2 * The simplest AC3 encoder
3 * Copyright (c) 2000 Fabrice Bellard.
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20 //#define DEBUG_BITALLOC
25 typedef struct AC3EncodeContext {
33 int frame_size_min; /* minimum frame size in case rounding is necessary */
34 int frame_size; /* current frame size in words */
37 int fscod; /* frequency */
41 short last_samples[AC3_MAX_CHANNELS][256];
42 int chbwcod[AC3_MAX_CHANNELS];
43 int nb_coefs[AC3_MAX_CHANNELS];
45 /* bitrate allocation control */
46 int sgaincod, sdecaycod, fdecaycod, dbkneecod, floorcod;
47 AC3BitAllocParameters bit_alloc;
49 int fgaincod[AC3_MAX_CHANNELS];
50 int fsnroffst[AC3_MAX_CHANNELS];
51 /* mantissa encoding */
52 int mant1_cnt, mant2_cnt, mant4_cnt;
58 #define N (1 << MDCT_NBITS)
60 /* new exponents are sent if their Norm 1 exceed this number */
61 #define EXP_DIFF_THRESHOLD 1000
63 static void fft_init(int ln);
64 static void ac3_crc_init(void);
66 static inline INT16 fix15(float a)
69 v = (int)(a * (float)(1 << 15));
77 static inline int calc_lowcomp1(int a, int b0, int b1)
79 if ((b0 + 256) == b1) {
88 static inline int calc_lowcomp(int a, int b0, int b1, int bin)
91 if ((b0 + 256) == b1) {
97 } else if (bin < 20) {
98 if ((b0 + 256) == b1) {
100 } else if (b0 > b1) {
111 /* AC3 bit allocation. The algorithm is the one described in the AC3
113 void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, UINT8 *bap,
114 INT8 *exp, int start, int end,
115 int snroffset, int fgain, int is_lfe,
116 int deltbae,int deltnseg,
117 UINT8 *deltoffst, UINT8 *deltlen, UINT8 *deltba)
119 int bin,i,j,k,end1,v,v1,bndstrt,bndend,lowcomp,begin;
120 int fastleak,slowleak,address,tmp;
121 INT16 psd[256]; /* scaled exponents */
122 INT16 bndpsd[50]; /* interpolated exponents */
123 INT16 excite[50]; /* excitation */
124 INT16 mask[50]; /* masking value */
126 /* exponent mapping to PSD */
127 for(bin=start;bin<end;bin++) {
128 psd[bin]=(3072 - (exp[bin] << 7));
131 /* PSD integration */
138 if (end1 > end) end1=end;
139 for(i=j;i<end1;i++) {
146 if (adr > 255) adr=255;
150 if (adr > 255) adr=255;
157 } while (end > bndtab[k]);
159 /* excitation function */
160 bndstrt = masktab[start];
161 bndend = masktab[end-1] + 1;
165 lowcomp = calc_lowcomp1(lowcomp, bndpsd[0], bndpsd[1]) ;
166 excite[0] = bndpsd[0] - fgain - lowcomp ;
167 lowcomp = calc_lowcomp1(lowcomp, bndpsd[1], bndpsd[2]) ;
168 excite[1] = bndpsd[1] - fgain - lowcomp ;
170 for (bin = 2; bin < 7; bin++) {
171 if (!(is_lfe && bin == 6))
172 lowcomp = calc_lowcomp1(lowcomp, bndpsd[bin], bndpsd[bin+1]) ;
173 fastleak = bndpsd[bin] - fgain ;
174 slowleak = bndpsd[bin] - s->sgain ;
175 excite[bin] = fastleak - lowcomp ;
176 if (!(is_lfe && bin == 6)) {
177 if (bndpsd[bin] <= bndpsd[bin+1]) {
185 if (end1 > 22) end1=22;
187 for (bin = begin; bin < end1; bin++) {
188 if (!(is_lfe && bin == 6))
189 lowcomp = calc_lowcomp(lowcomp, bndpsd[bin], bndpsd[bin+1], bin) ;
191 fastleak -= s->fdecay ;
192 v = bndpsd[bin] - fgain;
193 if (fastleak < v) fastleak = v;
195 slowleak -= s->sdecay ;
196 v = bndpsd[bin] - s->sgain;
197 if (slowleak < v) slowleak = v;
199 v=fastleak - lowcomp;
200 if (slowleak > v) v=slowleak;
206 /* coupling channel */
209 fastleak = (s->cplfleak << 8) + 768;
210 slowleak = (s->cplsleak << 8) + 768;
213 for (bin = begin; bin < bndend; bin++) {
