/*

  * The simplest AC-3 encoder

  * Copyright (c) 2000 Fabrice Bellard

  * Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com>
  * Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>

  *

  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or

  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either

  * version 2.1 of the License, or (at your option) any later version.

  *

  * FFmpeg 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
  * Lesser General Public License for more details.

  *

  * You should have received a copy of the GNU Lesser General Public

  * License along with FFmpeg; if not, write to the Free Software

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

  */

 
 /**

  * @file

  * The simplest AC-3 encoder.

  */

 #include <stdint.h>
 

 #include "libavutil/attributes.h"

 #include "libavutil/avassert.h"

 #include "libavutil/avstring.h"

 #include "libavutil/channel_layout.h"

 #include "libavutil/crc.h"

 #include "libavutil/internal.h"

 #include "libavutil/opt.h"

 #include "avcodec.h"

 #include "put_bits.h"

 #include "ac3dsp.h"

 #include "ac3.h"

 #include "fft.h"

 #include "ac3enc.h"
 #include "eac3enc.h"

 typedef struct AC3Mant {

     int16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr; ///< mantissa pointers for bap=1,2,4

     int mant1_cnt, mant2_cnt, mant4_cnt;    ///< mantissa counts for bap=1,2,4
 } AC3Mant;

 #define CMIXLEV_NUM_OPTIONS 3
 static const float cmixlev_options[CMIXLEV_NUM_OPTIONS] = {
     LEVEL_MINUS_3DB, LEVEL_MINUS_4POINT5DB, LEVEL_MINUS_6DB
 };
 
 #define SURMIXLEV_NUM_OPTIONS 3
 static const float surmixlev_options[SURMIXLEV_NUM_OPTIONS] = {
     LEVEL_MINUS_3DB, LEVEL_MINUS_6DB, LEVEL_ZERO
 };
 
 #define EXTMIXLEV_NUM_OPTIONS 8
 static const float extmixlev_options[EXTMIXLEV_NUM_OPTIONS] = {
     LEVEL_PLUS_3DB,  LEVEL_PLUS_1POINT5DB,  LEVEL_ONE,       LEVEL_MINUS_4POINT5DB,
     LEVEL_MINUS_3DB, LEVEL_MINUS_4POINT5DB, LEVEL_MINUS_6DB, LEVEL_ZERO
 };
 
 

 /**
  * LUT for number of exponent groups.

  * exponent_group_tab[coupling][exponent strategy-1][number of coefficients]

  */

 static uint8_t exponent_group_tab[2][3][256];

 /**

  * List of supported channel layouts.
  */

 const uint64_t ff_ac3_channel_layouts[19] = {

      AV_CH_LAYOUT_MONO,
      AV_CH_LAYOUT_STEREO,
      AV_CH_LAYOUT_2_1,
      AV_CH_LAYOUT_SURROUND,
      AV_CH_LAYOUT_2_2,
      AV_CH_LAYOUT_QUAD,
      AV_CH_LAYOUT_4POINT0,
      AV_CH_LAYOUT_5POINT0,
      AV_CH_LAYOUT_5POINT0_BACK,
     (AV_CH_LAYOUT_MONO     | AV_CH_LOW_FREQUENCY),
     (AV_CH_LAYOUT_STEREO   | AV_CH_LOW_FREQUENCY),
     (AV_CH_LAYOUT_2_1      | AV_CH_LOW_FREQUENCY),
     (AV_CH_LAYOUT_SURROUND | AV_CH_LOW_FREQUENCY),
     (AV_CH_LAYOUT_2_2      | AV_CH_LOW_FREQUENCY),
     (AV_CH_LAYOUT_QUAD     | AV_CH_LOW_FREQUENCY),
     (AV_CH_LAYOUT_4POINT0  | AV_CH_LOW_FREQUENCY),
      AV_CH_LAYOUT_5POINT1,
      AV_CH_LAYOUT_5POINT1_BACK,
      0
 };
 
 
 /**

  * LUT to select the bandwidth code based on the bit rate, sample rate, and
  * number of full-bandwidth channels.
  * bandwidth_tab[fbw_channels-1][sample rate code][bit rate code]
  */
 static const uint8_t ac3_bandwidth_tab[5][3][19] = {
 //      32  40  48  56  64  80  96 112 128 160 192 224 256 320 384 448 512 576 640
 
     { {  0,  0,  0, 12, 16, 32, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48 },
       {  0,  0,  0, 16, 20, 36, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56 },
       {  0,  0,  0, 32, 40, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60 } },
 
     { {  0,  0,  0,  0,  0,  0,  0, 20, 24, 32, 48, 48, 48, 48, 48, 48, 48, 48, 48 },
       {  0,  0,  0,  0,  0,  0,  4, 24, 28, 36, 56, 56, 56, 56, 56, 56, 56, 56, 56 },
       {  0,  0,  0,  0,  0,  0, 20, 44, 52, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60 } },
 
     { {  0,  0,  0,  0,  0,  0,  0,  0,  0, 16, 24, 32, 40, 48, 48, 48, 48, 48, 48 },
       {  0,  0,  0,  0,  0,  0,  0,  0,  4, 20, 28, 36, 44, 56, 56, 56, 56, 56, 56 },
       {  0,  0,  0,  0,  0,  0,  0,  0, 20, 40, 48, 60, 60, 60, 60, 60, 60, 60, 60 } },
 
     { {  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 12, 24, 32, 48, 48, 48, 48, 48, 48 },
       {  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 16, 28, 36, 56, 56, 56, 56, 56, 56 },
       {  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 32, 48, 60, 60, 60, 60, 60, 60, 60 } },
 
     { {  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  8, 20, 32, 40, 48, 48, 48, 48 },
       {  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 12, 24, 36, 44, 56, 56, 56, 56 },
       {  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 28, 44, 60, 60, 60, 60, 60, 60 } }
 };
 
 
 /**

  * LUT to select the coupling start band based on the bit rate, sample rate, and
  * number of full-bandwidth channels. -1 = coupling off
  * ac3_coupling_start_tab[channel_mode-2][sample rate code][bit rate code]
  *
  * TODO: more testing for optimal parameters.
  *       multi-channel tests at 44.1kHz and 32kHz.
  */
 static const int8_t ac3_coupling_start_tab[6][3][19] = {
 //      32  40  48  56  64  80  96 112 128 160 192 224 256 320 384 448 512 576 640
 
     // 2/0
     { {  0,  0,  0,  0,  0,  0,  0,  1,  1,  7,  8, 11, 12, -1, -1, -1, -1, -1, -1 },
       {  0,  0,  0,  0,  0,  0,  1,  3,  5,  7, 10, 12, 13, -1, -1, -1, -1, -1, -1 },
       {  0,  0,  0,  0,  1,  2,  2,  9, 13, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1 } },
 
     // 3/0
     { {  0,  0,  0,  0,  0,  0,  0,  0,  2,  2,  6,  9, 11, 12, 13, -1, -1, -1, -1 },
       {  0,  0,  0,  0,  0,  0,  0,  0,  2,  2,  6,  9, 11, 12, 13, -1, -1, -1, -1 },
       { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 } },
 
     // 2/1 - untested
     { {  0,  0,  0,  0,  0,  0,  0,  0,  2,  2,  6,  9, 11, 12, 13, -1, -1, -1, -1 },
       {  0,  0,  0,  0,  0,  0,  0,  0,  2,  2,  6,  9, 11, 12, 13, -1, -1, -1, -1 },
       { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 } },
 
     // 3/1
     { {  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  3,  2, 10, 11, 11, 12, 12, 14, -1 },
       {  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  3,  2, 10, 11, 11, 12, 12, 14, -1 },
       { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 } },
 
     // 2/2 - untested
     { {  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  3,  2, 10, 11, 11, 12, 12, 14, -1 },
       {  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  3,  2, 10, 11, 11, 12, 12, 14, -1 },
       { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 } },
 
     // 3/2
     { {  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  1,  6,  8, 11, 12, 12, -1, -1 },
       {  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  1,  6,  8, 11, 12, 12, -1, -1 },
       { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 } },
 };
 
 
 /**

  * Adjust the frame size to make the average bit rate match the target bit rate.

  * This is only needed for 11025, 22050, and 44100 sample rates or any E-AC-3.

  *
  * @param s  AC-3 encoder private context

  */

 void ff_ac3_adjust_frame_size(AC3EncodeContext *s)

 {
     while (s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
         s->bits_written    -= s->bit_rate;
         s->samples_written -= s->sample_rate;
     }

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

     s->bits_written    += s->frame_size * 8;

     s->samples_written += AC3_BLOCK_SIZE * s->num_blocks;

 }
 
 

 /**
  * Set the initial coupling strategy parameters prior to coupling analysis.
  *
  * @param s  AC-3 encoder private context
  */

 void ff_ac3_compute_coupling_strategy(AC3EncodeContext *s)

 {
     int blk, ch;
     int got_cpl_snr;

     int num_cpl_blocks;

 
     /* set coupling use flags for each block/channel */
     /* TODO: turn coupling on/off and adjust start band based on bit usage */

     for (blk = 0; blk < s->num_blocks; blk++) {

         AC3Block *block = &s->blocks[blk];
         for (ch = 1; ch <= s->fbw_channels; ch++)
             block->channel_in_cpl[ch] = s->cpl_on;
     }
 
     /* enable coupling for each block if at least 2 channels have coupling
        enabled for that block */
     got_cpl_snr = 0;

     num_cpl_blocks = 0;

     for (blk = 0; blk < s->num_blocks; blk++) {

         AC3Block *block = &s->blocks[blk];
         block->num_cpl_channels = 0;
         for (ch = 1; ch <= s->fbw_channels; ch++)
             block->num_cpl_channels += block->channel_in_cpl[ch];
         block->cpl_in_use = block->num_cpl_channels > 1;

         num_cpl_blocks += block->cpl_in_use;

         if (!block->cpl_in_use) {
             block->num_cpl_channels = 0;
             for (ch = 1; ch <= s->fbw_channels; ch++)
                 block->channel_in_cpl[ch] = 0;
         }
 
         block->new_cpl_strategy = !blk;
         if (blk) {
             for (ch = 1; ch <= s->fbw_channels; ch++) {
                 if (block->channel_in_cpl[ch] != s->blocks[blk-1].channel_in_cpl[ch]) {
                     block->new_cpl_strategy = 1;
                     break;
                 }
             }
         }
         block->new_cpl_leak = block->new_cpl_strategy;
 
         if (!blk || (block->cpl_in_use && !got_cpl_snr)) {
             block->new_snr_offsets = 1;
             if (block->cpl_in_use)
                 got_cpl_snr = 1;
         } else {
             block->new_snr_offsets = 0;
         }
     }

     if (!num_cpl_blocks)
         s->cpl_on = 0;

 
     /* set bandwidth for each channel */

     for (blk = 0; blk < s->num_blocks; blk++) {

         AC3Block *block = &s->blocks[blk];
         for (ch = 1; ch <= s->fbw_channels; ch++) {
             if (block->channel_in_cpl[ch])
                 block->end_freq[ch] = s->start_freq[CPL_CH];
             else
                 block->end_freq[ch] = s->bandwidth_code * 3 + 73;
         }
     }
 }
 
 
 /**

  * Apply stereo rematrixing to coefficients based on rematrixing flags.

