #define FIX(a)   ((int)((a) * (1 << FRAC_BITS)))
  28
  29 #define SAMPLES_BUF_SIZE 4096
  30
  31 typedef struct MpegAudioContext {
  32     PutBitContext pb;
  33     int nb_channels;
  34     int freq, bit_rate;
  35     int lsf;           /* 1 if mpeg2 low bitrate selected */
  36     int bitrate_index; /* bit rate */
  37     int freq_index;
  38     int frame_size; /* frame size, in bits, without padding */
  39     INT64 nb_samples; /* total number of samples encoded */
  40     /* padding computation */
  41     int frame_frac, frame_frac_incr, do_padding;
  42     short samples_buf[MPA_MAX_CHANNELS][SAMPLES_BUF_SIZE]; /* buffer for filter */
  43     int samples_offset[MPA_MAX_CHANNELS];       /* offset in samples_buf */
  44     int sb_samples[MPA_MAX_CHANNELS][3][12][SBLIMIT];
  45     unsigned char scale_factors[MPA_MAX_CHANNELS][SBLIMIT][3]; /* scale factors */
  46     /* code to group 3 scale factors */
  47     unsigned char scale_code[MPA_MAX_CHANNELS][SBLIMIT];
  48     int sblimit; /* number of used subbands */
  49     const unsigned char *alloc_table;
  50 } MpegAudioContext;
  51
  52 /* define it to use floats in quantization (I don't like floats !) */
  53 //#define USE_FLOATS
  54
  55 #include "mpegaudiotab.h"
  56
  57 int MPA_encode_init(AVCodecContext *avctx)
  58 {
  59     MpegAudioContext *s = avctx->priv_data;
  60     int freq = avctx->sample_rate;
  61     int bitrate = avctx->bit_rate;
  62     int channels = avctx->channels;
  63     int i, v, table;
  64     float a;
  65
  66     if (channels > 2)
  67         return -1;
  68     bitrate = bitrate / 1000;
  69     s->nb_channels = channels;
  70     s->freq = freq;
  71     s->bit_rate = bitrate * 1000;
  72     avctx->frame_size = MPA_FRAME_SIZE;
  73
  74     /* encoding freq */
  75     s->lsf = 0;
  76     for(i=0;i<3;i++) {
  77         if (mpa_freq_tab[i] == freq)
  78             break;
  79         if ((mpa_freq_tab[i] / 2) == freq) {
  80             s->lsf = 1;
  81             break;
  82         }
  83     }
  84     if (i == 3)
  85         return -1;
  86     s->freq_index = i;
  87
  88     /* encoding bitrate & frequency */
  89     for(i=0;i<15;i++) {
  90         if (mpa_bitrate_tab[s->lsf][1][i] == bitrate)
  91             break;
  92     }
  93     if (i == 15)
  94         return -1;
  95     s->bitrate_index = i;
  96
  97     /* compute total header size & pad bit */
  98
  99     a = (float)(bitrate * 1000 * MPA_FRAME_SIZE) / (freq * 8.0);
 100     s->frame_size = ((int)a) * 8;
 101
 102     /* frame fractional size to compute padding */
 103     s->frame_frac = 0;
 104     s->frame_frac_incr = (int)((a - floor(a)) * 65536.0);
 105
 106     /* select the right allocation table */
 107     table = l2_select_table(bitrate, s->nb_channels, freq, s->lsf);
 108
 109     /* number of used subbands */
 110     s->sblimit = sblimit_table[table];
 111     s->alloc_table = alloc_tables[table];
 112
 113 #ifdef DEBUG
 114     printf("%d kb/s, %d Hz, frame_size=%d bits, table=%d, padincr=%x\n",
 115            bitrate, freq, s->frame_size, table, s->frame_frac_incr);
 116 #endif
 117
 118     for(i=0;i<s->nb_channels;i++)
 119         s->samples_offset[i] = 0;
 120
 121     for(i=0;i<257;i++) {
 122         int v;
 123         v = mpa_enwindow[i];
 124 #if WFRAC_BITS != 16
 125         v = (v + (1 << (16 - WFRAC_BITS - 1))) >> (16 - WFRAC_BITS);
 126 #endif
 127         filter_bank[i] = v;
 128         if ((i & 63) != 0)
 129             v = -v;
 130         if (i != 0)
 131             filter_bank[512 - i] = v;
 132     }
 133
 134     for(i=0;i<64;i++) {
