00001
00002
00003
00004
00005
00006
00007
00008
00009
00010
00011
00012
00013
00014
00015
00016
00017
00018
00019
00020
00021
00026
00027
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 bitstream_id;
00041 unsigned int frame_size_min;
00042 unsigned int frame_size;
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;
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
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
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
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 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
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
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
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
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
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
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
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
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
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
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
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
00248
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
00264
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
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
00298
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
00322 exp1[0] = exp[0];
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
00336 if (exp1[0] > 15)
00337 exp1[0] = 15;
00338
00339
00340
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
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
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
00378 break;
00379 case 1:
00380
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
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
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
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, 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 int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
00493
00494
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
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
00513 frame_bits += 65;
00514
00515
00516 frame_bits += frame_bits_inc[s->channel_mode];
00517
00518
00519 for(i=0;i<NB_BLOCKS;i++) {
00520 frame_bits += s->nb_channels * 2 + 2;
00521 if (s->channel_mode == AC3_CHMODE_STEREO) {
00522 frame_bits++;
00523 if(i==0) frame_bits += 4;
00524 }
00525 frame_bits += 2 * s->nb_channels;
00526 if (s->lfe)
00527 frame_bits++;
00528 for(ch=0;ch<s->nb_channels;ch++) {
00529 if (exp_strategy[i][ch] != EXP_REUSE)
00530 frame_bits += 6 + 2;
00531 }
00532 frame_bits++;
00533 frame_bits++;
00534 frame_bits += 2;
00535 }
00536 frame_bits++;
00537
00538
00539
00540
00541 frame_bits += 2*4 + 3 + 6 + s->nb_all_channels * (4 + 3);
00542
00543
00544 frame_bits += 2;
00545
00546
00547 frame_bits += 16;
00548
00549
00550 bit_alloc_masking(s, encoded_exp, exp_strategy, psd, mask);
00551
00552
00553
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 int AC3_encode_init(AVCodecContext *avctx)
00612 {
00613 int freq = avctx->sample_rate;
00614 int bitrate = avctx->bit_rate;
00615 int channels = avctx->channels;
00616 AC3EncodeContext *s = avctx->priv_data;
00617 int i, j, ch;
00618 float alpha;
00619 int bw_code;
00620 static const uint8_t channel_mode_defs[6] = {
00621 0x01,
00622 0x02,
00623 0x03,
00624 0x06,
00625 0x07,
