falkTX
/
FFmpeg
mirror of https://github.com/falkTX/FFmpeg.git
1
0
Fork 0
Code Issues 0 Releases 338 Wiki Activity
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
5630 Commits
32 Branches
369MB
Tree: 176c142abc
Branches Tags
${ item.name }
Create branch ${ searchTerm }
from '176c142abc'
${ noResults }
FFmpeg/libavcodec/ac3enc.c

1603 lines
44KB
Raw Blame History 

  1. /*

  2.  * The simplest AC3 encoder

  3.  * Copyright (c) 2000 Fabrice Bellard.

  4.  *

  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.

  9.  *

  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.

  14.  *

  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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

  18.  */

  19. 

  20. /**

  21.  * @file ac3enc.c

  22.  * The simplest AC3 encoder.

  23.  */

  24. //#define DEBUG

  25. //#define DEBUG_BITALLOC

  26. #include "avcodec.h"

  27. #include "bitstream.h"

  28. #include "crc.h"

  29. #include "ac3.h"

  30. 

  31. typedef struct AC3EncodeContext {

  32.     PutBitContext pb;

  33.     int nb_channels;

  34.     int nb_all_channels;

  35.     int lfe_channel;

  36.     int bit_rate;

  37.     unsigned int sample_rate;

  38.     unsigned int bsid;

  39.     unsigned int frame_size_min; /* minimum frame size in case rounding is necessary */

  40.     unsigned int frame_size; /* current frame size in words */

  41.     unsigned int bits_written;

  42.     unsigned int samples_written;

  43.     int halfratecod;

  44.     unsigned int frmsizecod;

  45.     unsigned int fscod; /* frequency */

  46.     unsigned int acmod;

  47.     int lfe;

  48.     unsigned int bsmod;

  49.     short last_samples[AC3_MAX_CHANNELS][256];

  50.     unsigned int chbwcod[AC3_MAX_CHANNELS];

  51.     int nb_coefs[AC3_MAX_CHANNELS];

  52. 

  53.     /* bitrate allocation control */

  54.     int sgaincod, sdecaycod, fdecaycod, dbkneecod, floorcod;

  55.     AC3BitAllocParameters bit_alloc;

  56.     int csnroffst;

  57.     int fgaincod[AC3_MAX_CHANNELS];

  58.     int fsnroffst[AC3_MAX_CHANNELS];

  59.     /* mantissa encoding */

  60.     int mant1_cnt, mant2_cnt, mant4_cnt;

  61. } AC3EncodeContext;

  62. 

  63. #include "ac3tab.h"

  64. 

  65. #define MDCT_NBITS 9

  66. #define N         (1 << MDCT_NBITS)

  67. 

  68. /* new exponents are sent if their Norm 1 exceed this number */

  69. #define EXP_DIFF_THRESHOLD 1000

  70. 

  71. static void fft_init(int ln);

  72. 

  73. static inline int16_t fix15(float a)

  74. {

  75.     int v;

  76.     v = (int)(a * (float)(1 << 15));

  77.     if (v < -32767)

  78.         v = -32767;

  79.     else if (v > 32767)

  80.         v = 32767;

  81.     return v;

  82. }

  83. 

  84. 

  85. /**

  86.  * Generate a Kaiser Window.

  87.  */

  88. static void k_window_init(int alpha, double *window, int n, int iter)

  89. {

  90.     int j, k;

  91.     double a, x;

  92.     a = alpha * M_PI / n;

  93.     a = a*a;

  94.     for(k=0; k<n; k++) {

  95.         x = k * (n - k) * a;

  96.         window[k] = 1.0;

  97.         for(j=iter; j>0; j--) {

  98.             window[k] = (window[k] * x / (j*j)) + 1.0;

  99.         }

  100.     }

  101. }

  102. 

  103. /**

  104.  * Generate a Kaiser-Bessel Derived Window.

  105.  * @param alpha  determines window shape

  106.  * @param window array to fill with window values

  107.  * @param iter   number of iterations to use in BesselI0

  108.  */

  109. 

  110. static void kbd_window_init(int alpha, int16_t *out_window, int iter)

  111. {

  112.     int k, n2;

  113.     double kwindow[256];

  114.     double window[256];

  115. 

  116.     n2 = 256;

  117.     k_window_init(alpha, kwindow, n2, iter);

  118.     window[0] = kwindow[0];

  119.     for(k=1; k<n2; k++) {

  120.         window[k] = window[k-1] + kwindow[k];

  121.     }

  122.     for(k=0; k<n2; k++) {

  123.         window[k] = sqrt(window[k] / (window[n2-1]+1));

  124.         //out_window[k] = round(window[k]*((1<<15)-1)); //enable this for a rounded window

  125.         out_window[k] = fix15(window[k]);

  126.     }

  127. }

  128. 

  129. static inline int calc_lowcomp1(int a, int b0, int b1)

  130. {

  131.     if ((b0 + 256) == b1) {

  132.         a = 384 ;

  133.     } else if (b0 > b1) {

  134.         a = a - 64;

  135.         if (a < 0) a=0;

  136.     }

  137.     return a;

  138. }

  139. 

  140. static inline int calc_lowcomp(int a, int b0, int b1, int bin)

  141. {

  142.     if (bin < 7) {

  143.         if ((b0 + 256) == b1) {

  144.             a = 384 ;

  145.         } else if (b0 > b1) {

  146.             a = a - 64;

  147.             if (a < 0) a=0;

  148.         }

  149.     } else if (bin < 20) {

  150.         if ((b0 + 256) == b1) {

  151.             a = 320 ;

  152.         } else if (b0 > b1) {

  153.             a= a - 64;

  154.             if (a < 0) a=0;

  155.         }

  156.     } else {

  157.         a = a - 128;

  158.         if (a < 0) a=0;

  159.     }

  160.     return a;

  161. }

  162. 

  163. /* AC3 bit allocation. The algorithm is the one described in the AC3

  164.    spec. */

  165. void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,

  166.                                    int8_t *exp, int start, int end,

  167.                                    int snroffset, int fgain, int is_lfe,

  168.                                    int deltbae,int deltnseg,

  169.                                    uint8_t *deltoffst, uint8_t *deltlen, uint8_t *deltba)

  170. {

  171.     int bin,i,j,k,end1,v,v1,bndstrt,bndend,lowcomp,begin;

  172.     int fastleak,slowleak,address,tmp;

  173.     int16_t psd[256]; /* scaled exponents */

  174.     int16_t bndpsd[50]; /* interpolated exponents */

  175.     int16_t excite[50]; /* excitation */

  176.     int16_t mask[50];   /* masking value */

  177. 

  178.     /* exponent mapping to PSD */

  179.     for(bin=start;bin<end;bin++) {

  180.         psd[bin]=(3072 - (exp[bin] << 7));

  181.     }

  182. 

  183.     /* PSD integration */

  184.     j=start;

  185.     k=masktab[start];

  186.     do {

  187.         v=psd[j];

  188.         j++;

  189.         end1=bndtab[k+1];

  190.         if (end1 > end) end1=end;

  191.         for(i=j;i<end1;i++) {

  192.             int c,adr;

  193.             /* logadd */

  194.             v1=psd[j];

  195.             c=v-v1;

  196.             if (c >= 0) {

  197.                 adr=c >> 1;

  198.                 if (adr > 255) adr=255;

  199.                 v=v + latab[adr];

  200.             } else {

  201.                 adr=(-c) >> 1;

  202.                 if (adr > 255) adr=255;

  203.                 v=v1 + latab[adr];

  204.             }

  205.             j++;

  206.         }

  207.         bndpsd[k]=v;

  208.         k++;

  209.     } while (end > bndtab[k]);

  210. 

  211.     /* excitation function */

  212.     bndstrt = masktab[start];

  213.     bndend = masktab[end-1] + 1;

  214. 

