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1
/*
2
 * The simplest AC-3 encoder
3
 * Copyright (c) 2000 Fabrice Bellard
4
 *
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 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
8
 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
10
 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
21

    
22
/**
23
 * @file
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 * The simplest AC-3 encoder.
25
 */
26

    
27
//#define DEBUG
28

    
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#include "libavcore/audioconvert.h"
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#include "libavutil/crc.h"
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#include "avcodec.h"
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#include "put_bits.h"
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#include "ac3.h"
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#include "audioconvert.h"
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36

    
37
#define MDCT_NBITS 9
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#define MDCT_SAMPLES (1 << MDCT_NBITS)
39

    
40
/** Maximum number of exponent groups. +1 for separate DC exponent. */
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#define AC3_MAX_EXP_GROUPS 85
42

    
43
/** Scale a float value by 2^bits and convert to an integer. */
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#define SCALE_FLOAT(a, bits) lrintf((a) * (float)(1 << (bits)))
45

    
46
/** Scale a float value by 2^15, convert to an integer, and clip to int16_t range. */
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#define FIX15(a) av_clip_int16(SCALE_FLOAT(a, 15))
48

    
49

    
50
/**
51
 * Compex number.
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 * Used in fixed-point MDCT calculation.
53
 */
54
typedef struct IComplex {
55
    int16_t re,im;
56
} IComplex;
57

    
58
/**
59
 * AC-3 encoder private context.
60
 */
61
typedef struct AC3EncodeContext {
62
    PutBitContext pb;                       ///< bitstream writer context
63

    
64
    int bitstream_id;                       ///< bitstream id                           (bsid)
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    int bitstream_mode;                     ///< bitstream mode                         (bsmod)
66

    
67
    int bit_rate;                           ///< target bit rate, in bits-per-second
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    int sample_rate;                        ///< sampling frequency, in Hz
69

    
70
    int frame_size_min;                     ///< minimum frame size in case rounding is necessary
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    int frame_size;                         ///< current frame size in bytes
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    int frame_size_code;                    ///< frame size code                        (frmsizecod)
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    int bits_written;                       ///< bit count    (used to avg. bitrate)
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    int samples_written;                    ///< sample count (used to avg. bitrate)
75

    
76
    int fbw_channels;                       ///< number of full-bandwidth channels      (nfchans)
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    int channels;                           ///< total number of channels               (nchans)
78
    int lfe_on;                             ///< indicates if there is an LFE channel   (lfeon)
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    int lfe_channel;                        ///< channel index of the LFE channel
80
    int channel_mode;                       ///< channel mode                           (acmod)
81
    const uint8_t *channel_map;             ///< channel map used to reorder channels
82

    
83
    int bandwidth_code[AC3_MAX_CHANNELS];   ///< bandwidth code (0 to 60)               (chbwcod)
84
    int nb_coefs[AC3_MAX_CHANNELS];
85

    
86
    /* bitrate allocation control */
87
    int slow_gain_code;                     ///< slow gain code                         (sgaincod)
88
    int slow_decay_code;                    ///< slow decay code                        (sdcycod)
89
    int fast_decay_code;                    ///< fast decay code                        (fdcycod)
90
    int db_per_bit_code;                    ///< dB/bit code                            (dbpbcod)
91
    int floor_code;                         ///< floor code                             (floorcod)
92
    AC3BitAllocParameters bit_alloc;        ///< bit allocation parameters
93
    int coarse_snr_offset;                  ///< coarse SNR offsets                     (csnroffst)
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    int fast_gain_code[AC3_MAX_CHANNELS];   ///< fast gain codes (signal-to-mask ratio) (fgaincod)
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    int fine_snr_offset[AC3_MAX_CHANNELS];  ///< fine SNR offsets                       (fsnroffst)
96

    
97
    /* mantissa encoding */
98
    int mant1_cnt, mant2_cnt, mant4_cnt;    ///< mantissa counts for bap=1,2,4
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    uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr; ///< mantissa pointers for bap=1,2,4
100

    
101
    int16_t last_samples[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE]; ///< last 256 samples from previous frame
102
} AC3EncodeContext;
103

    
104

    
105
/** MDCT and FFT tables */
106
static int16_t costab[64];
107
static int16_t sintab[64];
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static int16_t xcos1[128];
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static int16_t xsin1[128];
110

    
111

    
112
/**
113
 * Adjust the frame size to make the average bit rate match the target bit rate.
114
 * This is only needed for 11025, 22050, and 44100 sample rates.
115
 */
116
static void adjust_frame_size(AC3EncodeContext *s)
117
{
118
    while (s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
119
        s->bits_written    -= s->bit_rate;
120
        s->samples_written -= s->sample_rate;
121
    }
122
    s->frame_size = s->frame_size_min + 2 * (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
123
    s->bits_written    += s->frame_size * 8;
124
    s->samples_written += AC3_FRAME_SIZE;
125
}
126

    
127

    
128
/**
129
 * Deinterleave input samples.
130
 * Channels are reordered from FFmpeg's default order to AC-3 order.
131
 */
132
static void deinterleave_input_samples(AC3EncodeContext *s,
133
                                       const int16_t *samples,
134
                                       int16_t planar_samples[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE+AC3_FRAME_SIZE])
135
{
136
    int ch, i;
137

    
138
    /* deinterleave and remap input samples */
139
    for (ch = 0; ch < s->channels; ch++) {
140
        const int16_t *sptr;
141
        int sinc;
142

    
143
        /* copy last 256 samples of previous frame to the start of the current frame */
144
        memcpy(&planar_samples[ch][0], s->last_samples[ch],
145
               AC3_BLOCK_SIZE * sizeof(planar_samples[0][0]));
146

    
147
        /* deinterleave */
148
        sinc = s->channels;
149
        sptr = samples + s->channel_map[ch];
150
        for (i = AC3_BLOCK_SIZE; i < AC3_FRAME_SIZE+AC3_BLOCK_SIZE; i++) {
151
            planar_samples[ch][i] = *sptr;
152
            sptr += sinc;
153
        }
154

    
155
        /* save last 256 samples for next frame */
156
        memcpy(s->last_samples[ch], &planar_samples[ch][6* AC3_BLOCK_SIZE],
157
               AC3_BLOCK_SIZE * sizeof(planar_samples[0][0]));
158
    }
159
}
160

    
161

    
162
/**
163
 * Initialize FFT tables.
164
 * @param ln log2(FFT size)
165
 */
166
static av_cold void fft_init(int ln)
167
{
168
    int i, n, n2;
169
    float alpha;
170

    
171
    n  = 1 << ln;
172
    n2 = n >> 1;
173

    
174
    for (i = 0; i < n2; i++) {
175
        alpha     = 2.0 * M_PI * i / n;
176
        costab[i] = FIX15(cos(alpha));
177
        sintab[i] = FIX15(sin(alpha));
178
    }
179
}
180

    
181

    
182
/**
183
 * Initialize MDCT tables.
184
 * @param nbits log2(MDCT size)
185
 */
186
static av_cold void mdct_init(int nbits)
187
{
188
    int i, n, n4;
189

    
190
    n  = 1 << nbits;
191
    n4 = n >> 2;
192

    
193
    fft_init(nbits - 2);
194

    
195
    for (i = 0; i < n4; i++) {
196
        float alpha = 2.0 * M_PI * (i + 1.0 / 8.0) / n;
197
        xcos1[i] = FIX15(-cos(alpha));
198
        xsin1[i] = FIX15(-sin(alpha));
199
    }
200
}
201

    
202

    
203
/** Butterfly op */
204
#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1)  \
205
{                                                       \
206
  int ax, ay, bx, by;                                   \
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  bx  = pre1;                                           \
208
  by  = pim1;                                           \
209
  ax  = qre1;                                           \
210
  ay  = qim1;                                           \
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  pre = (bx + ax) >> 1;                                 \
212
  pim = (by + ay) >> 1;                                 \
213
  qre = (bx - ax) >> 1;                                 \
214
  qim = (by - ay) >> 1;                                 \
215
}
216