  *
  * @param s  AC-3 encoder private context

  */

 void ff_ac3_apply_rematrixing(AC3EncodeContext *s)

 {
     int nb_coefs;
     int blk, bnd, i;
     int start, end;

     uint8_t *flags = NULL;

     if (!s->rematrixing_enabled)

         return;
 

     for (blk = 0; blk < s->num_blocks; blk++) {

         AC3Block *block = &s->blocks[blk];
         if (block->new_rematrixing_strategy)
             flags = block->rematrixing_flags;

         nb_coefs = FFMIN(block->end_freq[1], block->end_freq[2]);
         for (bnd = 0; bnd < block->num_rematrixing_bands; bnd++) {

             if (flags[bnd]) {
                 start = ff_ac3_rematrix_band_tab[bnd];
                 end   = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]);
                 for (i = start; i < end; i++) {

                     int32_t lt = block->fixed_coef[1][i];
                     int32_t rt = block->fixed_coef[2][i];
                     block->fixed_coef[1][i] = (lt + rt) >> 1;
                     block->fixed_coef[2][i] = (lt - rt) >> 1;

                 }
             }
         }
     }
 }
 
 

 /*

  * Initialize exponent tables.
  */
 static av_cold void exponent_init(AC3EncodeContext *s)
 {

     int expstr, i, grpsize;
 
     for (expstr = EXP_D15-1; expstr <= EXP_D45-1; expstr++) {
         grpsize = 3 << expstr;

         for (i = 12; i < 256; i++) {
             exponent_group_tab[0][expstr][i] = (i + grpsize - 4) / grpsize;
             exponent_group_tab[1][expstr][i] = (i              ) / grpsize;

         }

     }

     /* LFE */

     exponent_group_tab[0][0][7] = 2;

 
     if (CONFIG_EAC3_ENCODER && s->eac3)
         ff_eac3_exponent_init();

 }
 
 

 /*

  * Extract exponents from the MDCT coefficients.
  */

 static void extract_exponents(AC3EncodeContext *s)

 {

     int ch        = !s->cpl_on;

     int chan_size = AC3_MAX_COEFS * s->num_blocks * (s->channels - ch + 1);

     AC3Block *block = &s->blocks[0];

     s->ac3dsp.extract_exponents(block->exp[ch], block->fixed_coef[ch], chan_size);

 }
 
 
 /**

  * Exponent Difference Threshold.
  * New exponents are sent if their SAD exceed this number.
  */

 #define EXP_DIFF_THRESHOLD 500

 /**
  * Table used to select exponent strategy based on exponent reuse block interval.
  */
 static const uint8_t exp_strategy_reuse_tab[4][6] = {
     { EXP_D15, EXP_D15, EXP_D15, EXP_D15, EXP_D15, EXP_D15 },
     { EXP_D15, EXP_D15, EXP_D15, EXP_D15, EXP_D15, EXP_D15 },
     { EXP_D25, EXP_D25, EXP_D15, EXP_D15, EXP_D15, EXP_D15 },
     { EXP_D45, EXP_D25, EXP_D25, EXP_D15, EXP_D15, EXP_D15 }
 };

 /*

  * Calculate exponent strategies for all channels.

  * Array arrangement is reversed to simplify the per-channel calculation.

  */

 static void compute_exp_strategy(AC3EncodeContext *s)

 {

     int ch, blk, blk1;

     for (ch = !s->cpl_on; ch <= s->fbw_channels; ch++) {

         uint8_t *exp_strategy = s->exp_strategy[ch];
         uint8_t *exp          = s->blocks[0].exp[ch];
         int exp_diff;
 
         /* estimate if the exponent variation & decide if they should be
            reused in the next frame */
         exp_strategy[0] = EXP_NEW;
         exp += AC3_MAX_COEFS;

         for (blk = 1; blk < s->num_blocks; blk++, exp += AC3_MAX_COEFS) {

             if (ch == CPL_CH) {
                 if (!s->blocks[blk-1].cpl_in_use) {
                     exp_strategy[blk] = EXP_NEW;
                     continue;
                 } else if (!s->blocks[blk].cpl_in_use) {
                     exp_strategy[blk] = EXP_REUSE;
                     continue;
                 }
             } else if (s->blocks[blk].channel_in_cpl[ch] != s->blocks[blk-1].channel_in_cpl[ch]) {

                 exp_strategy[blk] = EXP_NEW;
                 continue;
             }

             exp_diff = s->dsp.sad[0](NULL, exp, exp - AC3_MAX_COEFS, 16, 16);

             exp_strategy[blk] = EXP_REUSE;
             if (ch == CPL_CH && exp_diff > (EXP_DIFF_THRESHOLD * (s->blocks[blk].end_freq[ch] - s->start_freq[ch]) / AC3_MAX_COEFS))
                 exp_strategy[blk] = EXP_NEW;
             else if (ch > CPL_CH && exp_diff > EXP_DIFF_THRESHOLD)

                 exp_strategy[blk] = EXP_NEW;
         }
 
         /* now select the encoding strategy type : if exponents are often
            recoded, we use a coarse encoding */
         blk = 0;

         while (blk < s->num_blocks) {

             blk1 = blk + 1;

             while (blk1 < s->num_blocks && exp_strategy[blk1] == EXP_REUSE)

                 blk1++;

             exp_strategy[blk] = exp_strategy_reuse_tab[s->num_blks_code][blk1-blk-1];

             blk = blk1;
         }

     }
     if (s->lfe_on) {
         ch = s->lfe_channel;

         s->exp_strategy[ch][0] = EXP_D15;

         for (blk = 1; blk < s->num_blocks; blk++)

             s->exp_strategy[ch][blk] = EXP_REUSE;

     }

 
     /* for E-AC-3, determine frame exponent strategy */
     if (CONFIG_EAC3_ENCODER && s->eac3)
         ff_eac3_get_frame_exp_strategy(s);

 }
 
 
 /**

  * Update the exponents so that they are the ones the decoder will decode.

  *
  * @param[in,out] exp   array of exponents for 1 block in 1 channel
  * @param nb_exps       number of exponents in active bandwidth
  * @param exp_strategy  exponent strategy for the block
  * @param cpl           indicates if the block is in the coupling channel

  */

 static void encode_exponents_blk_ch(uint8_t *exp, int nb_exps, int exp_strategy,
                                     int cpl)

 {

     int nb_groups, i, k;

     nb_groups = exponent_group_tab[cpl][exp_strategy-1][nb_exps] * 3;

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

     switch(exp_strategy) {
     case EXP_D25:

         for (i = 1, k = 1-cpl; i <= nb_groups; i++) {

             uint8_t exp_min = exp[k];
             if (exp[k+1] < exp_min)
                 exp_min = exp[k+1];

             exp[i-cpl] = exp_min;

             k += 2;

         }

         break;
     case EXP_D45:

         for (i = 1, k = 1-cpl; i <= nb_groups; i++) {

             uint8_t exp_min = exp[k];
             if (exp[k+1] < exp_min)
                 exp_min = exp[k+1];
             if (exp[k+2] < exp_min)
                 exp_min = exp[k+2];
             if (exp[k+3] < exp_min)
                 exp_min = exp[k+3];

             exp[i-cpl] = exp_min;

             k += 4;
         }
         break;

     }

 
     /* constraint for DC exponent */

     if (!cpl && exp[0] > 15)

         exp[0] = 15;

     /* decrease the delta between each groups to within 2 so that they can be
        differentially encoded */
     for (i = 1; i <= nb_groups; i++)

         exp[i] = FFMIN(exp[i], exp[i-1] + 2);

     i--;
     while (--i >= 0)

         exp[i] = FFMIN(exp[i], exp[i+1] + 2);

     if (cpl)
         exp[-1] = exp[0] & ~1;
 

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

     switch (exp_strategy) {
     case EXP_D25:

         for (i = nb_groups, k = (nb_groups * 2)-cpl; i > 0; i--) {
             uint8_t exp1 = exp[i-cpl];

             exp[k--] = exp1;
             exp[k--] = exp1;
         }
         break;
     case EXP_D45:

         for (i = nb_groups, k = (nb_groups * 4)-cpl; i > 0; i--) {
             exp[k] = exp[k-1] = exp[k-2] = exp[k-3] = exp[i-cpl];

             k -= 4;
         }
         break;

     }
 }
 

 /*

  * Encode exponents from original extracted form to what the decoder will see.
  * This copies and groups exponents based on exponent strategy and reduces
  * deltas between adjacent exponent groups so that they can be differentially
  * encoded.
  */

 static void encode_exponents(AC3EncodeContext *s)

 {

     int blk, blk1, ch, cpl;

     uint8_t *exp, *exp_strategy;

     int nb_coefs, num_reuse_blocks;

     for (ch = !s->cpl_on; ch <= s->channels; ch++) {
         exp          = s->blocks[0].exp[ch] + s->start_freq[ch];

         exp_strategy = s->exp_strategy[ch];
 

         cpl = (ch == CPL_CH);

         blk = 0;

         while (blk < s->num_blocks) {

             AC3Block *block = &s->blocks[blk];
             if (cpl && !block->cpl_in_use) {
                 exp += AC3_MAX_COEFS;
                 blk++;
                 continue;
             }
             nb_coefs = block->end_freq[ch] - s->start_freq[ch];

             blk1 = blk + 1;

             /* count the number of EXP_REUSE blocks after the current block

                and set exponent reference block numbers */
             s->exp_ref_block[ch][blk] = blk;

             while (blk1 < s->num_blocks && exp_strategy[blk1] == EXP_REUSE) {

                 s->exp_ref_block[ch][blk1] = blk;

                 blk1++;

             }

             num_reuse_blocks = blk1 - blk - 1;
 
             /* for the EXP_REUSE case we select the min of the exponents */

             s->ac3dsp.ac3_exponent_min(exp-s->start_freq[ch], num_reuse_blocks,
                                        AC3_MAX_COEFS);

             encode_exponents_blk_ch(exp, nb_coefs, exp_strategy[blk], cpl);

             exp += AC3_MAX_COEFS * (num_reuse_blocks + 1);

             blk = blk1;
         }
     }

 
     /* reference block numbers have been changed, so reset ref_bap_set */
     s->ref_bap_set = 0;

 }
 
 

 /*

  * Count exponent bits based on bandwidth, coupling, and exponent strategies.
  */
 static int count_exponent_bits(AC3EncodeContext *s)
 {
     int blk, ch;
     int nb_groups, bit_count;
 
     bit_count = 0;
     for (blk = 0; blk < s->num_blocks; blk++) {
         AC3Block *block = &s->blocks[blk];
         for (ch = !block->cpl_in_use; ch <= s->channels; ch++) {
             int exp_strategy = s->exp_strategy[ch][blk];
             int cpl          = (ch == CPL_CH);
             int nb_coefs     = block->end_freq[ch] - s->start_freq[ch];
 
             if (exp_strategy == EXP_REUSE)
                 continue;
 
             nb_groups = exponent_group_tab[cpl][exp_strategy-1][nb_coefs];
             bit_count += 4 + (nb_groups * 7);
         }
     }
 
     return bit_count;
 }
 
 
 /**

  * Group exponents.
  * 3 delta-encoded exponents are in each 7-bit group. The number of groups
  * varies depending on exponent strategy and bandwidth.

  *
  * @param s  AC-3 encoder private context

  */

 void ff_ac3_group_exponents(AC3EncodeContext *s)

 {

     int blk, ch, i, cpl;

     int group_size, nb_groups;

     uint8_t *p;
     int delta0, delta1, delta2;
     int exp0, exp1;
 

     for (blk = 0; blk < s->num_blocks; blk++) {

         AC3Block *block = &s->blocks[blk];

         for (ch = !block->cpl_in_use; ch <= s->channels; ch++) {

             int exp_strategy = s->exp_strategy[ch][blk];
             if (exp_strategy == EXP_REUSE)

                 continue;

             cpl = (ch == CPL_CH);

             group_size = exp_strategy + (exp_strategy == EXP_D45);

             nb_groups = exponent_group_tab[cpl][exp_strategy-1][block->end_freq[ch]-s->start_freq[ch]];
             p = block->exp[ch] + s->start_freq[ch] - cpl;

 
             /* DC exponent */
             exp1 = *p++;

             block->grouped_exp[ch][0] = exp1;

 
             /* remaining exponents are delta encoded */

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

                 /* merge three delta in one code */
                 exp0   = exp1;
                 exp1   = p[0];
                 p     += group_size;
                 delta0 = exp1 - exp0 + 2;

                 av_assert2(delta0 >= 0 && delta0 <= 4);

 
                 exp0   = exp1;
                 exp1   = p[0];
                 p     += group_size;
                 delta1 = exp1 - exp0 + 2;

                 av_assert2(delta1 >= 0 && delta1 <= 4);

 
                 exp0   = exp1;
                 exp1   = p[0];
                 p     += group_size;
                 delta2 = exp1 - exp0 + 2;

                 av_assert2(delta2 >= 0 && delta2 <= 4);

                 block->grouped_exp[ch][i] = ((delta0 * 5 + delta1) * 5) + delta2;

             }
         }
     }

 }
 
 
 /**
  * Calculate final exponents from the supplied MDCT coefficients and exponent shift.
  * Extract exponents from MDCT coefficients, calculate exponent strategies,
  * and encode final exponents.

