Initial revision

Originally committed as revision 2 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 1460 insertions, 0 deletions

diff --git a/libav/ac3enc.c b/libav/ac3enc.c
new file mode 100644
index 0000000000..b1126c4943
--- /dev/null
+++ b/libav/ac3enc.c
@@ -0,0 +1,1460 @@
+/*
+ * The simplest AC3 encoder
+ * Copyright (c) 2000 Gerard Lantau.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <netinet/in.h>
+#include <math.h>
+#include "avcodec.h"
+
+#include "ac3enc.h"
+#include "ac3tab.h"
+
+//#define DEBUG
+//#define DEBUG_BITALLOC
+#define NDEBUG
+#include <assert.h>
+
+#define MDCT_NBITS 9
+#define N         (1 << MDCT_NBITS)
+#define NB_BLOCKS 6 /* number of PCM blocks inside an AC3 frame */
+
+/* new exponents are sent if their Norm 1 exceed this number */
+#define EXP_DIFF_THRESHOLD 1000
+
+/* exponent encoding strategy */
+#define EXP_REUSE 0
+#define EXP_NEW   1
+
+#define EXP_D15   1
+#define EXP_D25   2
+#define EXP_D45   3
+
+static void fft_init(int ln);
+static void ac3_crc_init(void);
+
+static inline INT16 fix15(float a)
+{
+    int v;
+    v = (int)(a * (float)(1 << 15));
+    if (v < -32767)
+        v = -32767;
+    else if (v > 32767) 
+        v = 32767;
+    return v;
+}
+
+static inline int calc_lowcomp1(int a, int b0, int b1)
+{
+    if ((b0 + 256) == b1) {
+        a = 384 ;
+    } else if (b0 > b1) { 
+        a = a - 64;
+        if (a < 0) a=0;
+    }
+    return a;
+}
+
+static inline int calc_lowcomp(int a, int b0, int b1, int bin)
+{
+    if (bin < 7) {
+        if ((b0 + 256) == b1) {
+            a = 384 ;
+        } else if (b0 > b1) { 
+            a = a - 64;
+            if (a < 0) a=0;
+        }
+    } else if (bin < 20) {
+        if ((b0 + 256) == b1) {
+            a = 320 ;
+        } else if (b0 > b1) {
+            a= a - 64;
+            if (a < 0) a=0;
+        }
+    } else {
+        a = a - 128;
+        if (a < 0) a=0;
+    }
+    return a;
+}
+
+/* AC3 bit allocation. The algorithm is the one described in the AC3
+   spec with some optimizations because of our simplified encoding
+   assumptions. */
+void parametric_bit_allocation(AC3EncodeContext *s, UINT8 *bap,
+                               INT8 *exp, int start, int end,
+                               int snroffset, int fgain)
+{
+    int bin,i,j,k,end1,v,v1,bndstrt,bndend,lowcomp,begin;
+    int fastleak,slowleak,address,tmp;
+    INT16 psd[256]; /* scaled exponents */
+    INT16 bndpsd[50]; /* interpolated exponents */
+    INT16 excite[50]; /* excitation */
+    INT16 mask[50];   /* masking value */
+
+    /* exponent mapping to PSD */
+    for(bin=start;bin<end;bin++) {
+        psd[bin]=(3072 - (exp[bin] << 7));
+    }
+
+    /* PSD integration */
+    j=start;
+    k=masktab[start];
+    do {
+        v=psd[j];
+        j++;
+        end1=bndtab[k+1];
+        if (end1 > end) end1=end;
+        for(i=j;i<end1;i++) {
+            int c,adr;
+            /* logadd */
+            v1=psd[j];
+            c=v-v1;
+            if (c >= 0) {
+                adr=c >> 1;
+                if (adr > 255) adr=255;
+                v=v + latab[adr];
+            } else {
+                adr=(-c) >> 1;
+                if (adr > 255) adr=255;
+                v=v1 + latab[adr];
+            }
+            j++;
+        }
+        bndpsd[k]=v;
+        k++;
+    } while (end > bndtab[k]);
+
+    /* excitation function */
+    bndstrt = masktab[start];
+    bndend = masktab[end-1] + 1;
+    
+    lowcomp = 0;
+    lowcomp = calc_lowcomp1(lowcomp, bndpsd[0], bndpsd[1]) ;
+    excite[0] = bndpsd[0] - fgain - lowcomp ;
+    lowcomp = calc_lowcomp1(lowcomp, bndpsd[1], bndpsd[2]) ;
+    excite[1] = bndpsd[1] - fgain - lowcomp ;
+    begin = 7 ;
+    for (bin = 2; bin < 7; bin++) {
+        lowcomp = calc_lowcomp1(lowcomp, bndpsd[bin], bndpsd[bin+1]) ;
+        fastleak = bndpsd[bin] - fgain ;
+        slowleak = bndpsd[bin] - s->sgain ;
+        excite[bin] = fastleak - lowcomp ;
+        if (bndpsd[bin] <= bndpsd[bin+1]) {
+            begin = bin + 1 ;
+            break ;
+        }
+    }
+    
+    end1=bndend;
+    if (end1 > 22) end1=22;
+    
+    for (bin = begin; bin < end1; bin++) {
+        lowcomp = calc_lowcomp(lowcomp, bndpsd[bin], bndpsd[bin+1], bin) ;
+        
+        fastleak -= s->fdecay ;
+        v = bndpsd[bin] - fgain;
+        if (fastleak < v) fastleak = v;
+        
+        slowleak -= s->sdecay ;
+        v = bndpsd[bin] - s->sgain;
+        if (slowleak < v) slowleak = v;
+        
+        v=fastleak - lowcomp;
+        if (slowleak > v) v=slowleak;
+        
+        excite[bin] = v;
+    }
+
+    for (bin = 22; bin < bndend; bin++) {
+        fastleak -= s->fdecay ;
+        v = bndpsd[bin] - fgain;
+        if (fastleak < v) fastleak = v;
+        slowleak -= s->sdecay ;
+        v = bndpsd[bin] - s->sgain;
+        if (slowleak < v) slowleak = v;
+
+        v=fastleak;
+        if (slowleak > v) v = slowleak;
+        excite[bin] = v;
+    }
+
+    /* compute masking curve */
+
+    for (bin = bndstrt; bin < bndend; bin++) {
+        v1 = excite[bin];
+        tmp = s->dbknee - bndpsd[bin];
+        if (tmp > 0) {
