ac3enc.c File Reference

#include "libavutil/crc.h"
#include "avcodec.h"
#include "bitstream.h"
#include "ac3.h"

Go to the source code of this file.

Data Structures

struct  AC3EncodeContext
struct  IComplex

Defines

#define MDCT_NBITS   9
#define N   (1 << MDCT_NBITS)
#define EXP_DIFF_THRESHOLD   1000
#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1)
#define MUL16(a, b)   ((a) * (b))
#define CMUL(pre, pim, are, aim, bre, bim)
#define SNR_INC1   4
#define CRC16_POLY   ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))

Functions

static int16_t fix15 (float a)
static void fft_init (int ln)
static void fft (IComplex *z, int ln)
static void mdct512 (int32_t *out, int16_t *in)
static int calc_exp_diff (uint8_t *exp1, uint8_t *exp2, int n)
static void compute_exp_strategy (uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS], uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2], int ch, int is_lfe)
static void exponent_min (uint8_t exp[N/2], uint8_t exp1[N/2], int n)
static int encode_exp (uint8_t encoded_exp[N/2], uint8_t exp[N/2], int nb_exps, int exp_strategy)
static int compute_mantissa_size (AC3EncodeContext *s, uint8_t *m, int nb_coefs)
static void bit_alloc_masking (AC3EncodeContext *s, uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2], uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS], int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2], int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50])
static int bit_alloc (AC3EncodeContext *s, int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50], int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2], uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2], int frame_bits, int coarse_snr_offset, int fine_snr_offset)
static int compute_bit_allocation (AC3EncodeContext *s, uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2], uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2], uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS], int frame_bits)
static av_cold int AC3_encode_init (AVCodecContext *avctx)
static void output_frame_header (AC3EncodeContext *s, unsigned char *frame)
static int sym_quant (int c, int e, int levels)
static int asym_quant (int c, int e, int qbits)
static void output_audio_block (AC3EncodeContext *s, uint8_t exp_strategy[AC3_MAX_CHANNELS], uint8_t encoded_exp[AC3_MAX_CHANNELS][N/2], uint8_t bap[AC3_MAX_CHANNELS][N/2], int32_t mdct_coefs[AC3_MAX_CHANNELS][N/2], int8_t global_exp[AC3_MAX_CHANNELS], int block_num)
static unsigned int mul_poly (unsigned int a, unsigned int b, unsigned int poly)
static unsigned int pow_poly (unsigned int a, unsigned int n, unsigned int poly)
static int log2_tab (int16_t *tab, int n)
static void lshift_tab (int16_t *tab, int n, int lshift)
static int output_frame_end (AC3EncodeContext *s)
static int AC3_encode_frame (AVCodecContext *avctx, unsigned char *frame, int buf_size, void *data)
static av_cold int AC3_encode_close (AVCodecContext *avctx)

Variables

static int16_t costab [64]
static int16_t sintab [64]
static int16_t xcos1 [128]
static int16_t xsin1 [128]
AVCodec ac3_encoder

Detailed Description

The simplest AC3 encoder.

Definition in file ac3enc.c.

Define Documentation

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

Value:

{\
  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;\
}

Definition at line 106 of file ac3enc.c.

Referenced by dct32(), ff_fft_calc_c(), ff_simple_idct248_put(), and fft().

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

Value:

{\
   pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15;\
   pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\
}

Definition at line 121 of file ac3enc.c.

Referenced by ff_fft_calc_c(), ff_mdct_calc(), fft(), imdct_c(), and mdct512().

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

Definition at line 1050 of file ac3enc.c.

Referenced by output_frame_end().

#define EXP_DIFF_THRESHOLD   1000

Definition at line 74 of file ac3enc.c.

Referenced by compute_exp_strategy().

#define MDCT_NBITS   9

Definition at line 70 of file ac3enc.c.

Referenced by mdct512().

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

Definition at line 119 of file ac3enc.c.

Referenced by AC3_encode_frame(), idctRowCondDC(), idctSparseCol(), idctSparseColAdd(), and idctSparseColPut().

#define N   (1 << MDCT_NBITS)

Definition at line 71 of file ac3enc.c.

Referenced by AC3_encode_frame(), bit_alloc_masking(), compute_bit_allocation(), compute_exp_strategy(), encode_exp(), mdct512(), and output_audio_block().

#define SNR_INC1   4

Definition at line 480 of file ac3enc.c.

Function Documentation

static av_cold int AC3_encode_close ( AVCodecContext *  avctx  )  [static]

Definition at line 1259 of file ac3enc.c.

References av_freep(), and AVCodecContext::coded_frame.

