FFmpeg: libavcodec/ac3enc.c Source File

00001 /*
00002  * The simplest AC-3 encoder
00003  * Copyright (c) 2000 Fabrice Bellard
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * FFmpeg is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with FFmpeg; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00026 //#define DEBUG
00027 //#define DEBUG_BITALLOC
00028 #include "libavutil/crc.h"
00029 #include "avcodec.h"
00030 #include "libavutil/common.h" /* for av_reverse */
00031 #include "put_bits.h"
00032 #include "ac3.h"
00033 #include "audioconvert.h"
00034 
00035 typedef struct AC3EncodeContext {
00036     PutBitContext pb;
00037     int nb_channels;
00038     int nb_all_channels;
00039     int lfe_channel;
00040     const uint8_t *channel_map;
00041     int bit_rate;
00042     unsigned int sample_rate;
00043     unsigned int bitstream_id;
00044     unsigned int frame_size_min; /* minimum frame size in case rounding is necessary */
00045     unsigned int frame_size; /* current frame size in words */
00046     unsigned int bits_written;
00047     unsigned int samples_written;
00048     int sr_shift;
00049     unsigned int frame_size_code;
00050     unsigned int sr_code; /* frequency */
00051     unsigned int channel_mode;
00052     int lfe;
00053     unsigned int bitstream_mode;
00054     short last_samples[AC3_MAX_CHANNELS][256];
00055     unsigned int chbwcod[AC3_MAX_CHANNELS];
00056     int nb_coefs[AC3_MAX_CHANNELS];
00057 
00058     /* bitrate allocation control */
00059     int slow_gain_code, slow_decay_code, fast_decay_code, db_per_bit_code, floor_code;
00060     AC3BitAllocParameters bit_alloc;
00061     int coarse_snr_offset;
00062     int fast_gain_code[AC3_MAX_CHANNELS];
00063     int fine_snr_offset[AC3_MAX_CHANNELS];
00064     /* mantissa encoding */
00065     int mant1_cnt, mant2_cnt, mant4_cnt;
00066 } AC3EncodeContext;
00067 
00068 static int16_t costab[64];
00069 static int16_t sintab[64];
00070 static int16_t xcos1[128];
00071 static int16_t xsin1[128];
00072 
00073 #define MDCT_NBITS 9
00074 #define N         (1 << MDCT_NBITS)
00075 
00076 /* new exponents are sent if their Norm 1 exceed this number */
00077 #define EXP_DIFF_THRESHOLD 1000
00078 
00079 static inline int16_t fix15(float a)
00080 {
00081     int v;
00082     v = (int)(a * (float)(1 << 15));
00083     if (v < -32767)
00084         v = -32767;
00085     else if (v > 32767)
00086         v = 32767;
00087     return v;
00088 }
00089 
00090 typedef struct IComplex {
00091     short re,im;
00092 } IComplex;
00093 
00094 static av_cold void fft_init(int ln)
00095 {
00096     int i, n;
00097     float alpha;
00098 
00099     n = 1 << ln;
00100 
00101     for(i=0;i<(n/2);i++) {
00102         alpha = 2 * M_PI * (float)i / (float)n;
00103         costab[i] = fix15(cos(alpha));
00104         sintab[i] = fix15(sin(alpha));
00105     }
00106 }
00107 
00108 /* butter fly op */
00109 #define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
00110 {\
00111   int ax, ay, bx, by;\
00112   bx=pre1;\
00113   by=pim1;\
00114   ax=qre1;\
00115   ay=qim1;\
00116   pre = (bx + ax) >> 1;\
00117   pim = (by + ay) >> 1;\
00118   qre = (bx - ax) >> 1;\
00119   qim = (by - ay) >> 1;\
00120 }
00121 
00122 #define CMUL(pre, pim, are, aim, bre, bim) \
00123 {\
00124    pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15;\
00125    pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\
00126 }
00127 
00128 
00129 /* do a 2^n point complex fft on 2^ln points. */
00130 static void fft(IComplex *z, int ln)
00131 {
00132     int        j, l, np, np2;
00133     int        nblocks, nloops;
00134     register IComplex *p,*q;
00135     int tmp_re, tmp_im;
00136 
00137     np = 1 << ln;
00138 
00139     /* reverse */
00140     for(j=0;j<np;j++) {
00141         int k = av_reverse[j] >> (8 - ln);
00142         if (k < j)
00143             FFSWAP(IComplex, z[k], z[j]);
00144     }
00145 
00146     /* pass 0 */
00147 
00148     p=&z[0];
00149     j=(np >> 1);
00150     do {
00151         BF(p[0].re, p[0].im, p[1].re, p[1].im,
00152            p[0].re, p[0].im, p[1].re, p[1].im);
00153         p+=2;
00154     } while (--j != 0);
00155 
00156     /* pass 1 */
00157 
00158     p=&z[0];
00159     j=np >> 2;
00160     do {
00161         BF(p[0].re, p[0].im, p[2].re, p[2].im,
00162            p[0].re, p[0].im, p[2].re, p[2].im);
00163         BF(p[1].re, p[1].im, p[3].re, p[3].im,
00164            p[1].re, p[1].im, p[3].im, -p[3].re);
00165         p+=4;
00166     } while (--j != 0);
00167 
00168     /* pass 2 .. ln-1 */
00169 
00170     nblocks = np >> 3;
00171     nloops = 1 << 2;
00172     np2 = np >> 1;
00173     do {
00174         p = z;
00175         q = z + nloops;
00176         for (j = 0; j < nblocks; ++j) {
00177 
00178             BF(p->re, p->im, q->re, q->im,
00179                p->re, p->im, q->re, q->im);
00180 
00181             p++;
00182             q++;
00183             for(l = nblocks; l < np2; l += nblocks) {
00184                 CMUL(tmp_re, tmp_im, costab[l], -sintab[l], q->re, q->im);
00185                 BF(p->re, p->im, q->re, q->im,
00186                    p->re, p->im, tmp_re, tmp_im);
00187                 p++;
00188                 q++;
00189             }
00190             p += nloops;
00191             q += nloops;
00192         }
00193         nblocks = nblocks >> 1;
00194         nloops = nloops << 1;
00195     } while (nblocks != 0);
00196 }
00197 
00198 /* do a 512 point mdct */
00199 static void mdct512(int32_t *out, int16_t *in)
00200 {
00201     int i, re, im, re1, im1;
00202     int16_t rot[N];
00203     IComplex x[N/4];
00204 
00205     /* shift to simplify computations */
00206     for(i=0;i<N/4;i++)
00207         rot[i] = -in[i + 3*N/4];
00208     for(i=N/4;i<N;i++)
00209         rot[i] = in[i - N/4];
00210 
00211     /* pre rotation */
00212     for(i=0;i<N/4;i++) {
00213         re = ((int)rot[2*i] - (int)rot[N-1-2*i]) >> 1;
00214         im = -((int)rot[N/2+2*i] - (int)rot[N/2-1-2*i]) >> 1;
00215         CMUL(x[i].re, x[i].im, re, im, -xcos1[i], xsin1[i]);
00216     }
00217 
00218     fft(x, MDCT_NBITS - 2);
00219 
00220     /* post rotation */
00221     for(i=0;i<N/4;i++) {
00222         re = x[i].re;
00223         im = x[i].im;
00224         CMUL(re1, im1, re, im, xsin1[i], xcos1[i]);