  *
  * @param s  AC-3 encoder private context

  */

 void ff_ac3_process_exponents(AC3EncodeContext *s)

 {

     extract_exponents(s);

     compute_exp_strategy(s);

     encode_exponents(s);

     emms_c();

 }
 
 

 /*

  * Count frame bits that are based solely on fixed parameters.
  * This only has to be run once when the encoder is initialized.
  */
 static void count_frame_bits_fixed(AC3EncodeContext *s)
 {
     static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
     int blk;
     int frame_bits;
 
     /* assumptions:
      *   no dynamic range codes
      *   bit allocation parameters do not change between blocks
      *   no delta bit allocation
      *   no skipped data

      *   no auxiliary data

      *   no E-AC-3 metadata

      */
 

     /* header */

     frame_bits = 16; /* sync info */
     if (s->eac3) {
         /* bitstream info header */
         frame_bits += 35;

         frame_bits += 1 + 1;
         if (s->num_blocks != 0x6)
             frame_bits++;
         frame_bits++;

         /* audio frame header */

         if (s->num_blocks == 6)
             frame_bits += 2;

         frame_bits += 10;
         /* exponent strategy */

         if (s->use_frame_exp_strategy)
             frame_bits += 5 * s->fbw_channels;
         else

             frame_bits += s->num_blocks * 2 * s->fbw_channels;

         if (s->lfe_on)

             frame_bits += s->num_blocks;

         /* converter exponent strategy */

         if (s->num_blks_code != 0x3)
             frame_bits++;
         else
             frame_bits += s->fbw_channels * 5;

         /* snr offsets */
         frame_bits += 10;
         /* block start info */

         if (s->num_blocks != 1)
             frame_bits++;

     } else {
         frame_bits += 49;
         frame_bits += frame_bits_inc[s->channel_mode];
     }

 
     /* audio blocks */

     for (blk = 0; blk < s->num_blocks; blk++) {

         if (!s->eac3) {

             /* block switch flags */
             frame_bits += s->fbw_channels;

             /* dither flags */
             frame_bits += s->fbw_channels;

         }

 
         /* dynamic range */
         frame_bits++;
 

         /* spectral extension */
         if (s->eac3)

             frame_bits++;
 

         if (!s->eac3) {

             /* exponent strategy */
             frame_bits += 2 * s->fbw_channels;
             if (s->lfe_on)
                 frame_bits++;

             /* bit allocation params */
             frame_bits++;
             if (!blk)
                 frame_bits += 2 + 2 + 2 + 2 + 3;

         }

         /* converter snr offset */
         if (s->eac3)
             frame_bits++;
 
         if (!s->eac3) {

             /* delta bit allocation */
             frame_bits++;

             /* skipped data */
             frame_bits++;

         }

     }
 

     /* auxiliary data */
     frame_bits++;

 
     /* CRC */

     frame_bits += 1 + 16;

 
     s->frame_bits_fixed = frame_bits;
 }
 
 

 /*

  * Initialize bit allocation.
  * Set default parameter codes and calculate parameter values.
  */

 static av_cold void bit_alloc_init(AC3EncodeContext *s)

 {
     int ch;
 
     /* init default parameters */
     s->slow_decay_code = 2;
     s->fast_decay_code = 1;
     s->slow_gain_code  = 1;

     s->db_per_bit_code = s->eac3 ? 2 : 3;

     s->floor_code      = 7;

     for (ch = 0; ch <= s->channels; ch++)

         s->fast_gain_code[ch] = 4;
 
     /* initial snr offset */
     s->coarse_snr_offset = 40;
 
     /* compute real values */
     /* currently none of these values change during encoding, so we can just
        set them once at initialization */
     s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->bit_alloc.sr_shift;
     s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->bit_alloc.sr_shift;
     s->bit_alloc.slow_gain  = ff_ac3_slow_gain_tab[s->slow_gain_code];
     s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
     s->bit_alloc.floor      = ff_ac3_floor_tab[s->floor_code];

     s->bit_alloc.cpl_fast_leak = 0;
     s->bit_alloc.cpl_slow_leak = 0;

 
     count_frame_bits_fixed(s);

 }
 
 

 /*

  * Count the bits used to encode the frame, minus exponents and mantissas.

  * Bits based on fixed parameters have already been counted, so now we just
  * have to add the bits based on parameters that change during encoding.

  */

 static void count_frame_bits(AC3EncodeContext *s)

 {

     AC3EncOptions *opt = &s->options;

     int blk, ch;

     int frame_bits = 0;

     /* header */

     if (s->eac3) {

         if (opt->eac3_mixing_metadata) {
             if (s->channel_mode > AC3_CHMODE_STEREO)
                 frame_bits += 2;
             if (s->has_center)
                 frame_bits += 6;
             if (s->has_surround)
                 frame_bits += 6;
             frame_bits += s->lfe_on;
             frame_bits += 1 + 1 + 2;
             if (s->channel_mode < AC3_CHMODE_STEREO)
                 frame_bits++;
             frame_bits++;
         }
         if (opt->eac3_info_metadata) {
             frame_bits += 3 + 1 + 1;
             if (s->channel_mode == AC3_CHMODE_STEREO)
                 frame_bits += 2 + 2;
             if (s->channel_mode >= AC3_CHMODE_2F2R)
                 frame_bits += 2;
             frame_bits++;
             if (opt->audio_production_info)
                 frame_bits += 5 + 2 + 1;
             frame_bits++;
         }

         /* coupling */
         if (s->channel_mode > AC3_CHMODE_MONO) {
             frame_bits++;

             for (blk = 1; blk < s->num_blocks; blk++) {

                 AC3Block *block = &s->blocks[blk];
                 frame_bits++;
                 if (block->new_cpl_strategy)
                     frame_bits++;
             }
         }
         /* coupling exponent strategy */

         if (s->cpl_on) {
             if (s->use_frame_exp_strategy) {
                 frame_bits += 5 * s->cpl_on;
             } else {

                 for (blk = 0; blk < s->num_blocks; blk++)

                     frame_bits += 2 * s->blocks[blk].cpl_in_use;
             }
         }

     } else {

         if (opt->audio_production_info)
             frame_bits += 7;
         if (s->bitstream_id == 6) {
             if (opt->extended_bsi_1)
                 frame_bits += 14;
             if (opt->extended_bsi_2)
                 frame_bits += 14;
         }

     }
 

     /* audio blocks */

     for (blk = 0; blk < s->num_blocks; blk++) {

         AC3Block *block = &s->blocks[blk];
 
         /* coupling strategy */

         if (!s->eac3)

             frame_bits++;
         if (block->new_cpl_strategy) {

             if (!s->eac3)

                 frame_bits++;

             if (block->cpl_in_use) {

                 if (s->eac3)
                     frame_bits++;
                 if (!s->eac3 || s->channel_mode != AC3_CHMODE_STEREO)

                     frame_bits += s->fbw_channels;

                 if (s->channel_mode == AC3_CHMODE_STEREO)
                     frame_bits++;
                 frame_bits += 4 + 4;

                 if (s->eac3)
                     frame_bits++;
                 else

                     frame_bits += s->num_cpl_subbands - 1;

             }
         }
 
         /* coupling coordinates */
         if (block->cpl_in_use) {
             for (ch = 1; ch <= s->fbw_channels; ch++) {
                 if (block->channel_in_cpl[ch]) {

                     if (!s->eac3 || block->new_cpl_coords[ch] != 2)

                         frame_bits++;

                     if (block->new_cpl_coords[ch]) {

                         frame_bits += 2;
                         frame_bits += (4 + 4) * s->num_cpl_bands;
                     }
                 }
             }
         }
 

         /* stereo rematrixing */

         if (s->channel_mode == AC3_CHMODE_STEREO) {

             if (!s->eac3 || blk > 0)

                 frame_bits++;

             if (s->blocks[blk].new_rematrixing_strategy)

                 frame_bits += block->num_rematrixing_bands;

         }
 

         /* bandwidth codes & gain range */

         for (ch = 1; ch <= s->fbw_channels; ch++) {
             if (s->exp_strategy[ch][blk] != EXP_REUSE) {
                 if (!block->channel_in_cpl[ch])
                     frame_bits += 6;
                 frame_bits += 2;
             }
         }
 
         /* coupling exponent strategy */

         if (!s->eac3 && block->cpl_in_use)

             frame_bits += 2;
 
         /* snr offsets and fast gain codes */

         if (!s->eac3) {

             frame_bits++;
             if (block->new_snr_offsets)
                 frame_bits += 6 + (s->channels + block->cpl_in_use) * (4 + 3);

         }

 
         /* coupling leak info */
         if (block->cpl_in_use) {

             if (!s->eac3 || block->new_cpl_leak != 2)

                 frame_bits++;

             if (block->new_cpl_leak)
                 frame_bits += 3 + 3;

         }
     }

     s->frame_bits = s->frame_bits_fixed + frame_bits;

 }
 
 

 /*

  * Calculate masking curve based on the final exponents.
  * Also calculate the power spectral densities to use in future calculations.
  */

 static void bit_alloc_masking(AC3EncodeContext *s)

 {
     int blk, ch;
 

     for (blk = 0; blk < s->num_blocks; blk++) {

         AC3Block *block = &s->blocks[blk];

         for (ch = !block->cpl_in_use; ch <= s->channels; ch++) {

             /* We only need psd and mask for calculating bap.
                Since we currently do not calculate bap when exponent
                strategy is EXP_REUSE we do not need to calculate psd or mask. */

             if (s->exp_strategy[ch][blk] != EXP_REUSE) {

                 ff_ac3_bit_alloc_calc_psd(block->exp[ch], s->start_freq[ch],
                                           block->end_freq[ch], block->psd[ch],
                                           block->band_psd[ch]);

                 ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, block->band_psd[ch],

                                            s->start_freq[ch], block->end_freq[ch],

                                            ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],

                                            ch == s->lfe_channel,

                                            DBA_NONE, 0, NULL, NULL, NULL,

                                            block->mask[ch]);

             }
         }
     }
 }
 

 /*

  * Ensure that bap for each block and channel point to the current bap_buffer.
  * They may have been switched during the bit allocation search.
  */
 static void reset_block_bap(AC3EncodeContext *s)
 {
     int blk, ch;

     uint8_t *ref_bap;
 
     if (s->ref_bap[0][0] == s->bap_buffer && s->ref_bap_set)

         return;

 
     ref_bap = s->bap_buffer;
     for (ch = 0; ch <= s->channels; ch++) {

         for (blk = 0; blk < s->num_blocks; blk++)

             s->ref_bap[ch][blk] = ref_bap + AC3_MAX_COEFS * s->exp_ref_block[ch][blk];

         ref_bap += AC3_MAX_COEFS * s->num_blocks;

     }

     s->ref_bap_set = 1;

 }
 
 

 /**
  * Initialize mantissa counts.
  * These are set so that they are padded to the next whole group size when bits
  * are counted in compute_mantissa_size.

  *
  * @param[in,out] mant_cnt  running counts for each bap value for each block

  */
 static void count_mantissa_bits_init(uint16_t mant_cnt[AC3_MAX_BLOCKS][16])

 {

     int blk;
 

     for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {

         memset(mant_cnt[blk], 0, sizeof(mant_cnt[blk]));
         mant_cnt[blk][1] = mant_cnt[blk][2] = 2;
         mant_cnt[blk][4] = 1;
     }
 }
 
 
 /**
  * Update mantissa bit counts for all blocks in 1 channel in a given bandwidth
  * range.