00626 0x07,
00627 };
00628
00629 avctx->frame_size = AC3_FRAME_SIZE;
00630
00631 ac3_common_init();
00632
00633
00634 if (channels < 1 || channels > 6)
00635 return -1;
00636 s->channel_mode = channel_mode_defs[channels - 1];
00637 s->lfe = (channels == 6) ? 1 : 0;
00638 s->nb_all_channels = channels;
00639 s->nb_channels = channels > 5 ? 5 : channels;
00640 s->lfe_channel = s->lfe ? 5 : -1;
00641
00642
00643 for(i=0;i<3;i++) {
00644 for(j=0;j<3;j++)
00645 if ((ff_ac3_sample_rate_tab[j] >> i) == freq)
00646 goto found;
00647 }
00648 return -1;
00649 found:
00650 s->sample_rate = freq;
00651 s->sr_shift = i;
00652 s->sr_code = j;
00653 s->bitstream_id = 8 + s->sr_shift;
00654 s->bitstream_mode = 0;
00655
00656
00657 for(i=0;i<19;i++) {
00658 if ((ff_ac3_bitrate_tab[i] >> s->sr_shift)*1000 == bitrate)
00659 break;
00660 }
00661 if (i == 19)
00662 return -1;
00663 s->bit_rate = bitrate;
00664 s->frame_size_code = i << 1;
00665 s->frame_size_min = ff_ac3_frame_size_tab[s->frame_size_code][s->sr_code];
00666 s->bits_written = 0;
00667 s->samples_written = 0;
00668 s->frame_size = s->frame_size_min;
00669
00670
00671 if(avctx->cutoff) {
00672
00673 int cutoff = av_clip(avctx->cutoff, 1, s->sample_rate >> 1);
00674 int fbw_coeffs = cutoff * 512 / s->sample_rate;
00675 bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);
00676 } else {
00677
00678
00679
00680 bw_code = 50;
00681 }
00682 for(ch=0;ch<s->nb_channels;ch++) {
00683
00684 s->chbwcod[ch] = bw_code;
00685 s->nb_coefs[ch] = bw_code * 3 + 73;
00686 }
00687 if (s->lfe) {
00688 s->nb_coefs[s->lfe_channel] = 7;
00689 }
00690
00691 s->coarse_snr_offset = 40;
00692
00693
00694 fft_init(MDCT_NBITS - 2);
00695 for(i=0;i<N/4;i++) {
00696 alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N;
00697 xcos1[i] = fix15(-cos(alpha));
00698 xsin1[i] = fix15(-sin(alpha));
00699 }
00700
00701 avctx->coded_frame= avcodec_alloc_frame();
00702 avctx->coded_frame->key_frame= 1;
00703
00704 return 0;
00705 }
00706
00707
00708 static void output_frame_header(AC3EncodeContext *s, unsigned char *frame)
00709 {
00710 init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
00711
00712 put_bits(&s->pb, 16, 0x0b77);
00713 put_bits(&s->pb, 16, 0);
00714 put_bits(&s->pb, 2, s->sr_code);
00715 put_bits(&s->pb, 6, s->frame_size_code + (s->frame_size - s->frame_size_min));
00716 put_bits(&s->pb, 5, s->bitstream_id);
00717 put_bits(&s->pb, 3, s->bitstream_mode);
00718 put_bits(&s->pb, 3, s->channel_mode);
00719 if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)
00720 put_bits(&s->pb, 2, 1);
00721 if (s->channel_mode & 0x04)
00722 put_bits(&s->pb, 2, 1);
00723 if (s->channel_mode == AC3_CHMODE_STEREO)
00724 put_bits(&s->pb, 2, 0);
00725 put_bits(&s->pb, 1, s->lfe);
00726 put_bits(&s->pb, 5, 31);
00727 put_bits(&s->pb, 1, 0);
00728 put_bits(&s->pb, 1, 0);
00729 put_bits(&s->pb, 1, 0);
00730 put_bits(&s->pb, 1, 0);
00731 put_bits(&s->pb, 1, 1);
00732 put_bits(&s->pb, 1, 0);
00733 put_bits(&s->pb, 1, 0);
00734 put_bits(&s->pb, 1, 0);
00735 }
00736
00737
00738 static inline int sym_quant(int c, int e, int levels)
00739 {
00740 int v;
00741
00742 if (c >= 0) {
00743 v = (levels * (c << e)) >> 24;
00744 v = (v + 1) >> 1;
00745 v = (levels >> 1) + v;
00746 } else {
00747 v = (levels * ((-c) << e)) >> 24;
00748 v = (v + 1) >> 1;
00749 v = (levels >> 1) - v;
00750 }
00751 assert (v >= 0 && v < levels);
00752 return v;
00753 }
00754
00755
00756 static inline int asym_quant(int c, int e, int qbits)
