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 "bitstream.h"
00031 #include "ac3.h"
00032 
00033 typedef struct AC3EncodeContext {
00034     PutBitContext pb;
00035     int nb_channels;
00036     int nb_all_channels;
00037     int lfe_channel;
00038     int bit_rate;
00039     unsigned int sample_rate;
00040     unsigned int bitstream_id;
00041     unsigned int frame_size_min; /* minimum frame size in case rounding is necessary */
00042     unsigned int frame_size; /* current frame size in words */
00043     unsigned int bits_written;
00044     unsigned int samples_written;
00045     int sr_shift;
00046     unsigned int frame_size_code;
00047     unsigned int sr_code; /* frequency */
00048     unsigned int channel_mode;
00049     int lfe;
00050     unsigned int bitstream_mode;
00051     short last_samples[AC3_MAX_CHANNELS][256];
00052     unsigned int chbwcod[AC3_MAX_CHANNELS];
00053     int nb_coefs[AC3_MAX_CHANNELS];
00054 
00055     /* bitrate allocation control */
00056     int slow_gain_code, slow_decay_code, fast_decay_code, db_per_bit_code, floor_code;
00057     AC3BitAllocParameters bit_alloc;
00058     int coarse_snr_offset;
00059     int fast_gain_code[AC3_MAX_CHANNELS];
00060     int fine_snr_offset[AC3_MAX_CHANNELS];
00061     /* mantissa encoding */
00062     int mant1_cnt, mant2_cnt, mant4_cnt;
00063 } AC3EncodeContext;
00064 
00065 static int16_t costab[64];
00066 static int16_t sintab[64];
00067 static int16_t xcos1[128];
00068 static int16_t xsin1[128];
00069 
00070 #define MDCT_NBITS 9
00071 #define N         (1 << MDCT_NBITS)
00072 
00073 /* new exponents are sent if their Norm 1 exceed this number */
00074 #define EXP_DIFF_THRESHOLD 1000
00075 
00076 static inline int16_t fix15(float a)
00077 {
00078     int v;
00079     v = (int)(a * (float)(1 << 15));
00080     if (v < -32767)
00081         v = -32767;
00082     else if (v > 32767)
00083         v = 32767;
00084     return v;
00085 }
00086 
00087 typedef struct IComplex {
00088     short re,im;
00089 } IComplex;
00090 
00091 static av_cold void fft_init(int ln)
00092 {
00093     int i, n;
00094     float alpha;
00095 
00096     n = 1 << ln;
00097 
00098     for(i=0;i<(n/2);i++) {
00099         alpha = 2 * M_PI * (float)i / (float)n;
00100         costab[i] = fix15(cos(alpha));
00101         sintab[i] = fix15(sin(alpha));
00102     }
00103 }
00104 
00105 /* butter fly op */
00106 #define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
00107 {\
00108   int ax, ay, bx, by;\
00109   bx=pre1;\
00110   by=pim1;\
00111   ax=qre1;\
00112   ay=qim1;\
00113   pre = (bx + ax) >> 1;\
00114   pim = (by + ay) >> 1;\
00115   qre = (bx - ax) >> 1;\
00116   qim = (by - ay) >> 1;\
00117 }
00118 
00119 #define MUL16(a,b) ((a) * (b))
00120 
00121 #define CMUL(pre, pim, are, aim, bre, bim) \
00122 {\
00123    pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15;\
00124    pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\
00125 }
00126 
00127 
00128 /* do a 2^n point complex fft on 2^ln points. */
00129 static void fft(IComplex *z, int ln)
00130 {
00131     int        j, l, np, np2;
00132     int        nblocks, nloops;
00133     register IComplex *p,*q;
00134     int tmp_re, tmp_im;
00135 
00136     np = 1 << ln;
00137 
00138     /* reverse */
00139     for(j=0;j<np;j++) {
00140         int k = ff_reverse[j] >> (8 - ln);
00141         if (k < j)
00142             FFSWAP(IComplex, z[k], z[j]);
00143     }
00144 
00145     /* pass 0 */
00146 
00147     p=&z[0];
00148     j=(np >> 1);
00149     do {
00150         BF(p[0].re, p[0].im, p[1].re, p[1].im,
00151            p[0].re, p[0].im, p[1].re, p[1].im);
00152         p+=2;
00153     } while (--j != 0);
00154 
00155     /* pass 1 */
00156 
00157     p=&z[0];
00158     j=np >> 2;
00159     do {
00160         BF(p[0].re, p[0].im, p[2].re, p[2].im,
00161            p[0].re, p[0].im, p[2].re, p[2].im);
00162         BF(p[1].re, p[1].im, p[3].re, p[3].im,
00163            p[1].re, p[1].im, p[3].im, -p[3].re);
00164         p+=4;
00165     } while (--j != 0);
00166 
00167     /* pass 2 .. ln-1 */
00168 
00169     nblocks = np >> 3;
00170     nloops = 1 << 2;
00171     np2 = np >> 1;
00172     do {
00173         p = z;
00174         q = z + nloops;
00175         for (j = 0; j < nblocks; ++j) {
00176 
00177             BF(p->re, p->im, q->re, q->im,
00178                p->re, p->im, q->re, q->im);
00179 
00180             p++;
00181             q++;
00182             for(l = nblocks; l < np2; l += nblocks) {
00183                 CMUL(tmp_re, tmp_im, costab[l], -sintab[l], q->re, q->im);
00184                 BF(p->re, p->im, q->re, q->im,
00185                    p->re, p->im, tmp_re, tmp_im);
00186                 p++;
00187                 q++;
00188             }
00189             p += nloops;
00190             q += nloops;
00191         }
00192         nblocks = nblocks >> 1;
00193         nloops = nloops << 1;
00194     } while (nblocks != 0);
00195 }
00196 
00197 /* do a 512 point mdct */
00198 static void mdct512(int32_t *out, int16_t *in)
00199 {
00200     int i, re, im, re1, im1;
00201     int16_t rot[N];
00202     IComplex x[N/4];
00203 
00204     /* shift to simplify computations */
00205     for(i=0;i<N/4;i++)
00206         rot[i] = -in[i + 3*N/4];
00207     for(i=N/4;i<N;i++)
00208         rot[i] = in[i - N/4];
00209 
00210     /* pre rotation */
00211     for(i=0;i<N/4;i++) {
00212         re = ((int)rot[2*i] - (int)rot[N-1-2*i]) >> 1;
00213         im = -((int)rot[N/2+2*i] - (int)rot[N/2-1-2*i]) >> 1;
00214         CMUL(x[i].re, x[i].im, re, im, -xcos1[i], xsin1[i]);
00215     }
00216 
00217     fft(x, MDCT_NBITS - 2);
00218 
00219     /* post rotation */
00220     for(i=0;i<N/4;i++) {
00221         re = x[i].re;
00222         im = x[i].im;
00223         CMUL(re1, im1, re, im, xsin1[i], xcos1[i]);
00224         out[2*i] = im1;
00225         out[N/2-1-2*i] = re1;
00226     }
00227 }
00228 