214 fastleak -= s->fdecay ;
215 v = bndpsd[bin] - fgain;
216 if (fastleak < v) fastleak = v;
217 slowleak -= s->sdecay ;
218 v = bndpsd[bin] - s->sgain;
219 if (slowleak < v) slowleak = v;
222 if (slowleak > v) v = slowleak;
226 /* compute masking curve */
228 for (bin = bndstrt; bin < bndend; bin++) {
230 tmp = s->dbknee - bndpsd[bin];
234 v=hth[bin >> s->halfratecod][s->fscod];
239 /* delta bit allocation */
241 if (deltbae == 0 || deltbae == 1) {
242 int band, seg, delta;
244 for (seg = 0; seg < deltnseg; seg++) {
245 band += deltoffst[seg] ;
246 if (deltba[seg] >= 4) {
247 delta = (deltba[seg] - 3) << 7;
249 delta = (deltba[seg] - 4) << 7;
251 for (k = 0; k < deltlen[seg]; k++) {
252 mask[band] += delta ;
258 /* compute bit allocation */
270 end1=bndtab[j] + bndsz[j];
271 if (end1 > end) end1=end;
273 for (k = i; k < end1; k++) {
274 address = (psd[i] - v) >> 5 ;
275 if (address < 0) address=0;
276 else if (address > 63) address=63;
277 bap[i] = baptab[address];
280 } while (end > bndtab[j++]) ;
283 typedef struct IComplex {
287 static void fft_init(int ln)
294 for(i=0;i<(n/2);i++) {
295 alpha = 2 * M_PI * (float)i / (float)n;
296 costab[i] = fix15(cos(alpha));
297 sintab[i] = fix15(sin(alpha));
303 m |= ((i >> j) & 1) << (ln-j-1);
310 #define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
317 pre = (bx + ax) >> 1;\
318 pim = (by + ay) >> 1;\
319 qre = (bx - ax) >> 1;\
320 qim = (by - ay) >> 1;\
323 #define MUL16(a,b) ((a) * (b))
325 #define CMUL(pre, pim, are, aim, bre, bim) \
327 pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15;\
328 pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\
332 /* do a 2^n point complex fft on 2^ln points. */
333 static void fft(IComplex *z, int ln)
337 register IComplex *p,*q;
359 BF(p[0].re, p[0].im, p[1].re, p[1].im,
360 p[0].re, p[0].im, p[1].re, p[1].im);
369 BF(p[0].re, p[0].im, p[2].re, p[2].im,
370 p[0].re, p[0].im, p[2].re, p[2].im);
371 BF(p[1].re, p[1].im, p[3].re, p[3].im,
372 p[1].re, p[1].im, p[3].im, -p[3].re);
384 for (j = 0; j < nblocks; ++j) {
386 BF(p->re, p->im, q->re, q->im,
387 p->re, p->im, q->re, q->im);
391 for(l = nblocks; l < np2; l += nblocks) {
392 CMUL(tmp_re, tmp_im, costab[l], -sintab[l], q->re, q->im);
393 BF(p->re, p->im, q->re, q->im,
394 p->re, p->im, tmp_re, tmp_im);
401 nblocks = nblocks >> 1;
402 nloops = nloops << 1;
403 } while (nblocks != 0);
406 /* do a 512 point mdct */
407 static void mdct512(INT32 *out, INT16 *in)
409 int i, re, im, re1, im1;
413 /* shift to simplify computations */
415 rot[i] = -in[i + 3*N/4];
417 rot[i] = in[i - N/4];
421 re = ((int)rot[2*i] - (int)rot[N-1-2*i]) >> 1;
422 im = -((int)rot[N/2+2*i] - (int)rot[N/2-1-2*i]) >> 1;
423 CMUL(x[i].re, x[i].im, re, im, -xcos1[i], xsin1[i]);
426 fft(x, MDCT_NBITS - 2);
432 CMUL(re1, im1, re, im, xsin1[i], xcos1[i]);
434 out[N/2-1-2*i] = re1;
438 /* XXX: use another norm ? */
439 static int calc_exp_diff(UINT8 *exp1, UINT8 *exp2, int n)
444 sum += abs(exp1[i] - exp2[i]);
449 static void compute_exp_strategy(UINT8 exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
450 UINT8 exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
456 /* estimate if the exponent variation & decide if they should be
457 reused in the next frame */
458 exp_strategy[0][ch] = EXP_NEW;
459 for(i=1;i<NB_BLOCKS;i++) {
460 exp_diff = calc_exp_diff(exp[i][ch], exp[i-1][ch], N/2);