00225         out[2*i] = im1;
00226         out[N/2-1-2*i] = re1;
00227     }
00228 }
00229 
00230 /* XXX: use another norm ? */
00231 static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n)
00232 {
00233     int sum, i;
00234     sum = 0;
00235     for(i=0;i<n;i++) {
00236         sum += abs(exp1[i] - exp2[i]);
00237     }
00238     return sum;
00239 }
00240 
00241 static void compute_exp_strategy(uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
00242                                  uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00243                                  int ch, int is_lfe)
00244 {
00245     int i, j;
00246     int exp_diff;
00247 
00248     /* estimate if the exponent variation & decide if they should be
00249        reused in the next frame */
00250     exp_strategy[0][ch] = EXP_NEW;
00251     for(i=1;i<NB_BLOCKS;i++) {
00252         exp_diff = calc_exp_diff(exp[i][ch], exp[i-1][ch], N/2);
00253         dprintf(NULL, "exp_diff=%d\n", exp_diff);
00254         if (exp_diff > EXP_DIFF_THRESHOLD)
00255             exp_strategy[i][ch] = EXP_NEW;
00256         else
00257             exp_strategy[i][ch] = EXP_REUSE;
00258     }
00259     if (is_lfe)
00260         return;
00261 
00262     /* now select the encoding strategy type : if exponents are often
00263        recoded, we use a coarse encoding */
00264     i = 0;
00265     while (i < NB_BLOCKS) {
00266         j = i + 1;
00267         while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)
00268             j++;
00269         switch(j - i) {
00270         case 1:
00271             exp_strategy[i][ch] = EXP_D45;
00272             break;
00273         case 2:
00274         case 3:
00275             exp_strategy[i][ch] = EXP_D25;
00276             break;
00277         default:
00278             exp_strategy[i][ch] = EXP_D15;
00279             break;
00280         }
00281         i = j;
00282     }
00283 }
00284 
00285 /* set exp[i] to min(exp[i], exp1[i]) */
00286 static void exponent_min(uint8_t exp[N/2], uint8_t exp1[N/2], int n)
00287 {
00288     int i;
00289 
00290     for(i=0;i<n;i++) {
00291         if (exp1[i] < exp[i])
00292             exp[i] = exp1[i];
00293     }
00294 }
00295 
00296 /* update the exponents so that they are the ones the decoder will
00297    decode. Return the number of bits used to code the exponents */
00298 static int encode_exp(uint8_t encoded_exp[N/2],
00299                       uint8_t exp[N/2],
00300                       int nb_exps,
00301                       int exp_strategy)
00302 {
00303     int group_size, nb_groups, i, j, k, exp_min;
00304     uint8_t exp1[N/2];
00305 
00306     switch(exp_strategy) {
00307     case EXP_D15:
00308         group_size = 1;
00309         break;
00310     case EXP_D25:
00311         group_size = 2;
00312         break;
00313     default:
00314     case EXP_D45:
00315         group_size = 4;
00316         break;
00317     }
00318     nb_groups = ((nb_exps + (group_size * 3) - 4) / (3 * group_size)) * 3;
00319 
00320     /* for each group, compute the minimum exponent */
00321     exp1[0] = exp[0]; /* DC exponent is handled separately */
00322     k = 1;
00323     for(i=1;i<=nb_groups;i++) {
00324         exp_min = exp[k];
00325         assert(exp_min >= 0 && exp_min <= 24);
00326         for(j=1;j<group_size;j++) {
00327             if (exp[k+j] < exp_min)
00328                 exp_min = exp[k+j];
00329         }
00330         exp1[i] = exp_min;
00331         k += group_size;
00332     }
00333 
00334     /* constraint for DC exponent */
00335     if (exp1[0] > 15)
00336         exp1[0] = 15;
00337 
00338     /* Decrease the delta between each groups to within 2
00339      * so that they can be differentially encoded */
00340     for (i=1;i<=nb_groups;i++)
00341         exp1[i] = FFMIN(exp1[i], exp1[i-1] + 2);
00342     for (i=nb_groups-1;i>=0;i--)
00343         exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2);
00344 
00345     /* now we have the exponent values the decoder will see */
00346     encoded_exp[0] = exp1[0];
00347     k = 1;
00348     for(i=1;i<=nb_groups;i++) {
00349         for(j=0;j<group_size;j++) {
00350             encoded_exp[k+j] = exp1[i];
00351         }
00352         k += group_size;
00353     }
00354 
00355 #if defined(DEBUG)
00356     av_log(NULL, AV_LOG_DEBUG, "exponents: strategy=%d\n", exp_strategy);
00357     for(i=0;i<=nb_groups * group_size;i++) {
00358         av_log(NULL, AV_LOG_DEBUG, "%d ", encoded_exp[i]);
00359     }
00360     av_log(NULL, AV_LOG_DEBUG, "\n");
00361 #endif
00362 
00363     return 4 + (nb_groups / 3) * 7;
00364 }
00365 
00366 /* return the size in bits taken by the mantissa */
00367 static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs)
00368 {
00369     int bits, mant, i;
00370 
00371     bits = 0;
00372     for(i=0;i<nb_coefs;i++) {
00373         mant = m[i];
00374         switch(mant) {
00375         case 0:
00376             /* nothing */
00377             break;
00378         case 1:
00379             /* 3 mantissa in 5 bits */
00380             if (s->mant1_cnt == 0)
00381                 bits += 5;
00382             if (++s->mant1_cnt == 3)
00383                 s->mant1_cnt = 0;
00384             break;
00385         case 2:
00386             /* 3 mantissa in 7 bits */
00387             if (s->mant2_cnt == 0)
00388                 bits += 7;
00389             if (++s->mant2_cnt == 3)
00390                 s->mant2_cnt = 0;
00391             break;
00392         case 3:
00393             bits += 3;
00394             break;
00395         case 4:
00396             /* 2 mantissa in 7 bits */
00397             if (s->mant4_cnt == 0)
00398                 bits += 7;
00399             if (++s->mant4_cnt == 2)
00400                 s->mant4_cnt = 0;
00401             break;
00402         case 14:
00403             bits += 14;
00404             break;
00405         case 15:
00406             bits += 16;
00407             break;
00408         default:
00409             bits += mant - 1;
00410             break;
00411         }
00412     }
00413     return bits;
00414 }
00415 
00416 
00417 static void bit_alloc_masking(AC3EncodeContext *s,
00418                               uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00419                               uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