+            v1 += tmp >> 2;
+        }
+        v=hth[bin >> s->halfratecod][s->fscod];
+        if (v1 > v) v=v1;
+        mask[bin] = v;
+    }
+
+    /* compute bit allocation */
+    
+    i = start ;
+    j = masktab[start] ;
+    do {
+        v=mask[j];
+        v -= snroffset ;
+        v -= s->floor ;
+        if (v < 0) v = 0;
+        v &= 0x1fe0 ;
+        v += s->floor ;
+
+        end1=bndtab[j] + bndsz[j];
+        if (end1 > end) end1=end;
+
+        for (k = i; k < end1; k++) {
+            address = (psd[i] - v) >> 5 ;
+            if (address < 0) address=0;
+            else if (address > 63) address=63;
+            bap[i] = baptab[address];
+            i++;
+        }
+    } while (end > bndtab[j++]) ;
+}
+
+typedef struct IComplex {
+    short re,im;
+} IComplex;
+
+static void fft_init(int ln)
+{
+    int i, j, m, n;
+    float alpha;
+
+    n = 1 << ln;
+
+    for(i=0;i<(n/2);i++) {
+        alpha = 2 * M_PI * (float)i / (float)n;
+        costab[i] = fix15(cos(alpha));
+        sintab[i] = fix15(sin(alpha));
+    }
+
+    for(i=0;i<n;i++) {
+        m=0;
+        for(j=0;j<ln;j++) {
+            m |= ((i >> j) & 1) << (ln-j-1);
+        }
+        fft_rev[i]=m;
+    }
+}
+
+/* butter fly op */
+#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
+{\
+  int ax, ay, bx, by;\
+  bx=pre1;\
+  by=pim1;\
+  ax=qre1;\
+  ay=qim1;\
+  pre = (bx + ax) >> 1;\
+  pim = (by + ay) >> 1;\
+  qre = (bx - ax) >> 1;\
+  qim = (by - ay) >> 1;\
+}
+
+#define MUL16(a,b) ((a) * (b))
+
+#define CMUL(pre, pim, are, aim, bre, bim) \
+{\
+   pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15;\
+   pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\
+}
+
+
+/* do a 2^n point complex fft on 2^ln points. */
+static void fft(IComplex *z, int ln)
+{
+    int	j, l, np, np2;
+    int	nblocks, nloops;
+    register IComplex *p,*q;
+    int tmp_re, tmp_im;
+
+    np = 1 << ln;
+
+    /* reverse */
+    for(j=0;j<np;j++) {
+        int k;
+        IComplex tmp;
+        k = fft_rev[j];
+        if (k < j) {
+            tmp = z[k];
+            z[k] = z[j];
+            z[j] = tmp;
+        }
+    }
+
+    /* pass 0 */
+
+    p=&z[0];
+    j=(np >> 1);
+    do {
+        BF(p[0].re, p[0].im, p[1].re, p[1].im, 
+           p[0].re, p[0].im, p[1].re, p[1].im);
+        p+=2;
+    } while (--j != 0);
+
+    /* pass 1 */
+
+    p=&z[0];
+    j=np >> 2;
+    do {
+        BF(p[0].re, p[0].im, p[2].re, p[2].im, 
+           p[0].re, p[0].im, p[2].re, p[2].im);
+        BF(p[1].re, p[1].im, p[3].re, p[3].im, 
+           p[1].re, p[1].im, p[3].im, -p[3].re);
+        p+=4;
+    } while (--j != 0);
+
+    /* pass 2 .. ln-1 */
+
+    nblocks = np >> 3;
+    nloops = 1 << 2;
+    np2 = np >> 1;
+    do {
+        p = z;
+        q = z + nloops;
+        for (j = 0; j < nblocks; ++j) {
+
+            BF(p->re, p->im, q->re, q->im,
+               p->re, p->im, q->re, q->im);
+            
+            p++;
+            q++;
+            for(l = nblocks; l < np2; l += nblocks) {
+                CMUL(tmp_re, tmp_im, costab[l], -sintab[l], q->re, q->im);
+                BF(p->re, p->im, q->re, q->im,
+                   p->re, p->im, tmp_re, tmp_im);
+                p++;
+                q++;
+            }
+            p += nloops;
+            q += nloops;
+        }
+        nblocks = nblocks >> 1;
+        nloops = nloops << 1;
+    } while (nblocks != 0);
+}
+
+/* do a 512 point mdct */
+static void mdct512(INT32 *out, INT16 *in)
+{
+    int i, re, im, re1, im1;
+    INT16 rot[N]; 
+    IComplex x[N/4];
+
+    /* shift to simplify computations */
+    for(i=0;i<N/4;i++)
+        rot[i] = -in[i + 3*N/4];
+    for(i=N/4;i<N;i++)
+        rot[i] = in[i - N/4];
+        
+    /* pre rotation */
+    for(i=0;i<N/4;i++) {
+        re = ((int)rot[2*i] - (int)rot[N-1-2*i]) >> 1;
+        im = -((int)rot[N/2+2*i] - (int)rot[N/2-1-2*i]) >> 1;
+        CMUL(x[i].re, x[i].im, re, im, -xcos1[i], xsin1[i]);
+    }
+
+    fft(x, MDCT_NBITS - 2);
+  
+    /* post rotation */
+    for(i=0;i<N/4;i++) {
+        re = x[i].re;
+        im = x[i].im;
+        CMUL(re1, im1, re, im, xsin1[i], xcos1[i]);
+        out[2*i] = im1;
+        out[N/2-1-2*i] = re1;
+    }
+}
+
+/* XXX: use another norm ? */
+static int calc_exp_diff(UINT8 *exp1, UINT8 *exp2, int n)
+{
+    int sum, i;
+    sum = 0;
+    for(i=0;i<n;i++) {
+        sum += abs(exp1[i] - exp2[i]);
+    }
+    return sum;
+}
+
+static void compute_exp_strategy(UINT8 exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
+                                 UINT8 exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
+                                 int ch)
+{
+    int i, j;
+    int exp_diff;
+    
+    /* estimate if the exponent variation & decide if they should be
+       reused in the next frame */
+    exp_strategy[0][ch] = EXP_NEW;
+    for(i=1;i<NB_BLOCKS;i++) {
+        exp_diff = calc_exp_diff(exp[i][ch], exp[i-1][ch], N/2);
+#ifdef DEBUG            
+        printf("exp_diff=%d\n", exp_diff);
+#endif
+        if (exp_diff > EXP_DIFF_THRESHOLD)
+            exp_strategy[i][ch] = EXP_NEW;
+        else