462 printf("exp_diff=%d\n", exp_diff);
464 if (exp_diff > EXP_DIFF_THRESHOLD)
465 exp_strategy[i][ch] = EXP_NEW;
467 exp_strategy[i][ch] = EXP_REUSE;
472 /* now select the encoding strategy type : if exponents are often
473 recoded, we use a coarse encoding */
475 while (i < NB_BLOCKS) {
477 while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)
481 exp_strategy[i][ch] = EXP_D45;
485 exp_strategy[i][ch] = EXP_D25;
488 exp_strategy[i][ch] = EXP_D15;
495 /* set exp[i] to min(exp[i], exp1[i]) */
496 static void exponent_min(UINT8 exp[N/2], UINT8 exp1[N/2], int n)
501 if (exp1[i] < exp[i])
506 /* update the exponents so that they are the ones the decoder will
507 decode. Return the number of bits used to code the exponents */
508 static int encode_exp(UINT8 encoded_exp[N/2],
513 int group_size, nb_groups, i, j, k, recurse, exp_min, delta;
516 switch(exp_strategy) {
528 nb_groups = ((nb_exps + (group_size * 3) - 4) / (3 * group_size)) * 3;
530 /* for each group, compute the minimum exponent */
531 exp1[0] = exp[0]; /* DC exponent is handled separately */
533 for(i=1;i<=nb_groups;i++) {
535 assert(exp_min >= 0 && exp_min <= 24);
536 for(j=1;j<group_size;j++) {
537 if (exp[k+j] < exp_min)
544 /* constraint for DC exponent */
548 /* Iterate until the delta constraints between each groups are
549 satisfyed. I'm sure it is possible to find a better algorithm,
553 for(i=1;i<=nb_groups;i++) {
554 delta = exp1[i] - exp1[i-1];
556 /* if delta too big, we encode a smaller exponent */
557 exp1[i] = exp1[i-1] + 2;
558 } else if (delta < -2) {
559 /* if delta is too small, we must decrease the previous
560 exponent, which means we must recurse */
562 exp1[i-1] = exp1[i] + 2;
567 /* now we have the exponent values the decoder will see */
568 encoded_exp[0] = exp1[0];
570 for(i=1;i<=nb_groups;i++) {
571 for(j=0;j<group_size;j++) {
572 encoded_exp[k+j] = exp1[i];
578 printf("exponents: strategy=%d\n", exp_strategy);
579 for(i=0;i<=nb_groups * group_size;i++) {
580 printf("%d ", encoded_exp[i]);
585 return 4 + (nb_groups / 3) * 7;
588 /* return the size in bits taken by the mantissa */
589 int compute_mantissa_size(AC3EncodeContext *s, UINT8 *m, int nb_coefs)
594 for(i=0;i<nb_coefs;i++) {
601 /* 3 mantissa in 5 bits */
602 if (s->mant1_cnt == 0)
604 if (++s->mant1_cnt == 3)
608 /* 3 mantissa in 7 bits */
609 if (s->mant2_cnt == 0)
611 if (++s->mant2_cnt == 3)
618 /* 2 mantissa in 7 bits */
619 if (s->mant4_cnt == 0)
621 if (++s->mant4_cnt == 2)
639 static int bit_alloc(AC3EncodeContext *s,
640 UINT8 bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
641 UINT8 encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
642 UINT8 exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
643 int frame_bits, int csnroffst, int fsnroffst)
648 for(i=0;i<NB_BLOCKS;i++) {
652 for(ch=0;ch<s->nb_all_channels;ch++) {
653 ac3_parametric_bit_allocation(&s->bit_alloc,
654 bap[i][ch], (INT8 *)encoded_exp[i][ch],
656 (((csnroffst-15) << 4) +
658 fgaintab[s->fgaincod[ch]],
659 ch == s->lfe_channel,
660 2, 0, NULL, NULL, NULL);
661 frame_bits += compute_mantissa_size(s, bap[i][ch],
666 printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n",
667 csnroffst, fsnroffst, frame_bits,
668 16 * s->frame_size - ((frame_bits + 7) & ~7));
670 return 16 * s->frame_size - frame_bits;