00420                               int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00421                               int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50])
00422 {
00423     int blk, ch;
00424     int16_t band_psd[NB_BLOCKS][AC3_MAX_CHANNELS][50];
00425 
00426     for(blk=0; blk<NB_BLOCKS; blk++) {
00427         for(ch=0;ch<s->nb_all_channels;ch++) {
00428             if(exp_strategy[blk][ch] == EXP_REUSE) {
00429                 memcpy(psd[blk][ch], psd[blk-1][ch], (N/2)*sizeof(int16_t));
00430                 memcpy(mask[blk][ch], mask[blk-1][ch], 50*sizeof(int16_t));
00431             } else {
00432                 ff_ac3_bit_alloc_calc_psd(encoded_exp[blk][ch], 0,
00433                                           s->nb_coefs[ch],
00434                                           psd[blk][ch], band_psd[blk][ch]);
00435                 ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, band_psd[blk][ch],
00436                                            0, s->nb_coefs[ch],
00437                                            ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
00438                                            ch == s->lfe_channel,
00439                                            DBA_NONE, 0, NULL, NULL, NULL,
00440                                            mask[blk][ch]);
00441             }
00442         }
00443     }
00444 }
00445 
00446 static int bit_alloc(AC3EncodeContext *s,
00447                      int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50],
00448                      int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00449                      uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00450                      int frame_bits, int coarse_snr_offset, int fine_snr_offset)
00451 {
00452     int i, ch;
00453     int snr_offset;
00454 
00455     snr_offset = (((coarse_snr_offset - 15) << 4) + fine_snr_offset) << 2;
00456 
00457     /* compute size */
00458     for(i=0;i<NB_BLOCKS;i++) {
00459         s->mant1_cnt = 0;
00460         s->mant2_cnt = 0;
00461         s->mant4_cnt = 0;
00462         for(ch=0;ch<s->nb_all_channels;ch++) {
00463             ff_ac3_bit_alloc_calc_bap(mask[i][ch], psd[i][ch], 0,
00464                                       s->nb_coefs[ch], snr_offset,
00465                                       s->bit_alloc.floor, ff_ac3_bap_tab,
00466                                       bap[i][ch]);
00467             frame_bits += compute_mantissa_size(s, bap[i][ch],
00468                                                  s->nb_coefs[ch]);
00469         }
00470     }
00471 #if 0
00472     printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n",
00473            coarse_snr_offset, fine_snr_offset, frame_bits,
00474            16 * s->frame_size - ((frame_bits + 7) & ~7));
00475 #endif
00476     return 16 * s->frame_size - frame_bits;
00477 }
00478 
00479 #define SNR_INC1 4
00480 
00481 static int compute_bit_allocation(AC3EncodeContext *s,
00482                                   uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00483                                   uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00484                                   uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
00485                                   int frame_bits)
00486 {
00487     int i, ch;
00488     int coarse_snr_offset, fine_snr_offset;
00489     uint8_t bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
00490     int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
00491     int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50];
00492     static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
00493 
00494     /* init default parameters */
00495     s->slow_decay_code = 2;
00496     s->fast_decay_code = 1;
00497     s->slow_gain_code = 1;
00498     s->db_per_bit_code = 2;
00499     s->floor_code = 4;
00500     for(ch=0;ch<s->nb_all_channels;ch++)
00501         s->fast_gain_code[ch] = 4;
00502 
00503     /* compute real values */
00504     s->bit_alloc.sr_code = s->sr_code;
00505     s->bit_alloc.sr_shift = s->sr_shift;
00506     s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->sr_shift;
00507     s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->sr_shift;
00508     s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
00509     s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
00510     s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
00511 
00512     /* header size */
00513     frame_bits += 65;
00514     // if (s->channel_mode == 2)
00515     //    frame_bits += 2;
00516     frame_bits += frame_bits_inc[s->channel_mode];
00517 
00518     /* audio blocks */
00519     for(i=0;i<NB_BLOCKS;i++) {
00520         frame_bits += s->nb_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
00521         if (s->channel_mode == AC3_CHMODE_STEREO) {
00522             frame_bits++; /* rematstr */
00523             if(i==0) frame_bits += 4;
00524         }
00525         frame_bits += 2 * s->nb_channels; /* chexpstr[2] * c */
00526         if (s->lfe)
00527             frame_bits++; /* lfeexpstr */
00528         for(ch=0;ch<s->nb_channels;ch++) {
00529             if (exp_strategy[i][ch] != EXP_REUSE)
00530                 frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
00531         }
00532         frame_bits++; /* baie */
00533         frame_bits++; /* snr */
00534         frame_bits += 2; /* delta / skip */
00535     }
00536     frame_bits++; /* cplinu for block 0 */
00537     /* bit alloc info */
00538     /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
00539     /* csnroffset[6] */
00540     /* (fsnoffset[4] + fgaincod[4]) * c */
00541     frame_bits += 2*4 + 3 + 6 + s->nb_all_channels * (4 + 3);
00542 
00543     /* auxdatae, crcrsv */
00544     frame_bits += 2;
00545 
00546     /* CRC */
00547     frame_bits += 16;
00548 
00549     /* calculate psd and masking curve before doing bit allocation */
00550     bit_alloc_masking(s, encoded_exp, exp_strategy, psd, mask);
00551 
00552     /* now the big work begins : do the bit allocation. Modify the snr
00553        offset until we can pack everything in the requested frame size */
00554 
00555     coarse_snr_offset = s->coarse_snr_offset;