 135         v = (int)(pow(2.0, (3 - i) / 3.0) * (1 << 20));
 136         if (v <= 0)
 137             v = 1;
 138         scale_factor_table[i] = v;
 139 #ifdef USE_FLOATS
 140         scale_factor_inv_table[i] = pow(2.0, -(3 - i) / 3.0) / (float)(1 << 20);
 141 #else
 142 #define P 15
 143         scale_factor_shift[i] = 21 - P - (i / 3);
 144         scale_factor_mult[i] = (1 << P) * pow(2.0, (i % 3) / 3.0);
 145 #endif
 146     }
 147     for(i=0;i<128;i++) {
 148         v = i - 64;
 149         if (v <= -3)
 150             v = 0;
 151         else if (v < 0)
 152             v = 1;
 153         else if (v == 0)
 154             v = 2;
 155         else if (v < 3)
 156             v = 3;
 157         else
 158             v = 4;
 159         scale_diff_table[i] = v;
 160     }
 161
 162     for(i=0;i<17;i++) {
 163         v = quant_bits[i];
 164         if (v < 0)
 165             v = -v;
 166         else
 167             v = v * 3;
 168         total_quant_bits[i] = 12 * v;
 169     }
 170
 171     avctx->coded_frame= avcodec_alloc_frame();
 172     avctx->coded_frame->key_frame= 1;
 173
 174     return 0;
 175 }
 176
 177 /* 32 point floating point IDCT without 1/sqrt(2) coef zero scaling */
 178 static void idct32(int *out, int *tab)
 179 {
 180     int i, j;
 181     int *t, *t1, xr;
 182     const int *xp = costab32;
 183
 184     for(j=31;j>=3;j-=2) tab[j] += tab[j - 2];
 185
 186     t = tab + 30;
 187     t1 = tab + 2;
 188     do {
 189         t[0] += t[-4];
 190         t[1] += t[1 - 4];
 191         t -= 4;
 192     } while (t != t1);
 193
 194     t = tab + 28;
 195     t1 = tab + 4;
 196     do {
 197         t[0] += t[-8];
 198         t[1] += t[1-8];
 199         t[2] += t[2-8];
 200         t[3] += t[3-8];
 201         t -= 8;
 202     } while (t != t1);
 203
 204     t = tab;
 205     t1 = tab + 32;
 206     do {
 207         t[ 3] = -t[ 3];
 208         t[ 6] = -t[ 6];
 209
 210         t[11] = -t[11];
 211         t[12] = -t[12];
 212         t[13] = -t[13];
 213         t[15] = -t[15];
 214         t += 16;
 215     } while (t != t1);
 216
 217
 218     t = tab;
 219     t1 = tab + 8;
 220     do {
 221         int x1, x2, x3, x4;
 222
 223         x3 = MUL(t[16], FIX(SQRT2*0.5));
 224         x4 = t[0] - x3;
 225         x3 = t[0] + x3;
 226
 227         x2 = MUL(-(t[24] + t[8]), FIX(SQRT2*0.5));
 228         x1 = MUL((t[8] - x2), xp[0]);
 229         x2 = MUL((t[8] + x2), xp[1]);
 230
 231         t[ 0] = x3 + x1;
 232         t[ 8] = x4 - x2;
 233         t[16] = x4 + x2;
 234         t[24] = x3 - x1;
 235         t++;
 236     } while (t != t1);
 237
 238     xp += 2;
 239     t = tab;
 240     t1 = tab + 4;
 241     do {
 242         xr = MUL(t[28],xp[0]);
 243         t[28] = (t[0] - xr);
 244         t[0] = (t[0] + xr);
 245
 246         xr = MUL(t[4],xp[1]);
 247         t[ 4] = (t[24] - xr);
 248         t[24] = (t[24] + xr);
 249
 250         xr = MUL(t[20],xp[2]);
 251         t[20] = (t[8] - xr);
 252         t[ 8] = (t[8] + xr);
 253
 254         xr = MUL(t[12],xp[3]);
 255         t[12] = (t[16] - xr);
 256         t[16] = (t[16] + xr);
 257         t++;
 258     } while (t != t1);
 259     xp += 4;
 260
 261     for (i = 0; i < 4; i++) {
 262         xr = MUL(tab[30-i*4],xp[0]);
 263         tab[30-i*4] = (tab[i*4] - xr);
 264         tab[   i*4] = (tab[i*4] + xr);
 265
 266         xr = MUL(tab[ 2+i*4],xp[1]);
 267         tab[ 2+i*4] = (tab[28-i*4] - xr);
 268         tab[28-i*4] = (tab[28-i*4] + xr);
 269
 270         xr = MUL(tab[31-i*4],xp[0]);
 271         tab[31-i*4] = (tab[1+i*4] - xr);
 272         tab[ 1+i*4] = (tab[1+i*4] + xr);
 273