01260 {
01261     av_freep(&avctx->coded_frame);
01262     return 0;
01263 }

static int AC3_encode_frame ( AVCodecContext *  avctx,
unsigned char *  frame,
int  buf_size,
void *  data 
) [static]

Definition at line 1145 of file ac3enc.c.

References AC3_MAX_CHANNELS, av_log2(), AC3EncodeContext::bit_rate, AC3EncodeContext::bits_written, compute_exp_strategy(), encode_exp(), EXP_REUSE, exponent_min(), ff_ac3_window, AC3EncodeContext::last_samples, AC3EncodeContext::lfe_channel, log2_tab(), lshift_tab(), mdct512(), MUL16, N, AC3EncodeContext::nb_all_channels, NB_BLOCKS, AC3EncodeContext::nb_coefs, AVCodecContext::priv_data, AC3EncodeContext::sample_rate, samples, and AC3EncodeContext::samples_written.

01147 {
01148     AC3EncodeContext *s = avctx->priv_data;
01149     int16_t *samples = data;
01150     int i, j, k, v, ch;
01151     int16_t input_samples[N];
01152     int32_t mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01153     uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01154     uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS];
01155     uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01156     uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
01157     int8_t exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS];
01158     int frame_bits;
01159 
01160     frame_bits = 0;
01161     for(ch=0;ch<s->nb_all_channels;ch++) {
01162         /* fixed mdct to the six sub blocks & exponent computation */
01163         for(i=0;i<NB_BLOCKS;i++) {
01164             int16_t *sptr;
01165             int sinc;
01166 
01167             /* compute input samples */
01168             memcpy(input_samples, s->last_samples[ch], N/2 * sizeof(int16_t));
01169             sinc = s->nb_all_channels;
01170             sptr = samples + (sinc * (N/2) * i) + ch;
01171             for(j=0;j<N/2;j++) {
01172                 v = *sptr;
01173                 input_samples[j + N/2] = v;
01174                 s->last_samples[ch][j] = v;
01175                 sptr += sinc;
01176             }
01177 
01178             /* apply the MDCT window */
01179             for(j=0;j<N/2;j++) {
01180                 input_samples[j] = MUL16(input_samples[j],
01181                                          ff_ac3_window[j]) >> 15;
01182                 input_samples[N-j-1] = MUL16(input_samples[N-j-1],
01183                                              ff_ac3_window[j]) >> 15;
01184             }
01185 
01186             /* Normalize the samples to use the maximum available
01187                precision */
01188             v = 14 - log2_tab(input_samples, N);
01189             if (v < 0)
01190                 v = 0;
01191             exp_samples[i][ch] = v - 9;
01192             lshift_tab(input_samples, N, v);
01193 
01194             /* do the MDCT */
01195             mdct512(mdct_coef[i][ch], input_samples);
01196 
01197             /* compute "exponents". We take into account the
01198                normalization there */
01199             for(j=0;j<N/2;j++) {
01200                 int e;
01201                 v = abs(mdct_coef[i][ch][j]);
01202                 if (v == 0)
01203                     e = 24;
01204                 else {
01205                     e = 23 - av_log2(v) + exp_samples[i][ch];
01206                     if (e >= 24) {
01207                         e = 24;
01208                         mdct_coef[i][ch][j] = 0;
01209                     }
01210                 }
01211                 exp[i][ch][j] = e;
01212             }
01213         }
01214 
01215         compute_exp_strategy(exp_strategy, exp, ch, ch == s->lfe_channel);
01216 
01217         /* compute the exponents as the decoder will see them. The
01218            EXP_REUSE case must be handled carefully : we select the
01219            min of the exponents */
01220         i = 0;
01221         while (i < NB_BLOCKS) {
01222             j = i + 1;
01223             while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {
01224                 exponent_min(exp[i][ch], exp[j][ch], s->nb_coefs[ch]);
01225                 j++;
01226             }
01227             frame_bits += encode_exp(encoded_exp[i][ch],
01228                                      exp[i][ch], s->nb_coefs[ch],
01229                                      exp_strategy[i][ch]);
01230             /* copy encoded exponents for reuse case */
01231             for(k=i+1;k<j;k++) {
01232                 memcpy(encoded_exp[k][ch], encoded_exp[i][ch],
01233                        s->nb_coefs[ch] * sizeof(uint8_t));
01234             }
01235             i = j;
01236         }
01237     }
01238 
01239     /* adjust for fractional frame sizes */
01240     while(s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
01241         s->bits_written -= s->bit_rate;
01242         s->samples_written -= s->sample_rate;
01243     }
01244     s->frame_size = s->frame_size_min + (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
01245     s->bits_written += s->frame_size * 16;
01246     s->samples_written += AC3_FRAME_SIZE;
01247 
01248     compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);
01249     /* everything is known... let's output the frame */
01250     output_frame_header(s, frame);
01251 
01252     for(i=0;i<NB_BLOCKS;i++) {
01253         output_audio_block(s, exp_strategy[i], encoded_exp[i],
01254                            bap[i], mdct_coef[i], exp_samples[i], i);
01255     }
01256     return output_frame_end(s);
01257 }

static av_cold int AC3_encode_init ( AVCodecContext *  avctx  )  [static]