  *
  * @param s                 AC-3 encoder private context
  * @param ch                channel index
  * @param[in,out] mant_cnt  running counts for each bap value for each block
  * @param start             starting coefficient bin
  * @param end               ending coefficient bin

  */
 static void count_mantissa_bits_update_ch(AC3EncodeContext *s, int ch,
                                           uint16_t mant_cnt[AC3_MAX_BLOCKS][16],
                                           int start, int end)
 {
     int blk;

     for (blk = 0; blk < s->num_blocks; blk++) {

         AC3Block *block = &s->blocks[blk];

         if (ch == CPL_CH && !block->cpl_in_use)
             continue;
         s->ac3dsp.update_bap_counts(mant_cnt[blk],
                                     s->ref_bap[ch][blk] + start,
                                     FFMIN(end, block->end_freq[ch]) - start);

     }
 }
 
 

 /*

  * Count the number of mantissa bits in the frame based on the bap values.
  */
 static int count_mantissa_bits(AC3EncodeContext *s)
 {
     int ch, max_end_freq;

     LOCAL_ALIGNED_16(uint16_t, mant_cnt, [AC3_MAX_BLOCKS], [16]);

 
     count_mantissa_bits_init(mant_cnt);
 
     max_end_freq = s->bandwidth_code * 3 + 73;
     for (ch = !s->cpl_enabled; ch <= s->channels; ch++)
         count_mantissa_bits_update_ch(s, ch, mant_cnt, s->start_freq[ch],
                                       max_end_freq);
 
     return s->ac3dsp.compute_mantissa_size(mant_cnt);

 }

 
 /**

  * Run the bit allocation with a given SNR offset.
  * This calculates the bit allocation pointers that will be used to determine
  * the quantization of each mantissa.

  *
  * @param s           AC-3 encoder private context
  * @param snr_offset  SNR offset, 0 to 1023

  * @return the number of bits needed for mantissas if the given SNR offset is
  *         is used.

  */

 static int bit_alloc(AC3EncodeContext *s, int snr_offset)

 {

     int blk, ch;

     snr_offset = (snr_offset - 240) << 2;

     reset_block_bap(s);

     for (blk = 0; blk < s->num_blocks; blk++) {

         AC3Block *block = &s->blocks[blk];

         for (ch = !block->cpl_in_use; ch <= s->channels; ch++) {

             /* Currently the only bit allocation parameters which vary across
                blocks within a frame are the exponent values.  We can take
                advantage of that by reusing the bit allocation pointers
                whenever we reuse exponents. */

             if (s->exp_strategy[ch][blk] != EXP_REUSE) {

                 s->ac3dsp.bit_alloc_calc_bap(block->mask[ch], block->psd[ch],

                                              s->start_freq[ch], block->end_freq[ch],
                                              snr_offset, s->bit_alloc.floor,

                                              ff_ac3_bap_tab, s->ref_bap[ch][blk]);

             }

         }
     }

     return count_mantissa_bits(s);

 }
 

 /*

  * Constant bitrate bit allocation search.
  * Find the largest SNR offset that will allow data to fit in the frame.

  */

 static int cbr_bit_allocation(AC3EncodeContext *s)

 {

     int ch;

     int bits_left;

     int snr_offset, snr_incr;

     bits_left = 8 * s->frame_size - (s->frame_bits + s->exponent_bits);

     if (bits_left < 0)
         return AVERROR(EINVAL);

     snr_offset = s->coarse_snr_offset << 4;

     /* if previous frame SNR offset was 1023, check if current frame can also
        use SNR offset of 1023. if so, skip the search. */

     if ((snr_offset | s->fine_snr_offset[1]) == 1023) {

         if (bit_alloc(s, 1023) <= bits_left)
             return 0;
     }
 

     while (snr_offset >= 0 &&

            bit_alloc(s, snr_offset) > bits_left) {

         snr_offset -= 64;

     }

     if (snr_offset < 0)

         return AVERROR(EINVAL);

     FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);

     for (snr_incr = 64; snr_incr > 0; snr_incr >>= 2) {

         while (snr_offset + snr_incr <= 1023 &&

                bit_alloc(s, snr_offset + snr_incr) <= bits_left) {
             snr_offset += snr_incr;
             FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
         }

     }

     FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
     reset_block_bap(s);

     s->coarse_snr_offset = snr_offset >> 4;

     for (ch = !s->cpl_on; ch <= s->channels; ch++)

         s->fine_snr_offset[ch] = snr_offset & 0xF;

     return 0;
 }
 

 /*

  * Perform bit allocation search.
  * Finds the SNR offset value that maximizes quality and fits in the specified
  * frame size.  Output is the SNR offset and a set of bit allocation pointers
  * used to quantize the mantissas.
  */

 int ff_ac3_compute_bit_allocation(AC3EncodeContext *s)

 {
     count_frame_bits(s);
 

     s->exponent_bits = count_exponent_bits(s);
 

     bit_alloc_masking(s);
 

     return cbr_bit_allocation(s);

 }
 
 
 /**

  * Symmetric quantization on 'levels' levels.

  *
  * @param c       unquantized coefficient
  * @param e       exponent
  * @param levels  number of quantization levels
  * @return        quantized coefficient

  */

 static inline int sym_quant(int c, int e, int levels)
 {

     int v = (((levels * c) >> (24 - e)) + levels) >> 1;

     av_assert2(v >= 0 && v < levels);

     return v;
 }
 

 /**
  * Asymmetric quantization on 2^qbits levels.

  *
  * @param c      unquantized coefficient
  * @param e      exponent
  * @param qbits  number of quantization bits
  * @return       quantized coefficient

  */

 static inline int asym_quant(int c, int e, int qbits)
 {

     int m;

     c = (((c << e) >> (24 - qbits)) + 1) >> 1;

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

     if (c >= m)
         c = m - 1;
     av_assert2(c >= -m);
     return c;

 }
 

 /**

  * Quantize a set of mantissas for a single channel in a single block.

  *
  * @param s           Mantissa count context
  * @param fixed_coef  unquantized fixed-point coefficients
  * @param exp         exponents
  * @param bap         bit allocation pointer indices
  * @param[out] qmant  quantized coefficients
  * @param start_freq  starting coefficient bin
  * @param end_freq    ending coefficient bin

  */

 static void quantize_mantissas_blk_ch(AC3Mant *s, int32_t *fixed_coef,

                                       uint8_t *exp, uint8_t *bap,

                                       int16_t *qmant, int start_freq,

                                       int end_freq)

 {
     int i;
 

     for (i = start_freq; i < end_freq; i++) {

         int c = fixed_coef[i];

         int e = exp[i];

         int v = bap[i];
         if (v)
         switch (v) {

         case 1:
             v = sym_quant(c, e, 3);
             switch (s->mant1_cnt) {
             case 0:
                 s->qmant1_ptr = &qmant[i];
                 v = 9 * v;
                 s->mant1_cnt = 1;
                 break;
             case 1:
                 *s->qmant1_ptr += 3 * v;
                 s->mant1_cnt = 2;
                 v = 128;
                 break;
             default:
                 *s->qmant1_ptr += v;
                 s->mant1_cnt = 0;
                 v = 128;
                 break;
             }
             break;
         case 2:
             v = sym_quant(c, e, 5);
             switch (s->mant2_cnt) {
             case 0:
                 s->qmant2_ptr = &qmant[i];
                 v = 25 * v;
                 s->mant2_cnt = 1;
                 break;
             case 1:
                 *s->qmant2_ptr += 5 * v;
                 s->mant2_cnt = 2;
                 v = 128;
                 break;
             default:
                 *s->qmant2_ptr += v;
                 s->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 (s->mant4_cnt) {
             case 0:
                 s->qmant4_ptr = &qmant[i];
                 v = 11 * v;
                 s->mant4_cnt = 1;
                 break;
             default:
                 *s->qmant4_ptr += v;
                 s->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, v - 1);

             break;
         }
         qmant[i] = v;
     }
 }
 
 
 /**
  * Quantize mantissas using coefficients, exponents, and bit allocation pointers.

  *
  * @param s  AC-3 encoder private context

  */

 void ff_ac3_quantize_mantissas(AC3EncodeContext *s)

 {

     int blk, ch, ch0=0, got_cpl;

     for (blk = 0; blk < s->num_blocks; blk++) {

         AC3Block *block = &s->blocks[blk];

         AC3Mant m = { 0 };

         got_cpl = !block->cpl_in_use;
         for (ch = 1; ch <= s->channels; ch++) {
             if (!got_cpl && ch > 1 && block->channel_in_cpl[ch-1]) {
                 ch0     = ch - 1;
                 ch      = CPL_CH;
                 got_cpl = 1;
             }

             quantize_mantissas_blk_ch(&m, block->fixed_coef[ch],

                                       s->blocks[s->exp_ref_block[ch][blk]].exp[ch],
                                       s->ref_bap[ch][blk], block->qmant[ch],

                                       s->start_freq[ch], block->end_freq[ch]);
             if (ch == CPL_CH)
                 ch = ch0;

         }
     }
 }
 
 

 /*

  * Write the AC-3 frame header to the output bitstream.
  */

 static void ac3_output_frame_header(AC3EncodeContext *s)

 {

     AC3EncOptions *opt = &s->options;
 

     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->bit_alloc.sr_code);
     put_bits(&s->pb, 6,  s->frame_size_code + (s->frame_size - s->frame_size_min) / 2);
     put_bits(&s->pb, 5,  s->bitstream_id);
     put_bits(&s->pb, 3,  s->bitstream_mode);
     put_bits(&s->pb, 3,  s->channel_mode);
     if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)

         put_bits(&s->pb, 2, s->center_mix_level);

     if (s->channel_mode & 0x04)

         put_bits(&s->pb, 2, s->surround_mix_level);

     if (s->channel_mode == AC3_CHMODE_STEREO)

         put_bits(&s->pb, 2, opt->dolby_surround_mode);

     put_bits(&s->pb, 1, s->lfe_on); /* LFE */

     put_bits(&s->pb, 5, -opt->dialogue_level);

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

     put_bits(&s->pb, 1, opt->audio_production_info);
     if (opt->audio_production_info) {
         put_bits(&s->pb, 5, opt->mixing_level - 80);
         put_bits(&s->pb, 2, opt->room_type);
     }
     put_bits(&s->pb, 1, opt->copyright);
     put_bits(&s->pb, 1, opt->original);
     if (s->bitstream_id == 6) {
         /* alternate bit stream syntax */
         put_bits(&s->pb, 1, opt->extended_bsi_1);
         if (opt->extended_bsi_1) {
             put_bits(&s->pb, 2, opt->preferred_stereo_downmix);
             put_bits(&s->pb, 3, s->ltrt_center_mix_level);
             put_bits(&s->pb, 3, s->ltrt_surround_mix_level);
             put_bits(&s->pb, 3, s->loro_center_mix_level);
             put_bits(&s->pb, 3, s->loro_surround_mix_level);
         }
         put_bits(&s->pb, 1, opt->extended_bsi_2);
         if (opt->extended_bsi_2) {
             put_bits(&s->pb, 2, opt->dolby_surround_ex_mode);
             put_bits(&s->pb, 2, opt->dolby_headphone_mode);
             put_bits(&s->pb, 1, opt->ad_converter_type);
             put_bits(&s->pb, 9, 0);     /* xbsi2 and encinfo : reserved */
         }
     } else {

     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 additional bit stream info */
 }
 
 

 /*

  * Write one audio block to the output bitstream.
  */

 static void output_audio_block(AC3EncodeContext *s, int blk)

 {

     int ch, i, baie, bnd, got_cpl, ch0;

     AC3Block *block = &s->blocks[blk];

     /* block switching */

     if (!s->eac3) {

         for (ch = 0; ch < s->fbw_channels; ch++)
             put_bits(&s->pb, 1, 0);