 274         xr = MUL(tab[ 3+i*4],xp[1]);
 275         tab[ 3+i*4] = (tab[29-i*4] - xr);
 276         tab[29-i*4] = (tab[29-i*4] + xr);
 277
 278         xp += 2;
 279     }
 280
 281     t = tab + 30;
 282     t1 = tab + 1;
 283     do {
 284         xr = MUL(t1[0], *xp);
 285         t1[0] = (t[0] - xr);
 286         t[0] = (t[0] + xr);
 287         t -= 2;
 288         t1 += 2;
 289         xp++;
 290     } while (t >= tab);
 291
 292     for(i=0;i<32;i++) {
 293         out[i] = tab[bitinv32[i]];
 294     }
 295 }
 296
 297 #define WSHIFT (WFRAC_BITS + 15 - FRAC_BITS)
 298
 299 static void filter(MpegAudioContext *s, int ch, short *samples, int incr)
 300 {
 301     short *p, *q;
 302     int sum, offset, i, j;
 303     int tmp[64];
 304     int tmp1[32];
 305     int *out;
 306
 307     //    print_pow1(samples, 1152);
 308
 309     offset = s->samples_offset[ch];
 310     out = &s->sb_samples[ch][0][0][0];
 311     for(j=0;j<36;j++) {
 312         /* 32 samples at once */
 313         for(i=0;i<32;i++) {
 314             s->samples_buf[ch][offset + (31 - i)] = samples[0];
 315             samples += incr;
 316         }
 317
 318         /* filter */
 319         p = s->samples_buf[ch] + offset;
 320         q = filter_bank;
 321         /* maxsum = 23169 */
 322         for(i=0;i<64;i++) {
 323             sum = p[0*64] * q[0*64];
 324             sum += p[1*64] * q[1*64];
 325             sum += p[2*64] * q[2*64];
 326             sum += p[3*64] * q[3*64];
 327             sum += p[4*64] * q[4*64];
 328             sum += p[5*64] * q[5*64];
 329             sum += p[6*64] * q[6*64];
 330             sum += p[7*64] * q[7*64];
 331             tmp[i] = sum;
 332             p++;
 333             q++;
 334         }
 335         tmp1[0] = tmp[16] >> WSHIFT;
 336         for( i=1; i<=16; i++ ) tmp1[i] = (tmp[i+16]+tmp[16-i]) >> WSHIFT;
 337         for( i=17; i<=31; i++ ) tmp1[i] = (tmp[i+16]-tmp[80-i]) >> WSHIFT;
 338
 339         idct32(out, tmp1);
 340
 341         /* advance of 32 samples */
 342         offset -= 32;
 343         out += 32;
 344         /* handle the wrap around */
 345         if (offset < 0) {
 346             memmove(s->samples_buf[ch] + SAMPLES_BUF_SIZE - (512 - 32),
 347                     s->samples_buf[ch], (512 - 32) * 2);
 348             offset = SAMPLES_BUF_SIZE - 512;
 349         }
 350     }
 351     s->samples_offset[ch] = offset;
 352
 353     //    print_pow(s->sb_samples, 1152);
 354 }
 355
 356 static void compute_scale_factors(unsigned char scale_code[SBLIMIT],
 357                                   unsigned char scale_factors[SBLIMIT][3],
 358                                   int sb_samples[3][12][SBLIMIT],
 359                                   int sblimit)
 360 {
 361     int *p, vmax, v, n, i, j, k, code;
 362     int index, d1, d2;
 363     unsigned char *sf = &scale_factors[0][0];
 364
 365     for(j=0;j<sblimit;j++) {
 366         for(i=0;i<3;i++) {
 367             /* find the max absolute value */
 368             p = &sb_samples[i][0][j];
 369             vmax = abs(*p);
 370             for(k=1;k<12;k++) {
 371                 p += SBLIMIT;
 372                 v = abs(*p);
 373                 if (v > vmax)
 374                     vmax = v;
 375             }
 376             /* compute the scale factor index using log 2 computations */
 377             if (vmax > 0) {
 378                 n = av_log2(vmax);
 379                 /* n is the position of the MSB of vmax. now
 380                    use at most 2 compares to find the index */
 381                 index = (21 - n) * 3 - 3;
 382                 if (index >= 0) {