    
217

    
218
/** Complex multiply */
219
#define CMUL(pre, pim, are, aim, bre, bim)              \
220
{                                                       \
221
   pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15;     \
222
   pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;     \
223
}
224

    
225

    
226
/**
227
 * Calculate a 2^n point complex FFT on 2^ln points.
228
 * @param z  complex input/output samples
229
 * @param ln log2(FFT size)
230
 */
231
static void fft(IComplex *z, int ln)
232
{
233
    int j, l, np, np2;
234
    int nblocks, nloops;
235
    register IComplex *p,*q;
236
    int tmp_re, tmp_im;
237

    
238
    np = 1 << ln;
239

    
240
    /* reverse */
241
    for (j = 0; j < np; j++) {
242
        int k = av_reverse[j] >> (8 - ln);
243
        if (k < j)
244
            FFSWAP(IComplex, z[k], z[j]);
245
    }
246

    
247
    /* pass 0 */
248

    
249
    p = &z[0];
250
    j = np >> 1;
251
    do {
252
        BF(p[0].re, p[0].im, p[1].re, p[1].im,
253
           p[0].re, p[0].im, p[1].re, p[1].im);
254
        p += 2;
255
    } while (--j);
256

    
257
    /* pass 1 */
258

    
259
    p = &z[0];
260
    j = np >> 2;
261
    do {
262
        BF(p[0].re, p[0].im, p[2].re,  p[2].im,
263
           p[0].re, p[0].im, p[2].re,  p[2].im);
264
        BF(p[1].re, p[1].im, p[3].re,  p[3].im,
265
           p[1].re, p[1].im, p[3].im, -p[3].re);
266
        p+=4;
267
    } while (--j);
268

    
269
    /* pass 2 .. ln-1 */
270

    
271
    nblocks = np >> 3;
272
    nloops  =  1 << 2;
273
    np2     = np >> 1;
274
    do {
275
        p = z;
276
        q = z + nloops;
277
        for (j = 0; j < nblocks; j++) {
278
            BF(p->re, p->im, q->re, q->im,
279
               p->re, p->im, q->re, q->im);
280
            p++;
281
            q++;
282
            for(l = nblocks; l < np2; l += nblocks) {
283
                CMUL(tmp_re, tmp_im, costab[l], -sintab[l], q->re, q->im);
284
                BF(p->re, p->im, q->re,  q->im,
285
                   p->re, p->im, tmp_re, tmp_im);
286
                p++;
287
                q++;
288
            }
289
            p += nloops;
290
            q += nloops;
291
        }
292
        nblocks = nblocks >> 1;
293
        nloops  = nloops  << 1;
294
    } while (nblocks);
295
}
296

    
297

    
298
/**
299
 * Calculate a 512-point MDCT
300
 * @param out 256 output frequency coefficients
301
 * @param in  512 windowed input audio samples
302
 */
303
static void mdct512(int32_t *out, int16_t *in)
304
{
305
    int i, re, im, re1, im1;
306
    int16_t rot[MDCT_SAMPLES];
307
    IComplex x[MDCT_SAMPLES/4];
308

    
309
    /* shift to simplify computations */
310
    for (i = 0; i < MDCT_SAMPLES/4; i++)
311
        rot[i] = -in[i + 3*MDCT_SAMPLES/4];
312
    for (;i < MDCT_SAMPLES; i++)
313
        rot[i] =  in[i -   MDCT_SAMPLES/4];
314

    
315
    /* pre rotation */
316
    for (i = 0; i < MDCT_SAMPLES/4; i++) {
317
        re =  ((int)rot[               2*i] - (int)rot[MDCT_SAMPLES  -1-2*i]) >> 1;
318
        im = -((int)rot[MDCT_SAMPLES/2+2*i] - (int)rot[MDCT_SAMPLES/2-1-2*i]) >> 1;
319
        CMUL(x[i].re, x[i].im, re, im, -xcos1[i], xsin1[i]);
320
    }
321

    
322
    fft(x, MDCT_NBITS - 2);
323

    
324
    /* post rotation */
325
    for (i = 0; i < MDCT_SAMPLES/4; i++) {
326
        re = x[i].re;
327
        im = x[i].im;
328
        CMUL(re1, im1, re, im, xsin1[i], xcos1[i]);
329
        out[                 2*i] = im1;
330
        out[MDCT_SAMPLES/2-1-2*i] = re1;
331
    }
332
}
333

    
334

    
335
/**
336
 * Apply KBD window to input samples prior to MDCT.
337
 */
338
static void apply_window(int16_t *output, const int16_t *input,
339
                         const int16_t *window, int n)
340
{
341
    int i;
342
    int n2 = n >> 1;
343

    
344
    for (i = 0; i < n2; i++) {
345
        output[i]     = MUL16(input[i],     window[i]) >> 15;
346
        output[n-i-1] = MUL16(input[n-i-1], window[i]) >> 15;
347
    }
348
}
349

    
350

    
351
/**
352
 * Calculate the log2() of the maximum absolute value in an array.
353
 * @param tab input array
354
 * @param n   number of values in the array
355
 * @return    log2(max(abs(tab[])))
356
 */
357
static int log2_tab(int16_t *tab, int n)
358
{
359
    int i, v;
360

    
361
    v = 0;
362
    for (i = 0; i < n; i++)
363
        v |= abs(tab[i]);
364

    
365
    return av_log2(v);
366
}
367

    
368

    
369
/**
370
 * Left-shift each value in an array by a specified amount.
371
 * @param tab    input array
372
 * @param n      number of values in the array
373
 * @param lshift left shift amount. a negative value means right shift.
374
 */
375
static void lshift_tab(int16_t *tab, int n, int lshift)
376
{
377
    int i;
378

    
379
    if (lshift > 0) {
380
        for(i = 0; i < n; i++)
381
            tab[i] <<= lshift;
382
    } else if (lshift < 0) {
383
        lshift = -lshift;
384
        for (i = 0; i < n; i++)
385
            tab[i] >>= lshift;
386
    }
387
}
388

    
389

    
390
/**
391
 * Normalize the input samples to use the maximum available precision.
392
 * This assumes signed 16-bit input samples. Exponents are reduced by 9 to
393
 * match the 24-bit internal precision for MDCT coefficients.
394
 *
395
 * @return exponent shift
396
 */
397
static int normalize_samples(AC3EncodeContext *s,
398
                             int16_t windowed_samples[AC3_WINDOW_SIZE])
399
{
400
    int v = 14 - log2_tab(windowed_samples, AC3_WINDOW_SIZE);
401
    v = FFMAX(0, v);
402
    lshift_tab(windowed_samples, AC3_WINDOW_SIZE, v);
403
    return v - 9;
404
}
405

    
406

    
407
/**
408
 * Apply the MDCT to input samples to generate frequency coefficients.
409
 * This applies the KBD window and normalizes the input to reduce precision
410
 * loss due to fixed-point calculations.
411
 */
412
static void apply_mdct(AC3EncodeContext *s,
413
                       int16_t planar_samples[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE+AC3_FRAME_SIZE],
414
                       int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
415
                       int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
416
{
417
    int blk, ch;
418
    int16_t windowed_samples[AC3_WINDOW_SIZE];
419

    
420
    for (ch = 0; ch < s->channels; ch++) {
421
        for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
422
            const int16_t *input_samples = &planar_samples[ch][blk * AC3_BLOCK_SIZE];
423

    
424
            apply_window(windowed_samples, input_samples, ff_ac3_window, AC3_WINDOW_SIZE);
425

    
426
            exp_shift[blk][ch] = normalize_samples(s, windowed_samples);
427

    
428
            mdct512(mdct_coef[blk][ch], windowed_samples);
429
        }
430
    }
431
}
432

    
433

    
434
/**
435
 * Extract exponents from the MDCT coefficients.
436
 * This takes into account the normalization that was done to the input samples
437
 * by adjusting the exponents by the exponent shift values.
438
 */
439
static void extract_exponents(AC3EncodeContext *s,
440
                              int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
441
                              int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
442
                              uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
443
{
444
    int blk, ch, i;
445