  215.     if (bndstrt == 0) {

  216.         lowcomp = 0;

  217.         lowcomp = calc_lowcomp1(lowcomp, bndpsd[0], bndpsd[1]) ;

  218.         excite[0] = bndpsd[0] - fgain - lowcomp ;

  219.         lowcomp = calc_lowcomp1(lowcomp, bndpsd[1], bndpsd[2]) ;

  220.         excite[1] = bndpsd[1] - fgain - lowcomp ;

  221.         begin = 7 ;

  222.         for (bin = 2; bin < 7; bin++) {

  223.             if (!(is_lfe && bin == 6))

  224.                 lowcomp = calc_lowcomp1(lowcomp, bndpsd[bin], bndpsd[bin+1]) ;

  225.             fastleak = bndpsd[bin] - fgain ;

  226.             slowleak = bndpsd[bin] - s->sgain ;

  227.             excite[bin] = fastleak - lowcomp ;

  228.             if (!(is_lfe && bin == 6)) {

  229.                 if (bndpsd[bin] <= bndpsd[bin+1]) {

  230.                     begin = bin + 1 ;

  231.                     break ;

  232.                 }

  233.             }

  234.         }

  235. 

  236.         end1=bndend;

  237.         if (end1 > 22) end1=22;

  238. 

  239.         for (bin = begin; bin < end1; bin++) {

  240.             if (!(is_lfe && bin == 6))

  241.                 lowcomp = calc_lowcomp(lowcomp, bndpsd[bin], bndpsd[bin+1], bin) ;

  242. 

  243.             fastleak -= s->fdecay ;

  244.             v = bndpsd[bin] - fgain;

  245.             if (fastleak < v) fastleak = v;

  246. 

  247.             slowleak -= s->sdecay ;

  248.             v = bndpsd[bin] - s->sgain;

  249.             if (slowleak < v) slowleak = v;

  250. 

  251.             v=fastleak - lowcomp;

  252.             if (slowleak > v) v=slowleak;

  253. 

  254.             excite[bin] = v;

  255.         }

  256.         begin = 22;

  257.     } else {

  258.         /* coupling channel */

  259.         begin = bndstrt;

  260. 

  261.         fastleak = (s->cplfleak << 8) + 768;

  262.         slowleak = (s->cplsleak << 8) + 768;

  263.     }

  264. 

  265.     for (bin = begin; bin < bndend; bin++) {

  266.         fastleak -= s->fdecay ;

  267.         v = bndpsd[bin] - fgain;

  268.         if (fastleak < v) fastleak = v;

  269.         slowleak -= s->sdecay ;

  270.         v = bndpsd[bin] - s->sgain;

  271.         if (slowleak < v) slowleak = v;

  272. 

  273.         v=fastleak;

  274.         if (slowleak > v) v = slowleak;

  275.         excite[bin] = v;

  276.     }

  277. 

  278.     /* compute masking curve */

  279. 

  280.     for (bin = bndstrt; bin < bndend; bin++) {

  281.         v1 = excite[bin];

  282.         tmp = s->dbknee - bndpsd[bin];

  283.         if (tmp > 0) {

  284.             v1 += tmp >> 2;

  285.         }

  286.         v=hth[bin >> s->halfratecod][s->fscod];

  287.         if (v1 > v) v=v1;

  288.         mask[bin] = v;

  289.     }

  290. 

  291.     /* delta bit allocation */

  292. 

  293.     if (deltbae == 0 || deltbae == 1) {

  294.         int band, seg, delta;

  295.         band = 0 ;

  296.         for (seg = 0; seg < deltnseg; seg++) {

  297.             band += deltoffst[seg] ;

  298.             if (deltba[seg] >= 4) {

  299.                 delta = (deltba[seg] - 3) << 7;

  300.             } else {

  301.                 delta = (deltba[seg] - 4) << 7;

  302.             }

  303.             for (k = 0; k < deltlen[seg]; k++) {

  304.                 mask[band] += delta ;

  305.                 band++ ;

  306.             }

  307.         }

  308.     }

  309. 

  310.     /* compute bit allocation */

  311. 

  312.     i = start ;

  313.     j = masktab[start] ;

  314.     do {

  315.         v=mask[j];

  316.         v -= snroffset ;

  317.         v -= s->floor ;

  318.         if (v < 0) v = 0;

  319.         v &= 0x1fe0 ;

  320.         v += s->floor ;

  321. 

  322.         end1=bndtab[j] + bndsz[j];

  323.         if (end1 > end) end1=end;

  324. 

  325.         for (k = i; k < end1; k++) {

  326.             address = (psd[i] - v) >> 5 ;

  327.             if (address < 0) address=0;

  328.             else if (address > 63) address=63;

  329.             bap[i] = baptab[address];

  330.             i++;

  331.         }

  332.     } while (end > bndtab[j++]) ;

  333. }

  334. 

  335. typedef struct IComplex {

  336.     short re,im;

  337. } IComplex;

  338. 

  339. static void fft_init(int ln)

  340. {

  341.     int i, j, m, n;

  342.     float alpha;

  343. 

  344.     n = 1 << ln;

  345. 

  346.     for(i=0;i<(n/2);i++) {

  347.         alpha = 2 * M_PI * (float)i / (float)n;

  348.         costab[i] = fix15(cos(alpha));

  349.         sintab[i] = fix15(sin(alpha));

  350.     }

  351. 

  352.     for(i=0;i<n;i++) {

  353.         m=0;

  354.         for(j=0;j<ln;j++) {

  355.             m |= ((i >> j) & 1) << (ln-j-1);

  356.         }

  357.         fft_rev[i]=m;

  358.     }

  359. }

  360. 

  361. /* butter fly op */

  362. #define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \

  363. {\

  364.   int ax, ay, bx, by;\

  365.   bx=pre1;\

  366.   by=pim1;\

  367.   ax=qre1;\

  368.   ay=qim1;\

  369.   pre = (bx + ax) >> 1;\

  370.   pim = (by + ay) >> 1;\

  371.   qre = (bx - ax) >> 1;\

  372.   qim = (by - ay) >> 1;\

  373. }

  374. 

  375. #define MUL16(a,b) ((a) * (b))

  376. 

  377. #define CMUL(pre, pim, are, aim, bre, bim) \

  378. {\

  379.    pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15;\

  380.    pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\

  381. }

  382. 

  383. 

  384. /* do a 2^n point complex fft on 2^ln points. */

  385. static void fft(IComplex *z, int ln)

  386. {

  387.     int        j, l, np, np2;

  388.     int        nblocks, nloops;

  389.     register IComplex *p,*q;

  390.     int tmp_re, tmp_im;

  391. 

  392.     np = 1 << ln;

  393. 

  394.     /* reverse */

  395.     for(j=0;j<np;j++) {

  396.         int k;

  397.         IComplex tmp;

  398.         k = fft_rev[j];

  399.         if (k < j) {

  400.             tmp = z[k];

  401.             z[k] = z[j];

  402.             z[j] = tmp;

  403.         }

  404.     }

  405. 

  406.     /* pass 0 */

  407. 

  408.     p=&z[0];

  409.     j=(np >> 1);

  410.     do {

  411.         BF(p[0].re, p[0].im, p[1].re, p[1].im,

  412.            p[0].re, p[0].im, p[1].re, p[1].im);

  413.         p+=2;

  414.     } while (--j != 0);

  415. 

  416.     /* pass 1 */

  417. 

  418.     p=&z[0];

  419.     j=np >> 2;

  420.     do {

  421.         BF(p[0].re, p[0].im, p[2].re, p[2].im,

  422.            p[0].re, p[0].im, p[2].re, p[2].im);

  423.         BF(p[1].re, p[1].im, p[3].re, p[3].im,

  424.            p[1].re, p[1].im, p[3].im, -p[3].re);

  425.         p+=4;

  426.     } while (--j != 0);

  427. 

