MythTV: ac3enc.c Source File

00001 /*
00002  * The simplest AC3 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 "avcodec.h"
00029 #include "bitstream.h"
00030 #include "crc.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 bsid;
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 halfratecod;
00046     unsigned int frmsizecod;
00047     unsigned int fscod; /* frequency */
00048     unsigned int acmod;
00049     int lfe;
00050     unsigned int bsmod;
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 sgaincod, sdecaycod, fdecaycod, dbkneecod, floorcod;
00057     AC3BitAllocParameters bit_alloc;
00058     int csnroffst;
00059     int fgaincod[AC3_MAX_CHANNELS];
00060     int fsnroffst[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 fft_rev[512];
00068 static int16_t xcos1[128];
00069 static int16_t xsin1[128];
00070 
00071 #define MDCT_NBITS 9
00072 #define N         (1 << MDCT_NBITS)
00073 
00074 /* new exponents are sent if their Norm 1 exceed this number */
00075 #define EXP_DIFF_THRESHOLD 1000
00076 
00077 static void fft_init(int ln);
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 void fft_init(int ln)
00095 {
00096     int i, j, m, 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     for(i=0;i<n;i++) {
00108         m=0;
00109         for(j=0;j<ln;j++) {
00110             m |= ((i >> j) & 1) << (ln-j-1);
00111         }
00112         fft_rev[i]=m;
00113     }
00114 }
00115 
00116 /* butter fly op */
00117 #define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
00118 {\
00119   int ax, ay, bx, by;\
00120   bx=pre1;\
00121   by=pim1;\
00122   ax=qre1;\
00123   ay=qim1;\
00124   pre = (bx + ax) >> 1;\
00125   pim = (by + ay) >> 1;\
00126   qre = (bx - ax) >> 1;\
00127   qim = (by - ay) >> 1;\
00128 }
00129 
00130 #define MUL16(a,b) ((a) * (b))
00131 
00132 #define CMUL(pre, pim, are, aim, bre, bim) \
00133 {\
00134    pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15;\
00135    pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\
00136 }
00137 
00138 
00139 /* do a 2^n point complex fft on 2^ln points. */
00140 static void fft(IComplex *z, int ln)
00141 {
00142     int        j, l, np, np2;
00143     int        nblocks, nloops;
00144     register IComplex *p,*q;
00145     int tmp_re, tmp_im;
00146 
00147     np = 1 << ln;
00148 
00149     /* reverse */
00150     for(j=0;j<np;j++) {
00151         int k;
00152         IComplex tmp;
00153         k = fft_rev[j];
00154         if (k < j) {
00155             tmp = z[k];
00156             z[k] = z[j];
00157             z[j] = tmp;
00158         }
00159     }
00160 
00161     /* pass 0 */
00162 
00163     p=&z[0];
00164     j=(np >> 1);
00165     do {
00166         BF(p[0].re, p[0].im, p[1].re, p[1].im,
00167            p[0].re, p[0].im, p[1].re, p[1].im);
00168         p+=2;
00169     } while (--j != 0);
00170 
00171     /* pass 1 */
00172 
00173     p=&z[0];
00174     j=np >> 2;
00175     do {
00176         BF(p[0].re, p[0].im, p[2].re, p[2].im,
00177            p[0].re, p[0].im, p[2].re, p[2].im);
00178         BF(p[1].re, p[1].im, p[3].re, p[3].im,
00179            p[1].re, p[1].im, p[3].im, -p[3].re);
00180         p+=4;
00181     } while (--j != 0);
00182 
00183     /* pass 2 .. ln-1 */
00184 
00185     nblocks = np >> 3;
00186     nloops = 1 << 2;
00187     np2 = np >> 1;
00188     do {
00189         p = z;
00190         q = z + nloops;
00191         for (j = 0; j < nblocks; ++j) {
00192 
00193             BF(p->re, p->im, q->re, q->im,
00194                p->re, p->im, q->re, q->im);
00195 
00196             p++;
00197             q++;
00198             for(l = nblocks; l < np2; l += nblocks) {
00199                 CMUL(tmp_re, tmp_im, costab[l], -sintab[l], q->re, q->im);
00200                 BF(p->re, p->im, q->re, q->im,
00201                    p->re, p->im, tmp_re, tmp_im);
00202                 p++;
00203                 q++;
00204             }
00205             p += nloops;
00206             q += nloops;
00207         }
00208         nblocks = nblocks >> 1;
00209         nloops = nloops << 1;
00210     } while (nblocks != 0);
00211 }
00212 
00213 /* do a 512 point mdct */
00214 static void mdct512(int32_t *out, int16_t *in)
00215 {
00216     int i, re, im, re1, im1;
00217     int16_t rot[N];
00218     IComplex x[N/4];
00219 
00220     /* shift to simplify computations */
00221     for(i=0;i<N/4;i++)
00222         rot[i] = -in[i + 3*N/4];
00223     for(i=N/4;i<N;i++)
00224         rot[i] = in[i - N/4];
00225 
00226     /* pre rotation */
00227     for(i=0;i<N/4;i++) {
00228         re = ((int)rot[2*i] - (int)rot[N-1-2*i]) >> 1;
00229         im = -((int)rot[N/2+2*i] - (int)rot[N/2-1-2*i]) >> 1;
00230         CMUL(x[i].re, x[i].im, re, im, -xcos1[i], xsin1[i]);
00231     }
00232 
00233     fft(x, MDCT_NBITS - 2);
00234 
00235     /* post rotation */
00236     for(i=0;i<N/4;i++) {
00237         re = x[i].re;
00238         im = x[i].im;
00239         CMUL(re1, im1, re, im, xsin1[i], xcos1[i]);
00240         out[2*i] = im1;
00241         out[N/2-1-2*i] = re1;
00242     }
00243 }
00244 
00245 /* XXX: use another norm ? */
00246 static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n)
00247 {
00248     int sum, i;
00249     sum = 0;
00250     for(i=0;i<n;i++) {
00251         sum += abs(exp1[i] - exp2[i]);
00252     }
00253     return sum;
00254 }
00255 
00256 static void compute_exp_strategy(uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
00257                                  uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00258                                  int ch, int is_lfe)
00259 {
00260     int i, j;
00261     int exp_diff;
00262 