675 static int compute_bit_allocation(AC3EncodeContext *s,
676 UINT8 bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
677 UINT8 encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
678 UINT8 exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
682 int csnroffst, fsnroffst;
683 UINT8 bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
684 static int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
686 /* init default parameters */
692 for(ch=0;ch<s->nb_all_channels;ch++)
695 /* compute real values */
696 s->bit_alloc.fscod = s->fscod;
697 s->bit_alloc.halfratecod = s->halfratecod;
698 s->bit_alloc.sdecay = sdecaytab[s->sdecaycod] >> s->halfratecod;
699 s->bit_alloc.fdecay = fdecaytab[s->fdecaycod] >> s->halfratecod;
700 s->bit_alloc.sgain = sgaintab[s->sgaincod];
701 s->bit_alloc.dbknee = dbkneetab[s->dbkneecod];
702 s->bit_alloc.floor = floortab[s->floorcod];
706 // if (s->acmod == 2)
708 frame_bits += frame_bits_inc[s->acmod];
711 for(i=0;i<NB_BLOCKS;i++) {
712 frame_bits += s->nb_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
714 frame_bits++; /* rematstr */
715 frame_bits += 2 * s->nb_channels; /* chexpstr[2] * c */
717 frame_bits++; /* lfeexpstr */
718 for(ch=0;ch<s->nb_channels;ch++) {
719 if (exp_strategy[i][ch] != EXP_REUSE)
720 frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
722 frame_bits++; /* baie */
723 frame_bits++; /* snr */
724 frame_bits += 2; /* delta / skip */
726 frame_bits++; /* cplinu for block 0 */
728 /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
730 /* (fsnoffset[4] + fgaincod[4]) * c */
731 frame_bits += 2*4 + 3 + 6 + s->nb_all_channels * (4 + 3);
736 /* now the big work begins : do the bit allocation. Modify the snr
737 offset until we can pack everything in the requested frame size */
739 csnroffst = s->csnroffst;
740 while (csnroffst >= 0 &&
741 bit_alloc(s, bap, encoded_exp, exp_strategy, frame_bits, csnroffst, 0) < 0)
742 csnroffst -= SNR_INC1;
744 fprintf(stderr, "Yack, Error !!!\n");
747 while ((csnroffst + SNR_INC1) <= 63 &&
748 bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits,
749 csnroffst + SNR_INC1, 0) >= 0) {
750 csnroffst += SNR_INC1;
751 memcpy(bap, bap1, sizeof(bap1));
753 while ((csnroffst + 1) <= 63 &&
754 bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits, csnroffst + 1, 0) >= 0) {
756 memcpy(bap, bap1, sizeof(bap1));
760 while ((fsnroffst + SNR_INC1) <= 15 &&
761 bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits,
762 csnroffst, fsnroffst + SNR_INC1) >= 0) {
763 fsnroffst += SNR_INC1;
764 memcpy(bap, bap1, sizeof(bap1));
766 while ((fsnroffst + 1) <= 15 &&
767 bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits,
768 csnroffst, fsnroffst + 1) >= 0) {
770 memcpy(bap, bap1, sizeof(bap1));
773 s->csnroffst = csnroffst;
774 for(ch=0;ch<s->nb_all_channels;ch++)
775 s->fsnroffst[ch] = fsnroffst;
776 #if defined(DEBUG_BITALLOC)
781 for(ch=0;ch<s->nb_all_channels;ch++) {
782 printf("Block #%d Ch%d:\n", i, ch);
784 for(j=0;j<s->nb_coefs[ch];j++) {
785 printf("%d ",bap[i][ch][j]);
795 void ac3_common_init(void)
798 /* compute bndtab and masktab from bandsz */
804 for(j=0;j<v;j++) masktab[k++]=i;
811 static int AC3_encode_init(AVCodecContext *avctx)
813 int freq = avctx->sample_rate;
814 int bitrate = avctx->bit_rate;
815 int channels = avctx->channels;
816 AC3EncodeContext *s = avctx->priv_data;