  428.     /* pass 2 .. ln-1 */

  429. 

  430.     nblocks = np >> 3;

  431.     nloops = 1 << 2;

  432.     np2 = np >> 1;

  433.     do {

  434.         p = z;

  435.         q = z + nloops;

  436.         for (j = 0; j < nblocks; ++j) {

  437. 

  438.             BF(p->re, p->im, q->re, q->im,

  439.                p->re, p->im, q->re, q->im);

  440. 

  441.             p++;

  442.             q++;

  443.             for(l = nblocks; l < np2; l += nblocks) {

  444.                 CMUL(tmp_re, tmp_im, costab[l], -sintab[l], q->re, q->im);

  445.                 BF(p->re, p->im, q->re, q->im,

  446.                    p->re, p->im, tmp_re, tmp_im);

  447.                 p++;

  448.                 q++;

  449.             }

  450.             p += nloops;

  451.             q += nloops;

  452.         }

  453.         nblocks = nblocks >> 1;

  454.         nloops = nloops << 1;

  455.     } while (nblocks != 0);

  456. }

  457. 

  458. /* do a 512 point mdct */

  459. static void mdct512(int32_t *out, int16_t *in)

  460. {

  461.     int i, re, im, re1, im1;

  462.     int16_t rot[N];

  463.     IComplex x[N/4];

  464. 

  465.     /* shift to simplify computations */

  466.     for(i=0;i<N/4;i++)

  467.         rot[i] = -in[i + 3*N/4];

  468.     for(i=N/4;i<N;i++)

  469.         rot[i] = in[i - N/4];

  470. 

  471.     /* pre rotation */

  472.     for(i=0;i<N/4;i++) {

  473.         re = ((int)rot[2*i] - (int)rot[N-1-2*i]) >> 1;

  474.         im = -((int)rot[N/2+2*i] - (int)rot[N/2-1-2*i]) >> 1;

  475.         CMUL(x[i].re, x[i].im, re, im, -xcos1[i], xsin1[i]);

  476.     }

  477. 

  478.     fft(x, MDCT_NBITS - 2);

  479. 

  480.     /* post rotation */

  481.     for(i=0;i<N/4;i++) {

  482.         re = x[i].re;

  483.         im = x[i].im;

  484.         CMUL(re1, im1, re, im, xsin1[i], xcos1[i]);

  485.         out[2*i] = im1;

  486.         out[N/2-1-2*i] = re1;

  487.     }

  488. }

  489. 

  490. /* XXX: use another norm ? */

  491. static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n)

  492. {

  493.     int sum, i;

  494.     sum = 0;

  495.     for(i=0;i<n;i++) {

  496.         sum += abs(exp1[i] - exp2[i]);

  497.     }

  498.     return sum;

  499. }

  500. 

  501. static void compute_exp_strategy(uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],

  502.                                  uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

  503.                                  int ch, int is_lfe)

  504. {

  505.     int i, j;

  506.     int exp_diff;

  507. 

  508.     /* estimate if the exponent variation & decide if they should be

  509.        reused in the next frame */

  510.     exp_strategy[0][ch] = EXP_NEW;

  511.     for(i=1;i<NB_BLOCKS;i++) {

  512.         exp_diff = calc_exp_diff(exp[i][ch], exp[i-1][ch], N/2);

  513. #ifdef DEBUG

  514.         av_log(NULL, AV_LOG_DEBUG, "exp_diff=%d\n", exp_diff);

  515. #endif

  516.         if (exp_diff > EXP_DIFF_THRESHOLD)

  517.             exp_strategy[i][ch] = EXP_NEW;

  518.         else

  519.             exp_strategy[i][ch] = EXP_REUSE;

  520.     }

  521.     if (is_lfe)

  522.         return;

  523. 

  524.     /* now select the encoding strategy type : if exponents are often

  525.        recoded, we use a coarse encoding */

  526.     i = 0;

  527.     while (i < NB_BLOCKS) {

  528.         j = i + 1;

  529.         while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)

  530.             j++;

  531.         switch(j - i) {

  532.         case 1:

  533.             exp_strategy[i][ch] = EXP_D45;

  534.             break;

  535.         case 2:

  536.         case 3:

  537.             exp_strategy[i][ch] = EXP_D25;

  538.             break;

  539.         default:

  540.             exp_strategy[i][ch] = EXP_D15;

  541.             break;

  542.         }

  543.         i = j;

  544.     }

  545. }

  546. 

  547. /* set exp[i] to min(exp[i], exp1[i]) */

  548. static void exponent_min(uint8_t exp[N/2], uint8_t exp1[N/2], int n)

  549. {

  550.     int i;

  551. 

  552.     for(i=0;i<n;i++) {

  553.         if (exp1[i] < exp[i])

  554.             exp[i] = exp1[i];

  555.     }

  556. }

  557. 

  558. /* update the exponents so that they are the ones the decoder will

  559.    decode. Return the number of bits used to code the exponents */

  560. static int encode_exp(uint8_t encoded_exp[N/2],

  561.                       uint8_t exp[N/2],

  562.                       int nb_exps,

  563.                       int exp_strategy)

  564. {

  565.     int group_size, nb_groups, i, j, k, exp_min;

  566.     uint8_t exp1[N/2];

  567. 

  568.     switch(exp_strategy) {

  569.     case EXP_D15:

  570.         group_size = 1;

  571.         break;

  572.     case EXP_D25:

  573.         group_size = 2;

  574.         break;

  575.     default:

  576.     case EXP_D45:

  577.         group_size = 4;

  578.         break;

  579.     }

  580.     nb_groups = ((nb_exps + (group_size * 3) - 4) / (3 * group_size)) * 3;

  581. 

  582.     /* for each group, compute the minimum exponent */

  583.     exp1[0] = exp[0]; /* DC exponent is handled separately */

  584.     k = 1;

  585.     for(i=1;i<=nb_groups;i++) {

  586.         exp_min = exp[k];

  587.         assert(exp_min >= 0 && exp_min <= 24);

  588.         for(j=1;j<group_size;j++) {

  589.             if (exp[k+j] < exp_min)

  590.                 exp_min = exp[k+j];

  591.         }

  592.         exp1[i] = exp_min;

  593.         k += group_size;

  594.     }

  595. 

  596.     /* constraint for DC exponent */

  597.     if (exp1[0] > 15)

  598.         exp1[0] = 15;

  599. 

  600.     /* Decrease the delta between each groups to within 2

  601.      * so that they can be differentially encoded */

  602.     for (i=1;i<=nb_groups;i++)

  603.         exp1[i] = FFMIN(exp1[i], exp1[i-1] + 2);

  604.     for (i=nb_groups-1;i>=0;i--)

  605.         exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2);

  606. 

  607.     /* now we have the exponent values the decoder will see */

  608.     encoded_exp[0] = exp1[0];

  609.     k = 1;

  610.     for(i=1;i<=nb_groups;i++) {

  611.         for(j=0;j<group_size;j++) {

  612.             encoded_exp[k+j] = exp1[i];

  613.         }

  614.         k += group_size;

  615.     }

  616. 

  617. #if defined(DEBUG)

  618.     av_log(NULL, AV_LOG_DEBUG, "exponents: strategy=%d\n", exp_strategy);

  619.     for(i=0;i<=nb_groups * group_size;i++) {

  620.         av_log(NULL, AV_LOG_DEBUG, "%d ", encoded_exp[i]);

  621.     }

  622.     av_log(NULL, AV_LOG_DEBUG, "\n");

  623. #endif

  624. 

  625.     return 4 + (nb_groups / 3) * 7;

  626. }

  627. 