00263     /* estimate if the exponent variation & decide if they should be
00264        reused in the next frame */
00265     exp_strategy[0][ch] = EXP_NEW;
00266     for(i=1;i<NB_BLOCKS;i++) {
00267         exp_diff = calc_exp_diff(exp[i][ch], exp[i-1][ch], N/2);
00268 #ifdef DEBUG
00269         av_log(NULL, AV_LOG_DEBUG, "exp_diff=%d\n", exp_diff);
00270 #endif
00271         if (exp_diff > EXP_DIFF_THRESHOLD)
00272             exp_strategy[i][ch] = EXP_NEW;
00273         else
00274             exp_strategy[i][ch] = EXP_REUSE;
00275     }
00276     if (is_lfe)
00277         return;
00278 
00279     /* now select the encoding strategy type : if exponents are often
00280        recoded, we use a coarse encoding */
00281     i = 0;
00282     while (i < NB_BLOCKS) {
00283         j = i + 1;
00284         while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)
00285             j++;
00286         switch(j - i) {
00287         case 1:
00288             exp_strategy[i][ch] = EXP_D45;
00289             break;
00290         case 2:
00291         case 3:
00292             exp_strategy[i][ch] = EXP_D25;
00293             break;
00294         default:
00295             exp_strategy[i][ch] = EXP_D15;
00296             break;
00297         }
00298         i = j;
00299     }
00300 }
00301 
00302 /* set exp[i] to min(exp[i], exp1[i]) */
00303 static void exponent_min(uint8_t exp[N/2], uint8_t exp1[N/2], int n)
00304 {
00305     int i;
00306 
00307     for(i=0;i<n;i++) {
00308         if (exp1[i] < exp[i])
00309             exp[i] = exp1[i];
00310     }
00311 }
00312 
00313 /* update the exponents so that they are the ones the decoder will
00314    decode. Return the number of bits used to code the exponents */
00315 static int encode_exp(uint8_t encoded_exp[N/2],
00316                       uint8_t exp[N/2],
00317                       int nb_exps,
00318                       int exp_strategy)
00319 {
00320     int group_size, nb_groups, i, j, k, exp_min;
00321     uint8_t exp1[N/2];
00322 
00323     switch(exp_strategy) {
00324     case EXP_D15:
00325         group_size = 1;
00326         break;
00327     case EXP_D25:
00328         group_size = 2;
00329         break;
00330     default:
00331     case EXP_D45:
00332         group_size = 4;
00333         break;
00334     }
00335     nb_groups = ((nb_exps + (group_size * 3) - 4) / (3 * group_size)) * 3;
00336 
00337     /* for each group, compute the minimum exponent */
00338     exp1[0] = exp[0]; /* DC exponent is handled separately */
00339     k = 1;
00340     for(i=1;i<=nb_groups;i++) {
00341         exp_min = exp[k];
00342         assert(exp_min >= 0 && exp_min <= 24);
00343         for(j=1;j<group_size;j++) {
00344             if (exp[k+j] < exp_min)
00345                 exp_min = exp[k+j];
00346         }
00347         exp1[i] = exp_min;
00348         k += group_size;
00349     }
00350 
00351     /* constraint for DC exponent */
00352     if (exp1[0] > 15)
00353         exp1[0] = 15;
00354 
00355     /* Decrease the delta between each groups to within 2
00356      * so that they can be differentially encoded */
00357     for (i=1;i<=nb_groups;i++)
00358         exp1[i] = FFMIN(exp1[i], exp1[i-1] + 2);
00359     for (i=nb_groups-1;i>=0;i--)
00360         exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2);
00361 
00362     /* now we have the exponent values the decoder will see */
00363     encoded_exp[0] = exp1[0];
00364     k = 1;
00365     for(i=1;i<=nb_groups;i++) {
00366         for(j=0;j<group_size;j++) {
00367             encoded_exp[k+j] = exp1[i];
00368         }
00369         k += group_size;
00370     }
00371 
00372 #if defined(DEBUG)
00373     av_log(NULL, AV_LOG_DEBUG, "exponents: strategy=%d\n", exp_strategy);
00374     for(i=0;i<=nb_groups * group_size;i++) {
00375         av_log(NULL, AV_LOG_DEBUG, "%d ", encoded_exp[i]);
00376     }
00377     av_log(NULL, AV_LOG_DEBUG, "\n");
00378 #endif
00379 
00380     return 4 + (nb_groups / 3) * 7;
00381 }
00382 
00383 /* return the size in bits taken by the mantissa */
00384 static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs)
00385 {
00386     int bits, mant, i;
00387 
00388     bits = 0;
00389     for(i=0;i<nb_coefs;i++) {
00390         mant = m[i];
00391         switch(mant) {
00392         case 0:
00393             /* nothing */
00394             break;
00395         case 1:
00396             /* 3 mantissa in 5 bits */
00397             if (s->mant1_cnt == 0)
00398                 bits += 5;
00399             if (++s->mant1_cnt == 3)
00400                 s->mant1_cnt = 0;
00401             break;
00402         case 2:
00403             /* 3 mantissa in 7 bits */
00404             if (s->mant2_cnt == 0)
00405                 bits += 7;
00406             if (++s->mant2_cnt == 3)
00407                 s->mant2_cnt = 0;
00408             break;
00409         case 3:
00410             bits += 3;
00411             break;
00412         case 4:
00413             /* 2 mantissa in 7 bits */
00414             if (s->mant4_cnt == 0)
00415                 bits += 7;
00416             if (++s->mant4_cnt == 2)
00417                 s->mant4_cnt = 0;
00418             break;
00419         case 14:
00420             bits += 14;
00421             break;
00422         case 15:
00423             bits += 16;
00424             break;
00425         default:
00426             bits += mant - 1;
00427             break;
00428         }
00429     }
00430     return bits;
00431 }
00432 
00433 
00434 static void bit_alloc_masking(AC3EncodeContext *s,
00435                               uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00436                               uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