819 static const UINT8 acmod_defs[6] = {
823 0x06, /* L R SL SR */
824 0x07, /* L C R SL SR */
825 0x07, /* L C R SL SR (+LFE) */
828 avctx->frame_size = AC3_FRAME_SIZE;
830 /* number of channels */
831 if (channels < 1 || channels > 6)
833 s->acmod = acmod_defs[channels - 1];
834 s->lfe = (channels == 6) ? 1 : 0;
835 s->nb_all_channels = channels;
836 s->nb_channels = channels > 5 ? 5 : channels;
837 s->lfe_channel = s->lfe ? 5 : -1;
842 if ((ac3_freqs[j] >> i) == freq)
847 s->sample_rate = freq;
850 s->bsid = 8 + s->halfratecod;
851 s->bsmod = 0; /* complete main audio service */
853 /* bitrate & frame size */
856 if ((ac3_bitratetab[i] >> s->halfratecod) == bitrate)
861 s->bit_rate = bitrate;
862 s->frmsizecod = i << 1;
863 s->frame_size_min = (bitrate * 1000 * AC3_FRAME_SIZE) / (freq * 16);
864 /* for now we do not handle fractional sizes */
865 s->frame_size = s->frame_size_min;
867 /* bit allocation init */
868 for(ch=0;ch<s->nb_channels;ch++) {
869 /* bandwidth for each channel */
870 /* XXX: should compute the bandwidth according to the frame
871 size, so that we avoid anoying high freq artefacts */
872 s->chbwcod[ch] = 50; /* sample bandwidth as mpeg audio layer 2 table 0 */
873 s->nb_coefs[ch] = ((s->chbwcod[ch] + 12) * 3) + 37;
876 s->nb_coefs[s->lfe_channel] = 7; /* fixed */
878 /* initial snr offset */
884 fft_init(MDCT_NBITS - 2);
886 alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N;
887 xcos1[i] = fix15(-cos(alpha));
888 xsin1[i] = fix15(-sin(alpha));
893 avctx->coded_frame= avcodec_alloc_frame();
894 avctx->coded_frame->key_frame= 1;
899 /* output the AC3 frame header */
900 static void output_frame_header(AC3EncodeContext *s, unsigned char *frame)
902 init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE, NULL, NULL);
904 put_bits(&s->pb, 16, 0x0b77); /* frame header */
905 put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
906 put_bits(&s->pb, 2, s->fscod);
907 put_bits(&s->pb, 6, s->frmsizecod + (s->frame_size - s->frame_size_min));
908 put_bits(&s->pb, 5, s->bsid);
909 put_bits(&s->pb, 3, s->bsmod);
910 put_bits(&s->pb, 3, s->acmod);
911 if ((s->acmod & 0x01) && s->acmod != 0x01)
912 put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
914 put_bits(&s->pb, 2, 1); /* XXX -6 dB */
915 if (s->acmod == 0x02)
916 put_bits(&s->pb, 2, 0); /* surround not indicated */
917 put_bits(&s->pb, 1, s->lfe); /* LFE */
918 put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
919 put_bits(&s->pb, 1, 0); /* no compression control word */
920 put_bits(&s->pb, 1, 0); /* no lang code */
921 put_bits(&s->pb, 1, 0); /* no audio production info */
922 put_bits(&s->pb, 1, 0); /* no copyright */
923 put_bits(&s->pb, 1, 1); /* original bitstream */
924 put_bits(&s->pb, 1, 0); /* no time code 1 */
925 put_bits(&s->pb, 1, 0); /* no time code 2 */
926 put_bits(&s->pb, 1, 0); /* no addtional bit stream info */
929 /* symetric quantization on 'levels' levels */
930 static inline int sym_quant(int c, int e, int levels)
935 v = (levels * (c << e)) >> 24;
937 v = (levels >> 1) + v;
939 v = (levels * ((-c) << e)) >> 24;
941 v = (levels >> 1) - v;
943 assert (v >= 0 && v < levels);
947 /* asymetric quantization on 2^qbits levels */
948 static inline int asym_quant(int c, int e, int qbits)
952 lshift = e + qbits - 24;
959 m = (1 << (qbits-1));