 383                     while (vmax <= scale_factor_table[index+1])
 384                         index++;
 385                 } else {
 386                     index = 0; /* very unlikely case of overflow */
 387                 }
 388             } else {
 389                 index = 62; /* value 63 is not allowed */
 390             }
 391
 392 #if 0
 393             printf("%2d:%d in=%x %x %d\n",
 394                    j, i, vmax, scale_factor_table[index], index);
 395 #endif
 396             /* store the scale factor */
 397             assert(index >=0 && index <= 63);
 398             sf[i] = index;
 399         }
 400
 401         /* compute the transmission factor : look if the scale factors
 402            are close enough to each other */
 403         d1 = scale_diff_table[sf[0] - sf[1] + 64];
 404         d2 = scale_diff_table[sf[1] - sf[2] + 64];
 405
 406         /* handle the 25 cases */
 407         switch(d1 * 5 + d2) {
 408         case 0*5+0:
 409         case 0*5+4:
 410         case 3*5+4:
 411         case 4*5+0:
 412         case 4*5+4:
 413             code = 0;
 414             break;
 415         case 0*5+1:
 416         case 0*5+2:
 417         case 4*5+1:
 418         case 4*5+2:
 419             code = 3;
 420             sf[2] = sf[1];
 421             break;
 422         case 0*5+3:
 423         case 4*5+3:
 424             code = 3;
 425             sf[1] = sf[2];
 426             break;
 427         case 1*5+0:
 428         case 1*5+4:
 429         case 2*5+4:
 430             code = 1;
 431             sf[1] = sf[0];
 432             break;
 433         case 1*5+1:
 434         case 1*5+2:
 435         case 2*5+0:
 436         case 2*5+1:
 437         case 2*5+2:
 438             code = 2;
 439             sf[1] = sf[2] = sf[0];
 440             break;
 441         case 2*5+3:
 442         case 3*5+3:
 443             code = 2;
 444             sf[0] = sf[1] = sf[2];
 445             break;
 446         case 3*5+0:
 447         case 3*5+1:
 448         case 3*5+2:
 449             code = 2;
 450             sf[0] = sf[2] = sf[1];
 451             break;
 452         case 1*5+3:
 453             code = 2;
 454             if (sf[0] > sf[2])
 455               sf[0] = sf[2];
 456             sf[1] = sf[2] = sf[0];
 457             break;
 458         default:
 459             av_abort();
 460         }
 461
 462 #if 0
 463         printf("%d: %2d %2d %2d %d %d -> %d\n", j,
 464                sf[0], sf[1], sf[2], d1, d2, code);
 465 #endif
 466         scale_code[j] = code;
 467         sf += 3;
 468     }
 469 }
 470
 471 /* The most important function : psycho acoustic module. In this
 472    encoder there is basically none, so this is the worst you can do,
 473    but also this is the simpler. */
 474 static void psycho_acoustic_model(MpegAudioContext *s, short smr[SBLIMIT])
 475 {
 476     int i;
 477
 478     for(i=0;i<s->sblimit;i++) {
 479         smr[i] = (int)(fixed_smr[i] * 10);
 480     }
 481 }
 482
 483
 484 #define SB_NOTALLOCATED  0
 485 #define SB_ALLOCATED     1
 486 #define SB_NOMORE        2
 487
 488 /* Try to maximize the smr while using a number of bits inferior to
 489    the frame size. I tried to make the code simpler, faster and
 490    smaller than other encoders :-) */
 491 static void compute_bit_allocation(MpegAudioContext *s,
 492                                    short smr1[MPA_MAX_CHANNELS][SBLIMIT],
 493                                    unsigned char bit_alloc[MPA_MAX_CHANNELS][SBLIMIT],
 494                                    int *padding)
 495 {
 496     int i, ch, b, max_smr, max_ch, max_sb, current_frame_size, max_frame_size;