+            exp_strategy[i][ch] = EXP_REUSE;
+    }
+    /* now select the encoding strategy type : if exponents are often
+       recoded, we use a coarse encoding */
+    i = 0;
+    while (i < NB_BLOCKS) {
+        j = i + 1;
+        while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)
+            j++;
+        switch(j - i) {
+        case 1:
+            exp_strategy[i][ch] = EXP_D45;
+            break;
+        case 2:
+        case 3:
+            exp_strategy[i][ch] = EXP_D25;
+            break;
+        default:
+            exp_strategy[i][ch] = EXP_D15;
+            break;
+        }
+        i = j;
+    }
+}
+
+/* set exp[i] to min(exp[i], exp1[i]) */
+static void exponent_min(UINT8 exp[N/2], UINT8 exp1[N/2], int n)
+{
+    int i;
+
+    for(i=0;i<n;i++) {
+        if (exp1[i] < exp[i])
+            exp[i] = exp1[i];
+    }
+}
+                                 
+/* update the exponents so that they are the ones the decoder will
+   decode. Return the number of bits used to code the exponents */
+static int encode_exp(UINT8 encoded_exp[N/2], 
+                      UINT8 exp[N/2], 
+                      int nb_exps,
+                      int exp_strategy)
+{
+    int group_size, nb_groups, i, j, k, recurse, exp_min, delta;
+    UINT8 exp1[N/2];
+
+    switch(exp_strategy) {
+    case EXP_D15:
+        group_size = 1;
+        break;
+    case EXP_D25:
+        group_size = 2;
+        break;
+    default:
+    case EXP_D45:
+        group_size = 4;
+        break;
+    }
+    nb_groups = ((nb_exps + (group_size * 3) - 4) / (3 * group_size)) * 3;
+
+    /* for each group, compute the minimum exponent */
+    exp1[0] = exp[0]; /* DC exponent is handled separately */
+    k = 1;
+    for(i=1;i<=nb_groups;i++) {
+        exp_min = exp[k];
+        assert(exp_min >= 0 && exp_min <= 24);
+        for(j=1;j<group_size;j++) {
+            if (exp[k+j] < exp_min)
+                exp_min = exp[k+j];
+        }
+        exp1[i] = exp_min;
+        k += group_size;
+    }
+
+    /* constraint for DC exponent */
+    if (exp1[0] > 15)
+        exp1[0] = 15;
+
+    /* Iterate until the delta constraints between each groups are
+       satisfyed. I'm sure it is possible to find a better algorithm,
+       but I am lazy */
+    do {
+        recurse = 0;
+        for(i=1;i<=nb_groups;i++) {
+            delta = exp1[i] - exp1[i-1];
+            if (delta > 2) {
+                /* if delta too big, we encode a smaller exponent */
+                exp1[i] = exp1[i-1] + 2;
+            } else if (delta < -2) {
+                /* if delta is too small, we must decrease the previous
+               exponent, which means we must recurse */
+                recurse = 1;
+                exp1[i-1] = exp1[i] + 2;
+            }
+        }
+    } while (recurse);
+    
+    /* now we have the exponent values the decoder will see */
+    encoded_exp[0] = exp1[0];
+    k = 1;
+    for(i=1;i<=nb_groups;i++) {
+        for(j=0;j<group_size;j++) {
+            encoded_exp[k+j] = exp1[i];
+        }
+        k += group_size;
+    }
+    
+#if defined(DEBUG)
+    printf("exponents: strategy=%d\n", exp_strategy);
+    for(i=0;i<=nb_groups * group_size;i++) {
+        printf("%d ", encoded_exp[i]);
+    }
+    printf("\n");
+#endif
+
+    return 4 + (nb_groups / 3) * 7;
+}
+
+/* return the size in bits taken by the mantissa */
+int compute_mantissa_size(AC3EncodeContext *s, UINT8 *m, int nb_coefs)
+{
+    int bits, mant, i;
+
+    bits = 0;
+    for(i=0;i<nb_coefs;i++) {
+        mant = m[i];
+        switch(mant) {
+        case 0:
+            /* nothing */
+            break;
+        case 1:
+            /* 3 mantissa in 5 bits */
+            if (s->mant1_cnt == 0) 
+                bits += 5;
+            if (++s->mant1_cnt == 3)
+                s->mant1_cnt = 0;
+            break;
+        case 2:
+            /* 3 mantissa in 7 bits */
+            if (s->mant2_cnt == 0) 
+                bits += 7;
+            if (++s->mant2_cnt == 3)
+                s->mant2_cnt = 0;
+            break;
+        case 3:
+            bits += 3;
+            break;
+        case 4:
+            /* 2 mantissa in 7 bits */
+            if (s->mant4_cnt == 0)
+                bits += 7;
+            if (++s->mant4_cnt == 2) 
+                s->mant4_cnt = 0;
+            break;
+        case 14:
+            bits += 14;
+            break;
+        case 15:
+            bits += 16;
+            break;
+        default:
+            bits += mant - 1;
+            break;
+        }
+    }
+    return bits;
+}
+
+
+static int bit_alloc(AC3EncodeContext *s,
+                     UINT8 bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
+                     UINT8 encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
+                     UINT8 exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
+                     int frame_bits, int csnroffst, int fsnroffst)
+{
+    int i, ch;
+
+    /* compute size */
+    for(i=0;i<NB_BLOCKS;i++) {
+        s->mant1_cnt = 0;
+        s->mant2_cnt = 0;
+        s->mant4_cnt = 0;
+        for(ch=0;ch<s->nb_channels;ch++) {