     }

 
     /* dither flags */

     if (!s->eac3) {

         for (ch = 0; ch < s->fbw_channels; ch++)
             put_bits(&s->pb, 1, 1);

     }

 
     /* dynamic range codes */
     put_bits(&s->pb, 1, 0);
 

     /* spectral extension */
     if (s->eac3)
         put_bits(&s->pb, 1, 0);
 

     /* channel coupling */

     if (!s->eac3)

         put_bits(&s->pb, 1, block->new_cpl_strategy);

     if (block->new_cpl_strategy) {

         if (!s->eac3)

             put_bits(&s->pb, 1, block->cpl_in_use);

         if (block->cpl_in_use) {
             int start_sub, end_sub;

             if (s->eac3)
                 put_bits(&s->pb, 1, 0); /* enhanced coupling */
             if (!s->eac3 || s->channel_mode != AC3_CHMODE_STEREO) {

                 for (ch = 1; ch <= s->fbw_channels; ch++)
                     put_bits(&s->pb, 1, block->channel_in_cpl[ch]);

             }

             if (s->channel_mode == AC3_CHMODE_STEREO)
                 put_bits(&s->pb, 1, 0); /* phase flags in use */
             start_sub = (s->start_freq[CPL_CH] - 37) / 12;
             end_sub   = (s->cpl_end_freq       - 37) / 12;
             put_bits(&s->pb, 4, start_sub);
             put_bits(&s->pb, 4, end_sub - 3);

             /* coupling band structure */
             if (s->eac3) {
                 put_bits(&s->pb, 1, 0); /* use default */
             } else {

                 for (bnd = start_sub+1; bnd < end_sub; bnd++)
                     put_bits(&s->pb, 1, ff_eac3_default_cpl_band_struct[bnd]);

             }

         }
     }
 
     /* coupling coordinates */
     if (block->cpl_in_use) {
         for (ch = 1; ch <= s->fbw_channels; ch++) {
             if (block->channel_in_cpl[ch]) {

                 if (!s->eac3 || block->new_cpl_coords[ch] != 2)
                     put_bits(&s->pb, 1, block->new_cpl_coords[ch]);
                 if (block->new_cpl_coords[ch]) {

                     put_bits(&s->pb, 2, block->cpl_master_exp[ch]);
                     for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
                         put_bits(&s->pb, 4, block->cpl_coord_exp [ch][bnd]);
                         put_bits(&s->pb, 4, block->cpl_coord_mant[ch][bnd]);
                     }
                 }
             }
         }

     }
 

     /* stereo rematrixing */

     if (s->channel_mode == AC3_CHMODE_STEREO) {

         if (!s->eac3 || blk > 0)

             put_bits(&s->pb, 1, block->new_rematrixing_strategy);

         if (block->new_rematrixing_strategy) {
             /* rematrixing flags */

             for (bnd = 0; bnd < block->num_rematrixing_bands; bnd++)
                 put_bits(&s->pb, 1, block->rematrixing_flags[bnd]);

         }
     }

 
     /* exponent strategy */

     if (!s->eac3) {

         for (ch = !block->cpl_in_use; ch <= s->fbw_channels; ch++)
             put_bits(&s->pb, 2, s->exp_strategy[ch][blk]);
         if (s->lfe_on)
             put_bits(&s->pb, 1, s->exp_strategy[s->lfe_channel][blk]);

     }

     /* bandwidth */

     for (ch = 1; ch <= s->fbw_channels; ch++) {
         if (s->exp_strategy[ch][blk] != EXP_REUSE && !block->channel_in_cpl[ch])

             put_bits(&s->pb, 6, s->bandwidth_code);

     }

     /* exponents */

     for (ch = !block->cpl_in_use; ch <= s->channels; ch++) {

         int nb_groups;

         int cpl = (ch == CPL_CH);

         if (s->exp_strategy[ch][blk] == EXP_REUSE)

             continue;
 

         /* DC exponent */

         put_bits(&s->pb, 4, block->grouped_exp[ch][0] >> cpl);

         /* exponent groups */

         nb_groups = exponent_group_tab[cpl][s->exp_strategy[ch][blk]-1][block->end_freq[ch]-s->start_freq[ch]];

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

             put_bits(&s->pb, 7, block->grouped_exp[ch][i]);

         /* gain range info */

         if (ch != s->lfe_channel && !cpl)

             put_bits(&s->pb, 2, 0);

     }
 
     /* bit allocation info */

     if (!s->eac3) {

         baie = (blk == 0);
         put_bits(&s->pb, 1, baie);
         if (baie) {
             put_bits(&s->pb, 2, s->slow_decay_code);
             put_bits(&s->pb, 2, s->fast_decay_code);
             put_bits(&s->pb, 2, s->slow_gain_code);
             put_bits(&s->pb, 2, s->db_per_bit_code);
             put_bits(&s->pb, 3, s->floor_code);
         }

     }
 
     /* snr offset */

     if (!s->eac3) {

         put_bits(&s->pb, 1, block->new_snr_offsets);
         if (block->new_snr_offsets) {
             put_bits(&s->pb, 6, s->coarse_snr_offset);
             for (ch = !block->cpl_in_use; ch <= s->channels; ch++) {
                 put_bits(&s->pb, 4, s->fine_snr_offset[ch]);
                 put_bits(&s->pb, 3, s->fast_gain_code[ch]);
             }

         }

     } else {
         put_bits(&s->pb, 1, 0); /* no converter snr offset */

     }

     /* coupling leak */
     if (block->cpl_in_use) {

         if (!s->eac3 || block->new_cpl_leak != 2)

             put_bits(&s->pb, 1, block->new_cpl_leak);

         if (block->new_cpl_leak) {
             put_bits(&s->pb, 3, s->bit_alloc.cpl_fast_leak);
             put_bits(&s->pb, 3, s->bit_alloc.cpl_slow_leak);
         }
     }
 

     if (!s->eac3) {

         put_bits(&s->pb, 1, 0); /* no delta bit allocation */
         put_bits(&s->pb, 1, 0); /* no data to skip */

     }

     /* mantissas */

     got_cpl = !block->cpl_in_use;
     for (ch = 1; ch <= s->channels; ch++) {

         int b, q;

 
         if (!got_cpl && ch > 1 && block->channel_in_cpl[ch-1]) {
             ch0     = ch - 1;
             ch      = CPL_CH;
             got_cpl = 1;
         }
         for (i = s->start_freq[ch]; i < block->end_freq[ch]; i++) {

             q = block->qmant[ch][i];

             b = s->ref_bap[ch][blk][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_sbits(&s->pb,   3, q); break;
             case 4: if (q != 128) put_bits (&s->pb,   7, q); break;
             case 14:              put_sbits(&s->pb,  14, q); break;
             case 15:              put_sbits(&s->pb,  16, q); break;
             default:              put_sbits(&s->pb, b-1, q); break;

             }
         }

         if (ch == CPL_CH)
             ch = ch0;

     }
 }
 

 /** CRC-16 Polynomial */

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

 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;
 }
 

 /*

  * Fill the end of the frame with 0's and compute the two CRCs.
  */

 static void output_frame_end(AC3EncodeContext *s)

 {

     const AVCRC *crc_ctx = av_crc_get_table(AV_CRC_16_ANSI);

     int frame_size_58, pad_bytes, crc1, crc2_partial, crc2, crc_inv;

     uint8_t *frame;

     frame_size_58 = ((s->frame_size >> 2) + (s->frame_size >> 4)) << 1;

 
     /* pad the remainder of the frame with zeros */

     av_assert2(s->frame_size * 8 - put_bits_count(&s->pb) >= 18);

     flush_put_bits(&s->pb);
     frame = s->pb.buf;

     pad_bytes = s->frame_size - (put_bits_ptr(&s->pb) - frame) - 2;

     av_assert2(pad_bytes >= 0);

     if (pad_bytes > 0)
         memset(put_bits_ptr(&s->pb), 0, pad_bytes);

     if (s->eac3) {
         /* compute crc2 */
         crc2_partial = av_crc(crc_ctx, 0, frame + 2, s->frame_size - 5);
     } else {

     /* compute crc1 */
     /* this is not so easy because it is at the beginning of the data... */

     crc1    = av_bswap16(av_crc(crc_ctx, 0, frame + 4, frame_size_58 - 4));

     crc_inv = s->crc_inv[s->frame_size > s->frame_size_min];

     crc1    = mul_poly(crc_inv, crc1, CRC16_POLY);
     AV_WB16(frame + 2, crc1);

     /* compute crc2 */

     crc2_partial = av_crc(crc_ctx, 0, frame + frame_size_58,
                           s->frame_size - frame_size_58 - 3);

     }

     crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1);
     /* ensure crc2 does not match sync word by flipping crcrsv bit if needed */
     if (crc2 == 0x770B) {
         frame[s->frame_size - 3] ^= 0x1;
         crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1);
     }
     crc2 = av_bswap16(crc2);

     AV_WB16(frame + s->frame_size - 2, crc2);

 }
 

 /**

  * Write the frame to the output bitstream.

  *
  * @param s      AC-3 encoder private context
  * @param frame  output data buffer

  */

 void ff_ac3_output_frame(AC3EncodeContext *s, unsigned char *frame)

 {
     int blk;
 
     init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
 

     s->output_frame_header(s);

     for (blk = 0; blk < s->num_blocks; blk++)

         output_audio_block(s, blk);

 
     output_frame_end(s);
 }
 
 

 static void dprint_options(AC3EncodeContext *s)

 {
 #ifdef DEBUG

     AVCodecContext *avctx = s->avctx;

     AC3EncOptions *opt = &s->options;
     char strbuf[32];
 
     switch (s->bitstream_id) {

     case  6:  av_strlcpy(strbuf, "AC-3 (alt syntax)",       32); break;
     case  8:  av_strlcpy(strbuf, "AC-3 (standard)",         32); break;
     case  9:  av_strlcpy(strbuf, "AC-3 (dnet half-rate)",   32); break;
     case 10:  av_strlcpy(strbuf, "AC-3 (dnet quater-rate)", 32); break;
     case 16:  av_strlcpy(strbuf, "E-AC-3 (enhanced)",       32); break;

     default: snprintf(strbuf, 32, "ERROR");
     }
     av_dlog(avctx, "bitstream_id: %s (%d)\n", strbuf, s->bitstream_id);
     av_dlog(avctx, "sample_fmt: %s\n", av_get_sample_fmt_name(avctx->sample_fmt));
     av_get_channel_layout_string(strbuf, 32, s->channels, avctx->channel_layout);
     av_dlog(avctx, "channel_layout: %s\n", strbuf);
     av_dlog(avctx, "sample_rate: %d\n", s->sample_rate);
     av_dlog(avctx, "bit_rate: %d\n", s->bit_rate);

     av_dlog(avctx, "blocks/frame: %d (code=%d)\n", s->num_blocks, s->num_blks_code);

     if (s->cutoff)
         av_dlog(avctx, "cutoff: %d\n", s->cutoff);
 
     av_dlog(avctx, "per_frame_metadata: %s\n",
             opt->allow_per_frame_metadata?"on":"off");
     if (s->has_center)
         av_dlog(avctx, "center_mixlev: %0.3f (%d)\n", opt->center_mix_level,
                 s->center_mix_level);
     else
         av_dlog(avctx, "center_mixlev: {not written}\n");
     if (s->has_surround)
         av_dlog(avctx, "surround_mixlev: %0.3f (%d)\n", opt->surround_mix_level,
                 s->surround_mix_level);
     else
         av_dlog(avctx, "surround_mixlev: {not written}\n");
     if (opt->audio_production_info) {
         av_dlog(avctx, "mixing_level: %ddB\n", opt->mixing_level);
         switch (opt->room_type) {

         case AC3ENC_OPT_NOT_INDICATED: av_strlcpy(strbuf, "notindicated", 32); break;
         case AC3ENC_OPT_LARGE_ROOM:    av_strlcpy(strbuf, "large", 32);        break;
         case AC3ENC_OPT_SMALL_ROOM:    av_strlcpy(strbuf, "small", 32);        break;