00437                               int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00438                               int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50])
00439 {
00440     int blk, ch;
00441     int16_t bndpsd[NB_BLOCKS][AC3_MAX_CHANNELS][50];
00442 
00443     for(blk=0; blk<NB_BLOCKS; blk++) {
00444         for(ch=0;ch<s->nb_all_channels;ch++) {
00445             if(exp_strategy[blk][ch] == EXP_REUSE) {
00446                 memcpy(psd[blk][ch], psd[blk-1][ch], (N/2)*sizeof(int16_t));
00447                 memcpy(mask[blk][ch], mask[blk-1][ch], 50*sizeof(int16_t));
00448             } else {
00449                 ff_ac3_bit_alloc_calc_psd(encoded_exp[blk][ch], 0,
00450                                           s->nb_coefs[ch],
00451                                           psd[blk][ch], bndpsd[blk][ch]);
00452                 ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, bndpsd[blk][ch],
00453                                            0, s->nb_coefs[ch],
00454                                            ff_fgaintab[s->fgaincod[ch]],
00455                                            ch == s->lfe_channel,
00456                                            DBA_NONE, 0, NULL, NULL, NULL,
00457                                            mask[blk][ch]);
00458             }
00459         }
00460     }
00461 }
00462 
00463 static int bit_alloc(AC3EncodeContext *s,
00464                      int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50],
00465                      int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00466                      uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00467                      int frame_bits, int csnroffst, int fsnroffst)
00468 {
00469     int i, ch;
00470     int snroffset;
00471 
00472     snroffset = (((csnroffst - 15) << 4) + fsnroffst) << 2;
00473 
00474     /* compute size */
00475     for(i=0;i<NB_BLOCKS;i++) {
00476         s->mant1_cnt = 0;
00477         s->mant2_cnt = 0;
00478         s->mant4_cnt = 0;
00479         for(ch=0;ch<s->nb_all_channels;ch++) {
00480             ff_ac3_bit_alloc_calc_bap(mask[i][ch], psd[i][ch], 0,
00481                                       s->nb_coefs[ch], snroffset,
00482                                       s->bit_alloc.floor, bap[i][ch]);
00483             frame_bits += compute_mantissa_size(s, bap[i][ch],
00484                                                  s->nb_coefs[ch]);
00485         }
00486     }
00487 #if 0
00488     printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n",
00489            csnroffst, fsnroffst, frame_bits,
00490            16 * s->frame_size - ((frame_bits + 7) & ~7));
00491 #endif
00492     return 16 * s->frame_size - frame_bits;
00493 }
00494 
00495 #define SNR_INC1 4
00496 
00497 static int compute_bit_allocation(AC3EncodeContext *s,
00498                                   uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00499                                   uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
00500                                   uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
00501                                   int frame_bits)
00502 {
00503     int i, ch;
00504     int csnroffst, fsnroffst;
00505     uint8_t bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
00506     int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
00507     int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50];
00508     static int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
00509 
00510     /* init default parameters */
00511     s->sdecaycod = 2;
00512     s->fdecaycod = 1;
00513     s->sgaincod = 1;
00514     s->dbkneecod = 2;
00515     s->floorcod = 4;
00516     for(ch=0;ch<s->nb_all_channels;ch++)
00517         s->fgaincod[ch] = 4;
00518 
00519     /* compute real values */
00520     s->bit_alloc.fscod = s->fscod;
00521     s->bit_alloc.halfratecod = s->halfratecod;
00522     s->bit_alloc.sdecay = ff_sdecaytab[s->sdecaycod] >> s->halfratecod;
00523     s->bit_alloc.fdecay = ff_fdecaytab[s->fdecaycod] >> s->halfratecod;
00524     s->bit_alloc.sgain = ff_sgaintab[s->sgaincod];
00525     s->bit_alloc.dbknee = ff_dbkneetab[s->dbkneecod];
00526     s->bit_alloc.floor = ff_floortab[s->floorcod];
00527 
00528     /* header size */
00529     frame_bits += 65;
00530     // if (s->acmod == 2)
00531     //    frame_bits += 2;
00532     frame_bits += frame_bits_inc[s->acmod];
00533 
00534     /* audio blocks */
00535     for(i=0;i<NB_BLOCKS;i++) {
00536         frame_bits += s->nb_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
00537         if (s->acmod == AC3_ACMOD_STEREO) {
00538             frame_bits++; /* rematstr */
00539             if(i==0) frame_bits += 4;
00540         }
00541         frame_bits += 2 * s->nb_channels; /* chexpstr[2] * c */
00542         if (s->lfe)
00543             frame_bits++; /* lfeexpstr */
00544         for(ch=0;ch<s->nb_channels;ch++) {
00545             if (exp_strategy[i][ch] != EXP_REUSE)
00546                 frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
00547         }
00548         frame_bits++; /* baie */
00549         frame_bits++; /* snr */
00550         frame_bits += 2; /* delta / skip */
00551     }
00552     frame_bits++; /* cplinu for block 0 */
00553     /* bit alloc info */
00554     /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
00555     /* csnroffset[6] */
00556     /* (fsnoffset[4] + fgaincod[4]) * c */
00557     frame_bits += 2*4 + 3 + 6 + s->nb_all_channels * (4 + 3);
00558 
00559     /* auxdatae, crcrsv */
00560     frame_bits += 2;
00561 
00562     /* CRC */