+            parametric_bit_allocation(s, bap[i][ch], encoded_exp[i][ch], 
+                                      0, s->nb_coefs[ch], 
+                                      (((csnroffst-15) << 4) + 
+                                       fsnroffst) << 2, 
+                                      fgaintab[s->fgaincod[ch]]);
+            frame_bits += compute_mantissa_size(s, bap[i][ch], 
+                                                 s->nb_coefs[ch]);
+        }
+    }
+#if 0
+    printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n", 
+           csnroffst, fsnroffst, frame_bits, 
+           16 * s->frame_size - ((frame_bits + 7) & ~7));
+#endif
+    return 16 * s->frame_size - frame_bits;
+}
+
+#define SNR_INC1 4
+
+static int compute_bit_allocation(AC3EncodeContext *s,
+                                  UINT8 bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
+                                  UINT8 encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
+                                  UINT8 exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
+                                  int frame_bits)
+{
+    int i, ch;
+    int csnroffst, fsnroffst;
+    UINT8 bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
+
+    /* init default parameters */
+    s->sdecaycod = 2;
+    s->fdecaycod = 1;
+    s->sgaincod = 1;
+    s->dbkneecod = 2;
+    s->floorcod = 4;
+    for(ch=0;ch<s->nb_channels;ch++) 
+        s->fgaincod[ch] = 4;
+    
+    /* compute real values */
+    s->sdecay = sdecaytab[s->sdecaycod] >> s->halfratecod;
+    s->fdecay = fdecaytab[s->fdecaycod] >> s->halfratecod;
+    s->sgain = sgaintab[s->sgaincod];
+    s->dbknee = dbkneetab[s->dbkneecod];
+    s->floor = floortab[s->floorcod];
+
+    /* header size */
+    frame_bits += 65;
+    if (s->acmod == 2)
+        frame_bits += 2;
+
+    /* audio blocks */
+    for(i=0;i<NB_BLOCKS;i++) {
+        frame_bits += s->nb_channels * 2 + 2;
+        if (s->acmod == 2)
+            frame_bits++;
+        frame_bits += 2 * s->nb_channels;
+        for(ch=0;ch<s->nb_channels;ch++) {
+            if (exp_strategy[i][ch] != EXP_REUSE)
+                frame_bits += 6 + 2;
+        }
+        frame_bits++; /* baie */
+        frame_bits++; /* snr */
+        frame_bits += 2; /* delta / skip */
+    }
+    frame_bits++; /* cplinu for block 0 */
+    /* bit alloc info */
+    frame_bits += 2*4 + 3 + 6 + s->nb_channels * (4 + 3);
+
+    /* CRC */
+    frame_bits += 16;
+
+    /* now the big work begins : do the bit allocation. Modify the snr
+       offset until we can pack everything in the requested frame size */
+
+    csnroffst = s->csnroffst;
+    while (csnroffst >= 0 && 
+           bit_alloc(s, bap, encoded_exp, exp_strategy, frame_bits, csnroffst, 0) < 0)
+        csnroffst -= SNR_INC1;
+    if (csnroffst < 0) {
+        fprintf(stderr, "Error !!!\n");
+        return -1;
+    }
+    while ((csnroffst + SNR_INC1) <= 63 && 
+           bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits, 
+                     csnroffst + SNR_INC1, 0) >= 0) {
+        csnroffst += SNR_INC1;
+        memcpy(bap, bap1, sizeof(bap1));
+    }
+    while ((csnroffst + 1) <= 63 && 
+           bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits, csnroffst + 1, 0) >= 0) {
+        csnroffst++;
+        memcpy(bap, bap1, sizeof(bap1));
+    }
+
+    fsnroffst = 0;
+    while ((fsnroffst + SNR_INC1) <= 15 && 
+           bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits, 
+                     csnroffst, fsnroffst + SNR_INC1) >= 0) {
+        fsnroffst += SNR_INC1;
+        memcpy(bap, bap1, sizeof(bap1));
+    }
+    while ((fsnroffst + 1) <= 15 && 
+           bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits, 
+                     csnroffst, fsnroffst + 1) >= 0) {
+        fsnroffst++;
+        memcpy(bap, bap1, sizeof(bap1));
+    }
+    
+    s->csnroffst = csnroffst;
+    for(ch=0;ch<s->nb_channels;ch++)
+        s->fsnroffst[ch] = fsnroffst;
+#if defined(DEBUG_BITALLOC)
+    {
+        int j;
+
+        for(i=0;i<6;i++) {
+            for(ch=0;ch<s->nb_channels;ch++) {
+                printf("Block #%d Ch%d:\n", i, ch);
+                printf("bap=");
+                for(j=0;j<s->nb_coefs[ch];j++) {
+                    printf("%d ",bap[i][ch][j]);
+                }
+                printf("\n");
+            }
+        }
+    }
+#endif
+    return 0;
+}
+
+static int AC3_encode_init(AVEncodeContext *avctx)
+{
+    int freq = avctx->rate;
+    int bitrate = avctx->bit_rate;
+    int channels = avctx->channels;
+    AC3EncodeContext *s = avctx->priv_data;
+    int i, j, k, l, ch, v;
+    float alpha;
+    static unsigned short freqs[3] = { 48000, 44100, 32000 };
+
+    avctx->frame_size = AC3_FRAME_SIZE;
+    avctx->key_frame = 1; /* always key frame */
+    
+    /* number of channels */
+    if (channels == 1)
+        s->acmod = 1;
+    else if (channels == 2)
+        s->acmod = 2;
+    else
+        return -1;
+    s->nb_channels = channels;
+
+    /* frequency */
+    for(i=0;i<3;i++) {
+        for(j=0;j<3;j++) 
+            if ((freqs[j] >> i) == freq)
+                goto found;