         default: snprintf(strbuf, 32, "ERROR (%d)", opt->room_type);
         }
         av_dlog(avctx, "room_type: %s\n", strbuf);
     } else {
         av_dlog(avctx, "mixing_level: {not written}\n");
         av_dlog(avctx, "room_type: {not written}\n");
     }
     av_dlog(avctx, "copyright: %s\n", opt->copyright?"on":"off");
     av_dlog(avctx, "dialnorm: %ddB\n", opt->dialogue_level);
     if (s->channel_mode == AC3_CHMODE_STEREO) {
         switch (opt->dolby_surround_mode) {

         case AC3ENC_OPT_NOT_INDICATED: av_strlcpy(strbuf, "notindicated", 32); break;
         case AC3ENC_OPT_MODE_ON:       av_strlcpy(strbuf, "on", 32);           break;
         case AC3ENC_OPT_MODE_OFF:      av_strlcpy(strbuf, "off", 32);          break;

         default: snprintf(strbuf, 32, "ERROR (%d)", opt->dolby_surround_mode);
         }
         av_dlog(avctx, "dsur_mode: %s\n", strbuf);
     } else {
         av_dlog(avctx, "dsur_mode: {not written}\n");
     }
     av_dlog(avctx, "original: %s\n", opt->original?"on":"off");
 
     if (s->bitstream_id == 6) {
         if (opt->extended_bsi_1) {
             switch (opt->preferred_stereo_downmix) {

             case AC3ENC_OPT_NOT_INDICATED: av_strlcpy(strbuf, "notindicated", 32); break;
             case AC3ENC_OPT_DOWNMIX_LTRT:  av_strlcpy(strbuf, "ltrt", 32);         break;
             case AC3ENC_OPT_DOWNMIX_LORO:  av_strlcpy(strbuf, "loro", 32);         break;

             default: snprintf(strbuf, 32, "ERROR (%d)", opt->preferred_stereo_downmix);
             }
             av_dlog(avctx, "dmix_mode: %s\n", strbuf);
             av_dlog(avctx, "ltrt_cmixlev: %0.3f (%d)\n",
                     opt->ltrt_center_mix_level, s->ltrt_center_mix_level);
             av_dlog(avctx, "ltrt_surmixlev: %0.3f (%d)\n",
                     opt->ltrt_surround_mix_level, s->ltrt_surround_mix_level);
             av_dlog(avctx, "loro_cmixlev: %0.3f (%d)\n",
                     opt->loro_center_mix_level, s->loro_center_mix_level);
             av_dlog(avctx, "loro_surmixlev: %0.3f (%d)\n",
                     opt->loro_surround_mix_level, s->loro_surround_mix_level);
         } else {
             av_dlog(avctx, "extended bitstream info 1: {not written}\n");
         }
         if (opt->extended_bsi_2) {
             switch (opt->dolby_surround_ex_mode) {

             case AC3ENC_OPT_NOT_INDICATED: av_strlcpy(strbuf, "notindicated", 32); break;
             case AC3ENC_OPT_MODE_ON:       av_strlcpy(strbuf, "on", 32);           break;
             case AC3ENC_OPT_MODE_OFF:      av_strlcpy(strbuf, "off", 32);          break;

             default: snprintf(strbuf, 32, "ERROR (%d)", opt->dolby_surround_ex_mode);
             }
             av_dlog(avctx, "dsurex_mode: %s\n", strbuf);
             switch (opt->dolby_headphone_mode) {

             case AC3ENC_OPT_NOT_INDICATED: av_strlcpy(strbuf, "notindicated", 32); break;
             case AC3ENC_OPT_MODE_ON:       av_strlcpy(strbuf, "on", 32);           break;
             case AC3ENC_OPT_MODE_OFF:      av_strlcpy(strbuf, "off", 32);          break;

             default: snprintf(strbuf, 32, "ERROR (%d)", opt->dolby_headphone_mode);
             }
             av_dlog(avctx, "dheadphone_mode: %s\n", strbuf);
 
             switch (opt->ad_converter_type) {

             case AC3ENC_OPT_ADCONV_STANDARD: av_strlcpy(strbuf, "standard", 32); break;
             case AC3ENC_OPT_ADCONV_HDCD:     av_strlcpy(strbuf, "hdcd", 32);     break;

             default: snprintf(strbuf, 32, "ERROR (%d)", opt->ad_converter_type);
             }
             av_dlog(avctx, "ad_conv_type: %s\n", strbuf);
         } else {
             av_dlog(avctx, "extended bitstream info 2: {not written}\n");
         }
     }
 #endif
 }
 
 
 #define FLT_OPTION_THRESHOLD 0.01
 
 static int validate_float_option(float v, const float *v_list, int v_list_size)
 {
     int i;
 
     for (i = 0; i < v_list_size; i++) {
         if (v < (v_list[i] + FLT_OPTION_THRESHOLD) &&
             v > (v_list[i] - FLT_OPTION_THRESHOLD))
             break;
     }
     if (i == v_list_size)
         return -1;
 
     return i;
 }
 
 
 static void validate_mix_level(void *log_ctx, const char *opt_name,
                                float *opt_param, const float *list,
                                int list_size, int default_value, int min_value,
                                int *ctx_param)
 {
     int mixlev = validate_float_option(*opt_param, list, list_size);
     if (mixlev < min_value) {
         mixlev = default_value;
         if (*opt_param >= 0.0) {
             av_log(log_ctx, AV_LOG_WARNING, "requested %s is not valid. using "
                    "default value: %0.3f\n", opt_name, list[mixlev]);
         }
     }
     *opt_param = list[mixlev];
     *ctx_param = mixlev;
 }
 
 
 /**
  * Validate metadata options as set by AVOption system.
  * These values can optionally be changed per-frame.

  *
  * @param s  AC-3 encoder private context

  */

 int ff_ac3_validate_metadata(AC3EncodeContext *s)

 {

     AVCodecContext *avctx = s->avctx;

     AC3EncOptions *opt = &s->options;
 

     opt->audio_production_info = 0;
     opt->extended_bsi_1        = 0;
     opt->extended_bsi_2        = 0;
     opt->eac3_mixing_metadata  = 0;
     opt->eac3_info_metadata    = 0;
 
     /* determine mixing metadata / xbsi1 use */

     if (s->channel_mode > AC3_CHMODE_STEREO && opt->preferred_stereo_downmix != AC3ENC_OPT_NONE) {

         opt->extended_bsi_1       = 1;
         opt->eac3_mixing_metadata = 1;
     }
     if (s->has_center &&
         (opt->ltrt_center_mix_level >= 0 || opt->loro_center_mix_level >= 0)) {
         opt->extended_bsi_1       = 1;
         opt->eac3_mixing_metadata = 1;

     }

     if (s->has_surround &&
         (opt->ltrt_surround_mix_level >= 0 || opt->loro_surround_mix_level >= 0)) {
         opt->extended_bsi_1       = 1;
         opt->eac3_mixing_metadata = 1;

     }
 

     if (s->eac3) {
         /* determine info metadata use */
         if (avctx->audio_service_type != AV_AUDIO_SERVICE_TYPE_MAIN)
             opt->eac3_info_metadata = 1;

         if (opt->copyright != AC3ENC_OPT_NONE || opt->original != AC3ENC_OPT_NONE)

             opt->eac3_info_metadata = 1;
         if (s->channel_mode == AC3_CHMODE_STEREO &&

             (opt->dolby_headphone_mode != AC3ENC_OPT_NONE || opt->dolby_surround_mode != AC3ENC_OPT_NONE))

             opt->eac3_info_metadata = 1;

         if (s->channel_mode >= AC3_CHMODE_2F2R && opt->dolby_surround_ex_mode != AC3ENC_OPT_NONE)

             opt->eac3_info_metadata = 1;

         if (opt->mixing_level != AC3ENC_OPT_NONE || opt->room_type != AC3ENC_OPT_NONE ||
             opt->ad_converter_type != AC3ENC_OPT_NONE) {

             opt->audio_production_info = 1;
             opt->eac3_info_metadata    = 1;

         }
     } else {

         /* determine audio production info use */

         if (opt->mixing_level != AC3ENC_OPT_NONE || opt->room_type != AC3ENC_OPT_NONE)

             opt->audio_production_info = 1;
 
         /* determine xbsi2 use */

         if (s->channel_mode >= AC3_CHMODE_2F2R && opt->dolby_surround_ex_mode != AC3ENC_OPT_NONE)

             opt->extended_bsi_2 = 1;

         if (s->channel_mode == AC3_CHMODE_STEREO && opt->dolby_headphone_mode != AC3ENC_OPT_NONE)

             opt->extended_bsi_2 = 1;

         if (opt->ad_converter_type != AC3ENC_OPT_NONE)

             opt->extended_bsi_2 = 1;

     }
 

     /* validate AC-3 mixing levels */
     if (!s->eac3) {
         if (s->has_center) {
             validate_mix_level(avctx, "center_mix_level", &opt->center_mix_level,
                             cmixlev_options, CMIXLEV_NUM_OPTIONS, 1, 0,
                             &s->center_mix_level);
         }
         if (s->has_surround) {
             validate_mix_level(avctx, "surround_mix_level", &opt->surround_mix_level,
                             surmixlev_options, SURMIXLEV_NUM_OPTIONS, 1, 0,
                             &s->surround_mix_level);
         }
     }
 
     /* validate extended bsi 1 / mixing metadata */
     if (opt->extended_bsi_1 || opt->eac3_mixing_metadata) {

         /* default preferred stereo downmix */

         if (opt->preferred_stereo_downmix == AC3ENC_OPT_NONE)
             opt->preferred_stereo_downmix = AC3ENC_OPT_NOT_INDICATED;

         if (!s->eac3 || s->has_center) {
             /* validate Lt/Rt center mix level */
             validate_mix_level(avctx, "ltrt_center_mix_level",
                                &opt->ltrt_center_mix_level, extmixlev_options,
                                EXTMIXLEV_NUM_OPTIONS, 5, 0,
                                &s->ltrt_center_mix_level);
             /* validate Lo/Ro center mix level */
             validate_mix_level(avctx, "loro_center_mix_level",
                                &opt->loro_center_mix_level, extmixlev_options,
                                EXTMIXLEV_NUM_OPTIONS, 5, 0,
                                &s->loro_center_mix_level);
         }
         if (!s->eac3 || s->has_surround) {
             /* validate Lt/Rt surround mix level */
             validate_mix_level(avctx, "ltrt_surround_mix_level",
                                &opt->ltrt_surround_mix_level, extmixlev_options,
                                EXTMIXLEV_NUM_OPTIONS, 6, 3,
                                &s->ltrt_surround_mix_level);
             /* validate Lo/Ro surround mix level */
             validate_mix_level(avctx, "loro_surround_mix_level",
                                &opt->loro_surround_mix_level, extmixlev_options,
                                EXTMIXLEV_NUM_OPTIONS, 6, 3,
                                &s->loro_surround_mix_level);
         }

     }
 

     /* validate audio service type / channels combination */
     if ((avctx->audio_service_type == AV_AUDIO_SERVICE_TYPE_KARAOKE &&
          avctx->channels == 1) ||
         ((avctx->audio_service_type == AV_AUDIO_SERVICE_TYPE_COMMENTARY ||
           avctx->audio_service_type == AV_AUDIO_SERVICE_TYPE_EMERGENCY  ||
           avctx->audio_service_type == AV_AUDIO_SERVICE_TYPE_VOICE_OVER)
          && avctx->channels > 1)) {
         av_log(avctx, AV_LOG_ERROR, "invalid audio service type for the "
                                     "specified number of channels\n");
         return AVERROR(EINVAL);
     }
 
     /* validate extended bsi 2 / info metadata */
     if (opt->extended_bsi_2 || opt->eac3_info_metadata) {