963 return v & ((1 << qbits)-1);
966 /* Output one audio block. There are NB_BLOCKS audio blocks in one AC3
968 static void output_audio_block(AC3EncodeContext *s,
969 UINT8 exp_strategy[AC3_MAX_CHANNELS],
970 UINT8 encoded_exp[AC3_MAX_CHANNELS][N/2],
971 UINT8 bap[AC3_MAX_CHANNELS][N/2],
972 INT32 mdct_coefs[AC3_MAX_CHANNELS][N/2],
973 INT8 global_exp[AC3_MAX_CHANNELS],
976 int ch, nb_groups, group_size, i, baie;
978 UINT16 qmant[AC3_MAX_CHANNELS][N/2];
980 int mant1_cnt, mant2_cnt, mant4_cnt;
981 UINT16 *qmant1_ptr, *qmant2_ptr, *qmant4_ptr;
982 int delta0, delta1, delta2;
984 for(ch=0;ch<s->nb_channels;ch++)
985 put_bits(&s->pb, 1, 0); /* 512 point MDCT */
986 for(ch=0;ch<s->nb_channels;ch++)
987 put_bits(&s->pb, 1, 1); /* no dither */
988 put_bits(&s->pb, 1, 0); /* no dynamic range */
989 if (block_num == 0) {
990 /* for block 0, even if no coupling, we must say it. This is a
992 put_bits(&s->pb, 1, 1); /* coupling strategy present */
993 put_bits(&s->pb, 1, 0); /* no coupling strategy */
995 put_bits(&s->pb, 1, 0); /* no new coupling strategy */
999 put_bits(&s->pb, 1, 0); /* no matrixing (but should be used in the future) */
1004 static int count = 0;
1005 printf("Block #%d (%d)\n", block_num, count++);
1008 /* exponent strategy */
1009 for(ch=0;ch<s->nb_channels;ch++) {
1010 put_bits(&s->pb, 2, exp_strategy[ch]);
1014 put_bits(&s->pb, 1, exp_strategy[s->lfe_channel]);
1017 for(ch=0;ch<s->nb_channels;ch++) {
1018 if (exp_strategy[ch] != EXP_REUSE)
1019 put_bits(&s->pb, 6, s->chbwcod[ch]);
1023 for (ch = 0; ch < s->nb_all_channels; ch++) {
1024 switch(exp_strategy[ch]) {
1038 nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
1039 p = encoded_exp[ch];
1041 /* first exponent */
1043 put_bits(&s->pb, 4, exp1);
1045 /* next ones are delta encoded */
1046 for(i=0;i<nb_groups;i++) {
1047 /* merge three delta in one code */
1051 delta0 = exp1 - exp0 + 2;
1056 delta1 = exp1 - exp0 + 2;
1061 delta2 = exp1 - exp0 + 2;
1063 put_bits(&s->pb, 7, ((delta0 * 5 + delta1) * 5) + delta2);
1066 if (ch != s->lfe_channel)
1067 put_bits(&s->pb, 2, 0); /* no gain range info */
1070 /* bit allocation info */
1071 baie = (block_num == 0);
1072 put_bits(&s->pb, 1, baie);
1074 put_bits(&s->pb, 2, s->sdecaycod);
1075 put_bits(&s->pb, 2, s->fdecaycod);
1076 put_bits(&s->pb, 2, s->sgaincod);
1077 put_bits(&s->pb, 2, s->dbkneecod);
1078 put_bits(&s->pb, 3, s->floorcod);
1082 put_bits(&s->pb, 1, baie); /* always present with bai */
1084 put_bits(&s->pb, 6, s->csnroffst);
1085 for(ch=0;ch<s->nb_all_channels;ch++) {
1086 put_bits(&s->pb, 4, s->fsnroffst[ch]);
1087 put_bits(&s->pb, 3, s->fgaincod[ch]);
1091 put_bits(&s->pb, 1, 0); /* no delta bit allocation */
1092 put_bits(&s->pb, 1, 0); /* no data to skip */
1094 /* mantissa encoding : we use two passes to handle the grouping. A
1095 one pass method may be faster, but it would necessitate to
1096 modify the output stream. */
1098 /* first pass: quantize */
1099 mant1_cnt = mant2_cnt = mant4_cnt = 0;
1100 qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;
1102 for (ch = 0; ch < s->nb_all_channels; ch++) {
1105 for(i=0;i<s->nb_coefs[ch];i++) {
1106 c = mdct_coefs[ch][i];
1107 e = encoded_exp[ch][i] - global_exp[ch];
1114 v = sym_quant(c, e, 3);
1117 qmant1_ptr = &qmant[ch][i];
1122 *qmant1_ptr += 3 * v;
1134 v = sym_quant(c, e, 5);
1137 qmant2_ptr = &qmant[ch][i];