  628. /* return the size in bits taken by the mantissa */

  629. static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs)

  630. {

  631.     int bits, mant, i;

  632. 

  633.     bits = 0;

  634.     for(i=0;i<nb_coefs;i++) {

  635.         mant = m[i];

  636.         switch(mant) {

  637.         case 0:

  638.             /* nothing */

  639.             break;

  640.         case 1:

  641.             /* 3 mantissa in 5 bits */

  642.             if (s->mant1_cnt == 0)

  643.                 bits += 5;

  644.             if (++s->mant1_cnt == 3)

  645.                 s->mant1_cnt = 0;

  646.             break;

  647.         case 2:

  648.             /* 3 mantissa in 7 bits */

  649.             if (s->mant2_cnt == 0)

  650.                 bits += 7;

  651.             if (++s->mant2_cnt == 3)

  652.                 s->mant2_cnt = 0;

  653.             break;

  654.         case 3:

  655.             bits += 3;

  656.             break;

  657.         case 4:

  658.             /* 2 mantissa in 7 bits */

  659.             if (s->mant4_cnt == 0)

  660.                 bits += 7;

  661.             if (++s->mant4_cnt == 2)

  662.                 s->mant4_cnt = 0;

  663.             break;

  664.         case 14:

  665.             bits += 14;

  666.             break;

  667.         case 15:

  668.             bits += 16;

  669.             break;

  670.         default:

  671.             bits += mant - 1;

  672.             break;

  673.         }

  674.     }

  675.     return bits;

  676. }

  677. 

  678. 

  679. static int bit_alloc(AC3EncodeContext *s,

  680.                      uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

  681.                      uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

  682.                      uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],

  683.                      int frame_bits, int csnroffst, int fsnroffst)

  684. {

  685.     int i, ch;

  686. 

  687.     /* compute size */

  688.     for(i=0;i<NB_BLOCKS;i++) {

  689.         s->mant1_cnt = 0;

  690.         s->mant2_cnt = 0;

  691.         s->mant4_cnt = 0;

  692.         for(ch=0;ch<s->nb_all_channels;ch++) {

  693.             ac3_parametric_bit_allocation(&s->bit_alloc,

  694.                                           bap[i][ch], (int8_t *)encoded_exp[i][ch],

  695.                                           0, s->nb_coefs[ch],

  696.                                           (((csnroffst-15) << 4) +

  697.                                            fsnroffst) << 2,

  698.                                           fgaintab[s->fgaincod[ch]],

  699.                                           ch == s->lfe_channel,

  700.                                           2, 0, NULL, NULL, NULL);

  701.             frame_bits += compute_mantissa_size(s, bap[i][ch],

  702.                                                  s->nb_coefs[ch]);

  703.         }

  704.     }

  705. #if 0

  706.     printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n",

  707.            csnroffst, fsnroffst, frame_bits,

  708.            16 * s->frame_size - ((frame_bits + 7) & ~7));

  709. #endif

  710.     return 16 * s->frame_size - frame_bits;

  711. }

  712. 

  713. #define SNR_INC1 4

  714. 

  715. static int compute_bit_allocation(AC3EncodeContext *s,

  716.                                   uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

  717.                                   uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

  718.                                   uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],

  719.                                   int frame_bits)

  720. {

  721.     int i, ch;

  722.     int csnroffst, fsnroffst;

  723.     uint8_t bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

  724.     static int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };

  725. 

  726.     /* init default parameters */

  727.     s->sdecaycod = 2;

  728.     s->fdecaycod = 1;

  729.     s->sgaincod = 1;

  730.     s->dbkneecod = 2;

  731.     s->floorcod = 4;

  732.     for(ch=0;ch<s->nb_all_channels;ch++)

  733.         s->fgaincod[ch] = 4;

  734. 

  735.     /* compute real values */

  736.     s->bit_alloc.fscod = s->fscod;

  737.     s->bit_alloc.halfratecod = s->halfratecod;

  738.     s->bit_alloc.sdecay = sdecaytab[s->sdecaycod] >> s->halfratecod;

  739.     s->bit_alloc.fdecay = fdecaytab[s->fdecaycod] >> s->halfratecod;

  740.     s->bit_alloc.sgain = sgaintab[s->sgaincod];

  741.     s->bit_alloc.dbknee = dbkneetab[s->dbkneecod];

  742.     s->bit_alloc.floor = floortab[s->floorcod];

  743. 

  744.     /* header size */

  745.     frame_bits += 65;

  746.     // if (s->acmod == 2)

  747.     //    frame_bits += 2;

  748.     frame_bits += frame_bits_inc[s->acmod];

  749. 

  750.     /* audio blocks */

  751.     for(i=0;i<NB_BLOCKS;i++) {

  752.         frame_bits += s->nb_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */

  753.         if (s->acmod == 2) {

  754.             frame_bits++; /* rematstr */

  755.             if(i==0) frame_bits += 4;

  756.         }

  757.         frame_bits += 2 * s->nb_channels; /* chexpstr[2] * c */

  758.         if (s->lfe)

  759.             frame_bits++; /* lfeexpstr */

  760.         for(ch=0;ch<s->nb_channels;ch++) {

  761.             if (exp_strategy[i][ch] != EXP_REUSE)

  762.                 frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */

  763.         }

  764.         frame_bits++; /* baie */

  765.         frame_bits++; /* snr */

  766.         frame_bits += 2; /* delta / skip */

  767.     }

  768.     frame_bits++; /* cplinu for block 0 */

  769.     /* bit alloc info */

  770.     /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */

  771.     /* csnroffset[6] */

  772.     /* (fsnoffset[4] + fgaincod[4]) * c */

  773.     frame_bits += 2*4 + 3 + 6 + s->nb_all_channels * (4 + 3);

  774. 

  775.     /* auxdatae, crcrsv */

  776.     frame_bits += 2;

  777. 

  778.     /* CRC */

  779.     frame_bits += 16;

  780. 

  781.     /* now the big work begins : do the bit allocation. Modify the snr

  782.        offset until we can pack everything in the requested frame size */

  783. 

  784.     csnroffst = s->csnroffst;

  785.     while (csnroffst >= 0 &&

  786.            bit_alloc(s, bap, encoded_exp, exp_strategy, frame_bits, csnroffst, 0) < 0)

  787.         csnroffst -= SNR_INC1;

  788.     if (csnroffst < 0) {

  789.         av_log(NULL, AV_LOG_ERROR, "Bit allocation failed, try increasing the bitrate, -ab 384 for example!\n");

  790.         return -1;

  791.     }

  792.     while ((csnroffst + SNR_INC1) <= 63 &&

  793.            bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits,

  794.                      csnroffst + SNR_INC1, 0) >= 0) {

  795.         csnroffst += SNR_INC1;

  796.         memcpy(bap, bap1, sizeof(bap1));

  797.     }

  798.     while ((csnroffst + 1) <= 63 &&

  799.            bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits, csnroffst + 1, 0) >= 0) {

  800.         csnroffst++;

  801.         memcpy(bap, bap1, sizeof(bap1));

  802.     }

  803. 

  804.     fsnroffst = 0;

  805.     while ((fsnroffst + SNR_INC1) <= 15 &&

  806.            bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits,

  807.                      csnroffst, fsnroffst + SNR_INC1) >= 0) {

  808.         fsnroffst += SNR_INC1;

  809.         memcpy(bap, bap1, sizeof(bap1));

  810.     }

  811.     while ((fsnroffst + 1) <= 15 &&

  812.            bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits,

  813.                      csnroffst, fsnroffst + 1) >= 0) {

  814.         fsnroffst++;

  815.         memcpy(bap, bap1, sizeof(bap1));

  816.     }

  817. 

  818.     s->csnroffst = csnroffst;

  819.     for(ch=0;ch<s->nb_all_channels;ch++)

  820.         s->fsnroffst[ch] = fsnroffst;

  821. #if defined(DEBUG_BITALLOC)

  822.     {

  823.         int j;

  824. 