Definition at line 612 of file ac3enc.c.

References ac3_common_init(), AC3_FRAME_SIZE, av_clip(), AC3EncodeContext::bit_rate, AVCodecContext::bit_rate, AC3EncodeContext::bits_written, AC3EncodeContext::bitstream_id, AC3EncodeContext::bitstream_mode, AC3EncodeContext::channel_mode, AVCodecContext::channels, AVCodecContext::cutoff, ff_ac3_bitrate_tab, ff_ac3_frame_size_tab, ff_ac3_sample_rate_tab, AC3EncodeContext::frame_size, AVCodecContext::frame_size, AC3EncodeContext::frame_size_code, AC3EncodeContext::frame_size_min, AC3EncodeContext::lfe, AC3EncodeContext::lfe_channel, AC3EncodeContext::nb_all_channels, AC3EncodeContext::nb_channels, AVCodecContext::priv_data, AC3EncodeContext::sample_rate, AVCodecContext::sample_rate, AC3EncodeContext::samples_written, AC3EncodeContext::sr_code, and AC3EncodeContext::sr_shift.

00613 {
00614     int freq = avctx->sample_rate;
00615     int bitrate = avctx->bit_rate;
00616     int channels = avctx->channels;
00617     AC3EncodeContext *s = avctx->priv_data;
00618     int i, j, ch;
00619     float alpha;
00620     int bw_code;
00621     static const uint8_t channel_mode_defs[6] = {
00622         0x01, /* C */
00623         0x02, /* L R */
00624         0x03, /* L C R */
00625         0x06, /* L R SL SR */
00626         0x07, /* L C R SL SR */
00627         0x07, /* L C R SL SR (+LFE) */
00628     };
00629 
00630     avctx->frame_size = AC3_FRAME_SIZE;
00631 
00632     ac3_common_init();
00633 
00634     /* number of channels */
00635     if (channels < 1 || channels > 6)
00636         return -1;
00637     s->channel_mode = channel_mode_defs[channels - 1];
00638     s->lfe = (channels == 6) ? 1 : 0;
00639     s->nb_all_channels = channels;
00640     s->nb_channels = channels > 5 ? 5 : channels;
00641     s->lfe_channel = s->lfe ? 5 : -1;
00642 
00643     /* frequency */
00644     for(i=0;i<3;i++) {
00645         for(j=0;j<3;j++)
00646             if ((ff_ac3_sample_rate_tab[j] >> i) == freq)
00647                 goto found;
00648     }
00649     return -1;
00650  found:
00651     s->sample_rate = freq;
00652     s->sr_shift = i;
00653     s->sr_code = j;
00654     s->bitstream_id = 8 + s->sr_shift;
00655     s->bitstream_mode = 0; /* complete main audio service */
00656 
00657     /* bitrate & frame size */
00658     for(i=0;i<19;i++) {
00659         if ((ff_ac3_bitrate_tab[i] >> s->sr_shift)*1000 == bitrate)
00660             break;
00661     }
00662     if (i == 19)
00663         return -1;
00664     s->bit_rate = bitrate;
00665     s->frame_size_code = i << 1;
00666     s->frame_size_min = ff_ac3_frame_size_tab[s->frame_size_code][s->sr_code];
00667     s->bits_written = 0;
00668     s->samples_written = 0;
00669     s->frame_size = s->frame_size_min;
00670 
00671     /* bit allocation init */
00672     if(avctx->cutoff) {
00673         /* calculate bandwidth based on user-specified cutoff frequency */
00674         int cutoff = av_clip(avctx->cutoff, 1, s->sample_rate >> 1);
00675         int fbw_coeffs = cutoff * 512 / s->sample_rate;
00676         bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);
00677     } else {
00678         /* use default bandwidth setting */
00679         /* XXX: should compute the bandwidth according to the frame
00680            size, so that we avoid annoying high frequency artifacts */
00681         bw_code = 50;
00682     }
00683     for(ch=0;ch<s->nb_channels;ch++) {
00684         /* bandwidth for each channel */
00685         s->chbwcod[ch] = bw_code;
00686         s->nb_coefs[ch] = bw_code * 3 + 73;
00687     }
00688     if (s->lfe) {
00689         s->nb_coefs[s->lfe_channel] = 7; /* fixed */
00690     }
00691     /* initial snr offset */
00692     s->coarse_snr_offset = 40;
00693 
00694     /* mdct init */
00695     fft_init(MDCT_NBITS - 2);
00696     for(i=0;i<N/4;i++) {
00697         alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N;
00698         xcos1[i] = fix15(-cos(alpha));
00699         xsin1[i] = fix15(-sin(alpha));
00700     }
00701 
00702     avctx->coded_frame= avcodec_alloc_frame();
00703     avctx->coded_frame->key_frame= 1;
00704 
00705     return 0;
00706 }