1142 *qmant2_ptr += 5 * v;
1154 v = sym_quant(c, e, 7);
1157 v = sym_quant(c, e, 11);
1160 qmant4_ptr = &qmant[ch][i];
1172 v = sym_quant(c, e, 15);
1175 v = asym_quant(c, e, 14);
1178 v = asym_quant(c, e, 16);
1181 v = asym_quant(c, e, b - 1);
1188 /* second pass : output the values */
1189 for (ch = 0; ch < s->nb_all_channels; ch++) {
1192 for(i=0;i<s->nb_coefs[ch];i++) {
1200 put_bits(&s->pb, 5, q);
1204 put_bits(&s->pb, 7, q);
1207 put_bits(&s->pb, 3, q);
1211 put_bits(&s->pb, 7, q);
1214 put_bits(&s->pb, 14, q);
1217 put_bits(&s->pb, 16, q);
1220 put_bits(&s->pb, b - 1, q);
1227 /* compute the ac3 crc */
1229 #define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
1231 static void ac3_crc_init(void)
1233 unsigned int c, n, k;
1235 for(n=0;n<256;n++) {
1237 for (k = 0; k < 8; k++) {
1239 c = ((c << 1) & 0xffff) ^ (CRC16_POLY & 0xffff);
1247 static unsigned int ac3_crc(UINT8 *data, int n, unsigned int crc)
1251 crc = (crc_table[data[i] ^ (crc >> 8)] ^ (crc << 8)) & 0xffff;
1256 static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
1272 static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
1278 r = mul_poly(r, a, poly);
1279 a = mul_poly(a, a, poly);
1286 /* compute log2(max(abs(tab[]))) */
1287 static int log2_tab(INT16 *tab, int n)
1298 static void lshift_tab(INT16 *tab, int n, int lshift)
1306 } else if (lshift < 0) {
1314 /* fill the end of the frame and compute the two crcs */
1315 static int output_frame_end(AC3EncodeContext *s)
1317 int frame_size, frame_size_58, n, crc1, crc2, crc_inv;
1320 frame_size = s->frame_size; /* frame size in words */
1321 /* align to 8 bits */
1322 flush_put_bits(&s->pb);
1323 /* add zero bytes to reach the frame size */
1325 n = 2 * s->frame_size - (pbBufPtr(&s->pb) - frame) - 2;
1327 memset(pbBufPtr(&s->pb), 0, n);
1329 /* Now we must compute both crcs : this is not so easy for crc1
1330 because it is at the beginning of the data... */
1331 frame_size_58 = (frame_size >> 1) + (frame_size >> 3);
1332 crc1 = ac3_crc(frame + 4, (2 * frame_size_58) - 4, 0);
1333 /* XXX: could precompute crc_inv */
1334 crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58) - 16, CRC16_POLY);
1335 crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
1336 frame[2] = crc1 >> 8;
1339 crc2 = ac3_crc(frame + 2 * frame_size_58, (frame_size - frame_size_58) * 2 - 2, 0);
1340 frame[2*frame_size - 2] = crc2 >> 8;
1341 frame[2*frame_size - 1] = crc2;
1343 // printf("n=%d frame_size=%d\n", n, frame_size);
1344 return frame_size * 2;
1347 static int AC3_encode_frame(AVCodecContext *avctx,
1348 unsigned char *frame, int buf_size, void *data)
1350 AC3EncodeContext *s = avctx->priv_data;
1351 short *samples = data;
1353 INT16 input_samples[N];
1354 INT32 mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1355 UINT8 exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1356 UINT8 exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS];
1357 UINT8 encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1358 UINT8 bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1359 INT8 exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS];
1363 for(ch=0;ch<s->nb_all_channels;ch++) {
1364 /* fixed mdct to the six sub blocks & exponent computation */
1365 for(i=0;i<NB_BLOCKS;i++) {
1369 /* compute input samples */