00757 {
00758 int lshift, m, v;
00759
00760 lshift = e + qbits - 24;
00761 if (lshift >= 0)
00762 v = c << lshift;
00763 else
00764 v = c >> (-lshift);
00765
00766 v = (v + 1) >> 1;
00767 m = (1 << (qbits-1));
00768 if (v >= m)
00769 v = m - 1;
00770 assert(v >= -m);
00771 return v & ((1 << qbits)-1);
00772 }
00773
00774
00775
00776 static void output_audio_block(AC3EncodeContext *s,
00777 uint8_t exp_strategy[AC3_MAX_CHANNELS],
00778 uint8_t encoded_exp[AC3_MAX_CHANNELS][N/2],
00779 uint8_t bap[AC3_MAX_CHANNELS][N/2],
00780 int32_t mdct_coefs[AC3_MAX_CHANNELS][N/2],
00781 int8_t global_exp[AC3_MAX_CHANNELS],
00782 int block_num)
00783 {
00784 int ch, nb_groups, group_size, i, baie, rbnd;
00785 uint8_t *p;
00786 uint16_t qmant[AC3_MAX_CHANNELS][N/2];
00787 int exp0, exp1;
00788 int mant1_cnt, mant2_cnt, mant4_cnt;
00789 uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr;
00790 int delta0, delta1, delta2;
00791
00792 for(ch=0;ch<s->nb_channels;ch++)
00793 put_bits(&s->pb, 1, 0);
00794 for(ch=0;ch<s->nb_channels;ch++)
00795 put_bits(&s->pb, 1, 1);
00796 put_bits(&s->pb, 1, 0);
00797 if (block_num == 0) {
00798
00799
00800 put_bits(&s->pb, 1, 1);
00801 put_bits(&s->pb, 1, 0);
00802 } else {
00803 put_bits(&s->pb, 1, 0);
00804 }
00805
00806 if (s->channel_mode == AC3_CHMODE_STEREO)
00807 {
00808 if(block_num==0)
00809 {
00810
00811 put_bits(&s->pb, 1, 1);
00812
00813
00814 for (rbnd=0;rbnd<4;rbnd++)
00815 put_bits(&s->pb, 1, 0);
00816 }
00817 else
00818 {
00819
00820 put_bits(&s->pb, 1, 0);
00821 }
00822 }
00823
00824 #if defined(DEBUG)
00825 {
00826 static int count = 0;
00827 av_log(NULL, AV_LOG_DEBUG, "Block #%d (%d)\n", block_num, count++);
00828 }
00829 #endif
00830
00831 for(ch=0;ch<s->nb_channels;ch++) {
00832 put_bits(&s->pb, 2, exp_strategy[ch]);
00833 }
00834
00835 if (s->lfe) {
00836 put_bits(&s->pb, 1, exp_strategy[s->lfe_channel]);
00837 }
00838
00839 for(ch=0;ch<s->nb_channels;ch++) {
00840 if (exp_strategy[ch] != EXP_REUSE)
00841 put_bits(&s->pb, 6, s->chbwcod[ch]);
00842 }
00843
00844
00845 for (ch = 0; ch < s->nb_all_channels; ch++) {
00846 switch(exp_strategy[ch]) {
00847 case EXP_REUSE:
00848 continue;
00849 case EXP_D15:
00850 group_size = 1;
00851 break;
00852 case EXP_D25:
00853 group_size = 2;
00854 break;
00855 default:
00856 case EXP_D45:
00857 group_size = 4;
00858 break;
00859 }
00860 nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
00861 p = encoded_exp[ch];
00862
00863
00864 exp1 = *p++;
00865 put_bits(&s->pb, 4, exp1);
00866
00867
00868 for(i=0;i<nb_groups;i++) {
00869
00870 exp0 = exp1;
00871 exp1 = p[0];
00872 p += group_size;
00873 delta0 = exp1 - exp0 + 2;
00874
00875 exp0 = exp1;
00876 exp1 = p[0];
00877 p += group_size;
00878 delta1 = exp1 - exp0 + 2;
00879
00880 exp0 = exp1;
00881 exp1 = p[0];
00882 p += group_size;
00883 delta2 = exp1 - exp0 + 2;
00884
00885 put_bits(&s->pb, 7, ((delta0 * 5 + delta1) * 5) + delta2);
00886 }
00887
00888 if (ch != s->lfe_channel)
00889 put_bits(&s->pb, 2, 0);
00890 }
00891
00892
00893 baie = (block_num == 0);
00894 put_bits(&s->pb, 1, baie);
00895 if (baie) {
00896 put_bits(&s->pb, 2, s->slow_decay_code);
00897 put_bits(&s->pb, 2, s->fast_decay_code);
00898 put_bits(&s->pb, 2, s->slow_gain_code);
00899 put_bits(&s->pb, 2, s->db_per_bit_code);
00900 put_bits(&s->pb, 3, s->floor_code);
00901 }
00902
00903
00904 put_bits(&s->pb, 1, baie);
00905 if (baie) {
00906 put_bits(&s->pb, 6, s->coarse_snr_offset);
00907 for(ch=0;ch<s->nb_all_channels;ch++) {
