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