+    }
+    return -1;
+ found:    
+    s->sample_rate = freq;
+    s->halfratecod = i;
+    s->fscod = j;
+    s->bsid = 8 + s->halfratecod;
+    s->bsmod = 0; /* complete main audio service */
+
+    /* bitrate & frame size */
+    bitrate /= 1000;
+    for(i=0;i<19;i++) {
+        if ((bitratetab[i] >> s->halfratecod) == bitrate)
+            break;
+    }
+    if (i == 19)
+        return -1;
+    s->bit_rate = bitrate;
+    s->frmsizecod = i << 1;
+    s->frame_size_min = (bitrate * 1000 * AC3_FRAME_SIZE) / (freq * 16);
+    /* for now we do not handle fractional sizes */
+    s->frame_size = s->frame_size_min;
+    
+    /* bit allocation init */
+    for(ch=0;ch<s->nb_channels;ch++) {
+        /* bandwidth for each channel */
+        /* XXX: should compute the bandwidth according to the frame
+           size, so that we avoid anoying high freq artefacts */
+        s->chbwcod[ch] = 50; /* sample bandwidth as mpeg audio layer 2 table 0 */
+        s->nb_coefs[ch] = ((s->chbwcod[ch] + 12) * 3) + 37;
+    }
+    /* initial snr offset */
+    s->csnroffst = 40;
+
+    /* compute bndtab and masktab from bandsz */
+    k = 0;
+    l = 0;
+    for(i=0;i<50;i++) {
+        bndtab[i] = l;
+        v = bndsz[i];
+        for(j=0;j<v;j++) masktab[k++]=i;
+        l += v;
+    }
+    bndtab[50] = 0;
+
+    /* mdct init */
+    fft_init(MDCT_NBITS - 2);
+    for(i=0;i<N/4;i++) {
+        alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N;
+        xcos1[i] = fix15(-cos(alpha));
+        xsin1[i] = fix15(-sin(alpha));
+    }
+
+    ac3_crc_init();
+
+    return 0;
+}
+
+/* output the AC3 frame header */
+static void output_frame_header(AC3EncodeContext *s, unsigned char *frame)
+{
+    init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE, NULL, NULL);
+
+    put_bits(&s->pb, 16, 0x0b77); /* frame header */
+    put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
+    put_bits(&s->pb, 2, s->fscod);
+    put_bits(&s->pb, 6, s->frmsizecod + (s->frame_size - s->frame_size_min));
+    put_bits(&s->pb, 5, s->bsid);
+    put_bits(&s->pb, 3, s->bsmod);
+    put_bits(&s->pb, 3, s->acmod);
+    if (s->acmod == 2) {
+        put_bits(&s->pb, 2, 0); /* surround not indicated */
+    }
+    put_bits(&s->pb, 1, 0); /* no LFE */
+    put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
+    put_bits(&s->pb, 1, 0); /* no compression control word */
+    put_bits(&s->pb, 1, 0); /* no lang code */
+    put_bits(&s->pb, 1, 0); /* no audio production info */
+    put_bits(&s->pb, 1, 0); /* no copyright */
+    put_bits(&s->pb, 1, 1); /* original bitstream */
+    put_bits(&s->pb, 1, 0); /* no time code 1 */
+    put_bits(&s->pb, 1, 0); /* no time code 2 */
+    put_bits(&s->pb, 1, 0); /* no addtional bit stream info */
+}
+
+/* symetric quantization on 'levels' levels */
+static inline int sym_quant(int c, int e, int levels)
+{
+    int v;
+
+    if (c >= 0) {
+        v = (levels * (c << e)) >> 25;
+        v = (levels >> 1) + v;
+    } else {
+        v = (levels * ((-c) << e)) >> 25;
+        v = (levels >> 1) - v;
+    }
+    assert (v >= 0 && v < levels);
+    return v;
+}
+
+/* asymetric quantization on 2^qbits levels */
+static inline int asym_quant(int c, int e, int qbits)
+{
+    int lshift, m, v;
+
+    lshift = e + qbits - 24;
+    if (lshift >= 0)
+        v = c << lshift;
+    else
+        v = c >> (-lshift);
+    /* rounding */
+    v = (v + 1) >> 1;
+    m = (1 << (qbits-1));
+    if (v >= m)
+        v = m - 1;
+    assert(v >= -m);
+    return v & ((1 << qbits)-1);
+}
+
+/* Output one audio block. There are NB_BLOCKS audio blocks in one AC3
+   frame */
+static void output_audio_block(AC3EncodeContext *s,
+                               UINT8 exp_strategy[AC3_MAX_CHANNELS],
+                               UINT8 encoded_exp[AC3_MAX_CHANNELS][N/2],
+                               UINT8 bap[AC3_MAX_CHANNELS][N/2],
+                               INT32 mdct_coefs[AC3_MAX_CHANNELS][N/2],
+                               INT8 global_exp[AC3_MAX_CHANNELS],
+                               int block_num)
+{
+    int ch, nb_groups, group_size, i, baie;
+    UINT8 *p;
+    UINT16 qmant[AC3_MAX_CHANNELS][N/2];
+    int exp0, exp1;
+    int mant1_cnt, mant2_cnt, mant4_cnt;
+    UINT16 *qmant1_ptr, *qmant2_ptr, *qmant4_ptr;
+    int delta0, delta1, delta2;
+
+    for(ch=0;ch<s->nb_channels;ch++) 
+        put_bits(&s->pb, 1, 0); /* 512 point MDCT */
+    for(ch=0;ch<s->nb_channels;ch++) 
+        put_bits(&s->pb, 1, 1); /* no dither */
+    put_bits(&s->pb, 1, 0); /* no dynamic range */
+    if (block_num == 0) {
+        /* for block 0, even if no coupling, we must say it. This is a
+           waste of bit :-) */
+        put_bits(&s->pb, 1, 1); /* coupling strategy present */
+        put_bits(&s->pb, 1, 0); /* no coupling strategy */
+    } else {
+        put_bits(&s->pb, 1, 0); /* no new coupling strategy */
+    }
+
+    if (s->acmod == 2) {
+        put_bits(&s->pb, 1, 0); /* no matrixing (but should be used in the future) */
+    }
+
+#if defined(DEBUG) 
+    {
+        static int count = 0;
+        printf("Block #%d (%d)\n", block_num, count++);