00229 /* XXX: use another norm ? */
00230 static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n)
00231 {
00232     int sum, i;
00233     sum = 0;
00234     for(i=0;i<n;i++) {
00235         sum += abs(exp1[i] - exp2[i]);
00236     }
00237     return sum;
00238 }
00239 
00240 static void compute_exp_strategy(uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
00241                                  uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00242                                  int ch, int is_lfe)
00243 {
00244     int i, j;
00245     int exp_diff;
00246 
00247     /* estimate if the exponent variation & decide if they should be
00248        reused in the next frame */
00249     exp_strategy[0][ch] = EXP_NEW;
00250     for(i=1;i<NB_BLOCKS;i++) {
00251         exp_diff = calc_exp_diff(exp[i][ch], exp[i-1][ch], N/2);
00252 #ifdef DEBUG
00253         av_log(NULL, AV_LOG_DEBUG, "exp_diff=%d\n", exp_diff);
00254 #endif
00255         if (exp_diff > EXP_DIFF_THRESHOLD)
00256             exp_strategy[i][ch] = EXP_NEW;
00257         else
00258             exp_strategy[i][ch] = EXP_REUSE;
00259     }
00260     if (is_lfe)
00261         return;
00262 
00263     /* now select the encoding strategy type : if exponents are often
00264        recoded, we use a coarse encoding */
00265     i = 0;
00266     while (i < NB_BLOCKS) {
00267         j = i + 1;
00268         while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)
00269             j++;
00270         switch(j - i) {
00271         case 1:
00272             exp_strategy[i][ch] = EXP_D45;
00273             break;
00274         case 2:
00275         case 3:
00276             exp_strategy[i][ch] = EXP_D25;
00277             break;
00278         default:
00279             exp_strategy[i][ch] = EXP_D15;
00280             break;
00281         }
00282         i = j;
00283     }
00284 }
00285 
00286 /* set exp[i] to min(exp[i], exp1[i]) */
00287 static void exponent_min(uint8_t exp[N/2], uint8_t exp1[N/2], int n)
00288 {
00289     int i;
00290 
00291     for(i=0;i<n;i++) {
00292         if (exp1[i] < exp[i])
00293             exp[i] = exp1[i];
00294     }
00295 }
00296 
00297 /* update the exponents so that they are the ones the decoder will
00298    decode. Return the number of bits used to code the exponents */
00299 static int encode_exp(uint8_t encoded_exp[N/2],
00300                       uint8_t exp[N/2],
00301                       int nb_exps,
00302                       int exp_strategy)
00303 {
00304     int group_size, nb_groups, i, j, k, exp_min;
00305     uint8_t exp1[N/2];
00306 
00307     switch(exp_strategy) {
00308     case EXP_D15:
00309         group_size = 1;
00310         break;
00311     case EXP_D25:
00312         group_size = 2;
00313         break;
00314     default:
00315     case EXP_D45:
00316         group_size = 4;
00317         break;
00318     }
00319     nb_groups = ((nb_exps + (group_size * 3) - 4) / (3 * group_size)) * 3;
00320 
00321     /* for each group, compute the minimum exponent */
00322     exp1[0] = exp[0]; /* DC exponent is handled separately */
00323     k = 1;
00324     for(i=1;i<=nb_groups;i++) {
00325         exp_min = exp[k];
00326         assert(exp_min >= 0 && exp_min <= 24);
00327         for(j=1;j<group_size;j++) {
00328             if (exp[k+j] < exp_min)
00329                 exp_min = exp[k+j];
00330         }
00331         exp1[i] = exp_min;
00332         k += group_size;
00333     }
00334 
00335     /* constraint for DC exponent */
00336     if (exp1[0] > 15)
00337         exp1[0] = 15;
00338 
00339     /* Decrease the delta between each groups to within 2
00340      * so that they can be differentially encoded */
00341     for (i=1;i<=nb_groups;i++)
00342         exp1[i] = FFMIN(exp1[i], exp1[i-1] + 2);
00343     for (i=nb_groups-1;i>=0;i--)
00344         exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2);
00345 
00346     /* now we have the exponent values the decoder will see */
00347     encoded_exp[0] = exp1[0];
00348     k = 1;
00349     for(i=1;i<=nb_groups;i++) {
00350         for(j=0;j<group_size;j++) {
00351             encoded_exp[k+j] = exp1[i];
00352         }
00353         k += group_size;
00354     }
00355 
00356 #if defined(DEBUG)
00357     av_log(NULL, AV_LOG_DEBUG, "exponents: strategy=%d\n", exp_strategy);
00358     for(i=0;i<=nb_groups * group_size;i++) {
00359         av_log(NULL, AV_LOG_DEBUG, "%d ", encoded_exp[i]);
00360     }
00361     av_log(NULL, AV_LOG_DEBUG, "\n");
00362 #endif
00363 
00364     return 4 + (nb_groups / 3) * 7;
00365 }
00366 
00367 /* return the size in bits taken by the mantissa */
00368 static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs)
00369 {
00370     int bits, mant, i;
00371 
00372     bits = 0;
00373     for(i=0;i<nb_coefs;i++) {
00374         mant = m[i];
00375         switch(mant) {
00376         case 0:
00377             /* nothing */
00378             break;
00379         case 1:
00380             /* 3 mantissa in 5 bits */
00381             if (s->mant1_cnt == 0)
00382                 bits += 5;
00383             if (++s->mant1_cnt == 3)
00384                 s->mant1_cnt = 0;
00385             break;
00386         case 2:
00387             /* 3 mantissa in 7 bits */
00388             if (s->mant2_cnt == 0)
00389                 bits += 7;
00390             if (++s->mant2_cnt == 3)
00391                 s->mant2_cnt = 0;
00392             break;
00393         case 3:
00394             bits += 3;
00395             break;
00396         case 4:
00397             /* 2 mantissa in 7 bits */
00398             if (s->mant4_cnt == 0)
00399                 bits += 7;
00400             if (++s->mant4_cnt == 2)
00401                 s->mant4_cnt = 0;
00402             break;
00403         case 14:
00404             bits += 14;
00405             break;
00406         case 15:
00407             bits += 16;
00408             break;
00409         default:
00410             bits += mant - 1;
00411             break;
00412         }
00413     }
00414     return bits;
00415 }
00416 
00417 
00418 static void bit_alloc_masking(AC3EncodeContext *s,
00419                               uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00420                               uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
00421                               int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00422                               int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50])
00423 {
00424     int blk, ch;
00425     int16_t band_psd[NB_BLOCKS][AC3_MAX_CHANNELS][50];
00426 
00427     for(blk=0; blk<NB_BLOCKS; blk++) {
00428         for(ch=0;ch<s->nb_all_channels;ch++) {
00429             if(exp_strategy[blk][ch] == EXP_REUSE) {
00430                 memcpy(psd[blk][ch], psd[blk-1][ch], (N/2)*sizeof(int16_t));
00431                 memcpy(mask[blk][ch], mask[blk-1][ch], 50*sizeof(int16_t));
00432             } else {
00433                 ff_ac3_bit_alloc_calc_psd(encoded_exp[blk][ch], 0,
00434                                           s->nb_coefs[ch],
00435                                           psd[blk][ch], band_psd[blk][ch]);
00436                 ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, band_psd[blk][ch],
00437                                            0, s->nb_coefs[ch],
00438                                            ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
00439                                            ch == s->lfe_channel,
00440                                            DBA_NONE, 0, NULL, NULL, NULL,
00441                                            mask[blk][ch]);
00442             }
00443         }
00444     }
00445 }
00446 
00447 static int bit_alloc(AC3EncodeContext *s,
00448                      int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50],
00449                      int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00450                      uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00451                      int frame_bits, int coarse_snr_offset, int fine_snr_offset)
00452 {
00453     int i, ch;
00454     int snr_offset;
00455 
00456     snr_offset = (((coarse_snr_offset - 15) << 4) + fine_snr_offset) << 2;
00457 
00458     /* compute size */
00459     for(i=0;i<NB_BLOCKS;i++) {
00460         s->mant1_cnt = 0;
00461         s->mant2_cnt = 0;
00462         s->mant4_cnt = 0;
00463         for(ch=0;ch<s->nb_all_channels;ch++) {
00464             ff_ac3_bit_alloc_calc_bap(mask[i][ch], psd[i][ch], 0,
00465                                       s->nb_coefs[ch], snr_offset,
00466                                       s->bit_alloc.floor, ff_ac3_bap_tab,
00467                                       bap[i][ch]);
00468             frame_bits += compute_mantissa_size(s, bap[i][ch],
00469                                                  s->nb_coefs[ch]);
00470         }
00471     }
00472 #if 0
00473     printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n",
00474            coarse_snr_offset, fine_snr_offset, frame_bits,
00475            16 * s->frame_size - ((frame_bits + 7) & ~7));
00476 #endif
00477     return 16 * s->frame_size - frame_bits;
00478 }
00479 
00480 #define SNR_INC1 4
00481 
00482 static int compute_bit_allocation(AC3EncodeContext *s,
00483                                   uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00484                                   uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00485                                   uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
00486                                   int frame_bits)
00487 {
00488     int i, ch;
00489     int coarse_snr_offset, fine_snr_offset;
00490     uint8_t bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
00491     int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
00492     int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50];
00493     static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
00494 
00495     /* init default parameters */
00496     s->slow_decay_code = 2;
00497     s->fast_decay_code = 1;
00498     s->slow_gain_code = 1;
00499     s->db_per_bit_code = 2;
00500     s->floor_code = 4;
00501     for(ch=0;ch<s->nb_all_channels;ch++)
00502         s->fast_gain_code[ch] = 4;
00503 
00504     /* compute real values */
00505     s->bit_alloc.sr_code = s->sr_code;
00506     s->bit_alloc.sr_shift = s->sr_shift;
00507     s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->sr_shift;
00508     s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->sr_shift;
00509     s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
00510     s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
00511     s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
00512 
00513     /* header size */
00514     frame_bits += 65;
00515     // if (s->channel_mode == 2)
00516     //    frame_bits += 2;
00517     frame_bits += frame_bits_inc[s->channel_mode];
00518 
00519     /* audio blocks */
00520     for(i=0;i<NB_BLOCKS;i++) {
00521         frame_bits += s->nb_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
00522         if (s->channel_mode == AC3_CHMODE_STEREO) {
00523             frame_bits++; /* rematstr */
00524             if(i==0) frame_bits += 4;
00525         }
00526         frame_bits += 2 * s->nb_channels; /* chexpstr[2] * c */
00527         if (s->lfe)
00528             frame_bits++; /* lfeexpstr */
00529         for(ch=0;ch<s->nb_channels;ch++) {
00530             if (exp_strategy[i][ch] != EXP_REUSE)
00531                 frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
00532         }
00533         frame_bits++; /* baie */
00534         frame_bits++; /* snr */
00535         frame_bits += 2; /* delta / skip */
00536     }
00537     frame_bits++; /* cplinu for block 0 */
00538     /* bit alloc info */