00908 put_bits(&s->pb, 4, s->fine_snr_offset[ch]);
00909 put_bits(&s->pb, 3, s->fast_gain_code[ch]);
00910 }
00911 }
00912
00913 put_bits(&s->pb, 1, 0);
00914 put_bits(&s->pb, 1, 0);
00915
00916
00917
00918
00919
00920
00921 mant1_cnt = mant2_cnt = mant4_cnt = 0;
00922 qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;
00923
00924 for (ch = 0; ch < s->nb_all_channels; ch++) {
00925 int b, c, e, v;
00926
00927 for(i=0;i<s->nb_coefs[ch];i++) {
00928 c = mdct_coefs[ch][i];
00929 e = encoded_exp[ch][i] - global_exp[ch];
00930 b = bap[ch][i];
00931 switch(b) {
00932 case 0:
00933 v = 0;
00934 break;
00935 case 1:
00936 v = sym_quant(c, e, 3);
00937 switch(mant1_cnt) {
00938 case 0:
00939 qmant1_ptr = &qmant[ch][i];
00940 v = 9 * v;
00941 mant1_cnt = 1;
00942 break;
00943 case 1:
00944 *qmant1_ptr += 3 * v;
00945 mant1_cnt = 2;
00946 v = 128;
00947 break;
00948 default:
00949 *qmant1_ptr += v;
00950 mant1_cnt = 0;
00951 v = 128;
00952 break;
00953 }
00954 break;
00955 case 2:
00956 v = sym_quant(c, e, 5);
00957 switch(mant2_cnt) {
00958 case 0:
00959 qmant2_ptr = &qmant[ch][i];
00960 v = 25 * v;
00961 mant2_cnt = 1;
00962 break;
00963 case 1:
00964 *qmant2_ptr += 5 * v;
00965 mant2_cnt = 2;
00966 v = 128;
00967 break;
00968 default:
00969 *qmant2_ptr += v;
00970 mant2_cnt = 0;
00971 v = 128;
00972 break;
00973 }
00974 break;
00975 case 3:
00976 v = sym_quant(c, e, 7);
00977 break;
00978 case 4:
00979 v = sym_quant(c, e, 11);
00980 switch(mant4_cnt) {
00981 case 0:
00982 qmant4_ptr = &qmant[ch][i];
00983 v = 11 * v;
00984 mant4_cnt = 1;
00985 break;
00986 default:
00987 *qmant4_ptr += v;
00988 mant4_cnt = 0;
00989 v = 128;
00990 break;
00991 }
00992 break;
00993 case 5:
00994 v = sym_quant(c, e, 15);
00995 break;
00996 case 14:
00997 v = asym_quant(c, e, 14);
00998 break;
00999 case 15:
01000 v = asym_quant(c, e, 16);
01001 break;
01002 default:
01003 v = asym_quant(c, e, b - 1);
01004 break;
01005 }
01006 qmant[ch][i] = v;
01007 }
01008 }
01009
01010
01011 for (ch = 0; ch < s->nb_all_channels; ch++) {
01012 int b, q;
01013
01014 for(i=0;i<s->nb_coefs[ch];i++) {
01015 q = qmant[ch][i];
01016 b = bap[ch][i];
01017 switch(b) {
01018 case 0:
01019 break;
01020 case 1:
01021 if (q != 128)
01022 put_bits(&s->pb, 5, q);
01023 break;
01024 case 2:
01025 if (q != 128)
01026 put_bits(&s->pb, 7, q);
01027 break;
01028 case 3:
01029 put_bits(&s->pb, 3, q);
01030 break;
01031 case 4:
01032 if (q != 128)
01033 put_bits(&s->pb, 7, q);
01034 break;
01035 case 14:
01036 put_bits(&s->pb, 14, q);
01037 break;
01038 case 15:
01039 put_bits(&s->pb, 16, q);
01040 break;
01041 default:
01042 put_bits(&s->pb, b - 1, q);
01043 break;
01044 }
01045 }
01046 }
01047 }
01048
01049 #define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
01050
01051 static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
01052 {
01053 unsigned int c;
01054
01055 c = 0;
01056 while (a) {
01057 if (a & 1)
01058 c ^= b;
01059 a = a >> 1;
01060 b = b << 1;
01061 if (b & (1 << 16))
01062 b ^= poly;
01063 }
01064 return c;
01065 }
01066
01067 static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
01068 {
01069 unsigned int r;
01070 r = 1;
01071 while (n) {
01072 if (n & 1)
01073 r = mul_poly(r, a, poly);
01074 a = mul_poly(a, a, poly);
01075 n >>= 1;
01076 }
01077 return r;
01078 }
01079
01080
01081
01082 static int log2_tab(int16_t *tab, int n)
01083 {
01084 int i, v;
01085
01086 v = 0;
01087 for(i=0;i<n;i++) {
01088 v |= abs(tab[i]);