static int asym_quant ( int  c,
int  e,
int  qbits 
) [inline, static]

Definition at line 757 of file ac3enc.c.

00758 {
00759     int lshift, m, v;
00760 
00761     lshift = e + qbits - 24;
00762     if (lshift >= 0)
00763         v = c << lshift;
00764     else
00765         v = c >> (-lshift);
00766     /* rounding */
00767     v = (v + 1) >> 1;
00768     m = (1 << (qbits-1));
00769     if (v >= m)
00770         v = m - 1;
00771     assert(v >= -m);
00772     return v & ((1 << qbits)-1);
00773 }

static int bit_alloc ( AC3EncodeContext *  s,
int16_t  mask[NB_BLOCKS][AC3_MAX_CHANNELS][50],
int16_t  psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
uint8_t  bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
int  frame_bits,
int  coarse_snr_offset,
int  fine_snr_offset 
) [static]

Definition at line 447 of file ac3enc.c.

References AC3EncodeContext::bit_alloc, compute_mantissa_size(), ff_ac3_bap_tab, ff_ac3_bit_alloc_calc_bap(), AC3BitAllocParameters::floor, AC3EncodeContext::frame_size, AC3EncodeContext::mant1_cnt, AC3EncodeContext::mant2_cnt, AC3EncodeContext::mant4_cnt, mask, NB_BLOCKS, AC3EncodeContext::nb_coefs, and printf.

Referenced by compute_bit_allocation(), encode_frame(), mp_decode_layer2(), and MPA_encode_frame().

00452 {
00453     int i, ch;
00454     int snr_offset;
00455 
00456     snr_offset = (((coarse_snr_offset - 15) << 4) + fine_snr_offset) << 2;
00457 
00458     /* compute size */
00459     for(i=0;i<NB_BLOCKS;i++) {
00460         s->mant1_cnt = 0;
00461         s->mant2_cnt = 0;
00462         s->mant4_cnt = 0;
00463         for(ch=0;ch<s->nb_all_channels;ch++) {
00464             ff_ac3_bit_alloc_calc_bap(mask[i][ch], psd[i][ch], 0,
00465                                       s->nb_coefs[ch], snr_offset,
00466                                       s->bit_alloc.floor, ff_ac3_bap_tab,
00467                                       bap[i][ch]);
00468             frame_bits += compute_mantissa_size(s, bap[i][ch],
00469                                                  s->nb_coefs[ch]);
00470         }
00471     }
00472 #if 0
00473     printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n",
00474            coarse_snr_offset, fine_snr_offset, frame_bits,
00475            16 * s->frame_size - ((frame_bits + 7) & ~7));
00476 #endif
00477     return 16 * s->frame_size - frame_bits;
00478 }

static void bit_alloc_masking ( AC3EncodeContext *  s,
uint8_t  encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
uint8_t  exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
int16_t  psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
int16_t  mask[NB_BLOCKS][AC3_MAX_CHANNELS][50] 
) [static]

Definition at line 418 of file ac3enc.c.

References AC3EncodeContext::bit_alloc, blk, DBA_NONE, EXP_REUSE, AC3EncodeContext::fast_gain_code, ff_ac3_bit_alloc_calc_mask(), ff_ac3_bit_alloc_calc_psd(), ff_ac3_fast_gain_tab, AC3EncodeContext::lfe_channel, mask, N, AC3EncodeContext::nb_all_channels, NB_BLOCKS, AC3EncodeContext::nb_coefs, and NULL.