00563     frame_bits += 16;
00564 
00565     /* calculate psd and masking curve before doing bit allocation */
00566     bit_alloc_masking(s, encoded_exp, exp_strategy, psd, mask);
00567 
00568     /* now the big work begins : do the bit allocation. Modify the snr
00569        offset until we can pack everything in the requested frame size */
00570 
00571     csnroffst = s->csnroffst;
00572     while (csnroffst >= 0 &&
00573            bit_alloc(s, mask, psd, bap, frame_bits, csnroffst, 0) < 0)
00574         csnroffst -= SNR_INC1;
00575     if (csnroffst < 0) {
00576         av_log(NULL, AV_LOG_ERROR, "Bit allocation failed, try increasing the bitrate, -ab 384 for example!\n");
00577         return -1;
00578     }
00579     while ((csnroffst + SNR_INC1) <= 63 &&
00580            bit_alloc(s, mask, psd, bap1, frame_bits,
00581                      csnroffst + SNR_INC1, 0) >= 0) {
00582         csnroffst += SNR_INC1;
00583         memcpy(bap, bap1, sizeof(bap1));
00584     }
00585     while ((csnroffst + 1) <= 63 &&
00586            bit_alloc(s, mask, psd, bap1, frame_bits, csnroffst + 1, 0) >= 0) {
00587         csnroffst++;
00588         memcpy(bap, bap1, sizeof(bap1));
00589     }
00590 
00591     fsnroffst = 0;
00592     while ((fsnroffst + SNR_INC1) <= 15 &&
00593            bit_alloc(s, mask, psd, bap1, frame_bits,
00594                      csnroffst, fsnroffst + SNR_INC1) >= 0) {
00595         fsnroffst += SNR_INC1;
00596         memcpy(bap, bap1, sizeof(bap1));
00597     }
00598     while ((fsnroffst + 1) <= 15 &&
00599            bit_alloc(s, mask, psd, bap1, frame_bits,
00600                      csnroffst, fsnroffst + 1) >= 0) {
00601         fsnroffst++;
00602         memcpy(bap, bap1, sizeof(bap1));
00603     }
00604 
00605     s->csnroffst = csnroffst;
00606     for(ch=0;ch<s->nb_all_channels;ch++)
00607         s->fsnroffst[ch] = fsnroffst;
00608 #if defined(DEBUG_BITALLOC)
00609     {
00610         int j;
00611 
00612         for(i=0;i<6;i++) {
00613             for(ch=0;ch<s->nb_all_channels;ch++) {
00614                 printf("Block #%d Ch%d:\n", i, ch);
00615                 printf("bap=");
00616                 for(j=0;j<s->nb_coefs[ch];j++) {
00617                     printf("%d ",bap[i][ch][j]);
00618                 }
00619                 printf("\n");
00620             }
00621         }
00622     }
00623 #endif
00624     return 0;
00625 }
00626 
00627 static int AC3_encode_init(AVCodecContext *avctx)
00628 {
00629     int freq = avctx->sample_rate;
00630     int bitrate = avctx->bit_rate;
00631     int channels = avctx->channels;
00632     AC3EncodeContext *s = avctx->priv_data;
00633     int i, j, ch;
00634     float alpha;
00635     static const uint8_t acmod_defs[6] = {
00636         0x01, /* C */
00637         0x02, /* L R */
00638         0x03, /* L C R */
00639         0x06, /* L R SL SR */
00640         0x07, /* L C R SL SR */
00641         0x07, /* L C R SL SR (+LFE) */
00642     };
00643 
00644     avctx->frame_size = AC3_FRAME_SIZE;
00645 
00646     ac3_common_init();
00647 
00648     /* number of channels */
00649     if (channels < 1 || channels > 6)
00650         return -1;
00651     s->acmod = acmod_defs[channels - 1];
00652     s->lfe = (channels == 6) ? 1 : 0;
00653     s->nb_all_channels = channels;
00654     s->nb_channels = channels > 5 ? 5 : channels;
00655     s->lfe_channel = s->lfe ? 5 : -1;
00656 
00657     /* frequency */
00658     for(i=0;i<3;i++) {
00659         for(j=0;j<3;j++)
00660             if ((ff_ac3_freqs[j] >> i) == freq)
00661                 goto found;
00662     }
00663     return -1;
00664  found:
00665     s->sample_rate = freq;
00666     s->halfratecod = i;
00667     s->fscod = j;
00668     s->bsid = 8 + s->halfratecod;
00669     s->bsmod = 0; /* complete main audio service */
00670 
00671     /* bitrate & frame size */
00672     bitrate /= 1000;
00673     for(i=0;i<19;i++) {
00674         if ((ff_ac3_bitratetab[i] >> s->halfratecod) == bitrate)
00675             break;
00676     }
00677     if (i == 19)
00678         return -1;
00679     s->bit_rate = bitrate;
00680     s->frmsizecod = i << 1;
00681     s->frame_size_min = ff_ac3_frame_sizes[s->frmsizecod][s->fscod];
00682     s->bits_written = 0;
00683     s->samples_written = 0;
00684     s->frame_size = s->frame_size_min;
00685 
00686     /* bit allocation init */
00687     for(ch=0;ch<s->nb_channels;ch++) {
00688         /* bandwidth for each channel */
00689         /* XXX: should compute the bandwidth according to the frame
00690            size, so that we avoid anoying high freq artefacts */
00691         s->chbwcod[ch] = 50; /* sample bandwidth as mpeg audio layer 2 table 0 */
00692         s->nb_coefs[ch] = ((s->chbwcod[ch] + 12) * 3) + 37;
00693     }
00694     if (s->lfe) {
00695         s->nb_coefs[s->lfe_channel] = 7; /* fixed */
00696     }
00697     /* initial snr offset */
00698     s->csnroffst = 40;
00699 
00700     /* mdct init */
00701     fft_init(MDCT_NBITS - 2);
00702     for(i=0;i<N/4;i++) {
00703         alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N;
00704         xcos1[i] = fix15(-cos(alpha));
00705         xsin1[i] = fix15(-sin(alpha));
00706     }
00707 
00708     avctx->coded_frame= avcodec_alloc_frame();
00709     avctx->coded_frame->key_frame= 1;
00710 
00711     return 0;
00712 }
00713 
00714 /* output the AC3 frame header */
00715 static void output_frame_header(AC3EncodeContext *s, unsigned char *frame)
00716 {
00717     init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
00718 
00719     put_bits(&s->pb, 16, 0x0b77); /* frame header */
00720     put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