    
446
    /* extract exponents */
447
    for (ch = 0; ch < s->channels; ch++) {
448
        for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
449
            /* compute "exponents". We take into account the normalization there */
450
            for (i = 0; i < AC3_MAX_COEFS; i++) {
451
                int e;
452
                int v = abs(mdct_coef[blk][ch][i]);
453
                if (v == 0)
454
                    e = 24;
455
                else {
456
                    e = 23 - av_log2(v) + exp_shift[blk][ch];
457
                    if (e >= 24) {
458
                        e = 24;
459
                        mdct_coef[blk][ch][i] = 0;
460
                    }
461
                }
462
                exp[blk][ch][i] = e;
463
            }
464
        }
465
    }
466
}
467

    
468

    
469
/**
470
 * Calculate the sum of absolute differences (SAD) between 2 sets of exponents.
471
 */
472
static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n)
473
{
474
    int sum, i;
475
    sum = 0;
476
    for (i = 0; i < n; i++)
477
        sum += abs(exp1[i] - exp2[i]);
478
    return sum;
479
}
480

    
481

    
482
/**
483
 * Exponent Difference Threshold.
484
 * New exponents are sent if their SAD exceed this number.
485
 */
486
#define EXP_DIFF_THRESHOLD 1000
487

    
488

    
489
/**
490
 * Calculate exponent strategies for all blocks in a single channel.
491
 */
492
static void compute_exp_strategy_ch(uint8_t *exp_strategy, uint8_t **exp)
493
{
494
    int blk, blk1;
495
    int exp_diff;
496

    
497
    /* estimate if the exponent variation & decide if they should be
498
       reused in the next frame */
499
    exp_strategy[0] = EXP_NEW;
500
    for (blk = 1; blk < AC3_MAX_BLOCKS; blk++) {
501
        exp_diff = calc_exp_diff(exp[blk], exp[blk-1], AC3_MAX_COEFS);
502
        if (exp_diff > EXP_DIFF_THRESHOLD)
503
            exp_strategy[blk] = EXP_NEW;
504
        else
505
            exp_strategy[blk] = EXP_REUSE;
506
    }
507

    
508
    /* now select the encoding strategy type : if exponents are often
509
       recoded, we use a coarse encoding */
510
    blk = 0;
511
    while (blk < AC3_MAX_BLOCKS) {
512
        blk1 = blk + 1;
513
        while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE)
514
            blk1++;
515
        switch (blk1 - blk) {
516
        case 1:  exp_strategy[blk] = EXP_D45; break;
517
        case 2:
518
        case 3:  exp_strategy[blk] = EXP_D25; break;
519
        default: exp_strategy[blk] = EXP_D15; break;
520
        }
521
        blk = blk1;
522
    }
523
}
524

    
525

    
526
/**
527
 * Calculate exponent strategies for all channels.
528
 * Array arrangement is reversed to simplify the per-channel calculation.
529
 */
530
static void compute_exp_strategy(AC3EncodeContext *s,
531
                                 uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
532
                                 uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
533
{
534
    uint8_t *exp1[AC3_MAX_CHANNELS][AC3_MAX_BLOCKS];
535
    uint8_t exp_str1[AC3_MAX_CHANNELS][AC3_MAX_BLOCKS];
536
    int ch, blk;
537

    
538
    for (ch = 0; ch < s->fbw_channels; ch++) {
539
        for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
540
            exp1[ch][blk]     = exp[blk][ch];
541
            exp_str1[ch][blk] = exp_strategy[blk][ch];
542
        }
543

    
544
        compute_exp_strategy_ch(exp_str1[ch], exp1[ch]);
545

    
546
        for (blk = 0; blk < AC3_MAX_BLOCKS; blk++)
547
            exp_strategy[blk][ch] = exp_str1[ch][blk];
548
    }
549
    if (s->lfe_on) {
550
        ch = s->lfe_channel;
551
        exp_strategy[0][ch] = EXP_D15;
552
        for (blk = 1; blk < 5; blk++)
553
            exp_strategy[blk][ch] = EXP_REUSE;
554
    }
555
}
556

    
557

    
558
/**
559
 * Set each encoded exponent in a block to the minimum of itself and the
560
 * exponent in the same frequency bin of a following block.
561
 * exp[i] = min(exp[i], exp1[i]
562
 */
563
static void exponent_min(uint8_t exp[AC3_MAX_COEFS], uint8_t exp1[AC3_MAX_COEFS], int n)
564
{
565
    int i;
566
    for (i = 0; i < n; i++) {
567
        if (exp1[i] < exp[i])
568
            exp[i] = exp1[i];
569
    }
570
}
571

    
572

    
573
/**
574
 * Update the exponents so that they are the ones the decoder will decode.
575
 */
576
static void encode_exponents_blk_ch(uint8_t encoded_exp[AC3_MAX_COEFS],
577
                                    uint8_t exp[AC3_MAX_COEFS],
578
                                    int nb_exps, int exp_strategy)
579
{
580
    int group_size, nb_groups, i, j, k, exp_min;
581
    uint8_t exp1[AC3_MAX_COEFS];
582

    
583
    group_size = exp_strategy + (exp_strategy == EXP_D45);
584
    nb_groups = ((nb_exps + (group_size * 3) - 4) / (3 * group_size)) * 3;
585

    
586
    /* for each group, compute the minimum exponent */
587
    exp1[0] = exp[0]; /* DC exponent is handled separately */
588
    k = 1;
589
    for (i = 1; i <= nb_groups; i++) {
590
        exp_min = exp[k];
591
        assert(exp_min >= 0 && exp_min <= 24);
592
        for (j = 1; j < group_size; j++) {
593
            if (exp[k+j] < exp_min)
594
                exp_min = exp[k+j];
595
        }
596
        exp1[i] = exp_min;
597
        k += group_size;
598
    }
599

    
600
    /* constraint for DC exponent */
601
    if (exp1[0] > 15)
602
        exp1[0] = 15;
603

    
604
    /* decrease the delta between each groups to within 2 so that they can be
605
       differentially encoded */
606
    for (i = 1; i <= nb_groups; i++)
607
        exp1[i] = FFMIN(exp1[i], exp1[i-1] + 2);
608
    for (i = nb_groups-1; i >= 0; i--)
609
        exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2);
610

    
611
    /* now we have the exponent values the decoder will see */
612
    encoded_exp[0] = exp1[0];
613
    k = 1;
614
    for (i = 1; i <= nb_groups; i++) {
615
        for (j = 0; j < group_size; j++)
616
            encoded_exp[k+j] = exp1[i];
617
        k += group_size;
618
    }
619
}
620

    
621

    
622
/**
623
 * Encode exponents from original extracted form to what the decoder will see.
624
 * This copies and groups exponents based on exponent strategy and reduces
625
 * deltas between adjacent exponent groups so that they can be differentially
626
 * encoded.
627
 */
628
static void encode_exponents(AC3EncodeContext *s,
629
                             uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
630
                             uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
631
                             uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
632
{
633
    int blk, blk1, blk2, ch;
634

    
635
    for (ch = 0; ch < s->channels; ch++) {
636
        /* for the EXP_REUSE case we select the min of the exponents */
637
        blk = 0;
638
        while (blk < AC3_MAX_BLOCKS) {
639
            blk1 = blk + 1;
640
            while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1][ch] == EXP_REUSE) {
641
                exponent_min(exp[blk][ch], exp[blk1][ch], s->nb_coefs[ch]);
642
                blk1++;
643
            }
644
            encode_exponents_blk_ch(encoded_exp[blk][ch],
645
                                                  exp[blk][ch], s->nb_coefs[ch],
646
                                                  exp_strategy[blk][ch]);
647
            /* copy encoded exponents for reuse case */
648
            for (blk2 = blk+1; blk2 < blk1; blk2++) {
649
                memcpy(encoded_exp[blk2][ch], encoded_exp[blk][ch],
650
                       s->nb_coefs[ch] * sizeof(uint8_t));
651
            }
652
            blk = blk1;
653
        }
654
    }
655
}
656