00423 {
00424     int blk, ch;
00425     int16_t band_psd[NB_BLOCKS][AC3_MAX_CHANNELS][50];
00426 
00427     for(blk=0; blk<NB_BLOCKS; blk++) {
00428         for(ch=0;ch<s->nb_all_channels;ch++) {
00429             if(exp_strategy[blk][ch] == EXP_REUSE) {
00430                 memcpy(psd[blk][ch], psd[blk-1][ch], (N/2)*sizeof(int16_t));
00431                 memcpy(mask[blk][ch], mask[blk-1][ch], 50*sizeof(int16_t));
00432             } else {
00433                 ff_ac3_bit_alloc_calc_psd(encoded_exp[blk][ch], 0,
00434                                           s->nb_coefs[ch],
00435                                           psd[blk][ch], band_psd[blk][ch]);
00436                 ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, band_psd[blk][ch],
00437                                            0, s->nb_coefs[ch],
00438                                            ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
00439                                            ch == s->lfe_channel,
00440                                            DBA_NONE, 0, NULL, NULL, NULL,
00441                                            mask[blk][ch]);
00442             }
00443         }
00444     }
00445 }

static int calc_exp_diff ( uint8_t *  exp1,
uint8_t *  exp2,
int  n 
) [static]

Definition at line 230 of file ac3enc.c.

Referenced by compute_exp_strategy().

00231 {
00232     int sum, i;
00233     sum = 0;
00234     for(i=0;i<n;i++) {
00235         sum += abs(exp1[i] - exp2[i]);
00236     }
00237     return sum;
00238 }

static int compute_bit_allocation ( AC3EncodeContext *  s,
uint8_t  bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
uint8_t  encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
uint8_t  exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
int  frame_bits 
) [static]

Definition at line 482 of file ac3enc.c.

References AC3_CHMODE_STEREO, AC3EncodeContext::bit_alloc, AC3EncodeContext::channel_mode, AC3BitAllocParameters::db_per_bit, AC3EncodeContext::db_per_bit_code, AC3BitAllocParameters::fast_decay, AC3EncodeContext::fast_decay_code, AC3EncodeContext::fast_gain_code, ff_ac3_db_per_bit_tab, ff_ac3_fast_decay_tab, ff_ac3_floor_tab, ff_ac3_slow_decay_tab, ff_ac3_slow_gain_tab, AC3BitAllocParameters::floor, AC3EncodeContext::floor_code, mask, N, AC3EncodeContext::nb_all_channels, NB_BLOCKS, AC3EncodeContext::nb_channels, AC3BitAllocParameters::slow_decay, AC3EncodeContext::slow_decay_code, AC3BitAllocParameters::slow_gain, AC3EncodeContext::slow_gain_code, AC3EncodeContext::sr_code, AC3BitAllocParameters::sr_code, AC3EncodeContext::sr_shift, and AC3BitAllocParameters::sr_shift.

Referenced by MPA_encode_frame().