00539     /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
00540     /* csnroffset[6] */
00541     /* (fsnoffset[4] + fgaincod[4]) * c */
00542     frame_bits += 2*4 + 3 + 6 + s->nb_all_channels * (4 + 3);
00543 
00544     /* auxdatae, crcrsv */
00545     frame_bits += 2;
00546 
00547     /* CRC */
00548     frame_bits += 16;
00549 
00550     /* calculate psd and masking curve before doing bit allocation */
00551     bit_alloc_masking(s, encoded_exp, exp_strategy, psd, mask);
00552 
00553     /* now the big work begins : do the bit allocation. Modify the snr
00554        offset until we can pack everything in the requested frame size */
00555 
00556     coarse_snr_offset = s->coarse_snr_offset;
00557     while (coarse_snr_offset >= 0 &&
00558            bit_alloc(s, mask, psd, bap, frame_bits, coarse_snr_offset, 0) < 0)
00559         coarse_snr_offset -= SNR_INC1;
00560     if (coarse_snr_offset < 0) {
00561         av_log(NULL, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
00562         return -1;
00563     }
00564     while ((coarse_snr_offset + SNR_INC1) <= 63 &&
00565            bit_alloc(s, mask, psd, bap1, frame_bits,
00566                      coarse_snr_offset + SNR_INC1, 0) >= 0) {
00567         coarse_snr_offset += SNR_INC1;
00568         memcpy(bap, bap1, sizeof(bap1));
00569     }
00570     while ((coarse_snr_offset + 1) <= 63 &&
00571            bit_alloc(s, mask, psd, bap1, frame_bits, coarse_snr_offset + 1, 0) >= 0) {
00572         coarse_snr_offset++;
00573         memcpy(bap, bap1, sizeof(bap1));
00574     }
00575 
00576     fine_snr_offset = 0;
00577     while ((fine_snr_offset + SNR_INC1) <= 15 &&
00578            bit_alloc(s, mask, psd, bap1, frame_bits,
00579                      coarse_snr_offset, fine_snr_offset + SNR_INC1) >= 0) {
00580         fine_snr_offset += SNR_INC1;
00581         memcpy(bap, bap1, sizeof(bap1));
00582     }
00583     while ((fine_snr_offset + 1) <= 15 &&
00584            bit_alloc(s, mask, psd, bap1, frame_bits,
00585                      coarse_snr_offset, fine_snr_offset + 1) >= 0) {
00586         fine_snr_offset++;
00587         memcpy(bap, bap1, sizeof(bap1));
00588     }
00589 
00590     s->coarse_snr_offset = coarse_snr_offset;
00591     for(ch=0;ch<s->nb_all_channels;ch++)
00592         s->fine_snr_offset[ch] = fine_snr_offset;
00593 #if defined(DEBUG_BITALLOC)
00594     {
00595         int j;
00596 
00597         for(i=0;i<6;i++) {
00598             for(ch=0;ch<s->nb_all_channels;ch++) {
00599                 printf("Block #%d Ch%d:\n", i, ch);
00600                 printf("bap=");
00601                 for(j=0;j<s->nb_coefs[ch];j++) {
00602                     printf("%d ",bap[i][ch][j]);
00603                 }
00604                 printf("\n");
00605             }
00606         }
00607     }
00608 #endif
00609     return 0;
00610 }
00611 
00612 static av_cold int AC3_encode_init(AVCodecContext *avctx)
00613 {
00614     int freq = avctx->sample_rate;
00615     int bitrate = avctx->bit_rate;
00616     int channels = avctx->channels;
00617     AC3EncodeContext *s = avctx->priv_data;
00618     int i, j, ch;
00619     float alpha;
00620     int bw_code;
00621     static const uint8_t channel_mode_defs[6] = {
00622         0x01, /* C */
00623         0x02, /* L R */
00624         0x03, /* L C R */
00625         0x06, /* L R SL SR */
00626         0x07, /* L C R SL SR */
00627         0x07, /* L C R SL SR (+LFE) */
00628     };
00629 
00630     avctx->frame_size = AC3_FRAME_SIZE;
00631 
00632     ac3_common_init();
00633 
00634     /* number of channels */
00635     if (channels < 1 || channels > 6)
00636         return -1;
00637     s->channel_mode = channel_mode_defs[channels - 1];
00638     s->lfe = (channels == 6) ? 1 : 0;
00639     s->nb_all_channels = channels;
00640     s->nb_channels = channels > 5 ? 5 : channels;
00641     s->lfe_channel = s->lfe ? 5 : -1;
00642 
00643     /* frequency */
00644     for(i=0;i<3;i++) {
00645         for(j=0;j<3;j++)
00646             if ((ff_ac3_sample_rate_tab[j] >> i) == freq)
00647                 goto found;
00648     }
00649     return -1;
00650  found:
00651     s->sample_rate = freq;
00652     s->sr_shift = i;
00653     s->sr_code = j;
00654     s->bitstream_id = 8 + s->sr_shift;
00655     s->bitstream_mode = 0; /* complete main audio service */
00656 
00657     /* bitrate & frame size */
00658     for(i=0;i<19;i++) {
00659         if ((ff_ac3_bitrate_tab[i] >> s->sr_shift)*1000 == bitrate)
00660             break;
00661     }
00662     if (i == 19)
00663         return -1;
00664     s->bit_rate = bitrate;
00665     s->frame_size_code = i << 1;
00666     s->frame_size_min = ff_ac3_frame_size_tab[s->frame_size_code][s->sr_code];
00667     s->bits_written = 0;
00668     s->samples_written = 0;
00669     s->frame_size = s->frame_size_min;
00670 
00671     /* bit allocation init */
00672     if(avctx->cutoff) {
00673         /* calculate bandwidth based on user-specified cutoff frequency */
00674         int cutoff = av_clip(avctx->cutoff, 1, s->sample_rate >> 1);
00675         int fbw_coeffs = cutoff * 512 / s->sample_rate;
00676         bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);
00677     } else {
00678         /* use default bandwidth setting */
00679         /* XXX: should compute the bandwidth according to the frame
00680            size, so that we avoid annoying high frequency artifacts */
00681         bw_code = 50;
00682     }
00683     for(ch=0;ch<s->nb_channels;ch++) {
00684         /* bandwidth for each channel */
00685         s->chbwcod[ch] = bw_code;
00686         s->nb_coefs[ch] = bw_code * 3 + 73;
00687     }
00688     if (s->lfe) {
00689         s->nb_coefs[s->lfe_channel] = 7; /* fixed */
00690     }
00691     /* initial snr offset */
00692     s->coarse_snr_offset = 40;
00693 
00694     /* mdct init */
00695     fft_init(MDCT_NBITS - 2);
00696     for(i=0;i<N/4;i++) {