+    }
+#endif
+    /* exponent strategy */
+    for(ch=0;ch<s->nb_channels;ch++) {
+        put_bits(&s->pb, 2, exp_strategy[ch]);
+    }
+    
+    for(ch=0;ch<s->nb_channels;ch++) {
+        if (exp_strategy[ch] != EXP_REUSE)
+            put_bits(&s->pb, 6, s->chbwcod[ch]);
+    }
+    
+    /* exponents */
+    for (ch = 0; ch < s->nb_channels; ch++) {
+        switch(exp_strategy[ch]) {
+        case EXP_REUSE:
+            continue;
+        case EXP_D15:
+            group_size = 1;
+            break;
+        case EXP_D25:
+            group_size = 2;
+            break;
+        default:
+        case EXP_D45:
+            group_size = 4;
+            break;
+        }
+        nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
+        p = encoded_exp[ch];
+
+        /* first exponent */
+        exp1 = *p++;
+        put_bits(&s->pb, 4, exp1);
+
+        /* next ones are delta encoded */
+        for(i=0;i<nb_groups;i++) {
+            /* merge three delta in one code */
+            exp0 = exp1;
+            exp1 = p[0];
+            p += group_size;
+            delta0 = exp1 - exp0 + 2;
+
+            exp0 = exp1;
+            exp1 = p[0];
+            p += group_size;
+            delta1 = exp1 - exp0 + 2;
+
+            exp0 = exp1;
+            exp1 = p[0];
+            p += group_size;
+            delta2 = exp1 - exp0 + 2;
+
+            put_bits(&s->pb, 7, ((delta0 * 5 + delta1) * 5) + delta2);
+        }
+
+        put_bits(&s->pb, 2, 0); /* no gain range info */
+    }
+
+    /* bit allocation info */
+    baie = (block_num == 0);
+    put_bits(&s->pb, 1, baie);
+    if (baie) {
+        put_bits(&s->pb, 2, s->sdecaycod);
+        put_bits(&s->pb, 2, s->fdecaycod);
+        put_bits(&s->pb, 2, s->sgaincod);
+        put_bits(&s->pb, 2, s->dbkneecod);
+        put_bits(&s->pb, 3, s->floorcod);
+    }
+
+    /* snr offset */
+    put_bits(&s->pb, 1, baie); /* always present with bai */
+    if (baie) {
+        put_bits(&s->pb, 6, s->csnroffst);
+        for(ch=0;ch<s->nb_channels;ch++) {
+            put_bits(&s->pb, 4, s->fsnroffst[ch]);
+            put_bits(&s->pb, 3, s->fgaincod[ch]);
+        }
+    }
+    
+    put_bits(&s->pb, 1, 0); /* no delta bit allocation */
+    put_bits(&s->pb, 1, 0); /* no data to skip */
+
+    /* mantissa encoding : we use two passes to handle the grouping. A
+       one pass method may be faster, but it would necessitate to
+       modify the output stream. */
+
+    /* first pass: quantize */
+    mant1_cnt = mant2_cnt = mant4_cnt = 0;
+    qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;
+
+    for (ch = 0; ch < s->nb_channels; ch++) {
+        int b, c, e, v;
+
+        for(i=0;i<s->nb_coefs[ch];i++) {
+            c = mdct_coefs[ch][i];
+            e = encoded_exp[ch][i] - global_exp[ch];
+            b = bap[ch][i];
+            switch(b) {
+            case 0:
+                v = 0;
+                break;
+            case 1:
+                v = sym_quant(c, e, 3);
+                switch(mant1_cnt) {
+                case 0:
+                    qmant1_ptr = &qmant[ch][i];
+                    v = 9 * v;
+                    mant1_cnt = 1;
+                    break;
+                case 1:
+                    *qmant1_ptr += 3 * v;
+                    mant1_cnt = 2;
+                    v = 128;
+                    break;
+                default:
+                    *qmant1_ptr += v;
+                    mant1_cnt = 0;
+                    v = 128;
+                    break;
+                }
+                break;
+            case 2:
+                v = sym_quant(c, e, 5);
+                switch(mant2_cnt) {
+                case 0:
+                    qmant2_ptr = &qmant[ch][i];
+                    v = 25 * v;
+                    mant2_cnt = 1;
+                    break;
+                case 1:
+                    *qmant2_ptr += 5 * v;
+                    mant2_cnt = 2;
+                    v = 128;
+                    break;
+                default:
+                    *qmant2_ptr += v;
+                    mant2_cnt = 0;
+                    v = 128;
+                    break;
+                }
+                break;
+            case 3:
+                v = sym_quant(c, e, 7);
+                break;
+            case 4:
+                v = sym_quant(c, e, 11);
+                switch(mant4_cnt) {
+                case 0:
+                    qmant4_ptr = &qmant[ch][i];
+                    v = 11 * v;
+                    mant4_cnt = 1;
+                    break;
+                default:
+                    *qmant4_ptr += v;
+                    mant4_cnt = 0;
+                    v = 128;
+                    break;
+                }
+                break;
+            case 5:
+                v = sym_quant(c, e, 15);
+                break;
+            case 14:
+                v = asym_quant(c, e, 14);
+                break;
+            case 15:
+                v = asym_quant(c, e, 16);
+                break;
+            default:
+                v = asym_quant(c, e, b - 1);
+                break;
+            }
+            qmant[ch][i] = v;