00487 {
00488     int i, ch;
00489     int coarse_snr_offset, fine_snr_offset;
00490     uint8_t bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
00491     int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
00492     int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50];
00493     static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
00494 
00495     /* init default parameters */
00496     s->slow_decay_code = 2;
00497     s->fast_decay_code = 1;
00498     s->slow_gain_code = 1;
00499     s->db_per_bit_code = 2;
00500     s->floor_code = 4;
00501     for(ch=0;ch<s->nb_all_channels;ch++)
00502         s->fast_gain_code[ch] = 4;
00503 
00504     /* compute real values */
00505     s->bit_alloc.sr_code = s->sr_code;
00506     s->bit_alloc.sr_shift = s->sr_shift;
00507     s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->sr_shift;
00508     s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->sr_shift;
00509     s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
00510     s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
00511     s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
00512 
00513     /* header size */
00514     frame_bits += 65;
00515     // if (s->channel_mode == 2)
00516     //    frame_bits += 2;
00517     frame_bits += frame_bits_inc[s->channel_mode];
00518 
00519     /* audio blocks */
00520     for(i=0;i<NB_BLOCKS;i++) {
00521         frame_bits += s->nb_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
00522         if (s->channel_mode == AC3_CHMODE_STEREO) {
00523             frame_bits++; /* rematstr */
00524             if(i==0) frame_bits += 4;
00525         }
00526         frame_bits += 2 * s->nb_channels; /* chexpstr[2] * c */
00527         if (s->lfe)
00528             frame_bits++; /* lfeexpstr */
00529         for(ch=0;ch<s->nb_channels;ch++) {
00530             if (exp_strategy[i][ch] != EXP_REUSE)
00531                 frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
00532         }
00533         frame_bits++; /* baie */
00534         frame_bits++; /* snr */
00535         frame_bits += 2; /* delta / skip */
00536     }
00537     frame_bits++; /* cplinu for block 0 */
00538     /* bit alloc info */
00539     /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
00540     /* csnroffset[6] */
00541     /* (fsnoffset[4] + fgaincod[4]) * c */
00542     frame_bits += 2*4 + 3 + 6 + s->nb_all_channels * (4 + 3);
00543 
00544     /* auxdatae, crcrsv */
00545     frame_bits += 2;
00546 
00547     /* CRC */
00548     frame_bits += 16;
00549 
00550     /* calculate psd and masking curve before doing bit allocation */
00551     bit_alloc_masking(s, encoded_exp, exp_strategy, psd, mask);
00552 
00553     /* now the big work begins : do the bit allocation. Modify the snr
00554        offset until we can pack everything in the requested frame size */
00555 
00556     coarse_snr_offset = s->coarse_snr_offset;
00557     while (coarse_snr_offset >= 0 &&
00558            bit_alloc(s, mask, psd, bap, frame_bits, coarse_snr_offset, 0) < 0)
00559         coarse_snr_offset -= SNR_INC1;
00560     if (coarse_snr_offset < 0) {
00561         av_log(NULL, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
00562         return -1;
00563     }
00564     while ((coarse_snr_offset + SNR_INC1) <= 63 &&
00565            bit_alloc(s, mask, psd, bap1, frame_bits,
00566                      coarse_snr_offset + SNR_INC1, 0) >= 0) {
00567         coarse_snr_offset += SNR_INC1;
00568         memcpy(bap, bap1, sizeof(bap1));
00569     }
00570     while ((coarse_snr_offset + 1) <= 63 &&
00571            bit_alloc(s, mask, psd, bap1, frame_bits, coarse_snr_offset + 1, 0) >= 0) {
00572         coarse_snr_offset++;
00573         memcpy(bap, bap1, sizeof(bap1));
00574     }
00575 
00576     fine_snr_offset = 0;
00577     while ((fine_snr_offset + SNR_INC1) <= 15 &&
00578            bit_alloc(s, mask, psd, bap1, frame_bits,
00579                      coarse_snr_offset, fine_snr_offset + SNR_INC1) >= 0) {
00580         fine_snr_offset += SNR_INC1;
00581         memcpy(bap, bap1, sizeof(bap1));
00582     }
00583     while ((fine_snr_offset + 1) <= 15 &&
00584            bit_alloc(s, mask, psd, bap1, frame_bits,
00585                      coarse_snr_offset, fine_snr_offset + 1) >= 0) {
00586         fine_snr_offset++;
00587         memcpy(bap, bap1, sizeof(bap1));
00588     }
00589 
00590     s->coarse_snr_offset = coarse_snr_offset;
00591     for(ch=0;ch<s->nb_all_channels;ch++)
00592         s->fine_snr_offset[ch] = fine_snr_offset;
00593 #if defined(DEBUG_BITALLOC)
00594     {
00595         int j;
00596 
00597         for(i=0;i<6;i++) {
00598             for(ch=0;ch<s->nb_all_channels;ch++) {
00599                 printf("Block #%d Ch%d:\n", i, ch);
00600                 printf("bap=");
00601                 for(j=0;j<s->nb_coefs[ch];j++) {
00602                     printf("%d ",bap[i][ch][j]);
00603                 }
00604                 printf("\n");
00605             }
00606         }
00607     }
00608 #endif
00609     return 0;
00610 }

static void compute_exp_strategy ( uint8_t  exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
uint8_t  exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
int  ch,
int  is_lfe 
) [static]

Definition at line 240 of file ac3enc.c.

References av_log(), AV_LOG_DEBUG, calc_exp_diff(), EXP_D15, EXP_D25, EXP_D45, EXP_DIFF_THRESHOLD, EXP_NEW, EXP_REUSE, N, NB_BLOCKS, and NULL.

Referenced by AC3_encode_frame().

00243 {
00244     int i, j;
00245     int exp_diff;
00246 
00247     /* estimate if the exponent variation & decide if they should be
00248        reused in the next frame */
00249     exp_strategy[0][ch] = EXP_NEW;
00250     for(i=1;i<NB_BLOCKS;i++) {
00251         exp_diff = calc_exp_diff(exp[i][ch], exp[i-1][ch], N/2);
00252 #ifdef DEBUG
00253         av_log(NULL, AV_LOG_DEBUG, "exp_diff=%d\n", exp_diff);
00254 #endif
00255         if (exp_diff > EXP_DIFF_THRESHOLD)
00256             exp_strategy[i][ch] = EXP_NEW;
00257         else
00258             exp_strategy[i][ch] = EXP_REUSE;
00259     }
00260     if (is_lfe)
00261         return;
00262 
00263     /* now select the encoding strategy type : if exponents are often
00264        recoded, we use a coarse encoding */
00265     i = 0;
00266     while (i < NB_BLOCKS) {
00267         j = i + 1;
00268         while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)
00269             j++;
00270         switch(j - i) {
00271         case 1:
00272             exp_strategy[i][ch] = EXP_D45;
00273             break;
00274         case 2:
00275         case 3:
00276             exp_strategy[i][ch] = EXP_D25;
00277             break;
00278         default:
00279             exp_strategy[i][ch] = EXP_D15;
00280             break;
00281         }
00282         i = j;
00283     }
00284 }