 497     int incr;
 498     short smr[MPA_MAX_CHANNELS][SBLIMIT];
 499     unsigned char subband_status[MPA_MAX_CHANNELS][SBLIMIT];
 500     const unsigned char *alloc;
 501
 502     memcpy(smr, smr1, s->nb_channels * sizeof(short) * SBLIMIT);
 503     memset(subband_status, SB_NOTALLOCATED, s->nb_channels * SBLIMIT);
 504     memset(bit_alloc, 0, s->nb_channels * SBLIMIT);
 505
 506     /* compute frame size and padding */
 507     max_frame_size = s->frame_size;
 508     s->frame_frac += s->frame_frac_incr;
 509     if (s->frame_frac >= 65536) {
 510         s->frame_frac -= 65536;
 511         s->do_padding = 1;
 512         max_frame_size += 8;
 513     } else {
 514         s->do_padding = 0;
 515     }
 516
 517     /* compute the header + bit alloc size */
 518     current_frame_size = 32;
 519     alloc = s->alloc_table;
 520     for(i=0;i<s->sblimit;i++) {
 521         incr = alloc[0];
 522         current_frame_size += incr * s->nb_channels;
 523         alloc += 1 << incr;
 524     }
 525     for(;;) {
 526         /* look for the subband with the largest signal to mask ratio */
 527         max_sb = -1;
 528         max_ch = -1;
 529         max_smr = 0x80000000;
 530         for(ch=0;ch<s->nb_channels;ch++) {
 531             for(i=0;i<s->sblimit;i++) {
 532                 if (smr[ch][i] > max_smr && subband_status[ch][i] != SB_NOMORE) {
 533                     max_smr = smr[ch][i];
 534                     max_sb = i;
 535                     max_ch = ch;
 536                 }
 537             }
 538         }
 539 #if 0
 540         printf("current=%d max=%d max_sb=%d alloc=%d\n",
 541                current_frame_size, max_frame_size, max_sb,
 542                bit_alloc[max_sb]);
 543 #endif
 544         if (max_sb < 0)
 545             break;
 546
 547         /* find alloc table entry (XXX: not optimal, should use
 548            pointer table) */
 549         alloc = s->alloc_table;
 550         for(i=0;i<max_sb;i++) {
 551             alloc += 1 << alloc[0];
 552         }
 553
 554         if (subband_status[max_ch][max_sb] == SB_NOTALLOCATED) {
 555             /* nothing was coded for this band: add the necessary bits */
 556             incr = 2 + nb_scale_factors[s->scale_code[max_ch][max_sb]] * 6;
 557             incr += total_quant_bits[alloc[1]];
 558         } else {
 559             /* increments bit allocation */
 560             b = bit_alloc[max_ch][max_sb];
 561             incr = total_quant_bits[alloc[b + 1]] -
 562                 total_quant_bits[alloc[b]];
 563         }
 564
 565         if (current_frame_size + incr <= max_frame_size) {
 566             /* can increase size */
 567             b = ++bit_alloc[max_ch][max_sb];
 568             current_frame_size += incr;
 569             /* decrease smr by the resolution we added */
 570             smr[max_ch][max_sb] = smr1[max_ch][max_sb] - quant_snr[alloc[b]];
 571             /* max allocation size reached ? */
 572             if (b == ((1 << alloc[0]) - 1))
 573                 subband_status[max_ch][max_sb] = SB_NOMORE;
 574             else
 575                 subband_status[max_ch][max_sb] = SB_ALLOCATED;
 576         } else {
 577             /* cannot increase the size of this subband */
 578             subband_status[max_ch][max_sb] = SB_NOMORE;
 579         }
 580     }
 581     *padding = max_frame_size - current_frame_size;
 582     assert(*padding >= 0);
 583
 584 #if 0
 585     for(i=0;i<s->sblimit;i++) {
 586         printf("%d ", bit_alloc[i]);
 587     }
 588     printf("\n");
 589 #endif
 590 }
 591
 592 /*