+        }
+    }
+
+    /* second pass : output the values */
+    for (ch = 0; ch < s->nb_channels; ch++) {
+        int b, q;
+        
+        for(i=0;i<s->nb_coefs[ch];i++) {
+            q = qmant[ch][i];
+            b = bap[ch][i];
+            switch(b) {
+            case 0:
+                break;
+            case 1:
+                if (q != 128) 
+                    put_bits(&s->pb, 5, q);
+                break;
+            case 2:
+                if (q != 128) 
+                    put_bits(&s->pb, 7, q);
+                break;
+            case 3:
+                put_bits(&s->pb, 3, q);
+                break;
+            case 4:
+                if (q != 128)
+                    put_bits(&s->pb, 7, q);
+                break;
+            case 14:
+                put_bits(&s->pb, 14, q);
+                break;
+            case 15:
+                put_bits(&s->pb, 16, q);
+                break;
+            default:
+                put_bits(&s->pb, b - 1, q);
+                break;
+            }
+        }
+    }
+}
+
+/* compute the ac3 crc */
+
+#define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
+
+static void ac3_crc_init(void)
+{
+    unsigned int c, n, k;
+
+    for(n=0;n<256;n++) {
+        c = n << 8;
+        for (k = 0; k < 8; k++) {
+            if (c & (1 << 15)) 
+                c = ((c << 1) & 0xffff) ^ (CRC16_POLY & 0xffff);
+            else
+                c = c << 1;
+        }
+        crc_table[n] = c;
+    }
+}
+
+static unsigned int ac3_crc(UINT8 *data, int n, unsigned int crc)
+{
+    int i;
+    for(i=0;i<n;i++) {
+        crc = (crc_table[data[i] ^ (crc >> 8)] ^ (crc << 8)) & 0xffff;
+    }
+    return crc;
+}
+
+static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
+{
+    unsigned int c;
+
+    c = 0;
+    while (a) {
+        if (a & 1)
+            c ^= b;
+        a = a >> 1;
+        b = b << 1;
+        if (b & (1 << 16))
+            b ^= poly;
+    }
+    return c;
+}
+
+static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
+{
+    unsigned int r;
+    r = 1;
+    while (n) {
+        if (n & 1)
+            r = mul_poly(r, a, poly);
+        a = mul_poly(a, a, poly);
+        n >>= 1;
+    }
+    return r;
+}
+
+
+/* compute log2(max(abs(tab[]))) */
+static int log2_tab(INT16 *tab, int n)
+{
+    int i, v;
+
+    v = 0;
+    for(i=0;i<n;i++) {
+        v |= abs(tab[i]);
+    }
+    return log2(v);
+}
+
+static void lshift_tab(INT16 *tab, int n, int lshift)
+{
+    int i;
+
+    if (lshift > 0) {
+        for(i=0;i<n;i++) {
+            tab[i] <<= lshift;
+        }
+    } else if (lshift < 0) {
+        lshift = -lshift;
+        for(i=0;i<n;i++) {
+            tab[i] >>= lshift;
+        }
+    }
+}
+
+/* fill the end of the frame and compute the two crcs */
+static int output_frame_end(AC3EncodeContext *s)
+{
+    int frame_size, frame_size_58, n, crc1, crc2, crc_inv;
+    UINT8 *frame;
+
+    frame_size = s->frame_size; /* frame size in words */
+    /* align to 8 bits */
+    flush_put_bits(&s->pb);
+    /* add zero bytes to reach the frame size */
+    frame = s->pb.buf;
+    n = 2 * s->frame_size - (s->pb.buf_ptr - frame) - 2;
+    assert(n >= 0);
+    memset(s->pb.buf_ptr, 0, n);
+    
+    /* Now we must compute both crcs : this is not so easy for crc1
+       because it is at the beginning of the data... */
+    frame_size_58 = (frame_size >> 1) + (frame_size >> 3);
+    crc1 = ac3_crc(frame + 4, (2 * frame_size_58) - 4, 0);
+    /* XXX: could precompute crc_inv */
+    crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58) - 16, CRC16_POLY);
+    crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
+    frame[2] = crc1 >> 8;
+    frame[3] = crc1;
+    
+    crc2 = ac3_crc(frame + 2 * frame_size_58, (frame_size - frame_size_58) * 2 - 2, 0);
+    frame[2*frame_size - 2] = crc2 >> 8;
+    frame[2*frame_size - 1] = crc2;
+
+    //    printf("n=%d frame_size=%d\n", n, frame_size);
+    return frame_size * 2;
+}
+
+int AC3_encode_frame(AVEncodeContext *avctx,
+                     unsigned char *frame, int buf_size, void *data)
+{
+    AC3EncodeContext *s = avctx->priv_data;
+    short *samples = data;
+    int i, j, k, v, ch;
+    INT16 input_samples[N];
+    INT32 mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
+    UINT8 exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
+    UINT8 exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS];
+    UINT8 encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
+    UINT8 bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
+    INT8 exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS];
+    int frame_bits;
+
+    frame_bits = 0;
+    for(ch=0;ch<s->nb_channels;ch++) {
+        /* fixed mdct to the six sub blocks & exponent computation */
+        for(i=0;i<NB_BLOCKS;i++) {
+            INT16 *sptr;
+            int sinc;
+
+            /* compute input samples */
+            memcpy(input_samples, s->last_samples[ch], N/2 * sizeof(INT16));
+            sinc = s->nb_channels;
+            sptr = samples + (sinc * (N/2) * i) + ch;
+            for(j=0;j<N/2;j++) {
+                v = *sptr;