static int compute_mantissa_size ( AC3EncodeContext *  s,
uint8_t *  m,
int  nb_coefs 
) [static]

Definition at line 368 of file ac3enc.c.

References bits, AC3EncodeContext::mant1_cnt, AC3EncodeContext::mant2_cnt, and AC3EncodeContext::mant4_cnt.

Referenced by bit_alloc().

00369 {
00370     int bits, mant, i;
00371 
00372     bits = 0;
00373     for(i=0;i<nb_coefs;i++) {
00374         mant = m[i];
00375         switch(mant) {
00376         case 0:
00377             /* nothing */
00378             break;
00379         case 1:
00380             /* 3 mantissa in 5 bits */
00381             if (s->mant1_cnt == 0)
00382                 bits += 5;
00383             if (++s->mant1_cnt == 3)
00384                 s->mant1_cnt = 0;
00385             break;
00386         case 2:
00387             /* 3 mantissa in 7 bits */
00388             if (s->mant2_cnt == 0)
00389                 bits += 7;
00390             if (++s->mant2_cnt == 3)
00391                 s->mant2_cnt = 0;
00392             break;
00393         case 3:
00394             bits += 3;
00395             break;
00396         case 4:
00397             /* 2 mantissa in 7 bits */
00398             if (s->mant4_cnt == 0)
00399                 bits += 7;
00400             if (++s->mant4_cnt == 2)
00401                 s->mant4_cnt = 0;
00402             break;
00403         case 14:
00404             bits += 14;
00405             break;
00406         case 15:
00407             bits += 16;
00408             break;
00409         default:
00410             bits += mant - 1;
00411             break;
00412         }
00413     }
00414     return bits;
00415 }

static int encode_exp ( uint8_t  encoded_exp[N/2],
uint8_t  exp[N/2],
int  nb_exps,
int  exp_strategy 
) [static]

Definition at line 299 of file ac3enc.c.

References av_log(), AV_LOG_DEBUG, EXP_D15, EXP_D25, EXP_D45, FFMIN, N, and NULL.

Referenced by AC3_encode_frame().

00303 {
00304     int group_size, nb_groups, i, j, k, exp_min;
00305     uint8_t exp1[N/2];
00306 
00307     switch(exp_strategy) {
00308     case EXP_D15:
00309         group_size = 1;
00310         break;
00311     case EXP_D25:
00312         group_size = 2;
00313         break;
00314     default:
00315     case EXP_D45:
00316         group_size = 4;
00317         break;
00318     }
00319     nb_groups = ((nb_exps + (group_size * 3) - 4) / (3 * group_size)) * 3;
00320 
00321     /* for each group, compute the minimum exponent */
00322     exp1[0] = exp[0]; /* DC exponent is handled separately */
00323     k = 1;
00324     for(i=1;i<=nb_groups;i++) {
00325         exp_min = exp[k];
00326         assert(exp_min >= 0 && exp_min <= 24);
00327         for(j=1;j<group_size;j++) {
00328             if (exp[k+j] < exp_min)
00329                 exp_min = exp[k+j];
00330         }
00331         exp1[i] = exp_min;
00332         k += group_size;
00333     }
00334 
00335     /* constraint for DC exponent */
00336     if (exp1[0] > 15)
00337         exp1[0] = 15;
00338 
00339     /* Decrease the delta between each groups to within 2
00340      * so that they can be differentially encoded */
00341     for (i=1;i<=nb_groups;i++)
00342         exp1[i] = FFMIN(exp1[i], exp1[i-1] + 2);
00343     for (i=nb_groups-1;i>=0;i--)
00344         exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2);
00345 
00346     /* now we have the exponent values the decoder will see */
00347     encoded_exp[0] = exp1[0];
00348     k = 1;
00349     for(i=1;i<=nb_groups;i++) {
00350         for(j=0;j<group_size;j++) {
00351             encoded_exp[k+j] = exp1[i];
00352         }
00353         k += group_size;
00354     }
00355 
00356 #if defined(DEBUG)
00357     av_log(NULL, AV_LOG_DEBUG, "exponents: strategy=%d\n", exp_strategy);
00358     for(i=0;i<=nb_groups * group_size;i++) {
00359         av_log(NULL, AV_LOG_DEBUG, "%d ", encoded_exp[i]);
00360     }
00361     av_log(NULL, AV_LOG_DEBUG, "\n");
00362 #endif
00363 
00364     return 4 + (nb_groups / 3) * 7;
00365 }

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

Definition at line 287 of file ac3enc.c.