00721     put_bits(&s->pb, 2, s->fscod);
00722     put_bits(&s->pb, 6, s->frmsizecod + (s->frame_size - s->frame_size_min));
00723     put_bits(&s->pb, 5, s->bsid);
00724     put_bits(&s->pb, 3, s->bsmod);
00725     put_bits(&s->pb, 3, s->acmod);
00726     if ((s->acmod & 0x01) && s->acmod != AC3_ACMOD_MONO)
00727         put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
00728     if (s->acmod & 0x04)
00729         put_bits(&s->pb, 2, 1); /* XXX -6 dB */
00730     if (s->acmod == AC3_ACMOD_STEREO)
00731         put_bits(&s->pb, 2, 0); /* surround not indicated */
00732     put_bits(&s->pb, 1, s->lfe); /* LFE */
00733     put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
00734     put_bits(&s->pb, 1, 0); /* no compression control word */
00735     put_bits(&s->pb, 1, 0); /* no lang code */
00736     put_bits(&s->pb, 1, 0); /* no audio production info */
00737     put_bits(&s->pb, 1, 0); /* no copyright */
00738     put_bits(&s->pb, 1, 1); /* original bitstream */
00739     put_bits(&s->pb, 1, 0); /* no time code 1 */
00740     put_bits(&s->pb, 1, 0); /* no time code 2 */
00741     put_bits(&s->pb, 1, 0); /* no addtional bit stream info */
00742 }
00743 
00744 /* symetric quantization on 'levels' levels */
00745 static inline int sym_quant(int c, int e, int levels)
00746 {
00747     int v;
00748 
00749     if (c >= 0) {
00750         v = (levels * (c << e)) >> 24;
00751         v = (v + 1) >> 1;
00752         v = (levels >> 1) + v;
00753     } else {
00754         v = (levels * ((-c) << e)) >> 24;
00755         v = (v + 1) >> 1;
00756         v = (levels >> 1) - v;
00757     }
00758     assert (v >= 0 && v < levels);
00759     return v;
00760 }
00761 
00762 /* asymetric quantization on 2^qbits levels */
00763 static inline int asym_quant(int c, int e, int qbits)
00764 {
00765     int lshift, m, v;
00766 
00767     lshift = e + qbits - 24;
00768     if (lshift >= 0)
00769         v = c << lshift;
00770     else
00771         v = c >> (-lshift);
00772     /* rounding */
00773     v = (v + 1) >> 1;
00774     m = (1 << (qbits-1));
00775     if (v >= m)
00776         v = m - 1;
00777     assert(v >= -m);
00778     return v & ((1 << qbits)-1);
00779 }
00780 
00781 /* Output one audio block. There are NB_BLOCKS audio blocks in one AC3
00782    frame */
00783 static void output_audio_block(AC3EncodeContext *s,
00784                                uint8_t exp_strategy[AC3_MAX_CHANNELS],
00785                                uint8_t encoded_exp[AC3_MAX_CHANNELS][N/2],
00786                                uint8_t bap[AC3_MAX_CHANNELS][N/2],
00787                                int32_t mdct_coefs[AC3_MAX_CHANNELS][N/2],
00788                                int8_t global_exp[AC3_MAX_CHANNELS],
00789                                int block_num)
00790 {
00791     int ch, nb_groups, group_size, i, baie, rbnd;
00792     uint8_t *p;
00793     uint16_t qmant[AC3_MAX_CHANNELS][N/2];
00794     int exp0, exp1;
00795     int mant1_cnt, mant2_cnt, mant4_cnt;
00796     uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr;
00797     int delta0, delta1, delta2;
00798 
00799     for(ch=0;ch<s->nb_channels;ch++)
00800         put_bits(&s->pb, 1, 0); /* 512 point MDCT */
00801     for(ch=0;ch<s->nb_channels;ch++)
00802         put_bits(&s->pb, 1, 1); /* no dither */
00803     put_bits(&s->pb, 1, 0); /* no dynamic range */
00804     if (block_num == 0) {
00805         /* for block 0, even if no coupling, we must say it. This is a
00806            waste of bit :-) */
00807         put_bits(&s->pb, 1, 1); /* coupling strategy present */
00808         put_bits(&s->pb, 1, 0); /* no coupling strategy */
00809     } else {
00810         put_bits(&s->pb, 1, 0); /* no new coupling strategy */
00811     }
00812 
00813     if (s->acmod == AC3_ACMOD_STEREO)
00814       {
00815         if(block_num==0)
00816           {
00817             /* first block must define rematrixing (rematstr)  */
00818             put_bits(&s->pb, 1, 1);
00819 
00820             /* dummy rematrixing rematflg(1:4)=0 */
00821             for (rbnd=0;rbnd<4;rbnd++)
00822               put_bits(&s->pb, 1, 0);
00823           }
00824         else
00825           {
00826             /* no matrixing (but should be used in the future) */
00827             put_bits(&s->pb, 1, 0);
00828           }
00829       }
00830 
00831 #if defined(DEBUG)
00832     {
00833       static int count = 0;
00834       av_log(NULL, AV_LOG_DEBUG, "Block #%d (%d)\n", block_num, count++);
00835     }
00836 #endif
00837     /* exponent strategy */
00838     for(ch=0;ch<s->nb_channels;ch++) {
00839         put_bits(&s->pb, 2, exp_strategy[ch]);
00840     }
00841 
00842     if (s->lfe) {
00843         put_bits(&s->pb, 1, exp_strategy[s->lfe_channel]);
00844     }
00845 
00846     for(ch=0;ch<s->nb_channels;ch++) {
00847         if (exp_strategy[ch] != EXP_REUSE)
00848             put_bits(&s->pb, 6, s->chbwcod[ch]);
00849     }
00850 
00851     /* exponents */
00852     for (ch = 0; ch < s->nb_all_channels; ch++) {
00853         switch(exp_strategy[ch]) {
00854         case EXP_REUSE:
00855             continue;
00856         case EXP_D15:
00857             group_size = 1;
00858             break;
00859         case EXP_D25:
00860             group_size = 2;
00861             break;
00862         default:
00863         case EXP_D45:
00864             group_size = 4;
00865             break;
00866         }
00867         nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
00868         p = encoded_exp[ch];
00869 
00870         /* first exponent */
00871         exp1 = *p++;
00872         put_bits(&s->pb, 4, exp1);
00873 
00874         /* next ones are delta encoded */