00697         alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N;
00698         xcos1[i] = fix15(-cos(alpha));
00699         xsin1[i] = fix15(-sin(alpha));
00700     }
00701 
00702     avctx->coded_frame= avcodec_alloc_frame();
00703     avctx->coded_frame->key_frame= 1;
00704 
00705     return 0;
00706 }
00707 
00708 /* output the AC-3 frame header */
00709 static void output_frame_header(AC3EncodeContext *s, unsigned char *frame)
00710 {
00711     init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
00712 
00713     put_bits(&s->pb, 16, 0x0b77); /* frame header */
00714     put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
00715     put_bits(&s->pb, 2, s->sr_code);
00716     put_bits(&s->pb, 6, s->frame_size_code + (s->frame_size - s->frame_size_min));
00717     put_bits(&s->pb, 5, s->bitstream_id);
00718     put_bits(&s->pb, 3, s->bitstream_mode);
00719     put_bits(&s->pb, 3, s->channel_mode);
00720     if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)
00721         put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
00722     if (s->channel_mode & 0x04)
00723         put_bits(&s->pb, 2, 1); /* XXX -6 dB */
00724     if (s->channel_mode == AC3_CHMODE_STEREO)
00725         put_bits(&s->pb, 2, 0); /* surround not indicated */
00726     put_bits(&s->pb, 1, s->lfe); /* LFE */
00727     put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
00728     put_bits(&s->pb, 1, 0); /* no compression control word */
00729     put_bits(&s->pb, 1, 0); /* no lang code */
00730     put_bits(&s->pb, 1, 0); /* no audio production info */
00731     put_bits(&s->pb, 1, 0); /* no copyright */
00732     put_bits(&s->pb, 1, 1); /* original bitstream */
00733     put_bits(&s->pb, 1, 0); /* no time code 1 */
00734     put_bits(&s->pb, 1, 0); /* no time code 2 */
00735     put_bits(&s->pb, 1, 0); /* no additional bit stream info */
00736 }
00737 
00738 /* symetric quantization on 'levels' levels */
00739 static inline int sym_quant(int c, int e, int levels)
00740 {
00741     int v;
00742 
00743     if (c >= 0) {
00744         v = (levels * (c << e)) >> 24;
00745         v = (v + 1) >> 1;
00746         v = (levels >> 1) + v;
00747     } else {
00748         v = (levels * ((-c) << e)) >> 24;
00749         v = (v + 1) >> 1;
00750         v = (levels >> 1) - v;
00751     }
00752     assert (v >= 0 && v < levels);
00753     return v;
00754 }
00755 
00756 /* asymetric quantization on 2^qbits levels */
00757 static inline int asym_quant(int c, int e, int qbits)
00758 {
00759     int lshift, m, v;
00760 
00761     lshift = e + qbits - 24;
00762     if (lshift >= 0)
00763         v = c << lshift;
00764     else
00765         v = c >> (-lshift);
00766     /* rounding */
00767     v = (v + 1) >> 1;
00768     m = (1 << (qbits-1));
00769     if (v >= m)
00770         v = m - 1;
00771     assert(v >= -m);
00772     return v & ((1 << qbits)-1);
00773 }
00774 
00775 /* Output one audio block. There are NB_BLOCKS audio blocks in one AC-3
00776    frame */
00777 static void output_audio_block(AC3EncodeContext *s,
00778                                uint8_t exp_strategy[AC3_MAX_CHANNELS],
00779                                uint8_t encoded_exp[AC3_MAX_CHANNELS][N/2],
00780                                uint8_t bap[AC3_MAX_CHANNELS][N/2],
00781                                int32_t mdct_coefs[AC3_MAX_CHANNELS][N/2],
00782                                int8_t global_exp[AC3_MAX_CHANNELS],
00783                                int block_num)
00784 {
00785     int ch, nb_groups, group_size, i, baie, rbnd;
00786     uint8_t *p;
00787     uint16_t qmant[AC3_MAX_CHANNELS][N/2];
00788     int exp0, exp1;
00789     int mant1_cnt, mant2_cnt, mant4_cnt;
00790     uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr;
00791     int delta0, delta1, delta2;
00792 
00793     for(ch=0;ch<s->nb_channels;ch++)
00794         put_bits(&s->pb, 1, 0); /* 512 point MDCT */
00795     for(ch=0;ch<s->nb_channels;ch++)
00796         put_bits(&s->pb, 1, 1); /* no dither */
00797     put_bits(&s->pb, 1, 0); /* no dynamic range */
00798     if (block_num == 0) {
00799         /* for block 0, even if no coupling, we must say it. This is a
00800            waste of bit :-) */
00801         put_bits(&s->pb, 1, 1); /* coupling strategy present */
00802         put_bits(&s->pb, 1, 0); /* no coupling strategy */
00803     } else {
00804         put_bits(&s->pb, 1, 0); /* no new coupling strategy */
00805     }
00806 
00807     if (s->channel_mode == AC3_CHMODE_STEREO)
00808       {
00809         if(block_num==0)
00810           {
00811             /* first block must define rematrixing (rematstr)  */
00812             put_bits(&s->pb, 1, 1);
00813 
00814             /* dummy rematrixing rematflg(1:4)=0 */
00815             for (rbnd=0;rbnd<4;rbnd++)
00816               put_bits(&s->pb, 1, 0);
00817           }
00818         else
00819           {
00820             /* no matrixing (but should be used in the future) */
00821             put_bits(&s->pb, 1, 0);
00822           }
00823       }
00824 
00825 #if defined(DEBUG)
00826     {
00827       static int count = 0;
00828       av_log(NULL, AV_LOG_DEBUG, "Block #%d (%d)\n", block_num, count++);
00829     }
00830 #endif
00831     /* exponent strategy */
00832     for(ch=0;ch<s->nb_channels;ch++) {
00833         put_bits(&s->pb, 2, exp_strategy[ch]);
00834     }
00835 
00836     if (s->lfe) {
00837         put_bits(&s->pb, 1, exp_strategy[s->lfe_channel]);
00838     }
00839 
00840     for(ch=0;ch<s->nb_channels;ch++) {
00841         if (exp_strategy[ch] != EXP_REUSE)
00842             put_bits(&s->pb, 6, s->chbwcod[ch]);
00843     }
00844 
00845     /* exponents */
00846     for (ch = 0; ch < s->nb_all_channels; ch++) {
00847         switch(exp_strategy[ch]) {
00848         case EXP_REUSE:
00849             continue;
00850         case EXP_D15:
00851             group_size = 1;
00852             break;
00853         case EXP_D25:
00854             group_size = 2;
00855             break;
00856         default:
00857         case EXP_D45:
00858             group_size = 4;
00859             break;
00860         }
00861         nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
00862         p = encoded_exp[ch];
00863 
00864         /* first exponent */
00865         exp1 = *p++;
00866         put_bits(&s->pb, 4, exp1);
00867 
00868         /* next ones are delta encoded */
00869         for(i=0;i<nb_groups;i++) {
00870             /* merge three delta in one code */
00871             exp0 = exp1;
00872             exp1 = p[0];
00873             p += group_size;
00874             delta0 = exp1 - exp0 + 2;
00875 
00876             exp0 = exp1;
00877             exp1 = p[0];
00878             p += group_size;
00879             delta1 = exp1 - exp0 + 2;
00880 
00881             exp0 = exp1;
00882             exp1 = p[0];
00883             p += group_size;
00884             delta2 = exp1 - exp0 + 2;
00885 
00886             put_bits(&s->pb, 7, ((delta0 * 5 + delta1) * 5) + delta2);
00887         }
00888 
00889         if (ch != s->lfe_channel)
00890             put_bits(&s->pb, 2, 0); /* no gain range info */
00891     }
00892 
00893     /* bit allocation info */
00894     baie = (block_num == 0);
00895     put_bits(&s->pb, 1, baie);
00896     if (baie) {
00897         put_bits(&s->pb, 2, s->slow_decay_code);
00898         put_bits(&s->pb, 2, s->fast_decay_code);
00899         put_bits(&s->pb, 2, s->slow_gain_code);
00900         put_bits(&s->pb, 2, s->db_per_bit_code);
00901         put_bits(&s->pb, 3, s->floor_code);
00902     }
00903 
00904     /* snr offset */
00905     put_bits(&s->pb, 1, baie); /* always present with bai */
00906     if (baie) {
00907         put_bits(&s->pb, 6, s->coarse_snr_offset);
00908         for(ch=0;ch<s->nb_all_channels;ch++) {
00909             put_bits(&s->pb, 4, s->fine_snr_offset[ch]);
00910             put_bits(&s->pb, 3, s->fast_gain_code[ch]);
00911         }
00912     }
00913 
00914     put_bits(&s->pb, 1, 0); /* no delta bit allocation */
00915     put_bits(&s->pb, 1, 0); /* no data to skip */
00916 
00917     /* mantissa encoding : we use two passes to handle the grouping. A
00918        one pass method may be faster, but it would necessitate to
00919        modify the output stream. */
00920 
00921     /* first pass: quantize */
00922     mant1_cnt = mant2_cnt = mant4_cnt = 0;
00923     qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;
00924 
00925     for (ch = 0; ch < s->nb_all_channels; ch++) {
00926         int b, c, e, v;
00927 
00928         for(i=0;i<s->nb_coefs[ch];i++) {
00929             c = mdct_coefs[ch][i];
00930             e = encoded_exp[ch][i] - global_exp[ch];
00931             b = bap[ch][i];
00932             switch(b) {
00933             case 0:
00934                 v = 0;
00935                 break;
00936             case 1:
00937                 v = sym_quant(c, e, 3);
00938                 switch(mant1_cnt) {
00939                 case 0:
00940                     qmant1_ptr = &qmant[ch][i];
00941                     v = 9 * v;
00942                     mant1_cnt = 1;
00943                     break;
00944                 case 1:
00945                     *qmant1_ptr += 3 * v;
00946                     mant1_cnt = 2;
00947                     v = 128;
00948                     break;
00949                 default:
00950                     *qmant1_ptr += v;
00951                     mant1_cnt = 0;
00952                     v = 128;
00953                     break;
00954                 }
00955                 break;
00956             case 2:
00957                 v = sym_quant(c, e, 5);
00958                 switch(mant2_cnt) {
00959                 case 0:
00960                     qmant2_ptr = &qmant[ch][i];
00961                     v = 25 * v;
00962                     mant2_cnt = 1;
00963                     break;
00964                 case 1:
00965                     *qmant2_ptr += 5 * v;
00966                     mant2_cnt = 2;
00967                     v = 128;
00968                     break;
00969                 default:
00970                     *qmant2_ptr += v;
00971                     mant2_cnt = 0;
00972                     v = 128;
00973                     break;
00974                 }
00975                 break;
00976             case 3:
00977                 v = sym_quant(c, e, 7);
00978                 break;
00979             case 4:
00980                 v = sym_quant(c, e, 11);
00981                 switch(mant4_cnt) {
00982                 case 0:
00983                     qmant4_ptr = &qmant[ch][i];
00984                     v = 11 * v;
00985                     mant4_cnt = 1;
00986                     break;
00987                 default:
00988                     *qmant4_ptr += v;
00989                     mant4_cnt = 0;
00990                     v = 128;
00991                     break;
00992                 }
00993                 break;
00994             case 5:
00995                 v = sym_quant(c, e, 15);
00996                 break;
00997             case 14:
00998                 v = asym_quant(c, e, 14);
00999                 break;
01000             case 15:
01001                 v = asym_quant(c, e, 16);
01002                 break;
01003             default:
01004                 v = asym_quant(c, e, b - 1);
01005                 break;
01006             }
01007             qmant[ch][i] = v;
01008         }
01009     }
01010 
01011     /* second pass : output the values */
01012     for (ch = 0; ch < s->nb_all_channels; ch++) {
01013         int b, q;
01014 
01015         for(i=0;i<s->nb_coefs[ch];i++) {
01016             q = qmant[ch][i];
01017             b = bap[ch][i];
01018             switch(b) {
01019             case 0:
01020                 break;
01021             case 1:
01022                 if (q != 128)
01023                     put_bits(&s->pb, 5, q);