  825.         for(i=0;i<6;i++) {

  826.             for(ch=0;ch<s->nb_all_channels;ch++) {

  827.                 printf("Block #%d Ch%d:\n", i, ch);

  828.                 printf("bap=");

  829.                 for(j=0;j<s->nb_coefs[ch];j++) {

  830.                     printf("%d ",bap[i][ch][j]);

  831.                 }

  832.                 printf("\n");

  833.             }

  834.         }

  835.     }

  836. #endif

  837.     return 0;

  838. }

  839. 

  840. void ac3_common_init(void)

  841. {

  842.     int i, j, k, l, v;

  843.     /* compute bndtab and masktab from bandsz */

  844.     k = 0;

  845.     l = 0;

  846.     for(i=0;i<50;i++) {

  847.         bndtab[i] = l;

  848.         v = bndsz[i];

  849.         for(j=0;j<v;j++) masktab[k++]=i;

  850.         l += v;

  851.     }

  852.     bndtab[50] = 0;

  853. }

  854. 

  855. 

  856. static int AC3_encode_init(AVCodecContext *avctx)

  857. {

  858.     int freq = avctx->sample_rate;

  859.     int bitrate = avctx->bit_rate;

  860.     int channels = avctx->channels;

  861.     AC3EncodeContext *s = avctx->priv_data;

  862.     int i, j, ch;

  863.     float alpha;

  864.     static const uint8_t acmod_defs[6] = {

  865.         0x01, /* C */

  866.         0x02, /* L R */

  867.         0x03, /* L C R */

  868.         0x06, /* L R SL SR */

  869.         0x07, /* L C R SL SR */

  870.         0x07, /* L C R SL SR (+LFE) */

  871.     };

  872. 

  873.     avctx->frame_size = AC3_FRAME_SIZE;

  874. 

  875.     /* number of channels */

  876.     if (channels < 1 || channels > 6)

  877.         return -1;

  878.     s->acmod = acmod_defs[channels - 1];

  879.     s->lfe = (channels == 6) ? 1 : 0;

  880.     s->nb_all_channels = channels;

  881.     s->nb_channels = channels > 5 ? 5 : channels;

  882.     s->lfe_channel = s->lfe ? 5 : -1;

  883. 

  884.     /* frequency */

  885.     for(i=0;i<3;i++) {

  886.         for(j=0;j<3;j++)

  887.             if ((ac3_freqs[j] >> i) == freq)

  888.                 goto found;

  889.     }

  890.     return -1;

  891.  found:

  892.     s->sample_rate = freq;

  893.     s->halfratecod = i;

  894.     s->fscod = j;

  895.     s->bsid = 8 + s->halfratecod;

  896.     s->bsmod = 0; /* complete main audio service */

  897. 

  898.     /* bitrate & frame size */

  899.     bitrate /= 1000;

  900.     for(i=0;i<19;i++) {

  901.         if ((ac3_bitratetab[i] >> s->halfratecod) == bitrate)

  902.             break;

  903.     }

  904.     if (i == 19)

  905.         return -1;

  906.     s->bit_rate = bitrate;

  907.     s->frmsizecod = i << 1;

  908.     s->frame_size_min = (bitrate * 1000 * AC3_FRAME_SIZE) / (freq * 16);

  909.     s->bits_written = 0;

  910.     s->samples_written = 0;

  911.     s->frame_size = s->frame_size_min;

  912. 

  913.     /* bit allocation init */

  914.     for(ch=0;ch<s->nb_channels;ch++) {

  915.         /* bandwidth for each channel */

  916.         /* XXX: should compute the bandwidth according to the frame

  917.            size, so that we avoid anoying high freq artefacts */

  918.         s->chbwcod[ch] = 50; /* sample bandwidth as mpeg audio layer 2 table 0 */

  919.         s->nb_coefs[ch] = ((s->chbwcod[ch] + 12) * 3) + 37;

  920.     }

  921.     if (s->lfe) {

  922.         s->nb_coefs[s->lfe_channel] = 7; /* fixed */

  923.     }

  924.     /* initial snr offset */

  925.     s->csnroffst = 40;

  926. 

  927.     ac3_common_init();

  928. 

  929.     /* mdct init */

  930.     kbd_window_init(5.0, ac3_window, 50);

  931. 

  932.     fft_init(MDCT_NBITS - 2);

  933.     for(i=0;i<N/4;i++) {

  934.         alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N;

  935.         xcos1[i] = fix15(-cos(alpha));

  936.         xsin1[i] = fix15(-sin(alpha));

  937.     }

  938. 

  939.     avctx->coded_frame= avcodec_alloc_frame();

  940.     avctx->coded_frame->key_frame= 1;

  941. 

  942.     return 0;

  943. }

  944. 

  945. /* output the AC3 frame header */

  946. static void output_frame_header(AC3EncodeContext *s, unsigned char *frame)

  947. {

  948.     init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);

  949. 

  950.     put_bits(&s->pb, 16, 0x0b77); /* frame header */

  951.     put_bits(&s->pb, 16, 0); /* crc1: will be filled later */

  952.     put_bits(&s->pb, 2, s->fscod);

  953.     put_bits(&s->pb, 6, s->frmsizecod + (s->frame_size - s->frame_size_min));

  954.     put_bits(&s->pb, 5, s->bsid);

  955.     put_bits(&s->pb, 3, s->bsmod);

  956.     put_bits(&s->pb, 3, s->acmod);

  957.     if ((s->acmod & 0x01) && s->acmod != 0x01)

  958.         put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */

  959.     if (s->acmod & 0x04)

  960.         put_bits(&s->pb, 2, 1); /* XXX -6 dB */

  961.     if (s->acmod == 0x02)

  962.         put_bits(&s->pb, 2, 0); /* surround not indicated */

  963.     put_bits(&s->pb, 1, s->lfe); /* LFE */

  964.     put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */

  965.     put_bits(&s->pb, 1, 0); /* no compression control word */

  966.     put_bits(&s->pb, 1, 0); /* no lang code */

  967.     put_bits(&s->pb, 1, 0); /* no audio production info */

  968.     put_bits(&s->pb, 1, 0); /* no copyright */

  969.     put_bits(&s->pb, 1, 1); /* original bitstream */

  970.     put_bits(&s->pb, 1, 0); /* no time code 1 */

  971.     put_bits(&s->pb, 1, 0); /* no time code 2 */

  972.     put_bits(&s->pb, 1, 0); /* no addtional bit stream info */

  973. }

  974. 

  975. /* symetric quantization on 'levels' levels */

  976. static inline int sym_quant(int c, int e, int levels)

  977. {

  978.     int v;

  979. 

  980.     if (c >= 0) {

  981.         v = (levels * (c << e)) >> 24;

  982.         v = (v + 1) >> 1;

  983.         v = (levels >> 1) + v;

  984.     } else {

  985.         v = (levels * ((-c) << e)) >> 24;

  986.         v = (v + 1) >> 1;

  987.         v = (levels >> 1) - v;

  988.     }

  989.     assert (v >= 0 && v < levels);

  990.     return v;

  991. }

  992. 

  993. /* asymetric quantization on 2^qbits levels */

  994. static inline int asym_quant(int c, int e, int qbits)

  995. {

  996.     int lshift, m, v;

  997. 

  998.     lshift = e + qbits - 24;

  999.     if (lshift >= 0)

  1000.         v = c << lshift;

  1001.     else

  1002.         v = c >> (-lshift);

  1003.     /* rounding */

  1004.     v = (v + 1) >> 1;

  1005.     m = (1 << (qbits-1));

  1006.     if (v >= m)

  1007.         v = m - 1;

  1008.     assert(v >= -m);

  1009.     return v & ((1 << qbits)-1);

  1010. }

  1011. 