         /* default dolby headphone mode */

         if (opt->dolby_headphone_mode == AC3ENC_OPT_NONE)
             opt->dolby_headphone_mode = AC3ENC_OPT_NOT_INDICATED;

         /* default dolby surround ex mode */

         if (opt->dolby_surround_ex_mode == AC3ENC_OPT_NONE)
             opt->dolby_surround_ex_mode = AC3ENC_OPT_NOT_INDICATED;

         /* default A/D converter type */

         if (opt->ad_converter_type == AC3ENC_OPT_NONE)
             opt->ad_converter_type = AC3ENC_OPT_ADCONV_STANDARD;

     }
 
     /* copyright & original defaults */
     if (!s->eac3 || opt->eac3_info_metadata) {
         /* default copyright */

         if (opt->copyright == AC3ENC_OPT_NONE)
             opt->copyright = AC3ENC_OPT_OFF;

         /* default original */

         if (opt->original == AC3ENC_OPT_NONE)
             opt->original = AC3ENC_OPT_ON;

     }
 
     /* dolby surround mode default */
     if (!s->eac3 || opt->eac3_info_metadata) {

         if (opt->dolby_surround_mode == AC3ENC_OPT_NONE)
             opt->dolby_surround_mode = AC3ENC_OPT_NOT_INDICATED;

     }
 
     /* validate audio production info */
     if (opt->audio_production_info) {

         if (opt->mixing_level == AC3ENC_OPT_NONE) {

             av_log(avctx, AV_LOG_ERROR, "mixing_level must be set if "
                    "room_type is set\n");
             return AVERROR(EINVAL);
         }
         if (opt->mixing_level < 80) {
             av_log(avctx, AV_LOG_ERROR, "invalid mixing level. must be between "
                    "80dB and 111dB\n");
             return AVERROR(EINVAL);
         }
         /* default room type */

         if (opt->room_type == AC3ENC_OPT_NONE)
             opt->room_type = AC3ENC_OPT_NOT_INDICATED;

     }
 
     /* set bitstream id for alternate bitstream syntax */

     if (!s->eac3 && (opt->extended_bsi_1 || opt->extended_bsi_2)) {

         if (s->bitstream_id > 8 && s->bitstream_id < 11) {
             static int warn_once = 1;
             if (warn_once) {
                 av_log(avctx, AV_LOG_WARNING, "alternate bitstream syntax is "
                        "not compatible with reduced samplerates. writing of "
                        "extended bitstream information will be disabled.\n");
                 warn_once = 0;
             }
         } else {
             s->bitstream_id = 6;
         }
     }
 
     return 0;
 }
 
 

 /**

  * Finalize encoding and free any memory allocated by the encoder.

  *
  * @param avctx  Codec context

  */

 av_cold int ff_ac3_encode_close(AVCodecContext *avctx)

 {

     int blk, ch;

     AC3EncodeContext *s = avctx->priv_data;
 

     av_freep(&s->windowed_samples);

     if (s->planar_samples)

     for (ch = 0; ch < s->channels; ch++)
         av_freep(&s->planar_samples[ch]);
     av_freep(&s->planar_samples);

     av_freep(&s->bap_buffer);
     av_freep(&s->bap1_buffer);

     av_freep(&s->mdct_coef_buffer);

     av_freep(&s->fixed_coef_buffer);

     av_freep(&s->exp_buffer);
     av_freep(&s->grouped_exp_buffer);
     av_freep(&s->psd_buffer);
     av_freep(&s->band_psd_buffer);
     av_freep(&s->mask_buffer);
     av_freep(&s->qmant_buffer);

     av_freep(&s->cpl_coord_exp_buffer);
     av_freep(&s->cpl_coord_mant_buffer);

     for (blk = 0; blk < s->num_blocks; blk++) {

         AC3Block *block = &s->blocks[blk];

         av_freep(&block->mdct_coef);

         av_freep(&block->fixed_coef);

         av_freep(&block->exp);
         av_freep(&block->grouped_exp);
         av_freep(&block->psd);
         av_freep(&block->band_psd);
         av_freep(&block->mask);
         av_freep(&block->qmant);

         av_freep(&block->cpl_coord_exp);
         av_freep(&block->cpl_coord_mant);

     }
 

     s->mdct_end(s);

     return 0;

 }
 

 /*

  * Set channel information during initialization.
  */

 static av_cold int set_channel_info(AC3EncodeContext *s, int channels,

                                     uint64_t *channel_layout)

 {
     int ch_layout;
 
     if (channels < 1 || channels > AC3_MAX_CHANNELS)

         return AVERROR(EINVAL);

     if (*channel_layout > 0x7FF)

         return AVERROR(EINVAL);

     ch_layout = *channel_layout;
     if (!ch_layout)

         ch_layout = av_get_default_channel_layout(channels);

 
     s->lfe_on       = !!(ch_layout & AV_CH_LOW_FREQUENCY);
     s->channels     = channels;
     s->fbw_channels = channels - s->lfe_on;

     s->lfe_channel  = s->lfe_on ? s->fbw_channels + 1 : -1;

     if (s->lfe_on)
         ch_layout -= AV_CH_LOW_FREQUENCY;
 
     switch (ch_layout) {
     case AV_CH_LAYOUT_MONO:           s->channel_mode = AC3_CHMODE_MONO;   break;
     case AV_CH_LAYOUT_STEREO:         s->channel_mode = AC3_CHMODE_STEREO; break;
     case AV_CH_LAYOUT_SURROUND:       s->channel_mode = AC3_CHMODE_3F;     break;
     case AV_CH_LAYOUT_2_1:            s->channel_mode = AC3_CHMODE_2F1R;   break;
     case AV_CH_LAYOUT_4POINT0:        s->channel_mode = AC3_CHMODE_3F1R;   break;
     case AV_CH_LAYOUT_QUAD:
     case AV_CH_LAYOUT_2_2:            s->channel_mode = AC3_CHMODE_2F2R;   break;
     case AV_CH_LAYOUT_5POINT0:
     case AV_CH_LAYOUT_5POINT0_BACK:   s->channel_mode = AC3_CHMODE_3F2R;   break;
     default:

         return AVERROR(EINVAL);

     }

     s->has_center   = (s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO;
     s->has_surround =  s->channel_mode & 0x04;

 
     s->channel_map  = ff_ac3_enc_channel_map[s->channel_mode][s->lfe_on];
     *channel_layout = ch_layout;
     if (s->lfe_on)
         *channel_layout |= AV_CH_LOW_FREQUENCY;
 
     return 0;
 }
 

 static av_cold int validate_options(AC3EncodeContext *s)

 {

     AVCodecContext *avctx = s->avctx;

     int i, ret, max_sr;

     /* validate channel layout */

     if (!avctx->channel_layout) {
         av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The "
                                       "encoder will guess the layout, but it "
                                       "might be incorrect.\n");
     }

     ret = set_channel_info(s, avctx->channels, &avctx->channel_layout);
     if (ret) {

         av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n");

         return ret;

     }
 

     /* validate sample rate */

     /* note: max_sr could be changed from 2 to 5 for E-AC-3 once we find a
              decoder that supports half sample rate so we can validate that
              the generated files are correct. */
     max_sr = s->eac3 ? 2 : 8;
     for (i = 0; i <= max_sr; i++) {
         if ((ff_ac3_sample_rate_tab[i % 3] >> (i / 3)) == avctx->sample_rate)

             break;

     }

     if (i > max_sr) {

         av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
         return AVERROR(EINVAL);

     }

     s->sample_rate        = avctx->sample_rate;

     s->bit_alloc.sr_shift = i / 3;
     s->bit_alloc.sr_code  = i % 3;
     s->bitstream_id       = s->eac3 ? 16 : 8 + s->bit_alloc.sr_shift;

     /* select a default bit rate if not set by the user */
     if (!avctx->bit_rate) {
         switch (s->fbw_channels) {
         case 1: avctx->bit_rate =  96000; break;
         case 2: avctx->bit_rate = 192000; break;
         case 3: avctx->bit_rate = 320000; break;
         case 4: avctx->bit_rate = 384000; break;
         case 5: avctx->bit_rate = 448000; break;
         }
     }
 

     /* validate bit rate */

     if (s->eac3) {
         int max_br, min_br, wpf, min_br_dist, min_br_code;

         int num_blks_code, num_blocks, frame_samples;

 
         /* calculate min/max bitrate */

         /* TODO: More testing with 3 and 2 blocks. All E-AC-3 samples I've
                  found use either 6 blocks or 1 block, even though 2 or 3 blocks
                  would work as far as the bit rate is concerned. */
         for (num_blks_code = 3; num_blks_code >= 0; num_blks_code--) {
             num_blocks = ((int[]){ 1, 2, 3, 6 })[num_blks_code];
             frame_samples  = AC3_BLOCK_SIZE * num_blocks;
             max_br = 2048 * s->sample_rate / frame_samples * 16;
             min_br = ((s->sample_rate + (frame_samples-1)) / frame_samples) * 16;
             if (avctx->bit_rate <= max_br)
                 break;
         }

         if (avctx->bit_rate < min_br || avctx->bit_rate > max_br) {
             av_log(avctx, AV_LOG_ERROR, "invalid bit rate. must be %d to %d "
                    "for this sample rate\n", min_br, max_br);
             return AVERROR(EINVAL);
         }

         s->num_blks_code = num_blks_code;
         s->num_blocks    = num_blocks;

 
         /* calculate words-per-frame for the selected bitrate */

         wpf = (avctx->bit_rate / 16) * frame_samples / s->sample_rate;

         av_assert1(wpf > 0 && wpf <= 2048);
 
         /* find the closest AC-3 bitrate code to the selected bitrate.
            this is needed for lookup tables for bandwidth and coupling
            parameter selection */
         min_br_code = -1;
         min_br_dist = INT_MAX;
         for (i = 0; i < 19; i++) {
             int br_dist = abs(ff_ac3_bitrate_tab[i] * 1000 - avctx->bit_rate);
             if (br_dist < min_br_dist) {
                 min_br_dist = br_dist;
                 min_br_code = i;
             }
         }
 
         /* make sure the minimum frame size is below the average frame size */
         s->frame_size_code = min_br_code << 1;
         while (wpf > 1 && wpf * s->sample_rate / AC3_FRAME_SIZE * 16 > avctx->bit_rate)
             wpf--;
         s->frame_size_min = 2 * wpf;
     } else {

         int best_br = 0, best_code = 0, best_diff = INT_MAX;

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

             int br   = (ff_ac3_bitrate_tab[i] >> s->bit_alloc.sr_shift) * 1000;
             int diff = abs(br - avctx->bit_rate);
             if (diff < best_diff) {
                 best_br   = br;
                 best_code = i;
                 best_diff = diff;
             }
             if (!best_diff)

                 break;
         }

         avctx->bit_rate    = best_br;
         s->frame_size_code = best_code << 1;

         s->frame_size_min  = 2 * ff_ac3_frame_size_tab[s->frame_size_code][s->bit_alloc.sr_code];

         s->num_blks_code   = 0x3;
         s->num_blocks      = 6;

     }

     s->bit_rate   = avctx->bit_rate;
     s->frame_size = s->frame_size_min;

     /* validate cutoff */
     if (avctx->cutoff < 0) {
         av_log(avctx, AV_LOG_ERROR, "invalid cutoff frequency\n");
         return AVERROR(EINVAL);
     }
     s->cutoff = avctx->cutoff;
     if (s->cutoff > (s->sample_rate >> 1))
         s->cutoff = s->sample_rate >> 1;
 

     ret = ff_ac3_validate_metadata(s);
     if (ret)
         return ret;

     s->rematrixing_enabled = s->options.stereo_rematrixing &&
                              (s->channel_mode == AC3_CHMODE_STEREO);
 

     s->cpl_enabled = s->options.channel_coupling &&

                      s->channel_mode >= AC3_CHMODE_STEREO;

     return 0;
 }
 
 