01024                 break;
01025             case 2:
01026                 if (q != 128)
01027                     put_bits(&s->pb, 7, q);
01028                 break;
01029             case 3:
01030                 put_bits(&s->pb, 3, q);
01031                 break;
01032             case 4:
01033                 if (q != 128)
01034                     put_bits(&s->pb, 7, q);
01035                 break;
01036             case 14:
01037                 put_bits(&s->pb, 14, q);
01038                 break;
01039             case 15:
01040                 put_bits(&s->pb, 16, q);
01041                 break;
01042             default:
01043                 put_bits(&s->pb, b - 1, q);
01044                 break;
01045             }
01046         }
01047     }
01048 }
01049 
01050 #define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
01051 
01052 static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
01053 {
01054     unsigned int c;
01055 
01056     c = 0;
01057     while (a) {
01058         if (a & 1)
01059             c ^= b;
01060         a = a >> 1;
01061         b = b << 1;
01062         if (b & (1 << 16))
01063             b ^= poly;
01064     }
01065     return c;
01066 }
01067 
01068 static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
01069 {
01070     unsigned int r;
01071     r = 1;
01072     while (n) {
01073         if (n & 1)
01074             r = mul_poly(r, a, poly);
01075         a = mul_poly(a, a, poly);
01076         n >>= 1;
01077     }
01078     return r;
01079 }
01080 
01081 
01082 /* compute log2(max(abs(tab[]))) */
01083 static int log2_tab(int16_t *tab, int n)
01084 {
01085     int i, v;
01086 
01087     v = 0;
01088     for(i=0;i<n;i++) {
01089         v |= abs(tab[i]);
01090     }
01091     return av_log2(v);
01092 }
01093 
01094 static void lshift_tab(int16_t *tab, int n, int lshift)
01095 {
01096     int i;
01097 
01098     if (lshift > 0) {
01099         for(i=0;i<n;i++) {
01100             tab[i] <<= lshift;
01101         }
01102     } else if (lshift < 0) {
01103         lshift = -lshift;
01104         for(i=0;i<n;i++) {
01105             tab[i] >>= lshift;
01106         }
01107     }
01108 }
01109 
01110 /* fill the end of the frame and compute the two crcs */
01111 static int output_frame_end(AC3EncodeContext *s)
01112 {
01113     int frame_size, frame_size_58, n, crc1, crc2, crc_inv;
01114     uint8_t *frame;
01115 
01116     frame_size = s->frame_size; /* frame size in words */
01117     /* align to 8 bits */
01118     flush_put_bits(&s->pb);
01119     /* add zero bytes to reach the frame size */
01120     frame = s->pb.buf;
01121     n = 2 * s->frame_size - (pbBufPtr(&s->pb) - frame) - 2;
01122     assert(n >= 0);
01123     if(n>0)
01124       memset(pbBufPtr(&s->pb), 0, n);
01125 
01126     /* Now we must compute both crcs : this is not so easy for crc1
01127        because it is at the beginning of the data... */
01128     frame_size_58 = (frame_size >> 1) + (frame_size >> 3);
01129     crc1 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
01130                            frame + 4, 2 * frame_size_58 - 4));
01131     /* XXX: could precompute crc_inv */
01132     crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58) - 16, CRC16_POLY);
01133     crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
01134     AV_WB16(frame+2,crc1);
01135 
01136     crc2 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
01137                            frame + 2 * frame_size_58,
01138                            (frame_size - frame_size_58) * 2 - 2));
01139     AV_WB16(frame+2*frame_size-2,crc2);
01140 
01141     //    printf("n=%d frame_size=%d\n", n, frame_size);
01142     return frame_size * 2;
01143 }
01144 
01145 static int AC3_encode_frame(AVCodecContext *avctx,
01146                             unsigned char *frame, int buf_size, void *data)
01147 {
01148     AC3EncodeContext *s = avctx->priv_data;
01149     int16_t *samples = data;
01150     int i, j, k, v, ch;
01151     int16_t input_samples[N];
01152     int32_t mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01153     uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01154     uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS];
01155     uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01156     uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01157     int8_t exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS];
01158     int frame_bits;
01159 
01160     frame_bits = 0;
01161     for(ch=0;ch<s->nb_all_channels;ch++) {
01162         /* fixed mdct to the six sub blocks & exponent computation */
01163         for(i=0;i<NB_BLOCKS;i++) {
01164             int16_t *sptr;
01165             int sinc;
01166 
01167             /* compute input samples */
01168             memcpy(input_samples, s->last_samples[ch], N/2 * sizeof(int16_t));
01169             sinc = s->nb_all_channels;
01170             sptr = samples + (sinc * (N/2) * i) + ch;
01171             for(j=0;j<N/2;j++) {
01172                 v = *sptr;
01173                 input_samples[j + N/2] = v;
01174                 s->last_samples[ch][j] = v;
01175                 sptr += sinc;
01176             }
01177 
01178             /* apply the MDCT window */
01179             for(j=0;j<N/2;j++) {
01180                 input_samples[j] = MUL16(input_samples[j],
01181                                          ff_ac3_window[j]) >> 15;
01182                 input_samples[N-j-1] = MUL16(input_samples[N-j-1],
01183                                              ff_ac3_window[j]) >> 15;
01184             }
01185 
01186             /* Normalize the samples to use the maximum available
01187                precision */
01188             v = 14 - log2_tab(input_samples, N);
01189             if (v < 0)
01190                 v = 0;
01191             exp_samples[i][ch] = v - 9;
01192             lshift_tab(input_samples, N, v);