  1012. /* Output one audio block. There are NB_BLOCKS audio blocks in one AC3

  1013.    frame */

  1014. static void output_audio_block(AC3EncodeContext *s,

  1015.                                uint8_t exp_strategy[AC3_MAX_CHANNELS],

  1016.                                uint8_t encoded_exp[AC3_MAX_CHANNELS][N/2],

  1017.                                uint8_t bap[AC3_MAX_CHANNELS][N/2],

  1018.                                int32_t mdct_coefs[AC3_MAX_CHANNELS][N/2],

  1019.                                int8_t global_exp[AC3_MAX_CHANNELS],

  1020.                                int block_num)

  1021. {

  1022.     int ch, nb_groups, group_size, i, baie, rbnd;

  1023.     uint8_t *p;

  1024.     uint16_t qmant[AC3_MAX_CHANNELS][N/2];

  1025.     int exp0, exp1;

  1026.     int mant1_cnt, mant2_cnt, mant4_cnt;

  1027.     uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr;

  1028.     int delta0, delta1, delta2;

  1029. 

  1030.     for(ch=0;ch<s->nb_channels;ch++)

  1031.         put_bits(&s->pb, 1, 0); /* 512 point MDCT */

  1032.     for(ch=0;ch<s->nb_channels;ch++)

  1033.         put_bits(&s->pb, 1, 1); /* no dither */

  1034.     put_bits(&s->pb, 1, 0); /* no dynamic range */

  1035.     if (block_num == 0) {

  1036.         /* for block 0, even if no coupling, we must say it. This is a

  1037.            waste of bit :-) */

  1038.         put_bits(&s->pb, 1, 1); /* coupling strategy present */

  1039.         put_bits(&s->pb, 1, 0); /* no coupling strategy */

  1040.     } else {

  1041.         put_bits(&s->pb, 1, 0); /* no new coupling strategy */

  1042.     }

  1043. 

  1044.     if (s->acmod == 2)

  1045.       {

  1046.         if(block_num==0)

  1047.           {

  1048.             /* first block must define rematrixing (rematstr)  */

  1049.             put_bits(&s->pb, 1, 1);

  1050. 

  1051.             /* dummy rematrixing rematflg(1:4)=0 */

  1052.             for (rbnd=0;rbnd<4;rbnd++)

  1053.               put_bits(&s->pb, 1, 0);

  1054.           }

  1055.         else

  1056.           {

  1057.             /* no matrixing (but should be used in the future) */

  1058.             put_bits(&s->pb, 1, 0);

  1059.           }

  1060.       }

  1061. 

  1062. #if defined(DEBUG)

  1063.     {

  1064.       static int count = 0;

  1065.       av_log(NULL, AV_LOG_DEBUG, "Block #%d (%d)\n", block_num, count++);

  1066.     }

  1067. #endif

  1068.     /* exponent strategy */

  1069.     for(ch=0;ch<s->nb_channels;ch++) {

  1070.         put_bits(&s->pb, 2, exp_strategy[ch]);

  1071.     }

  1072. 

  1073.     if (s->lfe) {

  1074.         put_bits(&s->pb, 1, exp_strategy[s->lfe_channel]);

  1075.     }

  1076. 

  1077.     for(ch=0;ch<s->nb_channels;ch++) {

  1078.         if (exp_strategy[ch] != EXP_REUSE)

  1079.             put_bits(&s->pb, 6, s->chbwcod[ch]);

  1080.     }

  1081. 

  1082.     /* exponents */

  1083.     for (ch = 0; ch < s->nb_all_channels; ch++) {

  1084.         switch(exp_strategy[ch]) {

  1085.         case EXP_REUSE:

  1086.             continue;

  1087.         case EXP_D15:

  1088.             group_size = 1;

  1089.             break;

  1090.         case EXP_D25:

  1091.             group_size = 2;

  1092.             break;

  1093.         default:

  1094.         case EXP_D45:

  1095.             group_size = 4;

  1096.             break;

  1097.         }

  1098.         nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);

  1099.         p = encoded_exp[ch];

  1100. 

  1101.         /* first exponent */

  1102.         exp1 = *p++;

  1103.         put_bits(&s->pb, 4, exp1);

  1104. 

  1105.         /* next ones are delta encoded */

  1106.         for(i=0;i<nb_groups;i++) {

  1107.             /* merge three delta in one code */

  1108.             exp0 = exp1;

  1109.             exp1 = p[0];

  1110.             p += group_size;

  1111.             delta0 = exp1 - exp0 + 2;

  1112. 

  1113.             exp0 = exp1;

  1114.             exp1 = p[0];

  1115.             p += group_size;

  1116.             delta1 = exp1 - exp0 + 2;

  1117. 

  1118.             exp0 = exp1;

  1119.             exp1 = p[0];

  1120.             p += group_size;

  1121.             delta2 = exp1 - exp0 + 2;

  1122. 

  1123.             put_bits(&s->pb, 7, ((delta0 * 5 + delta1) * 5) + delta2);

  1124.         }

  1125. 

  1126.         if (ch != s->lfe_channel)

  1127.             put_bits(&s->pb, 2, 0); /* no gain range info */

  1128.     }

  1129. 

  1130.     /* bit allocation info */

  1131.     baie = (block_num == 0);

  1132.     put_bits(&s->pb, 1, baie);

  1133.     if (baie) {

  1134.         put_bits(&s->pb, 2, s->sdecaycod);

  1135.         put_bits(&s->pb, 2, s->fdecaycod);

  1136.         put_bits(&s->pb, 2, s->sgaincod);

  1137.         put_bits(&s->pb, 2, s->dbkneecod);

  1138.         put_bits(&s->pb, 3, s->floorcod);

  1139.     }

  1140. 

  1141.     /* snr offset */

  1142.     put_bits(&s->pb, 1, baie); /* always present with bai */

  1143.     if (baie) {

  1144.         put_bits(&s->pb, 6, s->csnroffst);

  1145.         for(ch=0;ch<s->nb_all_channels;ch++) {

  1146.             put_bits(&s->pb, 4, s->fsnroffst[ch]);

  1147.             put_bits(&s->pb, 3, s->fgaincod[ch]);

  1148.         }

  1149.     }

  1150. 

  1151.     put_bits(&s->pb, 1, 0); /* no delta bit allocation */

  1152.     put_bits(&s->pb, 1, 0); /* no data to skip */

  1153. 

  1154.     /* mantissa encoding : we use two passes to handle the grouping. A

  1155.        one pass method may be faster, but it would necessitate to

  1156.        modify the output stream. */

  1157. 

  1158.     /* first pass: quantize */

  1159.     mant1_cnt = mant2_cnt = mant4_cnt = 0;

  1160.     qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;

  1161. 

  1162.     for (ch = 0; ch < s->nb_all_channels; ch++) {

  1163.         int b, c, e, v;

  1164. 