00556     while (coarse_snr_offset >= 0 &&
00557            bit_alloc(s, mask, psd, bap, frame_bits, coarse_snr_offset, 0) < 0)
00558         coarse_snr_offset -= SNR_INC1;
00559     if (coarse_snr_offset < 0) {
00560         av_log(NULL, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
00561         return -1;
00562     }
00563     while ((coarse_snr_offset + SNR_INC1) <= 63 &&
00564            bit_alloc(s, mask, psd, bap1, frame_bits,
00565                      coarse_snr_offset + SNR_INC1, 0) >= 0) {
00566         coarse_snr_offset += SNR_INC1;
00567         memcpy(bap, bap1, sizeof(bap1));
00568     }
00569     while ((coarse_snr_offset + 1) <= 63 &&
00570            bit_alloc(s, mask, psd, bap1, frame_bits, coarse_snr_offset + 1, 0) >= 0) {
00571         coarse_snr_offset++;
00572         memcpy(bap, bap1, sizeof(bap1));
00573     }
00574 
00575     fine_snr_offset = 0;
00576     while ((fine_snr_offset + SNR_INC1) <= 15 &&
00577            bit_alloc(s, mask, psd, bap1, frame_bits,
00578                      coarse_snr_offset, fine_snr_offset + SNR_INC1) >= 0) {
00579         fine_snr_offset += SNR_INC1;
00580         memcpy(bap, bap1, sizeof(bap1));
00581     }
00582     while ((fine_snr_offset + 1) <= 15 &&
00583            bit_alloc(s, mask, psd, bap1, frame_bits,
00584                      coarse_snr_offset, fine_snr_offset + 1) >= 0) {
00585         fine_snr_offset++;
00586         memcpy(bap, bap1, sizeof(bap1));
00587     }
00588 
00589     s->coarse_snr_offset = coarse_snr_offset;
00590     for(ch=0;ch<s->nb_all_channels;ch++)
00591         s->fine_snr_offset[ch] = fine_snr_offset;
00592 #if defined(DEBUG_BITALLOC)
00593     {
00594         int j;
00595 
00596         for(i=0;i<6;i++) {
00597             for(ch=0;ch<s->nb_all_channels;ch++) {
00598                 printf("Block #%d Ch%d:\n", i, ch);
00599                 printf("bap=");
00600                 for(j=0;j<s->nb_coefs[ch];j++) {
00601                     printf("%d ",bap[i][ch][j]);
00602                 }
00603                 printf("\n");
00604             }
00605         }
00606     }
00607 #endif
00608     return 0;
00609 }
00610 
00611 static av_cold int set_channel_info(AC3EncodeContext *s, int channels,
00612                                     int64_t *channel_layout)
00613 {
00614     int ch_layout;
00615 
00616     if (channels < 1 || channels > AC3_MAX_CHANNELS)
00617         return -1;
00618     if ((uint64_t)*channel_layout > 0x7FF)
00619         return -1;
00620     ch_layout = *channel_layout;
00621     if (!ch_layout)
00622         ch_layout = avcodec_guess_channel_layout(channels, CODEC_ID_AC3, NULL);
00623     if (avcodec_channel_layout_num_channels(ch_layout) != channels)
00624         return -1;
00625 
00626     s->lfe = !!(ch_layout & CH_LOW_FREQUENCY);
00627     s->nb_all_channels = channels;
00628     s->nb_channels = channels - s->lfe;
00629     s->lfe_channel = s->lfe ? s->nb_channels : -1;
00630     if (s->lfe)
00631         ch_layout -= CH_LOW_FREQUENCY;
00632 
00633     switch (ch_layout) {
00634     case CH_LAYOUT_MONO:           s->channel_mode = AC3_CHMODE_MONO;   break;
00635     case CH_LAYOUT_STEREO:         s->channel_mode = AC3_CHMODE_STEREO; break;
00636     case CH_LAYOUT_SURROUND:       s->channel_mode = AC3_CHMODE_3F;     break;
00637     case CH_LAYOUT_2_1:            s->channel_mode = AC3_CHMODE_2F1R;   break;
00638     case CH_LAYOUT_4POINT0:        s->channel_mode = AC3_CHMODE_3F1R;   break;
00639     case CH_LAYOUT_QUAD:
00640     case CH_LAYOUT_2_2:            s->channel_mode = AC3_CHMODE_2F2R;   break;
00641     case CH_LAYOUT_5POINT0:
00642     case CH_LAYOUT_5POINT0_BACK:   s->channel_mode = AC3_CHMODE_3F2R;   break;
00643     default:
00644         return -1;
00645     }
00646 
00647     s->channel_map = ff_ac3_enc_channel_map[s->channel_mode][s->lfe];
00648     *channel_layout = ch_layout;
00649     if (s->lfe)
00650         *channel_layout |= CH_LOW_FREQUENCY;
00651 
00652     return 0;
00653 }
00654 
00655 static av_cold int AC3_encode_init(AVCodecContext *avctx)
00656 {
00657     int freq = avctx->sample_rate;
00658     int bitrate = avctx->bit_rate;
00659     AC3EncodeContext *s = avctx->priv_data;
00660     int i, j, ch;
00661     float alpha;
00662     int bw_code;
00663 
00664     avctx->frame_size = AC3_FRAME_SIZE;
00665 
00666     ac3_common_init();
00667 
00668     if (!avctx->channel_layout) {
00669         av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The "
00670                                       "encoder will guess the layout, but it "
00671                                       "might be incorrect.\n");
00672     }
00673     if (set_channel_info(s, avctx->channels, &avctx->channel_layout)) {
00674         av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n");
00675         return -1;
00676     }
00677 
00678     /* frequency */
00679     for(i=0;i<3;i++) {
00680         for(j=0;j<3;j++)
00681             if ((ff_ac3_sample_rate_tab[j] >> i) == freq)
00682                 goto found;
00683     }
00684     return -1;
00685  found:
00686     s->sample_rate = freq;
00687     s->sr_shift = i;
00688     s->sr_code = j;
00689     s->bitstream_id = 8 + s->sr_shift;
00690     s->bitstream_mode = 0; /* complete main audio service */
00691 
00692     /* bitrate & frame size */
00693     for(i=0;i<19;i++) {
00694         if ((ff_ac3_bitrate_tab[i] >> s->sr_shift)*1000 == bitrate)
00695             break;
00696     }
00697     if (i == 19)
00698         return -1;
00699     s->bit_rate = bitrate;
00700     s->frame_size_code = i << 1;
00701     s->frame_size_min = ff_ac3_frame_size_tab[s->frame_size_code][s->sr_code];
00702     s->bits_written = 0;
00703     s->samples_written = 0;
00704     s->frame_size = s->frame_size_min;
00705 
00706     /* bit allocation init */
00707     if(avctx->cutoff) {
00708         /* calculate bandwidth based on user-specified cutoff frequency */
00709         int cutoff = av_clip(avctx->cutoff, 1, s->sample_rate >> 1);
00710         int fbw_coeffs = cutoff * 512 / s->sample_rate;
00711         bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);
00712     } else {
00713         /* use default bandwidth setting */
00714         /* XXX: should compute the bandwidth according to the frame