    
657

    
658
/**
659
 * Group exponents.
660
 * 3 delta-encoded exponents are in each 7-bit group. The number of groups
661
 * varies depending on exponent strategy and bandwidth.
662
 * @return bits needed to encode the exponents
663
 */
664
static int group_exponents(AC3EncodeContext *s,
665
                           uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
666
                           uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
667
                           uint8_t num_exp_groups[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
668
                           uint8_t grouped_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_EXP_GROUPS])
669
{
670
    int blk, ch, i;
671
    int group_size, bit_count;
672
    uint8_t *p;
673
    int delta0, delta1, delta2;
674
    int exp0, exp1;
675

    
676
    bit_count = 0;
677
    for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
678
        for (ch = 0; ch < s->channels; ch++) {
679
            if (exp_strategy[blk][ch] == EXP_REUSE) {
680
                num_exp_groups[blk][ch] = 0;
681
                continue;
682
            }
683
            group_size = exp_strategy[blk][ch] + (exp_strategy[blk][ch] == EXP_D45);
684
            num_exp_groups[blk][ch] = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
685
            bit_count += 4 + (num_exp_groups[blk][ch] * 7);
686
            p = encoded_exp[blk][ch];
687

    
688
            /* DC exponent */
689
            exp1 = *p++;
690
            grouped_exp[blk][ch][0] = exp1;
691

    
692
            /* remaining exponents are delta encoded */
693
            for (i = 1; i <= num_exp_groups[blk][ch]; i++) {
694
                /* merge three delta in one code */
695
                exp0   = exp1;
696
                exp1   = p[0];
697
                p     += group_size;
698
                delta0 = exp1 - exp0 + 2;
699

    
700
                exp0   = exp1;
701
                exp1   = p[0];
702
                p     += group_size;
703
                delta1 = exp1 - exp0 + 2;
704

    
705
                exp0   = exp1;
706
                exp1   = p[0];
707
                p     += group_size;
708
                delta2 = exp1 - exp0 + 2;
709

    
710
                grouped_exp[blk][ch][i] = ((delta0 * 5 + delta1) * 5) + delta2;
711
            }
712
        }
713
    }
714

    
715
    return bit_count;
716
}
717

    
718

    
719
/**
720
 * Calculate final exponents from the supplied MDCT coefficients and exponent shift.
721
 * Extract exponents from MDCT coefficients, calculate exponent strategies,
722
 * and encode final exponents.
723
 * @return bits needed to encode the exponents
724
 */
725
static int process_exponents(AC3EncodeContext *s,
726
                             int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
727
                             int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
728
                             uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
729
                             uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
730
                             uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
731
                             uint8_t num_exp_groups[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
732
                             uint8_t grouped_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_EXP_GROUPS])
733
{
734
    extract_exponents(s, mdct_coef, exp_shift, exp);
735

    
736
    compute_exp_strategy(s, exp_strategy, exp);
737

    
738
    encode_exponents(s, exp, exp_strategy, encoded_exp);
739

    
740
    return group_exponents(s, encoded_exp, exp_strategy, num_exp_groups, grouped_exp);
741
}
742

    
743

    
744
/**
745
 * Calculate the number of bits needed to encode a set of mantissas.
746
 */
747
static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs)
748
{
749
    int bits, mant, i;
750

    
751
    bits = 0;
752
    for (i = 0; i < nb_coefs; i++) {
753
        mant = m[i];
754
        switch (mant) {
755
        case 0:
756
            /* nothing */
757
            break;
758
        case 1:
759
            /* 3 mantissa in 5 bits */
760
            if (s->mant1_cnt == 0)
761
                bits += 5;
762
            if (++s->mant1_cnt == 3)
763
                s->mant1_cnt = 0;
764
            break;
765
        case 2:
766
            /* 3 mantissa in 7 bits */
767
            if (s->mant2_cnt == 0)
768
                bits += 7;
769
            if (++s->mant2_cnt == 3)
770
                s->mant2_cnt = 0;
771
            break;
772
        case 3:
773
            bits += 3;
774
            break;
775
        case 4:
776
            /* 2 mantissa in 7 bits */
777
            if (s->mant4_cnt == 0)
778
                bits += 7;
779
            if (++s->mant4_cnt == 2)
780
                s->mant4_cnt = 0;
781
            break;
782
        case 14:
783
            bits += 14;
784
            break;
785
        case 15:
786
            bits += 16;
787
            break;
788
        default:
789
            bits += mant - 1;
790
            break;
791
        }
792
    }
793
    return bits;
794
}
795

    
796

    
797
/**
798
 * Calculate masking curve based on the final exponents.
799
 * Also calculate the power spectral densities to use in future calculations.
800
 */
801
static void bit_alloc_masking(AC3EncodeContext *s,
802
                              uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
803
                              uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
804
                              int16_t psd[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
805
                              int16_t mask[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS])
806
{
807
    int blk, ch;
808
    int16_t band_psd[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS];
809

    
810
    for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
811
        for (ch = 0; ch < s->channels; ch++) {
812
            if(exp_strategy[blk][ch] == EXP_REUSE) {
813
                memcpy(psd[blk][ch],  psd[blk-1][ch],  AC3_MAX_COEFS*sizeof(psd[0][0][0]));
814
                memcpy(mask[blk][ch], mask[blk-1][ch], AC3_CRITICAL_BANDS*sizeof(mask[0][0][0]));
815
            } else {
816
                ff_ac3_bit_alloc_calc_psd(encoded_exp[blk][ch], 0,
817
                                          s->nb_coefs[ch],
818
                                          psd[blk][ch], band_psd[blk][ch]);
819
                ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, band_psd[blk][ch],
820
                                           0, s->nb_coefs[ch],
821
                                           ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
822
                                           ch == s->lfe_channel,
823
                                           DBA_NONE, 0, NULL, NULL, NULL,
824
                                           mask[blk][ch]);
825
            }
826
        }
827
    }
828
}
829

    
830

    
831
/**
832
 * Run the bit allocation with a given SNR offset.
833
 * This calculates the bit allocation pointers that will be used to determine
834
 * the quantization of each mantissa.
835
 * @return the number of remaining bits (positive or negative) if the given
836
 *         SNR offset is used to quantize the mantissas.
837
 */
838
static int bit_alloc(AC3EncodeContext *s,
839
                     int16_t mask[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS],
840
                     int16_t psd[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
841
                     uint8_t bap[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
842
                     int frame_bits, int coarse_snr_offset, int fine_snr_offset)
843
{
844
    int blk, ch;
845
    int snr_offset;
846

    
847
    snr_offset = (((coarse_snr_offset - 15) << 4) + fine_snr_offset) << 2;
848

    
849
    for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
850
        s->mant1_cnt = 0;
851
        s->mant2_cnt = 0;
852
        s->mant4_cnt = 0;
853
        for (ch = 0; ch < s->channels; ch++) {
854
            ff_ac3_bit_alloc_calc_bap(mask[blk][ch], psd[blk][ch], 0,
855
                                      s->nb_coefs[ch], snr_offset,
856
                                      s->bit_alloc.floor, ff_ac3_bap_tab,
857
                                      bap[blk][ch]);
858
            frame_bits += compute_mantissa_size(s, bap[blk][ch], s->nb_coefs[ch]);
859
        }
860
    }
861
    return 8 * s->frame_size - frame_bits;
862
}
863

    
864

    
865
#define SNR_INC1 4
866

    
867
/**
868
 * Perform bit allocation search.
869
 * Finds the SNR offset value that maximizes quality and fits in the specified
870
 * frame size.  Output is the SNR offset and a set of bit allocation pointers
871
 * used to quantize the mantissas.
872
 */
873
static int compute_bit_allocation(AC3EncodeContext *s,
874
                                  uint8_t bap[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
875
                                  uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
876
                                  uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
877
                                  int frame_bits)
878
{
879
    int blk, ch;
880
    int coarse_snr_offset, fine_snr_offset;
881
    uint8_t bap1[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
882
    int16_t psd[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
883
    int16_t mask[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS];
884
    static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
885