00875         for(i=0;i<nb_groups;i++) {
00876             /* merge three delta in one code */
00877             exp0 = exp1;
00878             exp1 = p[0];
00879             p += group_size;
00880             delta0 = exp1 - exp0 + 2;
00881 
00882             exp0 = exp1;
00883             exp1 = p[0];
00884             p += group_size;
00885             delta1 = exp1 - exp0 + 2;
00886 
00887             exp0 = exp1;
00888             exp1 = p[0];
00889             p += group_size;
00890             delta2 = exp1 - exp0 + 2;
00891 
00892             put_bits(&s->pb, 7, ((delta0 * 5 + delta1) * 5) + delta2);
00893         }
00894 
00895         if (ch != s->lfe_channel)
00896             put_bits(&s->pb, 2, 0); /* no gain range info */
00897     }
00898 
00899     /* bit allocation info */
00900     baie = (block_num == 0);
00901     put_bits(&s->pb, 1, baie);
00902     if (baie) {
00903         put_bits(&s->pb, 2, s->sdecaycod);
00904         put_bits(&s->pb, 2, s->fdecaycod);
00905         put_bits(&s->pb, 2, s->sgaincod);
00906         put_bits(&s->pb, 2, s->dbkneecod);
00907         put_bits(&s->pb, 3, s->floorcod);
00908     }
00909 
00910     /* snr offset */
00911     put_bits(&s->pb, 1, baie); /* always present with bai */
00912     if (baie) {
00913         put_bits(&s->pb, 6, s->csnroffst);
00914         for(ch=0;ch<s->nb_all_channels;ch++) {
00915             put_bits(&s->pb, 4, s->fsnroffst[ch]);
00916             put_bits(&s->pb, 3, s->fgaincod[ch]);
00917         }
00918     }
00919 
00920     put_bits(&s->pb, 1, 0); /* no delta bit allocation */
00921     put_bits(&s->pb, 1, 0); /* no data to skip */
00922 
00923     /* mantissa encoding : we use two passes to handle the grouping. A
00924        one pass method may be faster, but it would necessitate to
00925        modify the output stream. */
00926 
00927     /* first pass: quantize */
00928     mant1_cnt = mant2_cnt = mant4_cnt = 0;
00929     qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;
00930 
00931     for (ch = 0; ch < s->nb_all_channels; ch++) {
00932         int b, c, e, v;
00933 
00934         for(i=0;i<s->nb_coefs[ch];i++) {
00935             c = mdct_coefs[ch][i];
00936             e = encoded_exp[ch][i] - global_exp[ch];
00937             b = bap[ch][i];
00938             switch(b) {
00939             case 0:
00940                 v = 0;
00941                 break;
00942             case 1:
00943                 v = sym_quant(c, e, 3);
00944                 switch(mant1_cnt) {
00945                 case 0:
00946                     qmant1_ptr = &qmant[ch][i];
00947                     v = 9 * v;
00948                     mant1_cnt = 1;
00949                     break;
00950                 case 1:
00951                     *qmant1_ptr += 3 * v;
00952                     mant1_cnt = 2;
00953                     v = 128;
00954                     break;
00955                 default:
00956                     *qmant1_ptr += v;
00957                     mant1_cnt = 0;
00958                     v = 128;
00959                     break;
00960                 }
00961                 break;
00962             case 2:
00963                 v = sym_quant(c, e, 5);
00964                 switch(mant2_cnt) {
00965                 case 0:
00966                     qmant2_ptr = &qmant[ch][i];
00967                     v = 25 * v;
00968                     mant2_cnt = 1;
00969                     break;
00970                 case 1:
00971                     *qmant2_ptr += 5 * v;
00972                     mant2_cnt = 2;
00973                     v = 128;
00974                     break;
00975                 default:
00976                     *qmant2_ptr += v;
00977                     mant2_cnt = 0;
00978                     v = 128;
00979                     break;
00980                 }
00981                 break;
00982             case 3:
00983                 v = sym_quant(c, e, 7);
00984                 break;
00985             case 4:
00986                 v = sym_quant(c, e, 11);
00987                 switch(mant4_cnt) {
00988                 case 0:
00989                     qmant4_ptr = &qmant[ch][i];
00990                     v = 11 * v;
00991                     mant4_cnt = 1;
00992                     break;
00993                 default:
00994                     *qmant4_ptr += v;
00995                     mant4_cnt = 0;
00996                     v = 128;
00997                     break;
00998                 }
00999                 break;
01000             case 5:
01001                 v = sym_quant(c, e, 15);
01002                 break;
01003             case 14:
01004                 v = asym_quant(c, e, 14);
01005                 break;
01006             case 15:
01007                 v = asym_quant(c, e, 16);
01008                 break;
01009             default:
01010                 v = asym_quant(c, e, b - 1);
01011                 break;
01012             }
01013             qmant[ch][i] = v;
01014         }
01015     }
01016 
01017     /* second pass : output the values */
01018     for (ch = 0; ch < s->nb_all_channels; ch++) {
01019         int b, q;
01020 
01021         for(i=0;i<s->nb_coefs[ch];i++) {
01022             q = qmant[ch][i];
01023             b = bap[ch][i];
01024             switch(b) {
01025             case 0:
01026                 break;
01027             case 1:
01028                 if (q != 128)
01029                     put_bits(&s->pb, 5, q);
01030                 break;
01031             case 2:
01032                 if (q != 128)
01033                     put_bits(&s->pb, 7, q);
01034                 break;
01035             case 3:
01036                 put_bits(&s->pb, 3, q);
01037                 break;
01038             case 4:
01039                 if (q != 128)
01040                     put_bits(&s->pb, 7, q);
01041                 break;
01042             case 14:
01043                 put_bits(&s->pb, 14, q);
01044                 break;
01045             case 15:
01046                 put_bits(&s->pb, 16, q);
01047                 break;
01048             default:
01049                 put_bits(&s->pb, b - 1, q);
01050                 break;
01051             }
01052         }
01053     }
01054 }
01055 
01056 #define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
01057 
01058 static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
01059 {
01060     unsigned int c;
01061 
01062     c = 0;
01063     while (a) {
01064         if (a & 1)
01065             c ^= b;
01066         a = a >> 1;
01067         b = b << 1;
01068         if (b & (1 << 16))
01069             b ^= poly;
01070     }
01071     return c;
01072 }
01073 
01074 static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
01075 {
01076     unsigned int r;
01077     r = 1;
01078     while (n) {
01079         if (n & 1)
01080             r = mul_poly(r, a, poly);
01081         a = mul_poly(a, a, poly);
01082         n >>= 1;
01083     }
01084     return r;
01085 }
01086 
01087 
01088 /* compute log2(max(abs(tab[]))) */
01089 static int log2_tab(int16_t *tab, int n)
01090 {
01091     int i, v;
01092 
01093     v = 0;
01094     for(i=0;i<n;i++) {
01095         v |= abs(tab[i]);
01096     }
01097     return av_log2(v);
01098 }
01099 
01100 static void lshift_tab(int16_t *tab, int n, int lshift)
01101 {
01102     int i;
01103 
01104     if (lshift > 0) {
01105         for(i=0;i<n;i++) {
01106             tab[i] <<= lshift;
01107         }
01108     } else if (lshift < 0) {
01109         lshift = -lshift;
01110         for(i=0;i<n;i++) {
01111             tab[i] >>= lshift;
01112         }
01113     }
01114 }
01115 
01116 /* fill the end of the frame and compute the two crcs */
01117 static int output_frame_end(AC3EncodeContext *s)
01118 {
01119     int frame_size, frame_size_58, n, crc1, crc2, crc_inv;
01120     uint8_t *frame;
01121 
01122     frame_size = s->frame_size; /* frame size in words */
01123     /* align to 8 bits */
01124     flush_put_bits(&s->pb);
01125     /* add zero bytes to reach the frame size */
01126     frame = s->pb.buf;
01127     n = 2 * s->frame_size - (pbBufPtr(&s->pb) - frame) - 2;
01128     assert(n >= 0);
01129     if(n>0)
01130       memset(pbBufPtr(&s->pb), 0, n);
01131 
01132     /* Now we must compute both crcs : this is not so easy for crc1
01133        because it is at the beginning of the data... */
01134     frame_size_58 = (frame_size >> 1) + (frame_size >> 3);
01135     crc1 = bswap_16(av_crc(av_crc8005, 0, frame + 4, 2 * frame_size_58 - 4));
01136     /* XXX: could precompute crc_inv */
01137     crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58) - 16, CRC16_POLY);
01138     crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
01139     AV_WB16(frame+2,crc1);
01140 
01141     crc2 = bswap_16(av_crc(av_crc8005, 0, frame + 2 * frame_size_58, (frame_size - frame_size_58) * 2 - 2));
01142     AV_WB16(frame+2*frame_size-2,crc2);
01143 
01144     //    printf("n=%d frame_size=%d\n", n, frame_size);
01145     return frame_size * 2;
01146 }
01147 
01148 static int AC3_encode_frame(AVCodecContext *avctx,
01149                             unsigned char *frame, int buf_size, void *data)
01150 {
01151     AC3EncodeContext *s = avctx->priv_data;
01152     int16_t *samples = data;
01153     int i, j, k, v, ch;
01154     int16_t input_samples[N];
01155     int32_t mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01156     uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01157     uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS];
01158     uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01159     uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01160     int8_t exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS];
01161     int frame_bits;
01162 
01163     frame_bits = 0;
01164     for(ch=0;ch<s->nb_all_channels;ch++) {
01165         /* fixed mdct to the six sub blocks & exponent computation */
01166         for(i=0;i<NB_BLOCKS;i++) {
01167             int16_t *sptr;
01168             int sinc;
01169 
01170             /* compute input samples */
01171             memcpy(input_samples, s->last_samples[ch], N/2 * sizeof(int16_t));
01172             sinc = s->nb_all_channels;
01173             sptr = samples + (sinc * (N/2) * i) + ch;
01174             for(j=0;j<N/2;j++) {
01175                 v = *sptr;
01176                 input_samples[j + N/2] = v;
01177                 s->last_samples[ch][j] = v;
01178                 sptr += sinc;
01179             }
01180 
01181             /* apply the MDCT window */
01182             for(j=0;j<N/2;j++) {
01183                 input_samples[j] = MUL16(input_samples[j],
01184                                          ff_ac3_window[j]) >> 15;
01185                 input_samples[N-j-1] = MUL16(input_samples[N-j-1],
01186                                              ff_ac3_window[j]) >> 15;
01187             }
01188 
01189             /* Normalize the samples to use the maximum available
01190                precision */
01191             v = 14 - log2_tab(input_samples, N);
01192             if (v < 0)
01193                 v = 0;
01194             exp_samples[i][ch] = v - 9;
01195             lshift_tab(input_samples, N, v);
01196 
01197             /* do the MDCT */
01198             mdct512(mdct_coef[i][ch], input_samples);
01199 