00715            size, so that we avoid annoying high frequency artifacts */
00716         bw_code = 50;
00717     }
00718     for(ch=0;ch<s->nb_channels;ch++) {
00719         /* bandwidth for each channel */
00720         s->chbwcod[ch] = bw_code;
00721         s->nb_coefs[ch] = bw_code * 3 + 73;
00722     }
00723     if (s->lfe) {
00724         s->nb_coefs[s->lfe_channel] = 7; /* fixed */
00725     }
00726     /* initial snr offset */
00727     s->coarse_snr_offset = 40;
00728 
00729     /* mdct init */
00730     fft_init(MDCT_NBITS - 2);
00731     for(i=0;i<N/4;i++) {
00732         alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N;
00733         xcos1[i] = fix15(-cos(alpha));
00734         xsin1[i] = fix15(-sin(alpha));
00735     }
00736 
00737     avctx->coded_frame= avcodec_alloc_frame();
00738     avctx->coded_frame->key_frame= 1;
00739 
00740     return 0;
00741 }
00742 
00743 /* output the AC-3 frame header */
00744 static void output_frame_header(AC3EncodeContext *s, unsigned char *frame)
00745 {
00746     init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
00747 
00748     put_bits(&s->pb, 16, 0x0b77); /* frame header */
00749     put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
00750     put_bits(&s->pb, 2, s->sr_code);
00751     put_bits(&s->pb, 6, s->frame_size_code + (s->frame_size - s->frame_size_min));
00752     put_bits(&s->pb, 5, s->bitstream_id);
00753     put_bits(&s->pb, 3, s->bitstream_mode);
00754     put_bits(&s->pb, 3, s->channel_mode);
00755     if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)
00756         put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
00757     if (s->channel_mode & 0x04)
00758         put_bits(&s->pb, 2, 1); /* XXX -6 dB */
00759     if (s->channel_mode == AC3_CHMODE_STEREO)
00760         put_bits(&s->pb, 2, 0); /* surround not indicated */
00761     put_bits(&s->pb, 1, s->lfe); /* LFE */
00762     put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
00763     put_bits(&s->pb, 1, 0); /* no compression control word */
00764     put_bits(&s->pb, 1, 0); /* no lang code */
00765     put_bits(&s->pb, 1, 0); /* no audio production info */
00766     put_bits(&s->pb, 1, 0); /* no copyright */
00767     put_bits(&s->pb, 1, 1); /* original bitstream */
00768     put_bits(&s->pb, 1, 0); /* no time code 1 */
00769     put_bits(&s->pb, 1, 0); /* no time code 2 */
00770     put_bits(&s->pb, 1, 0); /* no additional bit stream info */
00771 }
00772 
00773 /* symetric quantization on 'levels' levels */
00774 static inline int sym_quant(int c, int e, int levels)
00775 {
00776     int v;
00777 
00778     if (c >= 0) {
00779         v = (levels * (c << e)) >> 24;
00780         v = (v + 1) >> 1;
00781         v = (levels >> 1) + v;
00782     } else {
00783         v = (levels * ((-c) << e)) >> 24;
00784         v = (v + 1) >> 1;
00785         v = (levels >> 1) - v;
00786     }
00787     assert (v >= 0 && v < levels);
00788     return v;
00789 }
00790 
00791 /* asymetric quantization on 2^qbits levels */
00792 static inline int asym_quant(int c, int e, int qbits)
00793 {
00794     int lshift, m, v;
00795 
00796     lshift = e + qbits - 24;
00797     if (lshift >= 0)
00798         v = c << lshift;
00799     else
00800         v = c >> (-lshift);
00801     /* rounding */
00802     v = (v + 1) >> 1;
00803     m = (1 << (qbits-1));
00804     if (v >= m)
00805         v = m - 1;
00806     assert(v >= -m);
00807     return v & ((1 << qbits)-1);
00808 }
00809 
00810 /* Output one audio block. There are NB_BLOCKS audio blocks in one AC-3
00811    frame */
00812 static void output_audio_block(AC3EncodeContext *s,
00813                                uint8_t exp_strategy[AC3_MAX_CHANNELS],
00814                                uint8_t encoded_exp[AC3_MAX_CHANNELS][N/2],
00815                                uint8_t bap[AC3_MAX_CHANNELS][N/2],
00816                                int32_t mdct_coefs[AC3_MAX_CHANNELS][N/2],
00817                                int8_t global_exp[AC3_MAX_CHANNELS],
00818                                int block_num)
00819 {
00820     int ch, nb_groups, group_size, i, baie, rbnd;
00821     uint8_t *p;
00822     uint16_t qmant[AC3_MAX_CHANNELS][N/2];
00823     int exp0, exp1;
00824     int mant1_cnt, mant2_cnt, mant4_cnt;
00825     uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr;
00826     int delta0, delta1, delta2;
00827 
00828     for(ch=0;ch<s->nb_channels;ch++)
00829         put_bits(&s->pb, 1, 0); /* 512 point MDCT */
00830     for(ch=0;ch<s->nb_channels;ch++)
00831         put_bits(&s->pb, 1, 1); /* no dither */
00832     put_bits(&s->pb, 1, 0); /* no dynamic range */
00833     if (block_num == 0) {
00834         /* for block 0, even if no coupling, we must say it. This is a
00835            waste of bit :-) */
00836         put_bits(&s->pb, 1, 1); /* coupling strategy present */
00837         put_bits(&s->pb, 1, 0); /* no coupling strategy */
00838     } else {
00839         put_bits(&s->pb, 1, 0); /* no new coupling strategy */
00840     }
00841 
00842     if (s->channel_mode == AC3_CHMODE_STEREO)
00843       {
00844         if(block_num==0)
00845           {
00846             /* first block must define rematrixing (rematstr)  */
00847             put_bits(&s->pb, 1, 1);
00848 
00849             /* dummy rematrixing rematflg(1:4)=0 */
00850             for (rbnd=0;rbnd<4;rbnd++)
00851               put_bits(&s->pb, 1, 0);
00852           }
00853         else
00854           {
00855             /* no matrixing (but should be used in the future) */
00856             put_bits(&s->pb, 1, 0);
00857           }
00858       }
00859 
00860 #if defined(DEBUG)
00861     {
00862       static int count = 0;
00863       av_log(NULL, AV_LOG_DEBUG, "Block #%d (%d)\n", block_num, count++);
00864     }
00865 #endif
00866     /* exponent strategy */
00867     for(ch=0;ch<s->nb_channels;ch++) {
00868         put_bits(&s->pb, 2, exp_strategy[ch]);
00869     }
00870 
00871     if (s->lfe) {
00872         put_bits(&s->pb, 1, exp_strategy[s->lfe_channel]);
00873     }
00874 
00875     for(ch=0;ch<s->nb_channels;ch++) {
00876         if (exp_strategy[ch] != EXP_REUSE)
00877             put_bits(&s->pb, 6, s->chbwcod[ch]);
00878     }
00879 
00880     /* exponents */
00881     for (ch = 0; ch < s->nb_all_channels; ch++) {