    
886
    /* init default parameters */
887
    s->slow_decay_code = 2;
888
    s->fast_decay_code = 1;
889
    s->slow_gain_code  = 1;
890
    s->db_per_bit_code = 2;
891
    s->floor_code      = 4;
892
    for (ch = 0; ch < s->channels; ch++)
893
        s->fast_gain_code[ch] = 4;
894

    
895
    /* compute real values */
896
    s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->bit_alloc.sr_shift;
897
    s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->bit_alloc.sr_shift;
898
    s->bit_alloc.slow_gain  = ff_ac3_slow_gain_tab[s->slow_gain_code];
899
    s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
900
    s->bit_alloc.floor      = ff_ac3_floor_tab[s->floor_code];
901

    
902
    /* header size */
903
    frame_bits += 65;
904
    // if (s->channel_mode == 2)
905
    //    frame_bits += 2;
906
    frame_bits += frame_bits_inc[s->channel_mode];
907

    
908
    /* audio blocks */
909
    for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
910
        frame_bits += s->fbw_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
911
        if (s->channel_mode == AC3_CHMODE_STEREO) {
912
            frame_bits++; /* rematstr */
913
            if (!blk)
914
                frame_bits += 4;
915
        }
916
        frame_bits += 2 * s->fbw_channels; /* chexpstr[2] * c */
917
        if (s->lfe_on)
918
            frame_bits++; /* lfeexpstr */
919
        for (ch = 0; ch < s->fbw_channels; ch++) {
920
            if (exp_strategy[blk][ch] != EXP_REUSE)
921
                frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
922
        }
923
        frame_bits++; /* baie */
924
        frame_bits++; /* snr */
925
        frame_bits += 2; /* delta / skip */
926
    }
927
    frame_bits++; /* cplinu for block 0 */
928
    /* bit alloc info */
929
    /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
930
    /* csnroffset[6] */
931
    /* (fsnoffset[4] + fgaincod[4]) * c */
932
    frame_bits += 2*4 + 3 + 6 + s->channels * (4 + 3);
933

    
934
    /* auxdatae, crcrsv */
935
    frame_bits += 2;
936

    
937
    /* CRC */
938
    frame_bits += 16;
939

    
940
    /* calculate psd and masking curve before doing bit allocation */
941
    bit_alloc_masking(s, encoded_exp, exp_strategy, psd, mask);
942

    
943
    /* now the big work begins : do the bit allocation. Modify the snr
944
       offset until we can pack everything in the requested frame size */
945

    
946
    coarse_snr_offset = s->coarse_snr_offset;
947
    while (coarse_snr_offset >= 0 &&
948
           bit_alloc(s, mask, psd, bap, frame_bits, coarse_snr_offset, 0) < 0)
949
        coarse_snr_offset -= SNR_INC1;
950
    if (coarse_snr_offset < 0) {
951
        av_log(NULL, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
952
        return -1;
953
    }
954
    while (coarse_snr_offset + SNR_INC1 <= 63 &&
955
           bit_alloc(s, mask, psd, bap1, frame_bits,
956
                     coarse_snr_offset + SNR_INC1, 0) >= 0) {
957
        coarse_snr_offset += SNR_INC1;
958
        memcpy(bap, bap1, sizeof(bap1));
959
    }
960
    while (coarse_snr_offset + 1 <= 63 &&
961
           bit_alloc(s, mask, psd, bap1, frame_bits, coarse_snr_offset + 1, 0) >= 0) {
962
        coarse_snr_offset++;
963
        memcpy(bap, bap1, sizeof(bap1));
964
    }
965

    
966
    fine_snr_offset = 0;
967
    while (fine_snr_offset + SNR_INC1 <= 15 &&
968
           bit_alloc(s, mask, psd, bap1, frame_bits,
969
                     coarse_snr_offset, fine_snr_offset + SNR_INC1) >= 0) {
970
        fine_snr_offset += SNR_INC1;
971
        memcpy(bap, bap1, sizeof(bap1));
972
    }
973
    while (fine_snr_offset + 1 <= 15 &&
974
           bit_alloc(s, mask, psd, bap1, frame_bits,
975
                     coarse_snr_offset, fine_snr_offset + 1) >= 0) {
976
        fine_snr_offset++;
977
        memcpy(bap, bap1, sizeof(bap1));
978
    }
979

    
980
    s->coarse_snr_offset = coarse_snr_offset;
981
    for (ch = 0; ch < s->channels; ch++)
982
        s->fine_snr_offset[ch] = fine_snr_offset;
983

    
984
    return 0;
985
}
986

    
987

    
988
/**
989
 * Symmetric quantization on 'levels' levels.
990
 */
991
static inline int sym_quant(int c, int e, int levels)
992
{
993
    int v;
994

    
995
    if (c >= 0) {
996
        v = (levels * (c << e)) >> 24;
997
        v = (v + 1) >> 1;
998
        v = (levels >> 1) + v;
999
    } else {
1000
        v = (levels * ((-c) << e)) >> 24;
1001
        v = (v + 1) >> 1;
1002
        v = (levels >> 1) - v;
1003
    }
1004
    assert (v >= 0 && v < levels);
1005
    return v;
1006
}
1007

    
1008

    
1009
/**
1010
 * Asymmetric quantization on 2^qbits levels.
1011
 */
1012
static inline int asym_quant(int c, int e, int qbits)
1013
{
1014
    int lshift, m, v;
1015

    
1016
    lshift = e + qbits - 24;
1017
    if (lshift >= 0)
1018
        v = c << lshift;
1019
    else
1020
        v = c >> (-lshift);
1021
    /* rounding */
1022
    v = (v + 1) >> 1;
1023
    m = (1 << (qbits-1));
1024
    if (v >= m)
1025
        v = m - 1;
1026
    assert(v >= -m);
1027
    return v & ((1 << qbits)-1);
1028
}
1029

    
1030

    
1031
/**
1032
 * Quantize a set of mantissas for a single channel in a single block.
1033
 */
1034
static void quantize_mantissas_blk_ch(AC3EncodeContext *s,
1035
                                      int32_t *mdct_coef, int8_t exp_shift,
1036
                                      uint8_t *encoded_exp, uint8_t *bap,
1037
                                      uint16_t *qmant, int n)
1038
{
1039
    int i;
1040

    
1041
    for (i = 0; i < n; i++) {
1042
        int v;
1043
        int c = mdct_coef[i];
1044
        int e = encoded_exp[i] - exp_shift;
1045
        int b = bap[i];
1046
        switch (b) {
1047
        case 0:
1048
            v = 0;
1049
            break;
1050
        case 1:
1051
            v = sym_quant(c, e, 3);
1052
            switch (s->mant1_cnt) {
1053
            case 0:
1054
                s->qmant1_ptr = &qmant[i];
1055
                v = 9 * v;
1056
                s->mant1_cnt = 1;
1057
                break;
1058
            case 1:
1059
                *s->qmant1_ptr += 3 * v;
1060
                s->mant1_cnt = 2;
1061
                v = 128;
1062
                break;
1063
            default:
1064
                *s->qmant1_ptr += v;
1065
                s->mant1_cnt = 0;
1066
                v = 128;
1067
                break;
1068
            }
1069
            break;
1070
        case 2:
1071
            v = sym_quant(c, e, 5);
1072
            switch (s->mant2_cnt) {
1073
            case 0:
1074
                s->qmant2_ptr = &qmant[i];
1075
                v = 25 * v;
1076
                s->mant2_cnt = 1;
1077
                break;
1078
            case 1:
1079
                *s->qmant2_ptr += 5 * v;
1080
                s->mant2_cnt = 2;
1081
                v = 128;
1082
                break;
1083
            default:
1084
                *s->qmant2_ptr += v;
1085
                s->mant2_cnt = 0;
1086
                v = 128;
1087
                break;
1088
            }
1089
            break;
1090
        case 3:
1091
            v = sym_quant(c, e, 7);
1092
            break;
1093
        case 4:
1094
            v = sym_quant(c, e, 11);
1095
            switch (s->mant4_cnt) {
1096
            case 0:
1097
                s->qmant4_ptr = &qmant[i];
1098
                v = 11 * v;
1099
                s->mant4_cnt = 1;
1100
                break;
1101
            default:
1102
                *s->qmant4_ptr += v;
1103
                s->mant4_cnt = 0;
1104
                v = 128;
1105
                break;
1106
            }
1107
            break;
1108
        case 5:
1109
            v = sym_quant(c, e, 15);
1110
            break;
1111
        case 14:
1112
            v = asym_quant(c, e, 14);
1113
            break;
1114
        case 15:
1115
            v = asym_quant(c, e, 16);
1116
            break;
1117
        default:
1118
            v = asym_quant(c, e, b - 1);
1119
            break;
1120
        }
1121
        qmant[i] = v;
1122
    }
1123
}
1124