+                input_samples[j + N/2] = v;
+                s->last_samples[ch][j] = v; 
+                sptr += sinc;
+            }
+
+            /* apply the MDCT window */
+            for(j=0;j<N/2;j++) {
+                input_samples[j] = MUL16(input_samples[j], 
+                                         ac3_window[j]) >> 15;
+                input_samples[N-j-1] = MUL16(input_samples[N-j-1], 
+                                             ac3_window[j]) >> 15;
+            }
+        
+            /* Normalize the samples to use the maximum available
+               precision */
+            v = 14 - log2_tab(input_samples, N);
+            if (v < 0)
+                v = 0;
+            exp_samples[i][ch] = v - 8;
+            lshift_tab(input_samples, N, v);
+
+            /* do the MDCT */
+            mdct512(mdct_coef[i][ch], input_samples);
+            
+            /* compute "exponents". We take into account the
+               normalization there */
+            for(j=0;j<N/2;j++) {
+                int e;
+                v = abs(mdct_coef[i][ch][j]);
+                if (v == 0)
+                    e = 24;
+                else {
+                    e = 23 - log2(v) + exp_samples[i][ch];
+                    if (e >= 24) {
+                        e = 24;
+                        mdct_coef[i][ch][j] = 0;
+                    }
+                }
+                exp[i][ch][j] = e;
+            }
+        }
+        
+        compute_exp_strategy(exp_strategy, exp, ch);
+
+        /* compute the exponents as the decoder will see them. The
+           EXP_REUSE case must be handled carefully : we select the
+           min of the exponents */
+        i = 0;
+        while (i < NB_BLOCKS) {
+            j = i + 1;
+            while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {
+                exponent_min(exp[i][ch], exp[j][ch], s->nb_coefs[ch]);
+                j++;
+            }
+            frame_bits += encode_exp(encoded_exp[i][ch],
+                                     exp[i][ch], s->nb_coefs[ch], 
+                                     exp_strategy[i][ch]);
+            /* copy encoded exponents for reuse case */
+            for(k=i+1;k<j;k++) {
+                memcpy(encoded_exp[k][ch], encoded_exp[i][ch], 
+                       s->nb_coefs[ch] * sizeof(UINT8));
+            }
+            i = j;
+        }
+    }
+
+    compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);
+    /* everything is known... let's output the frame */
+    output_frame_header(s, frame);
+        
+    for(i=0;i<NB_BLOCKS;i++) {
+        output_audio_block(s, exp_strategy[i], encoded_exp[i], 
+                           bap[i], mdct_coef[i], exp_samples[i], i);
+    }
+    return output_frame_end(s);
+}
+
+#if 0
+/*************************************************************************/
+/* TEST */
+
+#define FN (N/4)
+
+void fft_test(void)
+{
+    IComplex in[FN], in1[FN];
+    int k, n, i;
+    float sum_re, sum_im, a;
+
+    /* FFT test */
+
+    for(i=0;i<FN;i++) {
+        in[i].re = random() % 65535 - 32767;
+        in[i].im = random() % 65535 - 32767;
+        in1[i] = in[i];
+    }
+    fft(in, 7);
+
+    /* do it by hand */
+    for(k=0;k<FN;k++) {
+        sum_re = 0;
+        sum_im = 0;
+        for(n=0;n<FN;n++) {
+            a = -2 * M_PI * (n * k) / FN;
+            sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);
+            sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);
+        }
+        printf("%3d: %6d,%6d %6.0f,%6.0f\n", 
+               k, in[k].re, in[k].im, sum_re / FN, sum_im / FN); 
+    }
+}
+
+void mdct_test(void)
+{
+    INT16 input[N];
+    INT32 output[N/2];
+    float input1[N];
+    float output1[N/2];
+    float s, a, err, e, emax;
+    int i, k, n;
+
+    for(i=0;i<N;i++) {
+        input[i] = (random() % 65535 - 32767) * 9 / 10;
+        input1[i] = input[i];
+    }
+
+    mdct512(output, input);
+    
+    /* do it by hand */
+    for(k=0;k<N/2;k++) {
+        s = 0;
+        for(n=0;n<N;n++) {
+            a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));
+            s += input1[n] * cos(a);
+        }
+        output1[k] = -2 * s / N;
+    }
+    
+    err = 0;
+    emax = 0;
+    for(i=0;i<N/2;i++) {
+        printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);
+        e = output[i] - output1[i];
+        if (e > emax)
+            emax = e;
+        err += e * e;
+    }
+    printf("err2=%f emax=%f\n", err / (N/2), emax);
+}
+
+void test_ac3(void)
+{
+    AC3EncodeContext ctx;
+    unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];
+    short samples[AC3_FRAME_SIZE];
+    int ret, i;
+    
+    AC3_encode_init(&ctx, 44100, 64000, 1);
+
+    fft_test();
+    mdct_test();
+
+    for(i=0;i<AC3_FRAME_SIZE;i++)
+        samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);
+    ret = AC3_encode_frame(&ctx, frame, samples);
+    printf("ret=%d\n", ret);
+}
+#endif
+
+AVEncoder ac3_encoder = {
+    "ac3",
+    CODEC_TYPE_AUDIO,
+    CODEC_ID_AC3,
+    sizeof(AC3EncodeContext),
+    AC3_encode_init,
+    AC3_encode_frame,
+    NULL,
+};