01193 
01194             /* do the MDCT */
01195             mdct512(mdct_coef[i][ch], input_samples);
01196 
01197             /* compute "exponents". We take into account the
01198                normalization there */
01199             for(j=0;j<N/2;j++) {
01200                 int e;
01201                 v = abs(mdct_coef[i][ch][j]);
01202                 if (v == 0)
01203                     e = 24;
01204                 else {
01205                     e = 23 - av_log2(v) + exp_samples[i][ch];
01206                     if (e >= 24) {
01207                         e = 24;
01208                         mdct_coef[i][ch][j] = 0;
01209                     }
01210                 }
01211                 exp[i][ch][j] = e;
01212             }
01213         }
01214 
01215         compute_exp_strategy(exp_strategy, exp, ch, ch == s->lfe_channel);
01216 
01217         /* compute the exponents as the decoder will see them. The
01218            EXP_REUSE case must be handled carefully : we select the
01219            min of the exponents */
01220         i = 0;
01221         while (i < NB_BLOCKS) {
01222             j = i + 1;
01223             while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {
01224                 exponent_min(exp[i][ch], exp[j][ch], s->nb_coefs[ch]);
01225                 j++;
01226             }
01227             frame_bits += encode_exp(encoded_exp[i][ch],
01228                                      exp[i][ch], s->nb_coefs[ch],
01229                                      exp_strategy[i][ch]);
01230             /* copy encoded exponents for reuse case */
01231             for(k=i+1;k<j;k++) {
01232                 memcpy(encoded_exp[k][ch], encoded_exp[i][ch],
01233                        s->nb_coefs[ch] * sizeof(uint8_t));
01234             }
01235             i = j;
01236         }
01237     }
01238 
01239     /* adjust for fractional frame sizes */
01240     while(s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
01241         s->bits_written -= s->bit_rate;
01242         s->samples_written -= s->sample_rate;
01243     }
01244     s->frame_size = s->frame_size_min + (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
01245     s->bits_written += s->frame_size * 16;
01246     s->samples_written += AC3_FRAME_SIZE;
01247 
01248     compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);
01249     /* everything is known... let's output the frame */
01250     output_frame_header(s, frame);
01251 
01252     for(i=0;i<NB_BLOCKS;i++) {
01253         output_audio_block(s, exp_strategy[i], encoded_exp[i],
01254                            bap[i], mdct_coef[i], exp_samples[i], i);
01255     }
01256     return output_frame_end(s);
01257 }
01258 
01259 static av_cold int AC3_encode_close(AVCodecContext *avctx)
01260 {
01261     av_freep(&avctx->coded_frame);
01262     return 0;
01263 }
01264 
01265 #if 0
01266 /*************************************************************************/
01267 /* TEST */
01268 
01269 #undef random
01270 #define FN (N/4)
01271 
01272 void fft_test(void)
01273 {
01274     IComplex in[FN], in1[FN];
01275     int k, n, i;
01276     float sum_re, sum_im, a;
01277 
01278     /* FFT test */
01279 
01280     for(i=0;i<FN;i++) {
01281         in[i].re = random() % 65535 - 32767;
01282         in[i].im = random() % 65535 - 32767;
01283         in1[i] = in[i];
01284     }
01285     fft(in, 7);
01286 
01287     /* do it by hand */
01288     for(k=0;k<FN;k++) {
01289         sum_re = 0;
01290         sum_im = 0;
01291         for(n=0;n<FN;n++) {
01292             a = -2 * M_PI * (n * k) / FN;
01293             sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);
01294             sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);
01295         }
01296         printf("%3d: %6d,%6d %6.0f,%6.0f\n",
01297                k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);
01298     }
01299 }
01300 
01301 void mdct_test(void)
01302 {
01303     int16_t input[N];
01304     int32_t output[N/2];
01305     float input1[N];
01306     float output1[N/2];
01307     float s, a, err, e, emax;
01308     int i, k, n;
01309 
01310     for(i=0;i<N;i++) {
01311         input[i] = (random() % 65535 - 32767) * 9 / 10;
01312         input1[i] = input[i];
01313     }
01314 
01315     mdct512(output, input);
01316 
01317     /* do it by hand */
01318     for(k=0;k<N/2;k++) {
01319         s = 0;
01320         for(n=0;n<N;n++) {
01321             a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));
01322             s += input1[n] * cos(a);
01323         }
01324         output1[k] = -2 * s / N;
01325     }
01326 
01327     err = 0;
01328     emax = 0;
01329     for(i=0;i<N/2;i++) {
01330         printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);
01331         e = output[i] - output1[i];
01332         if (e > emax)
01333             emax = e;
01334         err += e * e;
01335     }
01336     printf("err2=%f emax=%f\n", err / (N/2), emax);
01337 }
01338 
01339 void test_ac3(void)
01340 {
01341     AC3EncodeContext ctx;
01342     unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];
01343     short samples[AC3_FRAME_SIZE];
01344     int ret, i;
01345 
01346     AC3_encode_init(&ctx, 44100, 64000, 1);
01347 
01348     fft_test();
01349     mdct_test();
01350 
01351     for(i=0;i<AC3_FRAME_SIZE;i++)
01352         samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);
01353     ret = AC3_encode_frame(&ctx, frame, samples);
01354     printf("ret=%d\n", ret);
01355 }
01356 #endif
01357 
01358 AVCodec ac3_encoder = {
01359     "ac3",
01360     CODEC_TYPE_AUDIO,
01361     CODEC_ID_AC3,
01362     sizeof(AC3EncodeContext),
01363     AC3_encode_init,
01364     AC3_encode_frame,
01365     AC3_encode_close,
01366     NULL,
01367     .sample_fmts = (enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE},
01368     .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
01369 };