01200             /* compute "exponents". We take into account the
01201                normalization there */
01202             for(j=0;j<N/2;j++) {
01203                 int e;
01204                 v = abs(mdct_coef[i][ch][j]);
01205                 if (v == 0)
01206                     e = 24;
01207                 else {
01208                     e = 23 - av_log2(v) + exp_samples[i][ch];
01209                     if (e >= 24) {
01210                         e = 24;
01211                         mdct_coef[i][ch][j] = 0;
01212                     }
01213                 }
01214                 exp[i][ch][j] = e;
01215             }
01216         }
01217 
01218         compute_exp_strategy(exp_strategy, exp, ch, ch == s->lfe_channel);
01219 
01220         /* compute the exponents as the decoder will see them. The
01221            EXP_REUSE case must be handled carefully : we select the
01222            min of the exponents */
01223         i = 0;
01224         while (i < NB_BLOCKS) {
01225             j = i + 1;
01226             while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {
01227                 exponent_min(exp[i][ch], exp[j][ch], s->nb_coefs[ch]);
01228                 j++;
01229             }
01230             frame_bits += encode_exp(encoded_exp[i][ch],
01231                                      exp[i][ch], s->nb_coefs[ch],
01232                                      exp_strategy[i][ch]);
01233             /* copy encoded exponents for reuse case */
01234             for(k=i+1;k<j;k++) {
01235                 memcpy(encoded_exp[k][ch], encoded_exp[i][ch],
01236                        s->nb_coefs[ch] * sizeof(uint8_t));
01237             }
01238             i = j;
01239         }
01240     }
01241 
01242     /* adjust for fractional frame sizes */
01243     while(s->bits_written >= s->bit_rate*1000 && s->samples_written >= s->sample_rate) {
01244         s->bits_written -= s->bit_rate*1000;
01245         s->samples_written -= s->sample_rate;
01246     }
01247     s->frame_size = s->frame_size_min + (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate*1000);
01248     s->bits_written += s->frame_size * 16;
01249     s->samples_written += AC3_FRAME_SIZE;
01250 
01251     compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);
01252     /* everything is known... let's output the frame */
01253     output_frame_header(s, frame);
01254 
01255     for(i=0;i<NB_BLOCKS;i++) {
01256         output_audio_block(s, exp_strategy[i], encoded_exp[i],
01257                            bap[i], mdct_coef[i], exp_samples[i], i);
01258     }
01259     return output_frame_end(s);
01260 }
01261 
01262 static int AC3_encode_close(AVCodecContext *avctx)
01263 {
01264     av_freep(&avctx->coded_frame);
01265     return 0;
01266 }
01267 
01268 #if 0
01269 /*************************************************************************/
01270 /* TEST */
01271 
01272 #undef random
01273 #define FN (N/4)
01274 
01275 void fft_test(void)
01276 {
01277     IComplex in[FN], in1[FN];
01278     int k, n, i;
01279     float sum_re, sum_im, a;
01280 
01281     /* FFT test */
01282 
01283     for(i=0;i<FN;i++) {
01284         in[i].re = random() % 65535 - 32767;
01285         in[i].im = random() % 65535 - 32767;
01286         in1[i] = in[i];
01287     }
01288     fft(in, 7);
01289 
01290     /* do it by hand */
01291     for(k=0;k<FN;k++) {
01292         sum_re = 0;
01293         sum_im = 0;
01294         for(n=0;n<FN;n++) {
01295             a = -2 * M_PI * (n * k) / FN;
01296             sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);
01297             sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);
01298         }
01299         printf("%3d: %6d,%6d %6.0f,%6.0f\n",
01300                k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);
01301     }
01302 }
01303 
01304 void mdct_test(void)
01305 {
01306     int16_t input[N];
01307     int32_t output[N/2];
01308     float input1[N];
01309     float output1[N/2];
01310     float s, a, err, e, emax;
01311     int i, k, n;
01312 
01313     for(i=0;i<N;i++) {
01314         input[i] = (random() % 65535 - 32767) * 9 / 10;
01315         input1[i] = input[i];
01316     }
01317 
01318     mdct512(output, input);
01319 
01320     /* do it by hand */
01321     for(k=0;k<N/2;k++) {
01322         s = 0;
01323         for(n=0;n<N;n++) {
01324             a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));
01325             s += input1[n] * cos(a);
01326         }
01327         output1[k] = -2 * s / N;
01328     }
01329 
01330     err = 0;
01331     emax = 0;
01332     for(i=0;i<N/2;i++) {
01333         printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);
01334         e = output[i] - output1[i];
01335         if (e > emax)
01336             emax = e;
01337         err += e * e;
01338     }
01339     printf("err2=%f emax=%f\n", err / (N/2), emax);
01340 }
01341 
01342 void test_ac3(void)
01343 {
01344     AC3EncodeContext ctx;
01345     unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];
01346     short samples[AC3_FRAME_SIZE];
01347     int ret, i;
01348 
01349     AC3_encode_init(&ctx, 44100, 64000, 1);
01350 
01351     fft_test();
01352     mdct_test();
01353 
01354     for(i=0;i<AC3_FRAME_SIZE;i++)
01355         samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);
01356     ret = AC3_encode_frame(&ctx, frame, samples);
01357     printf("ret=%d\n", ret);
01358 }
01359 #endif
01360 
01361 AVCodec ac3_encoder = {
01362     "ac3",
01363     CODEC_TYPE_AUDIO,
01364     CODEC_ID_AC3,
01365     sizeof(AC3EncodeContext),
01366     AC3_encode_init,
01367     AC3_encode_frame,
01368     AC3_encode_close,
01369     NULL,
01370 };