    
1125

    
1126
/**
1127
 * Quantize mantissas using coefficients, exponents, and bit allocation pointers.
1128
 */
1129
static void quantize_mantissas(AC3EncodeContext *s,
1130
                               int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
1131
                               int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
1132
                               uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
1133
                               uint8_t bap[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
1134
                               uint16_t qmant[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
1135
{
1136
    int blk, ch;
1137

    
1138

    
1139
    for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1140
        s->mant1_cnt  = s->mant2_cnt  = s->mant4_cnt  = 0;
1141
        s->qmant1_ptr = s->qmant2_ptr = s->qmant4_ptr = NULL;
1142

    
1143
        for (ch = 0; ch < s->channels; ch++) {
1144
            quantize_mantissas_blk_ch(s, mdct_coef[blk][ch], exp_shift[blk][ch],
1145
                                      encoded_exp[blk][ch], bap[blk][ch],
1146
                                      qmant[blk][ch], s->nb_coefs[ch]);
1147
        }
1148
    }
1149
}
1150

    
1151

    
1152
/**
1153
 * Write the AC-3 frame header to the output bitstream.
1154
 */
1155
static void output_frame_header(AC3EncodeContext *s)
1156
{
1157
    put_bits(&s->pb, 16, 0x0b77);   /* frame header */
1158
    put_bits(&s->pb, 16, 0);        /* crc1: will be filled later */
1159
    put_bits(&s->pb, 2,  s->bit_alloc.sr_code);
1160
    put_bits(&s->pb, 6,  s->frame_size_code + (s->frame_size - s->frame_size_min) / 2);
1161
    put_bits(&s->pb, 5,  s->bitstream_id);
1162
    put_bits(&s->pb, 3,  s->bitstream_mode);
1163
    put_bits(&s->pb, 3,  s->channel_mode);
1164
    if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)
1165
        put_bits(&s->pb, 2, 1);     /* XXX -4.5 dB */
1166
    if (s->channel_mode & 0x04)
1167
        put_bits(&s->pb, 2, 1);     /* XXX -6 dB */
1168
    if (s->channel_mode == AC3_CHMODE_STEREO)
1169
        put_bits(&s->pb, 2, 0);     /* surround not indicated */
1170
    put_bits(&s->pb, 1, s->lfe_on); /* LFE */
1171
    put_bits(&s->pb, 5, 31);        /* dialog norm: -31 db */
1172
    put_bits(&s->pb, 1, 0);         /* no compression control word */
1173
    put_bits(&s->pb, 1, 0);         /* no lang code */
1174
    put_bits(&s->pb, 1, 0);         /* no audio production info */
1175
    put_bits(&s->pb, 1, 0);         /* no copyright */
1176
    put_bits(&s->pb, 1, 1);         /* original bitstream */
1177
    put_bits(&s->pb, 1, 0);         /* no time code 1 */
1178
    put_bits(&s->pb, 1, 0);         /* no time code 2 */
1179
    put_bits(&s->pb, 1, 0);         /* no additional bit stream info */
1180
}
1181

    
1182

    
1183
/**
1184
 * Write one audio block to the output bitstream.
1185
 */
1186
static void output_audio_block(AC3EncodeContext *s,
1187
                               uint8_t exp_strategy[AC3_MAX_CHANNELS],
1188
                               uint8_t num_exp_groups[AC3_MAX_CHANNELS],
1189
                               uint8_t grouped_exp[AC3_MAX_CHANNELS][AC3_MAX_EXP_GROUPS],
1190
                               uint8_t bap[AC3_MAX_CHANNELS][AC3_MAX_COEFS],
1191
                               uint16_t qmant[AC3_MAX_CHANNELS][AC3_MAX_COEFS],
1192
                               int block_num)
1193
{
1194
    int ch, i, baie, rbnd;
1195

    
1196
    for (ch = 0; ch < s->fbw_channels; ch++)
1197
        put_bits(&s->pb, 1, 0); /* no block switching */
1198
    for (ch = 0; ch < s->fbw_channels; ch++)
1199
        put_bits(&s->pb, 1, 1); /* no dither */
1200
    put_bits(&s->pb, 1, 0);     /* no dynamic range */
1201
    if (!block_num) {
1202
        put_bits(&s->pb, 1, 1); /* coupling strategy present */
1203
        put_bits(&s->pb, 1, 0); /* no coupling strategy */
1204
    } else {
1205
        put_bits(&s->pb, 1, 0); /* no new coupling strategy */
1206
    }
1207

    
1208
    if (s->channel_mode == AC3_CHMODE_STEREO) {
1209
        if (!block_num) {
1210
            /* first block must define rematrixing (rematstr) */
1211
            put_bits(&s->pb, 1, 1);
1212

    
1213
            /* dummy rematrixing rematflg(1:4)=0 */
1214
            for (rbnd = 0; rbnd < 4; rbnd++)
1215
                put_bits(&s->pb, 1, 0);
1216
        } else {
1217
            /* no matrixing (but should be used in the future) */
1218
            put_bits(&s->pb, 1, 0);
1219
        }
1220
    }
1221

    
1222
    /* exponent strategy */
1223
    for (ch = 0; ch < s->fbw_channels; ch++)
1224
        put_bits(&s->pb, 2, exp_strategy[ch]);
1225

    
1226
    if (s->lfe_on)
1227
        put_bits(&s->pb, 1, exp_strategy[s->lfe_channel]);
1228

    
1229
    /* bandwidth */
1230
    for (ch = 0; ch < s->fbw_channels; ch++) {
1231
        if (exp_strategy[ch] != EXP_REUSE)
1232
            put_bits(&s->pb, 6, s->bandwidth_code[ch]);
1233
    }
1234

    
1235
    /* exponents */
1236
    for (ch = 0; ch < s->channels; ch++) {
1237
        if (exp_strategy[ch] == EXP_REUSE)
1238
            continue;
1239

    
1240
        /* first exponent */
1241
        put_bits(&s->pb, 4, grouped_exp[ch][0]);
1242

    
1243
        /* next ones are delta-encoded and grouped */
1244
        for (i = 1; i <= num_exp_groups[ch]; i++)
1245
            put_bits(&s->pb, 7, grouped_exp[ch][i]);
1246

    
1247
        if (ch != s->lfe_channel)
1248
            put_bits(&s->pb, 2, 0); /* no gain range info */
1249
    }
1250

    
1251
    /* bit allocation info */
1252
    baie = (block_num == 0);
1253
    put_bits(&s->pb, 1, baie);
1254
    if (baie) {
1255
        put_bits(&s->pb, 2, s->slow_decay_code);
1256
        put_bits(&s->pb, 2, s->fast_decay_code);
1257
        put_bits(&s->pb, 2, s->slow_gain_code);
1258
        put_bits(&s->pb, 2, s->db_per_bit_code);
1259
        put_bits(&s->pb, 3, s->floor_code);
1260
    }
1261

    
1262
    /* snr offset */
1263
    put_bits(&s->pb, 1, baie);
1264
    if (baie) {
1265
        put_bits(&s->pb, 6, s->coarse_snr_offset);
1266
        for (ch = 0; ch < s->channels; ch++) {
1267
            put_bits(&s->pb, 4, s->fine_snr_offset[ch]);
1268
            put_bits(&s->pb, 3, s->fast_gain_code[ch]);
1269
        }
1270
    }
1271