 /*

  * Set bandwidth for all channels.
  * The user can optionally supply a cutoff frequency. Otherwise an appropriate
  * default value will be used.
  */

 static av_cold void set_bandwidth(AC3EncodeContext *s)

 {

     int blk, ch, cpl_start;

     if (s->cutoff) {

         /* calculate bandwidth based on user-specified cutoff frequency */
         int fbw_coeffs;

         fbw_coeffs     = s->cutoff * 2 * AC3_MAX_COEFS / s->sample_rate;

         s->bandwidth_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);

     } else {
         /* use default bandwidth setting */

         s->bandwidth_code = ac3_bandwidth_tab[s->fbw_channels-1][s->bit_alloc.sr_code][s->frame_size_code/2];

     }
 
     /* set number of coefficients for each channel */

     for (ch = 1; ch <= s->fbw_channels; ch++) {
         s->start_freq[ch] = 0;

         for (blk = 0; blk < s->num_blocks; blk++)

             s->blocks[blk].end_freq[ch] = s->bandwidth_code * 3 + 73;
     }
     /* LFE channel always has 7 coefs */
     if (s->lfe_on) {
         s->start_freq[s->lfe_channel] = 0;

         for (blk = 0; blk < s->num_blocks; blk++)

             s->blocks[blk].end_freq[ch] = 7;
     }
 
     /* initialize coupling strategy */
     if (s->cpl_enabled) {

         if (s->options.cpl_start != AC3ENC_OPT_AUTO) {

             cpl_start = s->options.cpl_start;
         } else {
             cpl_start = ac3_coupling_start_tab[s->channel_mode-2][s->bit_alloc.sr_code][s->frame_size_code/2];

             if (cpl_start < 0) {

                 if (s->options.channel_coupling == AC3ENC_OPT_AUTO)

                     s->cpl_enabled = 0;
                 else
                     cpl_start = 15;
             }

         }
     }
     if (s->cpl_enabled) {
         int i, cpl_start_band, cpl_end_band;
         uint8_t *cpl_band_sizes = s->cpl_band_sizes;
 
         cpl_end_band   = s->bandwidth_code / 4 + 3;
         cpl_start_band = av_clip(cpl_start, 0, FFMIN(cpl_end_band-1, 15));
 
         s->num_cpl_subbands = cpl_end_band - cpl_start_band;
 
         s->num_cpl_bands = 1;
         *cpl_band_sizes  = 12;
         for (i = cpl_start_band + 1; i < cpl_end_band; i++) {
             if (ff_eac3_default_cpl_band_struct[i]) {
                 *cpl_band_sizes += 12;
             } else {
                 s->num_cpl_bands++;
                 cpl_band_sizes++;
                 *cpl_band_sizes = 12;
             }
         }
 
         s->start_freq[CPL_CH] = cpl_start_band * 12 + 37;
         s->cpl_end_freq       = cpl_end_band   * 12 + 37;

         for (blk = 0; blk < s->num_blocks; blk++)

             s->blocks[blk].end_freq[CPL_CH] = s->cpl_end_freq;

     }
 }
 
 

 static av_cold int allocate_buffers(AC3EncodeContext *s)

 {

     AVCodecContext *avctx = s->avctx;

     int blk, ch;

     int channels = s->channels + 1; /* includes coupling channel */

     int channel_blocks = channels * s->num_blocks;
     int total_coefs    = AC3_MAX_COEFS * channel_blocks;

     if (s->allocate_sample_buffers(s))
         goto alloc_fail;
 

     FF_ALLOC_OR_GOTO(avctx, s->bap_buffer, total_coefs *
                      sizeof(*s->bap_buffer), alloc_fail);
     FF_ALLOC_OR_GOTO(avctx, s->bap1_buffer, total_coefs *
                      sizeof(*s->bap1_buffer), alloc_fail);
     FF_ALLOCZ_OR_GOTO(avctx, s->mdct_coef_buffer, total_coefs *
                       sizeof(*s->mdct_coef_buffer), alloc_fail);
     FF_ALLOC_OR_GOTO(avctx, s->exp_buffer, total_coefs *
                      sizeof(*s->exp_buffer), alloc_fail);
     FF_ALLOC_OR_GOTO(avctx, s->grouped_exp_buffer, channel_blocks * 128 *
                      sizeof(*s->grouped_exp_buffer), alloc_fail);
     FF_ALLOC_OR_GOTO(avctx, s->psd_buffer, total_coefs *
                      sizeof(*s->psd_buffer), alloc_fail);
     FF_ALLOC_OR_GOTO(avctx, s->band_psd_buffer, channel_blocks * 64 *
                      sizeof(*s->band_psd_buffer), alloc_fail);
     FF_ALLOC_OR_GOTO(avctx, s->mask_buffer, channel_blocks * 64 *
                      sizeof(*s->mask_buffer), alloc_fail);
     FF_ALLOC_OR_GOTO(avctx, s->qmant_buffer, total_coefs *
                      sizeof(*s->qmant_buffer), alloc_fail);

     if (s->cpl_enabled) {

         FF_ALLOC_OR_GOTO(avctx, s->cpl_coord_exp_buffer, channel_blocks * 16 *
                          sizeof(*s->cpl_coord_exp_buffer), alloc_fail);
         FF_ALLOC_OR_GOTO(avctx, s->cpl_coord_mant_buffer, channel_blocks * 16 *
                          sizeof(*s->cpl_coord_mant_buffer), alloc_fail);

     }

     for (blk = 0; blk < s->num_blocks; blk++) {

         AC3Block *block = &s->blocks[blk];

         FF_ALLOCZ_OR_GOTO(avctx, block->mdct_coef, channels * sizeof(*block->mdct_coef),

                           alloc_fail);

         FF_ALLOCZ_OR_GOTO(avctx, block->exp, channels * sizeof(*block->exp),

                           alloc_fail);

         FF_ALLOCZ_OR_GOTO(avctx, block->grouped_exp, channels * sizeof(*block->grouped_exp),

                           alloc_fail);

         FF_ALLOCZ_OR_GOTO(avctx, block->psd, channels * sizeof(*block->psd),

                           alloc_fail);

         FF_ALLOCZ_OR_GOTO(avctx, block->band_psd, channels * sizeof(*block->band_psd),

                           alloc_fail);

         FF_ALLOCZ_OR_GOTO(avctx, block->mask, channels * sizeof(*block->mask),

                           alloc_fail);

         FF_ALLOCZ_OR_GOTO(avctx, block->qmant, channels * sizeof(*block->qmant),

                           alloc_fail);

         if (s->cpl_enabled) {
             FF_ALLOCZ_OR_GOTO(avctx, block->cpl_coord_exp, channels * sizeof(*block->cpl_coord_exp),
                               alloc_fail);
             FF_ALLOCZ_OR_GOTO(avctx, block->cpl_coord_mant, channels * sizeof(*block->cpl_coord_mant),
                               alloc_fail);
         }

         for (ch = 0; ch < channels; ch++) {

             /* arrangement: block, channel, coeff */

             block->grouped_exp[ch] = &s->grouped_exp_buffer[128           * (blk * channels + ch)];
             block->psd[ch]         = &s->psd_buffer        [AC3_MAX_COEFS * (blk * channels + ch)];
             block->band_psd[ch]    = &s->band_psd_buffer   [64            * (blk * channels + ch)];
             block->mask[ch]        = &s->mask_buffer       [64            * (blk * channels + ch)];
             block->qmant[ch]       = &s->qmant_buffer      [AC3_MAX_COEFS * (blk * channels + ch)];
             if (s->cpl_enabled) {
                 block->cpl_coord_exp[ch]  = &s->cpl_coord_exp_buffer [16  * (blk * channels + ch)];
                 block->cpl_coord_mant[ch] = &s->cpl_coord_mant_buffer[16  * (blk * channels + ch)];
             }

 
             /* arrangement: channel, block, coeff */

             block->exp[ch]         = &s->exp_buffer        [AC3_MAX_COEFS * (s->num_blocks * ch + blk)];
             block->mdct_coef[ch]   = &s->mdct_coef_buffer  [AC3_MAX_COEFS * (s->num_blocks * ch + blk)];

         }

     }
 

     if (!s->fixed_point) {

         FF_ALLOCZ_OR_GOTO(avctx, s->fixed_coef_buffer, total_coefs *
                           sizeof(*s->fixed_coef_buffer), alloc_fail);
         for (blk = 0; blk < s->num_blocks; blk++) {

             AC3Block *block = &s->blocks[blk];

             FF_ALLOCZ_OR_GOTO(avctx, block->fixed_coef, channels *

                               sizeof(*block->fixed_coef), alloc_fail);

             for (ch = 0; ch < channels; ch++)

                 block->fixed_coef[ch] = &s->fixed_coef_buffer[AC3_MAX_COEFS * (s->num_blocks * ch + blk)];

         }
     } else {

         for (blk = 0; blk < s->num_blocks; blk++) {

             AC3Block *block = &s->blocks[blk];

             FF_ALLOCZ_OR_GOTO(avctx, block->fixed_coef, channels *

                               sizeof(*block->fixed_coef), alloc_fail);

             for (ch = 0; ch < channels; ch++)

                 block->fixed_coef[ch] = (int32_t *)block->mdct_coef[ch];
         }
     }
 

     return 0;
 alloc_fail:
     return AVERROR(ENOMEM);
 }
 
 

 av_cold int ff_ac3_encode_init(AVCodecContext *avctx)

 {
     AC3EncodeContext *s = avctx->priv_data;

     int ret, frame_size_58;

     s->avctx = avctx;
 

     s->eac3 = avctx->codec_id == AV_CODEC_ID_EAC3;

     ff_ac3_common_init();

     ret = validate_options(s);

     if (ret)
         return ret;
 

     avctx->frame_size = AC3_BLOCK_SIZE * s->num_blocks;

     avctx->delay      = AC3_BLOCK_SIZE;

     s->bitstream_mode = avctx->audio_service_type;
     if (s->bitstream_mode == AV_AUDIO_SERVICE_TYPE_KARAOKE)
         s->bitstream_mode = 0x7;

     s->bits_written    = 0;
     s->samples_written = 0;
 

     /* calculate crc_inv for both possible frame sizes */
     frame_size_58 = (( s->frame_size    >> 2) + ( s->frame_size    >> 4)) << 1;
     s->crc_inv[0] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
     if (s->bit_alloc.sr_code == 1) {
         frame_size_58 = (((s->frame_size+2) >> 2) + ((s->frame_size+2) >> 4)) << 1;
         s->crc_inv[1] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
     }
 

     /* set function pointers */

     if (CONFIG_AC3_FIXED_ENCODER && s->fixed_point) {
         s->mdct_end                     = ff_ac3_fixed_mdct_end;
         s->mdct_init                    = ff_ac3_fixed_mdct_init;

         s->allocate_sample_buffers      = ff_ac3_fixed_allocate_sample_buffers;

     } else if (CONFIG_AC3_ENCODER || CONFIG_EAC3_ENCODER) {
         s->mdct_end                     = ff_ac3_float_mdct_end;
         s->mdct_init                    = ff_ac3_float_mdct_init;

         s->allocate_sample_buffers      = ff_ac3_float_allocate_sample_buffers;

     }

     if (CONFIG_EAC3_ENCODER && s->eac3)
         s->output_frame_header = ff_eac3_output_frame_header;
     else
         s->output_frame_header = ac3_output_frame_header;
 

     set_bandwidth(s);

     exponent_init(s);
 

     bit_alloc_init(s);

     ret = s->mdct_init(s);

     if (ret)

         goto init_fail;

     ret = allocate_buffers(s);

     if (ret)

         goto init_fail;

     ff_dsputil_init(&s->dsp, avctx);

     avpriv_float_dsp_init(&s->fdsp, avctx->flags & CODEC_FLAG_BITEXACT);

     ff_ac3dsp_init(&s->ac3dsp, avctx->flags & CODEC_FLAG_BITEXACT);

     dprint_options(s);

     return 0;

 init_fail:

     ff_ac3_encode_close(avctx);

     return ret;

 }