00882         switch(exp_strategy[ch]) {
00883         case EXP_REUSE:
00884             continue;
00885         case EXP_D15:
00886             group_size = 1;
00887             break;
00888         case EXP_D25:
00889             group_size = 2;
00890             break;
00891         default:
00892         case EXP_D45:
00893             group_size = 4;
00894             break;
00895         }
00896         nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
00897         p = encoded_exp[ch];
00898 
00899         /* first exponent */
00900         exp1 = *p++;
00901         put_bits(&s->pb, 4, exp1);
00902 
00903         /* next ones are delta encoded */
00904         for(i=0;i<nb_groups;i++) {
00905             /* merge three delta in one code */
00906             exp0 = exp1;
00907             exp1 = p[0];
00908             p += group_size;
00909             delta0 = exp1 - exp0 + 2;
00910 
00911             exp0 = exp1;
00912             exp1 = p[0];
00913             p += group_size;
00914             delta1 = exp1 - exp0 + 2;
00915 
00916             exp0 = exp1;
00917             exp1 = p[0];
00918             p += group_size;
00919             delta2 = exp1 - exp0 + 2;
00920 
00921             put_bits(&s->pb, 7, ((delta0 * 5 + delta1) * 5) + delta2);
00922         }
00923 
00924         if (ch != s->lfe_channel)
00925             put_bits(&s->pb, 2, 0); /* no gain range info */
00926     }
00927 
00928     /* bit allocation info */
00929     baie = (block_num == 0);
00930     put_bits(&s->pb, 1, baie);
00931     if (baie) {
00932         put_bits(&s->pb, 2, s->slow_decay_code);
00933         put_bits(&s->pb, 2, s->fast_decay_code);
00934         put_bits(&s->pb, 2, s->slow_gain_code);
00935         put_bits(&s->pb, 2, s->db_per_bit_code);
00936         put_bits(&s->pb, 3, s->floor_code);
00937     }
00938 
00939     /* snr offset */
00940     put_bits(&s->pb, 1, baie); /* always present with bai */
00941     if (baie) {
00942         put_bits(&s->pb, 6, s->coarse_snr_offset);
00943         for(ch=0;ch<s->nb_all_channels;ch++) {
00944             put_bits(&s->pb, 4, s->fine_snr_offset[ch]);
00945             put_bits(&s->pb, 3, s->fast_gain_code[ch]);
00946         }
00947     }
00948 
00949     put_bits(&s->pb, 1, 0); /* no delta bit allocation */
00950     put_bits(&s->pb, 1, 0); /* no data to skip */
00951 
00952     /* mantissa encoding : we use two passes to handle the grouping. A
00953        one pass method may be faster, but it would necessitate to
00954        modify the output stream. */
00955 
00956     /* first pass: quantize */
00957     mant1_cnt = mant2_cnt = mant4_cnt = 0;
00958     qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;
00959 
00960     for (ch = 0; ch < s->nb_all_channels; ch++) {
00961         int b, c, e, v;
00962 
00963         for(i=0;i<s->nb_coefs[ch];i++) {
00964             c = mdct_coefs[ch][i];
00965             e = encoded_exp[ch][i] - global_exp[ch];
00966             b = bap[ch][i];
00967             switch(b) {
00968             case 0:
00969                 v = 0;
00970                 break;
00971             case 1:
00972                 v = sym_quant(c, e, 3);
00973                 switch(mant1_cnt) {
00974                 case 0:
00975                     qmant1_ptr = &qmant[ch][i];
00976                     v = 9 * v;
00977                     mant1_cnt = 1;
00978                     break;
00979                 case 1:
00980                     *qmant1_ptr += 3 * v;
00981                     mant1_cnt = 2;
00982                     v = 128;
00983                     break;
00984                 default:
00985                     *qmant1_ptr += v;
00986                     mant1_cnt = 0;
00987                     v = 128;
00988                     break;
00989                 }
00990                 break;
00991             case 2:
00992                 v = sym_quant(c, e, 5);
00993                 switch(mant2_cnt) {
00994                 case 0:
00995                     qmant2_ptr = &qmant[ch][i];
00996                     v = 25 * v;
00997                     mant2_cnt = 1;
00998                     break;
00999                 case 1:
01000                     *qmant2_ptr += 5 * v;
01001                     mant2_cnt = 2;
01002                     v = 128;
01003                     break;
01004                 default:
01005                     *qmant2_ptr += v;
01006                     mant2_cnt = 0;
01007                     v = 128;
01008                     break;
01009                 }
01010                 break;
01011             case 3:
01012                 v = sym_quant(c, e, 7);
01013                 break;
01014             case 4:
01015                 v = sym_quant(c, e, 11);
01016                 switch(mant4_cnt) {
01017                 case 0:
01018                     qmant4_ptr = &qmant[ch][i];
01019                     v = 11 * v;
01020                     mant4_cnt = 1;
01021                     break;
01022                 default:
01023                     *qmant4_ptr += v;
01024                     mant4_cnt = 0;
01025                     v = 128;
01026                     break;
01027                 }
01028                 break;
01029             case 5:
01030                 v = sym_quant(c, e, 15);
01031                 break;
01032             case 14:
01033                 v = asym_quant(c, e, 14);
01034                 break;
01035             case 15:
01036                 v = asym_quant(c, e, 16);
01037                 break;
01038             default:
01039                 v = asym_quant(c, e, b - 1);
01040                 break;
01041             }
01042             qmant[ch][i] = v;
01043         }
01044     }
01045 
01046     /* second pass : output the values */
01047     for (ch = 0; ch < s->nb_all_channels; ch++) {
01048         int b, q;
01049 
01050         for(i=0;i<s->nb_coefs[ch];i++) {
01051             q = qmant[ch][i];
01052             b = bap[ch][i];
01053             switch(b) {
01054             case 0:
01055                 break;
01056             case 1:
01057                 if (q != 128)
01058                     put_bits(&s->pb, 5, q);
01059                 break;
01060             case 2:
01061                 if (q != 128)