    
1272
    put_bits(&s->pb, 1, 0); /* no delta bit allocation */
1273
    put_bits(&s->pb, 1, 0); /* no data to skip */
1274

    
1275
    /* mantissa encoding */
1276
    for (ch = 0; ch < s->channels; ch++) {
1277
        int b, q;
1278

    
1279
        for (i = 0; i < s->nb_coefs[ch]; i++) {
1280
            q = qmant[ch][i];
1281
            b = bap[ch][i];
1282
            switch (b) {
1283
            case 0:                                         break;
1284
            case 1: if (q != 128) put_bits(&s->pb,   5, q); break;
1285
            case 2: if (q != 128) put_bits(&s->pb,   7, q); break;
1286
            case 3:               put_bits(&s->pb,   3, q); break;
1287
            case 4: if (q != 128) put_bits(&s->pb,   7, q); break;
1288
            case 14:              put_bits(&s->pb,  14, q); break;
1289
            case 15:              put_bits(&s->pb,  16, q); break;
1290
            default:              put_bits(&s->pb, b-1, q); break;
1291
            }
1292
        }
1293
    }
1294
}
1295

    
1296

    
1297
/** CRC-16 Polynomial */
1298
#define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
1299

    
1300

    
1301
static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
1302
{
1303
    unsigned int c;
1304

    
1305
    c = 0;
1306
    while (a) {
1307
        if (a & 1)
1308
            c ^= b;
1309
        a = a >> 1;
1310
        b = b << 1;
1311
        if (b & (1 << 16))
1312
            b ^= poly;
1313
    }
1314
    return c;
1315
}
1316

    
1317

    
1318
static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
1319
{
1320
    unsigned int r;
1321
    r = 1;
1322
    while (n) {
1323
        if (n & 1)
1324
            r = mul_poly(r, a, poly);
1325
        a = mul_poly(a, a, poly);
1326
        n >>= 1;
1327
    }
1328
    return r;
1329
}
1330

    
1331

    
1332
/**
1333
 * Fill the end of the frame with 0's and compute the two CRCs.
1334
 */
1335
static void output_frame_end(AC3EncodeContext *s)
1336
{
1337
    int frame_size, frame_size_58, pad_bytes, crc1, crc2, crc_inv;
1338
    uint8_t *frame;
1339

    
1340
    frame_size = s->frame_size; /* frame size in words */
1341
    /* align to 8 bits */
1342
    flush_put_bits(&s->pb);
1343
    /* add zero bytes to reach the frame size */
1344
    frame = s->pb.buf;
1345
    pad_bytes = s->frame_size - (put_bits_ptr(&s->pb) - frame) - 2;
1346
    assert(pad_bytes >= 0);
1347
    if (pad_bytes > 0)
1348
        memset(put_bits_ptr(&s->pb), 0, pad_bytes);
1349

    
1350
    /* Now we must compute both crcs : this is not so easy for crc1
1351
       because it is at the beginning of the data... */
1352
    frame_size_58 = ((frame_size >> 2) + (frame_size >> 4)) << 1;
1353

    
1354
    crc1 = av_bswap16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
1355
                             frame + 4, frame_size_58 - 4));
1356

    
1357
    /* XXX: could precompute crc_inv */
1358
    crc_inv = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
1359
    crc1    = mul_poly(crc_inv, crc1, CRC16_POLY);
1360
    AV_WB16(frame + 2, crc1);
1361

    
1362
    crc2 = av_bswap16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
1363
                             frame + frame_size_58,
1364
                             frame_size - frame_size_58 - 2));
1365
    AV_WB16(frame + frame_size - 2, crc2);
1366
}
1367

    
1368

    
1369
/**
1370
 * Write the frame to the output bitstream.
1371
 */
1372
static void output_frame(AC3EncodeContext *s,
1373
                         unsigned char *frame,
1374
                         uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
1375
                         uint8_t num_exp_groups[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
1376
                         uint8_t grouped_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_EXP_GROUPS],
1377
                         uint8_t bap[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
1378
                         uint16_t qmant[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
1379
{
1380
    int blk;
1381

    
1382
    init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
1383

    
1384
    output_frame_header(s);
1385

    
1386
    for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1387
        output_audio_block(s, exp_strategy[blk], num_exp_groups[blk],
1388
                           grouped_exp[blk], bap[blk], qmant[blk], blk);
1389
    }
1390

    
1391
    output_frame_end(s);
1392
}
1393

    
1394

    
1395
/**
1396
 * Encode a single AC-3 frame.
1397
 */
1398
static int ac3_encode_frame(AVCodecContext *avctx,
1399
                            unsigned char *frame, int buf_size, void *data)
1400
{
1401
    AC3EncodeContext *s = avctx->priv_data;
1402
    const int16_t *samples = data;
1403
    int16_t planar_samples[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE+AC3_FRAME_SIZE];
1404
    int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
1405
    uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
1406
    uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS];
1407
    uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
1408
    uint8_t num_exp_groups[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS];
1409
    uint8_t grouped_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_EXP_GROUPS];
1410
    uint8_t bap[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
1411
    int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS];
1412
    uint16_t qmant[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
1413
    int frame_bits;
1414

    
1415
    if (s->bit_alloc.sr_code == 1)
1416
        adjust_frame_size(s);
1417

    
1418
    deinterleave_input_samples(s, samples, planar_samples);
1419

    
1420
    apply_mdct(s, planar_samples, exp_shift, mdct_coef);
1421

    
1422
    frame_bits = process_exponents(s, mdct_coef, exp_shift, exp, exp_strategy,
1423
                                   encoded_exp, num_exp_groups, grouped_exp);
1424

    
1425
    compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);
1426

    
1427
    quantize_mantissas(s, mdct_coef, exp_shift, encoded_exp, bap, qmant);
1428

    
1429
    output_frame(s, frame, exp_strategy, num_exp_groups, grouped_exp, bap, qmant);
1430

    
1431
    return s->frame_size;
1432
}
1433

    
1434

    
1435
/**
1436
 * Finalize encoding and free any memory allocated by the encoder.
1437
 */
1438
static av_cold int ac3_encode_close(AVCodecContext *avctx)
1439
{
1440
    av_freep(&avctx->coded_frame);
1441
    return 0;
1442
}
1443

    
1444

    
1445
/**
1446
 * Set channel information during initialization.
1447
 */
1448
static av_cold int set_channel_info(AC3EncodeContext *s, int channels,
1449
                                    int64_t *channel_layout)
1450
{
1451
    int ch_layout;
1452

    
1453
    if (channels < 1 || channels > AC3_MAX_CHANNELS)
1454
        return AVERROR(EINVAL);
1455
    if ((uint64_t)*channel_layout > 0x7FF)
1456
        return AVERROR(EINVAL);
1457
    ch_layout = *channel_layout;
1458
    if (!ch_layout)
1459
        ch_layout = avcodec_guess_channel_layout(channels, CODEC_ID_AC3, NULL);
1460
    if (av_get_channel_layout_nb_channels(ch_layout) != channels)
1461
        return AVERROR(EINVAL);
1462

    
1463
    s->lfe_on       = !!(ch_layout & AV_CH_LOW_FREQUENCY);
1464
    s->channels     = channels;
1465
    s->fbw_channels = channels - s->lfe_on;
1466
    s->lfe_channel  = s->lfe_on ? s->fbw_channels : -1;
1467
    if (s->lfe_on)
1468
        ch_layout -= AV_CH_LOW_FREQUENCY;
1469

    
1470
    switch (ch_layout) {
1471
    case AV_CH_LAYOUT_MONO:           s->channel_mode = AC3_CHMODE_MONO;   break;
1472
    case AV_CH_LAYOUT_STEREO:         s->channel_mode = AC3_CHMODE_STEREO; break;
1473
    case AV_CH_LAYOUT_SURROUND:       s->channel_mode = AC3_CHMODE_3F;     break;
1474
    case AV_CH_LAYOUT_2_1:            s->channel_mode = AC3_CHMODE_2F1R;   break;
1475
    case AV_CH_LAYOUT_4POINT0:        s->channel_mode = AC3_CHMODE_3F1R;   break;
1476
    case AV_CH_LAYOUT_QUAD:
1477
    case AV_CH_LAYOUT_2_2:            s->channel_mode = AC3_CHMODE_2F2R;   break;
1478
    case AV_CH_LAYOUT_5POINT0:
1479
    case AV_CH_LAYOUT_5POINT0_BACK:   s->channel_mode = AC3_CHMODE_3F2R;   break;
1480
    default:
1481
        return AVERROR(EINVAL);
1482
    }
1483