 593  * Output the mpeg audio layer 2 frame. Note how the code is small
 594  * compared to other encoders :-)
 595  */
 596 static void encode_frame(MpegAudioContext *s,
 597                          unsigned char bit_alloc[MPA_MAX_CHANNELS][SBLIMIT],
 598                          int padding)
 599 {
 600     int i, j, k, l, bit_alloc_bits, b, ch;
 601     unsigned char *sf;
 602     int q[3];
 603     PutBitContext *p = &s->pb;
 604
 605     /* header */
 606
 607     put_bits(p, 12, 0xfff);
 608     put_bits(p, 1, 1 - s->lsf); /* 1 = mpeg1 ID, 0 = mpeg2 lsf ID */
 609     put_bits(p, 2, 4-2);  /* layer 2 */
 610     put_bits(p, 1, 1); /* no error protection */
 611     put_bits(p, 4, s->bitrate_index);
 612     put_bits(p, 2, s->freq_index);
 613     put_bits(p, 1, s->do_padding); /* use padding */
 614     put_bits(p, 1, 0);             /* private_bit */
 615     put_bits(p, 2, s->nb_channels == 2 ? MPA_STEREO : MPA_MONO);
 616     put_bits(p, 2, 0); /* mode_ext */
 617     put_bits(p, 1, 0); /* no copyright */
 618     put_bits(p, 1, 1); /* original */
 619     put_bits(p, 2, 0); /* no emphasis */
 620
 621     /* bit allocation */
 622     j = 0;
 623     for(i=0;i<s->sblimit;i++) {
 624         bit_alloc_bits = s->alloc_table[j];
 625         for(ch=0;ch<s->nb_channels;ch++) {
 626             put_bits(p, bit_alloc_bits, bit_alloc[ch][i]);
 627         }
 628         j += 1 << bit_alloc_bits;
 629     }
 630
 631     /* scale codes */
 632     for(i=0;i<s->sblimit;i++) {
 633         for(ch=0;ch<s->nb_channels;ch++) {
 634             if (bit_alloc[ch][i])
 635                 put_bits(p, 2, s->scale_code[ch][i]);
 636         }
 637     }
 638
 639     /* scale factors */
 640     for(i=0;i<s->sblimit;i++) {
 641         for(ch=0;ch<s->nb_channels;ch++) {
 642             if (bit_alloc[ch][i]) {
 643                 sf = &s->scale_factors[ch][i][0];
 644                 switch(s->scale_code[ch][i]) {
 645                 case 0:
 646                     put_bits(p, 6, sf[0]);
 647                     put_bits(p, 6, sf[1]);
 648                     put_bits(p, 6, sf[2]);
 649                     break;
 650                 case 3:
 651                 case 1:
 652                     put_bits(p, 6, sf[0]);
 653                     put_bits(p, 6, sf[2]);
 654                     break;
 655                 case 2:
 656                     put_bits(p, 6, sf[0]);
 657                     break;
 658                 }
 659             }
 660         }
 661     }
 662
 663     /* quantization & write sub band samples */
 664
 665     for(k=0;k<3;k++) {
 666         for(l=0;l<12;l+=3) {
 667             j = 0;
 668             for(i=0;i<s->sblimit;i++) {
 669                 bit_alloc_bits = s->alloc_table[j];
 670                 for(ch=0;ch<s->nb_channels;ch++) {
 671                     b = bit_alloc[ch][i];
 672                     if (b) {
 673                         int qindex, steps, m, sample, bits;
 674                         /* we encode 3 sub band samples of the same sub band at a time */
 675                         qindex = s->alloc_table[j+b];
 676                         steps = quant_steps[qindex];
 677                         for(m=0;m<3;m++) {
 678                             sample = s->sb_samples[ch][k][l + m][i];
 679                             /* divide by scale factor */
 680 #ifdef USE_FLOATS
 681                             {
 682                                 float a;
 683                                 a = (float)sample * scale_factor_inv_table[s->scale_factors[ch][i][k]];
 684                                 q[m] = (int)((a + 1.0) * steps * 0.5);
 685                             }