01062                     put_bits(&s->pb, 7, q);
01063                 break;
01064             case 3:
01065                 put_bits(&s->pb, 3, q);
01066                 break;
01067             case 4:
01068                 if (q != 128)
01069                     put_bits(&s->pb, 7, q);
01070                 break;
01071             case 14:
01072                 put_bits(&s->pb, 14, q);
01073                 break;
01074             case 15:
01075                 put_bits(&s->pb, 16, q);
01076                 break;
01077             default:
01078                 put_bits(&s->pb, b - 1, q);
01079                 break;
01080             }
01081         }
01082     }
01083 }
01084 
01085 #define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
01086 
01087 static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
01088 {
01089     unsigned int c;
01090 
01091     c = 0;
01092     while (a) {
01093         if (a & 1)
01094             c ^= b;
01095         a = a >> 1;
01096         b = b << 1;
01097         if (b & (1 << 16))
01098             b ^= poly;
01099     }
01100     return c;
01101 }
01102 
01103 static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
01104 {
01105     unsigned int r;
01106     r = 1;
01107     while (n) {
01108         if (n & 1)
01109             r = mul_poly(r, a, poly);
01110         a = mul_poly(a, a, poly);
01111         n >>= 1;
01112     }
01113     return r;
01114 }
01115 
01116 
01117 /* compute log2(max(abs(tab[]))) */
01118 static int log2_tab(int16_t *tab, int n)
01119 {
01120     int i, v;
01121 
01122     v = 0;
01123     for(i=0;i<n;i++) {
01124         v |= abs(tab[i]);
01125     }
01126     return av_log2(v);
01127 }
01128 
01129 static void lshift_tab(int16_t *tab, int n, int lshift)
01130 {
01131     int i;
01132 
01133     if (lshift > 0) {
01134         for(i=0;i<n;i++) {
01135             tab[i] <<= lshift;
01136         }
01137     } else if (lshift < 0) {
01138         lshift = -lshift;
01139         for(i=0;i<n;i++) {
01140             tab[i] >>= lshift;
01141         }
01142     }
01143 }
01144 
01145 /* fill the end of the frame and compute the two crcs */
01146 static int output_frame_end(AC3EncodeContext *s)
01147 {
01148     int frame_size, frame_size_58, n, crc1, crc2, crc_inv;
01149     uint8_t *frame;
01150 
01151     frame_size = s->frame_size; /* frame size in words */
01152     /* align to 8 bits */
01153     flush_put_bits(&s->pb);
01154     /* add zero bytes to reach the frame size */
01155     frame = s->pb.buf;
01156     n = 2 * s->frame_size - (put_bits_ptr(&s->pb) - frame) - 2;
01157     assert(n >= 0);
01158     if(n>0)
01159       memset(put_bits_ptr(&s->pb), 0, n);
01160 
01161     /* Now we must compute both crcs : this is not so easy for crc1
01162        because it is at the beginning of the data... */
01163     frame_size_58 = (frame_size >> 1) + (frame_size >> 3);
01164     crc1 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
01165                            frame + 4, 2 * frame_size_58 - 4));
01166     /* XXX: could precompute crc_inv */
01167     crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58) - 16, CRC16_POLY);
01168     crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
01169     AV_WB16(frame+2,crc1);
01170 
01171     crc2 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
01172                            frame + 2 * frame_size_58,
01173                            (frame_size - frame_size_58) * 2 - 2));
01174     AV_WB16(frame+2*frame_size-2,crc2);
01175 
01176     //    printf("n=%d frame_size=%d\n", n, frame_size);
01177     return frame_size * 2;
01178 }
01179 
01180 static int AC3_encode_frame(AVCodecContext *avctx,
01181                             unsigned char *frame, int buf_size, void *data)
01182 {
01183     AC3EncodeContext *s = avctx->priv_data;
01184     int16_t *samples = data;
01185     int i, j, k, v, ch;
01186     int16_t input_samples[N];
01187     int32_t mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01188     uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01189     uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS];
01190     uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01191     uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01192     int8_t exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS];
01193     int frame_bits;
01194 
01195     frame_bits = 0;
01196     for(ch=0;ch<s->nb_all_channels;ch++) {
01197         int ich = s->channel_map[ch];
01198         /* fixed mdct to the six sub blocks & exponent computation */
01199         for(i=0;i<NB_BLOCKS;i++) {
01200             int16_t *sptr;
01201             int sinc;
01202 
01203             /* compute input samples */
01204             memcpy(input_samples, s->last_samples[ich], N/2 * sizeof(int16_t));
01205             sinc = s->nb_all_channels;
01206             sptr = samples + (sinc * (N/2) * i) + ich;
01207             for(j=0;j<N/2;j++) {
01208                 v = *sptr;
01209                 input_samples[j + N/2] = v;
01210                 s->last_samples[ich][j] = v;
01211                 sptr += sinc;
01212             }
01213 
01214             /* apply the MDCT window */
01215             for(j=0;j<N/2;j++) {
01216                 input_samples[j] = MUL16(input_samples[j],
01217                                          ff_ac3_window[j]) >> 15;
01218                 input_samples[N-j-1] = MUL16(input_samples[N-j-1],
01219                                              ff_ac3_window[j]) >> 15;
01220             }
01221 
01222             /* Normalize the samples to use the maximum available
01223                precision */
01224             v = 14 - log2_tab(input_samples, N);
01225             if (v < 0)
01226                 v = 0;
01227             exp_samples[i][ch] = v - 9;
01228             lshift_tab(input_samples, N, v);
01229 
01230             /* do the MDCT */
01231             mdct512(mdct_coef[i][ch], input_samples);
01232 
01233             /* compute "exponents". We take into account the
01234                normalization there */
01235             for(j=0;j<N/2;j++) {
01236                 int e;
01237                 v = abs(mdct_coef[i][ch][j]);
01238                 if (v == 0)
01239                     e = 24;
01240                 else {