01089 }
01090 return av_log2(v);
01091 }
01092
01093 static void lshift_tab(int16_t *tab, int n, int lshift)
01094 {
01095 int i;
01096
01097 if (lshift > 0) {
01098 for(i=0;i<n;i++) {
01099 tab[i] <<= lshift;
01100 }
01101 } else if (lshift < 0) {
01102 lshift = -lshift;
01103 for(i=0;i<n;i++) {
01104 tab[i] >>= lshift;
01105 }
01106 }
01107 }
01108
01109
01110 static int output_frame_end(AC3EncodeContext *s)
01111 {
01112 int frame_size, frame_size_58, n, crc1, crc2, crc_inv;
01113 uint8_t *frame;
01114
01115 frame_size = s->frame_size;
01116
01117 flush_put_bits(&s->pb);
01118
01119 frame = s->pb.buf;
01120 n = 2 * s->frame_size - (pbBufPtr(&s->pb) - frame) - 2;
01121 assert(n >= 0);
01122 if(n>0)
01123 memset(pbBufPtr(&s->pb), 0, n);
01124
01125
01126
01127 frame_size_58 = (frame_size >> 1) + (frame_size >> 3);
01128 crc1 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
01129 frame + 4, 2 * frame_size_58 - 4));
01130
01131 crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58) - 16, CRC16_POLY);
01132 crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
01133 AV_WB16(frame+2,crc1);
01134
01135 crc2 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
01136 frame + 2 * frame_size_58,
01137 (frame_size - frame_size_58) * 2 - 2));
01138 AV_WB16(frame+2*frame_size-2,crc2);
01139
01140
01141 return frame_size * 2;
01142 }
01143
01144 static int AC3_encode_frame(AVCodecContext *avctx,
01145 unsigned char *frame, int buf_size, void *data)
01146 {
01147 AC3EncodeContext *s = avctx->priv_data;
01148 int16_t *samples = data;
01149 int i, j, k, v, ch;
01150 int16_t input_samples[N];
01151 int32_t mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01152 uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01153 uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS];
01154 uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01155 uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01156 int8_t exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS];
01157 int frame_bits;
01158
01159 frame_bits = 0;
01160 for(ch=0;ch<s->nb_all_channels;ch++) {
01161
01162 for(i=0;i<NB_BLOCKS;i++) {
01163 int16_t *sptr;
01164 int sinc;
01165
01166
01167 memcpy(input_samples, s->last_samples[ch], N/2 * sizeof(int16_t));
01168 sinc = s->nb_all_channels;
01169 sptr = samples + (sinc * (N/2) * i) + ch;
01170 for(j=0;j<N/2;j++) {
01171 v = *sptr;
01172 input_samples[j + N/2] = v;
01173 s->last_samples[ch][j] = v;
01174 sptr += sinc;
01175 }
01176
01177
01178 for(j=0;j<N/2;j++) {
01179 input_samples[j] = MUL16(input_samples[j],
01180 ff_ac3_window[j]) >> 15;
01181 input_samples[N-j-1] = MUL16(input_samples[N-j-1],
01182 ff_ac3_window[j]) >> 15;
01183 }
01184
01185
01186
01187 v = 14 - log2_tab(input_samples, N);
01188 if (v < 0)
01189 v = 0;
01190 exp_samples[i][ch] = v - 9;
01191 lshift_tab(input_samples, N, v);
01192
01193
01194 mdct512(mdct_coef[i][ch], input_samples);
01195
01196
01197
01198 for(j=0;j<N/2;j++) {
01199 int e;
01200 v = abs(mdct_coef[i][ch][j]);
01201 if (v == 0)
01202 e = 24;
01203 else {
01204 e = 23 - av_log2(v) + exp_samples[i][ch];
01205 if (e >= 24) {
01206 e = 24;
01207 mdct_coef[i][ch][j] = 0;
01208 }
01209 }
01210 exp[i][ch][j] = e;
01211 }
01212 }
01213
01214 compute_exp_strategy(exp_strategy, exp, ch, ch == s->lfe_channel);
01215
01216
01217
01218
01219 i = 0;
01220 while (i < NB_BLOCKS) {
01221 j = i + 1;
01222 while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {
01223 exponent_min(exp[i][ch], exp[j][ch], s->nb_coefs[ch]);
01224 j++;
01225 }
01226 frame_bits += encode_exp(encoded_exp[i][ch],
01227 exp[i][ch], s->nb_coefs[ch],
01228 exp_strategy[i][ch]);
01229
01230 for(k=i+1;k<j;k++) {
01231 memcpy(encoded_exp[k][ch], encoded_exp[i][ch],
01232 s->nb_coefs[ch] * sizeof(uint8_t));
01233 }
01234 i = j;
01235 }
01236 }
01237
01238
01239 while(s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
01240 s->bits_written -= s->bit_rate;
01241 s->samples_written -= s->sample_rate;
01242 }
01243 s->frame_size = s->frame_size_min + (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
01244 s->bits_written += s->frame_size * 16;
01245 s->samples_written += AC3_FRAME_SIZE;
01246
01247 compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);
01248
01249 output_frame_header(s, frame);
01250
01251 for(i=0;i<NB_BLOCKS;i++) {
01252 output_audio_block(s, exp_strategy[i], encoded_exp[i],
01253 bap[i], mdct_coef[i], exp_samples[i], i);
01254 }
01255 return output_frame_end(s);
01256 }
01257
01258 static int AC3_encode_close(AVCodecContext *avctx)
01259 {
01260 av_freep(&avctx->coded_frame);
01261 return 0;
01262 }
01263
01264 #if 0
01265
01266
01267
01268 #undef random
01269 #define FN (N/4)
01270
01271 void fft_test(void)
01272 {
01273 IComplex in[FN], in1[FN];
01274 int k, n, i;
01275 float sum_re, sum_im, a;
01276
01277
01278
01279 for(i=0;i<FN;i++) {
01280 in[i].re = random() % 65535 - 32767;
01281 in[i].im = random() % 65535 - 32767;
01282 in1[i] = in[i];
01283 }
01284 fft(in, 7);
01285
01286
01287 for(k=0;k<FN;k++) {
01288 sum_re = 0;
01289 sum_im = 0;
01290 for(n=0;n<FN;n++) {
01291 a = -2 * M_PI * (n * k) / FN;
01292 sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);
01293 sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);
01294 }
01295 printf("%3d: %6d,%6d %6.0f,%6.0f\n",
01296 k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);
01297 }
01298 }
01299
01300 void mdct_test(void)
01301 {
01302 int16_t input[N];
01303 int32_t output[N/2];
01304 float input1[N];
01305 float output1[N/2];
01306 float s, a, err, e, emax;
01307 int i, k, n;
01308
01309 for(i=0;i<N;i++) {
01310 input[i] = (random() % 65535 - 32767) * 9 / 10;
01311 input1[i] = input[i];
01312 }
01313
01314 mdct512(output, input);
01315
01316
01317 for(k=0;k<N/2;k++) {
01318 s = 0;
01319 for(n=0;n<N;n++) {
01320 a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));
01321 s += input1[n] * cos(a);
01322 }
01323 output1[k] = -2 * s / N;
01324 }
01325
01326 err = 0;
01327 emax = 0;
01328 for(i=0;i<N/2;i++) {
01329 printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);
01330 e = output[i] - output1[i];
01331 if (e > emax)
01332 emax = e;
01333 err += e * e;
01334 }
01335 printf("err2=%f emax=%f\n", err / (N/2), emax);
01336 }
01337
01338 void test_ac3(void)
01339 {
01340 AC3EncodeContext ctx;
01341 unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];
01342 short samples[AC3_FRAME_SIZE];
01343 int ret, i;
01344
01345 AC3_encode_init(&ctx, 44100, 64000, 1);
01346
01347 fft_test();
01348 mdct_test();
01349
01350 for(i=0;i<AC3_FRAME_SIZE;i++)
01351 samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);
01352 ret = AC3_encode_frame(&ctx, frame, samples);
01353 printf("ret=%d\n", ret);
01354 }
01355 #endif
01356
01357 AVCodec ac3_encoder = {
01358 "ac3",
01359 CODEC_TYPE_AUDIO,
01360 CODEC_ID_AC3,
01361 sizeof(AC3EncodeContext),
01362 AC3_encode_init,
01363 AC3_encode_frame,
01364 AC3_encode_close,
01365 NULL,
01366 };