  1165.         for(i=0;i<s->nb_coefs[ch];i++) {

  1166.             c = mdct_coefs[ch][i];

  1167.             e = encoded_exp[ch][i] - global_exp[ch];

  1168.             b = bap[ch][i];

  1169.             switch(b) {

  1170.             case 0:

  1171.                 v = 0;

  1172.                 break;

  1173.             case 1:

  1174.                 v = sym_quant(c, e, 3);

  1175.                 switch(mant1_cnt) {

  1176.                 case 0:

  1177.                     qmant1_ptr = &qmant[ch][i];

  1178.                     v = 9 * v;

  1179.                     mant1_cnt = 1;

  1180.                     break;

  1181.                 case 1:

  1182.                     *qmant1_ptr += 3 * v;

  1183.                     mant1_cnt = 2;

  1184.                     v = 128;

  1185.                     break;

  1186.                 default:

  1187.                     *qmant1_ptr += v;

  1188.                     mant1_cnt = 0;

  1189.                     v = 128;

  1190.                     break;

  1191.                 }

  1192.                 break;

  1193.             case 2:

  1194.                 v = sym_quant(c, e, 5);

  1195.                 switch(mant2_cnt) {

  1196.                 case 0:

  1197.                     qmant2_ptr = &qmant[ch][i];

  1198.                     v = 25 * v;

  1199.                     mant2_cnt = 1;

  1200.                     break;

  1201.                 case 1:

  1202.                     *qmant2_ptr += 5 * v;

  1203.                     mant2_cnt = 2;

  1204.                     v = 128;

  1205.                     break;

  1206.                 default:

  1207.                     *qmant2_ptr += v;

  1208.                     mant2_cnt = 0;

  1209.                     v = 128;

  1210.                     break;

  1211.                 }

  1212.                 break;

  1213.             case 3:

  1214.                 v = sym_quant(c, e, 7);

  1215.                 break;

  1216.             case 4:

  1217.                 v = sym_quant(c, e, 11);

  1218.                 switch(mant4_cnt) {

  1219.                 case 0:

  1220.                     qmant4_ptr = &qmant[ch][i];

  1221.                     v = 11 * v;

  1222.                     mant4_cnt = 1;

  1223.                     break;

  1224.                 default:

  1225.                     *qmant4_ptr += v;

  1226.                     mant4_cnt = 0;

  1227.                     v = 128;

  1228.                     break;

  1229.                 }

  1230.                 break;

  1231.             case 5:

  1232.                 v = sym_quant(c, e, 15);

  1233.                 break;

  1234.             case 14:

  1235.                 v = asym_quant(c, e, 14);

  1236.                 break;

  1237.             case 15:

  1238.                 v = asym_quant(c, e, 16);

  1239.                 break;

  1240.             default:

  1241.                 v = asym_quant(c, e, b - 1);

  1242.                 break;

  1243.             }

  1244.             qmant[ch][i] = v;

  1245.         }

  1246.     }

  1247. 

  1248.     /* second pass : output the values */

  1249.     for (ch = 0; ch < s->nb_all_channels; ch++) {

  1250.         int b, q;

  1251. 

  1252.         for(i=0;i<s->nb_coefs[ch];i++) {

  1253.             q = qmant[ch][i];

  1254.             b = bap[ch][i];

  1255.             switch(b) {

  1256.             case 0:

  1257.                 break;

  1258.             case 1:

  1259.                 if (q != 128)

  1260.                     put_bits(&s->pb, 5, q);

  1261.                 break;

  1262.             case 2:

  1263.                 if (q != 128)

  1264.                     put_bits(&s->pb, 7, q);

  1265.                 break;

  1266.             case 3:

  1267.                 put_bits(&s->pb, 3, q);

  1268.                 break;

  1269.             case 4:

  1270.                 if (q != 128)

  1271.                     put_bits(&s->pb, 7, q);

  1272.                 break;

  1273.             case 14:

  1274.                 put_bits(&s->pb, 14, q);

  1275.                 break;

  1276.             case 15:

  1277.                 put_bits(&s->pb, 16, q);

  1278.                 break;

  1279.             default:

  1280.                 put_bits(&s->pb, b - 1, q);

  1281.                 break;

  1282.             }

  1283.         }

  1284.     }

  1285. }

  1286. 

  1287. #define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))

  1288. 

  1289. static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)

  1290. {

  1291.     unsigned int c;

  1292. 

  1293.     c = 0;

  1294.     while (a) {

  1295.         if (a & 1)

  1296.             c ^= b;

  1297.         a = a >> 1;

  1298.         b = b << 1;

  1299.         if (b & (1 << 16))

  1300.             b ^= poly;

  1301.     }

  1302.     return c;

  1303. }

  1304. 

  1305. static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)

  1306. {

  1307.     unsigned int r;

  1308.     r = 1;

  1309.     while (n) {

  1310.         if (n & 1)

  1311.             r = mul_poly(r, a, poly);

  1312.         a = mul_poly(a, a, poly);

  1313.         n >>= 1;

  1314.     }

  1315.     return r;

  1316. }

  1317. 

  1318. 

  1319. /* compute log2(max(abs(tab[]))) */

  1320. static int log2_tab(int16_t *tab, int n)

  1321. {

  1322.     int i, v;

  1323. 

  1324.     v = 0;

  1325.     for(i=0;i<n;i++) {

  1326.         v |= abs(tab[i]);

  1327.     }

  1328.     return av_log2(v);

  1329. }

  1330. 

  1331. static void lshift_tab(int16_t *tab, int n, int lshift)

  1332. {

  1333.     int i;

  1334. 

  1335.     if (lshift > 0) {

  1336.         for(i=0;i<n;i++) {

  1337.             tab[i] <<= lshift;

  1338.         }

  1339.     } else if (lshift < 0) {

  1340.         lshift = -lshift;

  1341.         for(i=0;i<n;i++) {

  1342.             tab[i] >>= lshift;

  1343.         }

  1344.     }

  1345. }

  1346. 

  1347. /* fill the end of the frame and compute the two crcs */

  1348. static int output_frame_end(AC3EncodeContext *s)

  1349. {

  1350.     int frame_size, frame_size_58, n, crc1, crc2, crc_inv;

  1351.     uint8_t *frame;

  1352. 

  1353.     frame_size = s->frame_size; /* frame size in words */

  1354.     /* align to 8 bits */

  1355.     flush_put_bits(&s->pb);

  1356.     /* add zero bytes to reach the frame size */

  1357.     frame = s->pb.buf;

  1358.     n = 2 * s->frame_size - (pbBufPtr(&s->pb) - frame) - 2;

  1359.     assert(n >= 0);

  1360.     if(n>0)

  1361.       memset(pbBufPtr(&s->pb), 0, n);

  1362. 

  1363.     /* Now we must compute both crcs : this is not so easy for crc1

  1364.        because it is at the beginning of the data... */

  1365.     frame_size_58 = (frame_size >> 1) + (frame_size >> 3);

  1366.     crc1 = bswap_16(av_crc(av_crc8005, 0, frame + 4, 2 * frame_size_58 - 4));

  1367.     /* XXX: could precompute crc_inv */

  1368.     crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58) - 16, CRC16_POLY);

  1369.     crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);

  1370.     frame[2] = crc1 >> 8;

  1371.     frame[3] = crc1;

  1372. 

  1373.     crc2 = bswap_16(av_crc(av_crc8005, 0, frame + 2 * frame_size_58, (frame_size - frame_size_58) * 2 - 2));

  1374.     frame[2*frame_size - 2] = crc2 >> 8;

  1375.     frame[2*frame_size - 1] = crc2;

  1376. 

  1377.     //    printf("n=%d frame_size=%d\n", n, frame_size);

  1378.     return frame_size * 2;

  1379. }

  1380. 

  1381. static int AC3_encode_frame(AVCodecContext *avctx,

  1382.                             unsigned char *frame, int buf_size, void *data)

  1383. {

  1384.     AC3EncodeContext *s = avctx->priv_data;

  1385.     int16_t *samples = data;

  1386.     int i, j, k, v, ch;

  1387.     int16_t input_samples[N];

  1388.     int32_t mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

  1389.     uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

  1390.     uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS];

  1391.     uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

  1392.     uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

  1393.     int8_t exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS];

  1394.     int frame_bits;

  1395. 

  1396.     frame_bits = 0;

  1397.     for(ch=0;ch<s->nb_all_channels;ch++) {

  1398.         /* fixed mdct to the six sub blocks & exponent computation */

  1399.         for(i=0;i<NB_BLOCKS;i++) {

  1400.             int16_t *sptr;

  1401.             int sinc;

  1402. 