Referenced by AC3_encode_frame().

00288 {
00289     int i;
00290 
00291     for(i=0;i<n;i++) {
00292         if (exp1[i] < exp[i])
00293             exp[i] = exp1[i];
00294     }
00295 }

static void fft ( IComplex *  z,
int  ln 
) [static]

Definition at line 129 of file ac3enc.c.

References BF, CMUL, costab, ff_reverse, FFSWAP, IComplex::im, IComplex::re, and sintab.

Referenced by mdct512().

00130 {
00131     int        j, l, np, np2;
00132     int        nblocks, nloops;
00133     register IComplex *p,*q;
00134     int tmp_re, tmp_im;
00135 
00136     np = 1 << ln;
00137 
00138     /* reverse */
00139     for(j=0;j<np;j++) {
00140         int k = ff_reverse[j] >> (8 - ln);
00141         if (k < j)
00142             FFSWAP(IComplex, z[k], z[j]);
00143     }
00144 
00145     /* pass 0 */
00146 
00147     p=&z[0];
00148     j=(np >> 1);
00149     do {
00150         BF(p[0].re, p[0].im, p[1].re, p[1].im,
00151            p[0].re, p[0].im, p[1].re, p[1].im);
00152         p+=2;
00153     } while (--j != 0);
00154 
00155     /* pass 1 */
00156 
00157     p=&z[0];
00158     j=np >> 2;
00159     do {
00160         BF(p[0].re, p[0].im, p[2].re, p[2].im,
00161            p[0].re, p[0].im, p[2].re, p[2].im);
00162         BF(p[1].re, p[1].im, p[3].re, p[3].im,
00163            p[1].re, p[1].im, p[3].im, -p[3].re);
00164         p+=4;
00165     } while (--j != 0);
00166 
00167     /* pass 2 .. ln-1 */
00168 
00169     nblocks = np >> 3;
00170     nloops = 1 << 2;
00171     np2 = np >> 1;
00172     do {
00173         p = z;
00174         q = z + nloops;
00175         for (j = 0; j < nblocks; ++j) {
00176 
00177             BF(p->re, p->im, q->re, q->im,
00178                p->re, p->im, q->re, q->im);
00179 
00180             p++;
00181             q++;
00182             for(l = nblocks; l < np2; l += nblocks) {
00183                 CMUL(tmp_re, tmp_im, costab[l], -sintab[l], q->re, q->im);
00184                 BF(p->re, p->im, q->re, q->im,
00185                    p->re, p->im, tmp_re, tmp_im);
00186                 p++;
00187                 q++;
00188             }
00189             p += nloops;
00190             q += nloops;
00191         }
00192         nblocks = nblocks >> 1;
00193         nloops = nloops << 1;
00194     } while (nblocks != 0);
00195 }

static void fft_init ( int  ln  )  [static]

Definition at line 91 of file ac3enc.c.

References costab, fix15(), M_PI, and sintab.

00092 {
00093     int i, n;
00094     float alpha;
00095 
00096     n = 1 << ln;
00097 
00098     for(i=0;i<(n/2);i++) {
00099         alpha = 2 * M_PI * (float)i / (float)n;
00100         costab[i] = fix15(cos(alpha));
00101         sintab[i] = fix15(sin(alpha));
00102     }
00103 }

static int16_t fix15 ( float  a  )  [inline, static]

Definition at line 76 of file ac3enc.c.

Referenced by fft_init().

00077 {
00078     int v;
00079     v = (int)(a * (float)(1 << 15));
00080     if (v < -32767)
00081         v = -32767;
00082     else if (v > 32767)
00083         v = 32767;
00084     return v;
00085 }

static int log2_tab ( int16_t *  tab,
int  n 
) [static]

Definition at line 1083 of file ac3enc.c.

References av_log2().

Referenced by AC3_encode_frame().

01084 {
01085     int i, v;
01086 
01087     v = 0;
01088     for(i=0;i<n;i++) {
01089         v |= abs(tab[i]);
01090     }
01091     return