01241                     e = 23 - av_log2(v) + exp_samples[i][ch];
01242                     if (e >= 24) {
01243                         e = 24;
01244                         mdct_coef[i][ch][j] = 0;
01245                     }
01246                 }
01247                 exp[i][ch][j] = e;
01248             }
01249         }
01250 
01251         compute_exp_strategy(exp_strategy, exp, ch, ch == s->lfe_channel);
01252 
01253         /* compute the exponents as the decoder will see them. The
01254            EXP_REUSE case must be handled carefully : we select the
01255            min of the exponents */
01256         i = 0;
01257         while (i < NB_BLOCKS) {
01258             j = i + 1;
01259             while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {
01260                 exponent_min(exp[i][ch], exp[j][ch], s->nb_coefs[ch]);
01261                 j++;
01262             }
01263             frame_bits += encode_exp(encoded_exp[i][ch],
01264                                      exp[i][ch], s->nb_coefs[ch],
01265                                      exp_strategy[i][ch]);
01266             /* copy encoded exponents for reuse case */
01267             for(k=i+1;k<j;k++) {
01268                 memcpy(encoded_exp[k][ch], encoded_exp[i][ch],
01269                        s->nb_coefs[ch] * sizeof(uint8_t));
01270             }
01271             i = j;
01272         }
01273     }
01274 
01275     /* adjust for fractional frame sizes */
01276     while(s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
01277         s->bits_written -= s->bit_rate;
01278         s->samples_written -= s->sample_rate;
01279     }
01280     s->frame_size = s->frame_size_min + (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
01281     s->bits_written += s->frame_size * 16;
01282     s->samples_written += AC3_FRAME_SIZE;
01283 
01284     compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);
01285     /* everything is known... let's output the frame */
01286     output_frame_header(s, frame);
01287 
01288     for(i=0;i<NB_BLOCKS;i++) {
01289         output_audio_block(s, exp_strategy[i], encoded_exp[i],
01290                            bap[i], mdct_coef[i], exp_samples[i], i);
01291     }
01292     return output_frame_end(s);
01293 }
01294 
01295 static av_cold int AC3_encode_close(AVCodecContext *avctx)
01296 {
01297     av_freep(&avctx->coded_frame);
01298     return 0;
01299 }
01300 
01301 #if 0
01302 /*************************************************************************/
01303 /* TEST */
01304 
01305 #undef random
01306 #define FN (N/4)
01307 
01308 void fft_test(void)
01309 {
01310     IComplex in[FN], in1[FN];
01311     int k, n, i;
01312     float sum_re, sum_im, a;
01313 
01314     /* FFT test */
01315 
01316     for(i=0;i<FN;i++) {
01317         in[i].re = random() % 65535 - 32767;
01318         in[i].im = random() % 65535 - 32767;
01319         in1[i] = in[i];
01320     }
01321     fft(in, 7);
01322 
01323     /* do it by hand */
01324     for(k=0;k<FN;k++) {
01325         sum_re = 0;
01326         sum_im = 0;
01327         for(n=0;n<FN;n++) {
01328             a = -2 * M_PI * (n * k) / FN;
01329             sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);
01330             sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);
01331         }
01332         printf("%3d: %6d,%6d %6.0f,%6.0f\n",
01333                k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);
01334     }
01335 }
01336 
01337 void mdct_test(void)
01338 {
01339     int16_t input[N];
01340     int32_t output[N/2];
01341     float input1[N];
01342     float output1[N/2];
01343     float s, a, err, e, emax;
01344     int i, k, n;
01345 
01346     for(i=0;i<N;i++) {
01347         input[i] = (random() % 65535 - 32767) * 9 / 10;
01348         input1[i] = input[i];
01349     }
01350 
01351     mdct512(output, input);
01352 
01353     /* do it by hand */
01354     for(k=0;k<N/2;k++) {
01355         s = 0;
01356         for(n=0;n<N;n++) {
01357             a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));
01358             s += input1[n] * cos(a);
01359         }
01360         output1[k] = -2 * s / N;
01361     }
01362 
01363     err = 0;
01364     emax = 0;
01365     for(i=0;i<N/2;i++) {
01366         printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);
01367         e = output[i] - output1[i];
01368         if (e > emax)
01369             emax = e;
01370         err += e * e;
01371     }
01372     printf("err2=%f emax=%f\n", err / (N/2), emax);
01373 }
01374 
01375 void test_ac3(void)
01376 {
01377     AC3EncodeContext ctx;
01378     unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];
01379     short samples[AC3_FRAME_SIZE];
01380     int ret, i;
01381 
01382     AC3_encode_init(&ctx, 44100, 64000, 1);
01383 
01384     fft_test();
01385     mdct_test();
01386 
01387     for(i=0;i<AC3_FRAME_SIZE;i++)
01388         samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);
01389     ret = AC3_encode_frame(&ctx, frame, samples);
01390     printf("ret=%d\n", ret);
01391 }
01392 #endif
01393 
01394 AVCodec ac3_encoder = {
01395     "ac3",
01396     AVMEDIA_TYPE_AUDIO,
01397     CODEC_ID_AC3,
01398     sizeof(AC3EncodeContext),
01399     AC3_encode_init,
01400     AC3_encode_frame,
01401     AC3_encode_close,
01402     NULL,
01403     .sample_fmts = (const enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE},
01404     .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
01405     .channel_layouts = (const int64_t[]){
01406         CH_LAYOUT_MONO,
01407         CH_LAYOUT_STEREO,
01408         CH_LAYOUT_2_1,
01409         CH_LAYOUT_SURROUND,
01410         CH_LAYOUT_2_2,
01411         CH_LAYOUT_QUAD,
01412         CH_LAYOUT_4POINT0,
01413         CH_LAYOUT_5POINT0,
01414         CH_LAYOUT_5POINT0_BACK,
01415        (CH_LAYOUT_MONO     | CH_LOW_FREQUENCY),
01416        (CH_LAYOUT_STEREO   | CH_LOW_FREQUENCY),
01417        (CH_LAYOUT_2_1      | CH_LOW_FREQUENCY),
01418        (CH_LAYOUT_SURROUND | CH_LOW_FREQUENCY),
01419        (CH_LAYOUT_2_2      | CH_LOW_FREQUENCY),
01420        (CH_LAYOUT_QUAD     | CH_LOW_FREQUENCY),
01421        (CH_LAYOUT_4POINT0  | CH_LOW_FREQUENCY),
01422         CH_LAYOUT_5POINT1,
01423         CH_LAYOUT_5POINT1_BACK,
01424         0 },
01425 };