1370 memcpy(input_samples, s->last_samples[ch], N/2 * sizeof(INT16));
1371 sinc = s->nb_all_channels;
1372 sptr = samples + (sinc * (N/2) * i) + ch;
1373 for(j=0;j<N/2;j++) {
1375 input_samples[j + N/2] = v;
1376 s->last_samples[ch][j] = v;
1380 /* apply the MDCT window */
1381 for(j=0;j<N/2;j++) {
1382 input_samples[j] = MUL16(input_samples[j],
1383 ac3_window[j]) >> 15;
1384 input_samples[N-j-1] = MUL16(input_samples[N-j-1],
1385 ac3_window[j]) >> 15;
1388 /* Normalize the samples to use the maximum available
1390 v = 14 - log2_tab(input_samples, N);
1393 exp_samples[i][ch] = v - 8;
1394 lshift_tab(input_samples, N, v);
1397 mdct512(mdct_coef[i][ch], input_samples);
1399 /* compute "exponents". We take into account the
1400 normalization there */
1401 for(j=0;j<N/2;j++) {
1403 v = abs(mdct_coef[i][ch][j]);
1407 e = 23 - av_log2(v) + exp_samples[i][ch];
1410 mdct_coef[i][ch][j] = 0;
1417 compute_exp_strategy(exp_strategy, exp, ch, ch == s->lfe_channel);
1419 /* compute the exponents as the decoder will see them. The
1420 EXP_REUSE case must be handled carefully : we select the
1421 min of the exponents */
1423 while (i < NB_BLOCKS) {
1425 while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {
1426 exponent_min(exp[i][ch], exp[j][ch], s->nb_coefs[ch]);
1429 frame_bits += encode_exp(encoded_exp[i][ch],
1430 exp[i][ch], s->nb_coefs[ch],
1431 exp_strategy[i][ch]);
1432 /* copy encoded exponents for reuse case */
1433 for(k=i+1;k<j;k++) {
1434 memcpy(encoded_exp[k][ch], encoded_exp[i][ch],
1435 s->nb_coefs[ch] * sizeof(UINT8));
1441 compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);
1442 /* everything is known... let's output the frame */
1443 output_frame_header(s, frame);
1445 for(i=0;i<NB_BLOCKS;i++) {
1446 output_audio_block(s, exp_strategy[i], encoded_exp[i],
1447 bap[i], mdct_coef[i], exp_samples[i], i);
1449 return output_frame_end(s);
1452 static int AC3_encode_close(AVCodecContext *avctx)
1454 av_freep(&avctx->coded_frame);
1459 /*************************************************************************/
1466 IComplex in[FN], in1[FN];
1468 float sum_re, sum_im, a;
1473 in[i].re = random() % 65535 - 32767;
1474 in[i].im = random() % 65535 - 32767;
1484 a = -2 * M_PI * (n * k) / FN;
1485 sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);
1486 sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);
1488 printf("%3d: %6d,%6d %6.0f,%6.0f\n",
1489 k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);
1493 void mdct_test(void)
1499 float s, a, err, e, emax;
1503 input[i] = (random() % 65535 - 32767) * 9 / 10;
1504 input1[i] = input[i];
1507 mdct512(output, input);
1510 for(k=0;k<N/2;k++) {
1513 a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));
1514 s += input1[n] * cos(a);
1516 output1[k] = -2 * s / N;
1521 for(i=0;i<N/2;i++) {
1522 printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);
1523 e = output[i] - output1[i];
1528 printf("err2=%f emax=%f\n", err / (N/2), emax);
1533 AC3EncodeContext ctx;
1534 unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];
1535 short samples[AC3_FRAME_SIZE];
1538 AC3_encode_init(&ctx, 44100, 64000, 1);
1543 for(i=0;i<AC3_FRAME_SIZE;i++)
1544 samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);
1545 ret = AC3_encode_frame(&ctx, frame, samples);
1546 printf("ret=%d\n", ret);
1550 AVCodec ac3_encoder = {
1554 sizeof(AC3EncodeContext),