 686 #else
 687                             {
 688                                 int q1, e, shift, mult;
 689                                 e = s->scale_factors[ch][i][k];
 690                                 shift = scale_factor_shift[e];
 691                                 mult = scale_factor_mult[e];
 692
 693                                 /* normalize to P bits */
 694                                 if (shift < 0)
 695                                     q1 = sample << (-shift);
 696                                 else
 697                                     q1 = sample >> shift;
 698                                 q1 = (q1 * mult) >> P;
 699                                 q[m] = ((q1 + (1 << P)) * steps) >> (P + 1);
 700                             }
 701 #endif
 702                             if (q[m] >= steps)
 703                                 q[m] = steps - 1;
 704                             assert(q[m] >= 0 && q[m] < steps);
 705                         }
 706                         bits = quant_bits[qindex];
 707                         if (bits < 0) {
 708                             /* group the 3 values to save bits */
 709                             put_bits(p, -bits,
 710                                      q[0] + steps * (q[1] + steps * q[2]));
 711 #if 0
 712                             printf("%d: gr1 %d\n",
 713                                    i, q[0] + steps * (q[1] + steps * q[2]));
 714 #endif
 715                         } else {
 716 #if 0
 717                             printf("%d: gr3 %d %d %d\n",
 718                                    i, q[0], q[1], q[2]);
 719 #endif
 720                             put_bits(p, bits, q[0]);
 721                             put_bits(p, bits, q[1]);
 722                             put_bits(p, bits, q[2]);
 723                         }
 724                     }
 725                 }
 726                 /* next subband in alloc table */
 727                 j += 1 << bit_alloc_bits;
 728             }
 729         }
 730     }
 731
 732     /* padding */
 733     for(i=0;i<padding;i++)
 734         put_bits(p, 1, 0);
 735
 736     /* flush */
 737     flush_put_bits(p);
 738 }
 739
 740 int MPA_encode_frame(AVCodecContext *avctx,
 741                      unsigned char *frame, int buf_size, void *data)
 742 {
 743     MpegAudioContext *s = avctx->priv_data;
 744     short *samples = data;
 745     short smr[MPA_MAX_CHANNELS][SBLIMIT];
 746     unsigned char bit_alloc[MPA_MAX_CHANNELS][SBLIMIT];
 747     int padding, i;
 748
 749     for(i=0;i<s->nb_channels;i++) {
 750         filter(s, i, samples + i, s->nb_channels);
 751     }
 752
 753     for(i=0;i<s->nb_channels;i++) {
 754         compute_scale_factors(s->scale_code[i], s->scale_factors[i],
 755                               s->sb_samples[i], s->sblimit);
 756     }
 757     for(i=0;i<s->nb_channels;i++) {
 758         psycho_acoustic_model(s, smr[i]);
 759     }
 760     compute_bit_allocation(s, smr, bit_alloc, &padding);
 761
 762     init_put_bits(&s->pb, frame, MPA_MAX_CODED_FRAME_SIZE, NULL, NULL);
 763
 764     encode_frame(s, bit_alloc, padding);
 765
 766     s->nb_samples += MPA_FRAME_SIZE;
 767     return pbBufPtr(&s->pb) - s->pb.buf;
 768 }
 769
 770 static int MPA_encode_close(AVCodecContext *avctx)
 771 {
 772     av_freep(&avctx->coded_frame);
 773 }
 774
 775 AVCodec mp2_encoder = {
 776     "mp2",
 777     CODEC_TYPE_AUDIO,
 778     CODEC_ID_MP2,
 779     sizeof(MpegAudioContext),
 780     MPA_encode_init,
 781     MPA_encode_frame,
 782     MPA_encode_close,
 783     NULL,
 784 };
 785
 786 #undef FIX