  1403.             /* compute input samples */

  1404.             memcpy(input_samples, s->last_samples[ch], N/2 * sizeof(int16_t));

  1405.             sinc = s->nb_all_channels;

  1406.             sptr = samples + (sinc * (N/2) * i) + ch;

  1407.             for(j=0;j<N/2;j++) {

  1408.                 v = *sptr;

  1409.                 input_samples[j + N/2] = v;

  1410.                 s->last_samples[ch][j] = v;

  1411.                 sptr += sinc;

  1412.             }

  1413. 

  1414.             /* apply the MDCT window */

  1415.             for(j=0;j<N/2;j++) {

  1416.                 input_samples[j] = MUL16(input_samples[j],

  1417.                                          ac3_window[j]) >> 15;

  1418.                 input_samples[N-j-1] = MUL16(input_samples[N-j-1],

  1419.                                              ac3_window[j]) >> 15;

  1420.             }

  1421. 

  1422.             /* Normalize the samples to use the maximum available

  1423.                precision */

  1424.             v = 14 - log2_tab(input_samples, N);

  1425.             if (v < 0)

  1426.                 v = 0;

  1427.             exp_samples[i][ch] = v - 9;

  1428.             lshift_tab(input_samples, N, v);

  1429. 

  1430.             /* do the MDCT */

  1431.             mdct512(mdct_coef[i][ch], input_samples);

  1432. 

  1433.             /* compute "exponents". We take into account the

  1434.                normalization there */

  1435.             for(j=0;j<N/2;j++) {

  1436.                 int e;

  1437.                 v = abs(mdct_coef[i][ch][j]);

  1438.                 if (v == 0)

  1439.                     e = 24;

  1440.                 else {

  1441.                     e = 23 - av_log2(v) + exp_samples[i][ch];

  1442.                     if (e >= 24) {

  1443.                         e = 24;

  1444.                         mdct_coef[i][ch][j] = 0;

  1445.                     }

  1446.                 }

  1447.                 exp[i][ch][j] = e;

  1448.             }

  1449.         }

  1450. 

  1451.         compute_exp_strategy(exp_strategy, exp, ch, ch == s->lfe_channel);

  1452. 

  1453.         /* compute the exponents as the decoder will see them. The

  1454.            EXP_REUSE case must be handled carefully : we select the

  1455.            min of the exponents */

  1456.         i = 0;

  1457.         while (i < NB_BLOCKS) {

  1458.             j = i + 1;

  1459.             while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {

  1460.                 exponent_min(exp[i][ch], exp[j][ch], s->nb_coefs[ch]);

  1461.                 j++;

  1462.             }

  1463.             frame_bits += encode_exp(encoded_exp[i][ch],

  1464.                                      exp[i][ch], s->nb_coefs[ch],

  1465.                                      exp_strategy[i][ch]);

  1466.             /* copy encoded exponents for reuse case */

  1467.             for(k=i+1;k<j;k++) {

  1468.                 memcpy(encoded_exp[k][ch], encoded_exp[i][ch],

  1469.                        s->nb_coefs[ch] * sizeof(uint8_t));

  1470.             }

  1471.             i = j;

  1472.         }

  1473.     }

  1474. 

  1475.     /* adjust for fractional frame sizes */

  1476.     while(s->bits_written >= s->bit_rate*1000 && s->samples_written >= s->sample_rate) {

  1477.         s->bits_written -= s->bit_rate*1000;

  1478.         s->samples_written -= s->sample_rate;

  1479.     }

  1480.     s->frame_size = s->frame_size_min + (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate*1000);

  1481.     s->bits_written += s->frame_size * 16;

  1482.     s->samples_written += AC3_FRAME_SIZE;

  1483. 

  1484.     compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);

  1485.     /* everything is known... let's output the frame */

  1486.     output_frame_header(s, frame);

  1487. 

  1488.     for(i=0;i<NB_BLOCKS;i++) {

  1489.         output_audio_block(s, exp_strategy[i], encoded_exp[i],

  1490.                            bap[i], mdct_coef[i], exp_samples[i], i);

  1491.     }

  1492.     return output_frame_end(s);

  1493. }

  1494. 

  1495. static int AC3_encode_close(AVCodecContext *avctx)

  1496. {

  1497.     av_freep(&avctx->coded_frame);

  1498.     return 0;

  1499. }

  1500. 

  1501. #if 0

  1502. /*************************************************************************/

  1503. /* TEST */

  1504. 

  1505. #define FN (N/4)

  1506. 

  1507. void fft_test(void)

  1508. {

  1509.     IComplex in[FN], in1[FN];

  1510.     int k, n, i;

  1511.     float sum_re, sum_im, a;

  1512. 

  1513.     /* FFT test */

  1514. 

  1515.     for(i=0;i<FN;i++) {

  1516.         in[i].re = random() % 65535 - 32767;

  1517.         in[i].im = random() % 65535 - 32767;

  1518.         in1[i] = in[i];

  1519.     }

  1520.     fft(in, 7);

  1521. 

  1522.     /* do it by hand */

  1523.     for(k=0;k<FN;k++) {

  1524.         sum_re = 0;

  1525.         sum_im = 0;

  1526.         for(n=0;n<FN;n++) {

  1527.             a = -2 * M_PI * (n * k) / FN;

  1528.             sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);

  1529.             sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);

  1530.         }

  1531.         printf("%3d: %6d,%6d %6.0f,%6.0f\n",

  1532.                k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);

  1533.     }

  1534. }

  1535. 

  1536. void mdct_test(void)

  1537. {

  1538.     int16_t input[N];

  1539.     int32_t output[N/2];

  1540.     float input1[N];

  1541.     float output1[N/2];

  1542.     float s, a, err, e, emax;

  1543.     int i, k, n;

  1544. 

  1545.     for(i=0;i<N;i++) {

  1546.         input[i] = (random() % 65535 - 32767) * 9 / 10;

  1547.         input1[i] = input[i];

  1548.     }

  1549. 

  1550.     mdct512(output, input);

  1551. 

  1552.     /* do it by hand */

  1553.     for(k=0;k<N/2;k++) {

  1554.         s = 0;

  1555.         for(n=0;n<N;n++) {

  1556.             a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));

  1557.             s += input1[n] * cos(a);

  1558.         }

  1559.         output1[k] = -2 * s / N;

  1560.     }

  1561. 

  1562.     err = 0;

  1563.     emax = 0;

  1564.     for(i=0;i<N/2;i++) {

  1565.         printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);

  1566.         e = output[i] - output1[i];

  1567.         if (e > emax)

  1568.             emax = e;

  1569.         err += e * e;

  1570.     }

  1571.     printf("err2=%f emax=%f\n", err / (N/2), emax);

  1572. }

  1573. 

  1574. void test_ac3(void)

  1575. {

  1576.     AC3EncodeContext ctx;

  1577.     unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];

  1578.     short samples[AC3_FRAME_SIZE];

  1579.     int ret, i;

  1580. 

  1581.     AC3_encode_init(&ctx, 44100, 64000, 1);

  1582. 

  1583.     fft_test();

  1584.     mdct_test();

  1585. 

  1586.     for(i=0;i<AC3_FRAME_SIZE;i++)

  1587.         samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);

  1588.     ret = AC3_encode_frame(&ctx, frame, samples);

  1589.     printf("ret=%d\n", ret);

  1590. }

  1591. #endif

  1592. 

  1593. AVCodec ac3_encoder = {

  1594.     "ac3",

  1595.     CODEC_TYPE_AUDIO,

  1596.     CODEC_ID_AC3,

  1597.     sizeof(AC3EncodeContext),

  1598.     AC3_encode_init,

  1599.     AC3_encode_frame,

  1600.     AC3_encode_close,

  1601.     NULL,

  1602. };