    
1484
    s->channel_map  = ff_ac3_enc_channel_map[s->channel_mode][s->lfe_on];
1485
    *channel_layout = ch_layout;
1486
    if (s->lfe_on)
1487
        *channel_layout |= AV_CH_LOW_FREQUENCY;
1488

    
1489
    return 0;
1490
}
1491

    
1492

    
1493
static av_cold int validate_options(AVCodecContext *avctx, AC3EncodeContext *s)
1494
{
1495
    int i, ret;
1496

    
1497
    /* validate channel layout */
1498
    if (!avctx->channel_layout) {
1499
        av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The "
1500
                                      "encoder will guess the layout, but it "
1501
                                      "might be incorrect.\n");
1502
    }
1503
    ret = set_channel_info(s, avctx->channels, &avctx->channel_layout);
1504
    if (ret) {
1505
        av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n");
1506
        return ret;
1507
    }
1508

    
1509
    /* validate sample rate */
1510
    for (i = 0; i < 9; i++) {
1511
        if ((ff_ac3_sample_rate_tab[i / 3] >> (i % 3)) == avctx->sample_rate)
1512
            break;
1513
    }
1514
    if (i == 9) {
1515
        av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1516
        return AVERROR(EINVAL);
1517
    }
1518
    s->sample_rate        = avctx->sample_rate;
1519
    s->bit_alloc.sr_shift = i % 3;
1520
    s->bit_alloc.sr_code  = i / 3;
1521

    
1522
    /* validate bit rate */
1523
    for (i = 0; i < 19; i++) {
1524
        if ((ff_ac3_bitrate_tab[i] >> s->bit_alloc.sr_shift)*1000 == avctx->bit_rate)
1525
            break;
1526
    }
1527
    if (i == 19) {
1528
        av_log(avctx, AV_LOG_ERROR, "invalid bit rate\n");
1529
        return AVERROR(EINVAL);
1530
    }
1531
    s->bit_rate        = avctx->bit_rate;
1532
    s->frame_size_code = i << 1;
1533

    
1534
    return 0;
1535
}
1536

    
1537

    
1538
/**
1539
 * Set bandwidth for all channels.
1540
 * The user can optionally supply a cutoff frequency. Otherwise an appropriate
1541
 * default value will be used.
1542
 */
1543
static av_cold void set_bandwidth(AC3EncodeContext *s, int cutoff)
1544
{
1545
    int ch, bw_code;
1546

    
1547
    if (cutoff) {
1548
        /* calculate bandwidth based on user-specified cutoff frequency */
1549
        int fbw_coeffs;
1550
        cutoff         = av_clip(cutoff, 1, s->sample_rate >> 1);
1551
        fbw_coeffs     = cutoff * 2 * AC3_MAX_COEFS / s->sample_rate;
1552
        bw_code        = av_clip((fbw_coeffs - 73) / 3, 0, 60);
1553
    } else {
1554
        /* use default bandwidth setting */
1555
        /* XXX: should compute the bandwidth according to the frame
1556
           size, so that we avoid annoying high frequency artifacts */
1557
        bw_code = 50;
1558
    }
1559

    
1560
    /* set number of coefficients for each channel */
1561
    for (ch = 0; ch < s->fbw_channels; ch++) {
1562
        s->bandwidth_code[ch] = bw_code;
1563
        s->nb_coefs[ch]       = bw_code * 3 + 73;
1564
    }
1565
    if (s->lfe_on)
1566
        s->nb_coefs[s->lfe_channel] = 7; /* LFE channel always has 7 coefs */
1567
}
1568

    
1569

    
1570
/**
1571
 * Initialize the encoder.
1572
 */
1573
static av_cold int ac3_encode_init(AVCodecContext *avctx)
1574
{
1575
    AC3EncodeContext *s = avctx->priv_data;
1576
    int ret;
1577

    
1578
    avctx->frame_size = AC3_FRAME_SIZE;
1579

    
1580
    ac3_common_init();
1581

    
1582
    ret = validate_options(avctx, s);
1583
    if (ret)
1584
        return ret;
1585

    
1586
    s->bitstream_id   = 8 + s->bit_alloc.sr_shift;
1587
    s->bitstream_mode = 0; /* complete main audio service */
1588

    
1589
    s->frame_size_min  = 2 * ff_ac3_frame_size_tab[s->frame_size_code][s->bit_alloc.sr_code];
1590
    s->bits_written    = 0;
1591
    s->samples_written = 0;
1592
    s->frame_size      = s->frame_size_min;
1593

    
1594
    set_bandwidth(s, avctx->cutoff);
1595

    
1596
    /* initial snr offset */
1597
    s->coarse_snr_offset = 40;
1598

    
1599
    mdct_init(9);
1600

    
1601
    avctx->coded_frame= avcodec_alloc_frame();
1602
    avctx->coded_frame->key_frame= 1;
1603

    
1604
    return 0;
1605
}
1606

    
1607

    
1608
#ifdef TEST
1609
/*************************************************************************/
1610
/* TEST */
1611

    
1612
#include "libavutil/lfg.h"
1613

    
1614
#define FN (MDCT_SAMPLES/4)
1615

    
1616

    
1617
static void fft_test(AVLFG *lfg)
1618
{
1619
    IComplex in[FN], in1[FN];
1620
    int k, n, i;
1621
    float sum_re, sum_im, a;
1622

    
1623
    for (i = 0; i < FN; i++) {
1624
        in[i].re = av_lfg_get(lfg) % 65535 - 32767;
1625
        in[i].im = av_lfg_get(lfg) % 65535 - 32767;
1626
        in1[i]   = in[i];
1627
    }
1628
    fft(in, 7);
1629

    
1630
    /* do it by hand */
1631
    for (k = 0; k < FN; k++) {
1632
        sum_re = 0;
1633
        sum_im = 0;
1634
        for (n = 0; n < FN; n++) {
1635
            a = -2 * M_PI * (n * k) / FN;
1636
            sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);
1637
            sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);
1638
        }
1639
        av_log(NULL, AV_LOG_DEBUG, "%3d: %6d,%6d %6.0f,%6.0f\n",
1640
               k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);
1641
    }
1642
}
1643

    
1644

    
1645
static void mdct_test(AVLFG *lfg)
1646
{
1647
    int16_t input[MDCT_SAMPLES];
1648
    int32_t output[AC3_MAX_COEFS];
1649
    float input1[MDCT_SAMPLES];
1650
    float output1[AC3_MAX_COEFS];
1651
    float s, a, err, e, emax;
1652
    int i, k, n;
1653

    
1654
    for (i = 0; i < MDCT_SAMPLES; i++) {
1655
        input[i]  = (av_lfg_get(lfg) % 65535 - 32767) * 9 / 10;
1656
        input1[i] = input[i];
1657
    }
1658

    
1659
    mdct512(output, input);
1660

    
1661
    /* do it by hand */
1662
    for (k = 0; k < AC3_MAX_COEFS; k++) {
1663
        s = 0;
1664
        for (n = 0; n < MDCT_SAMPLES; n++) {
1665
            a = (2*M_PI*(2*n+1+MDCT_SAMPLES/2)*(2*k+1) / (4 * MDCT_SAMPLES));
1666
            s += input1[n] * cos(a);
1667
        }
1668
        output1[k] = -2 * s / MDCT_SAMPLES;
1669
    }
1670

    
1671
    err  = 0;
1672
    emax = 0;
1673
    for (i = 0; i < AC3_MAX_COEFS; i++) {
1674
        av_log(NULL, AV_LOG_DEBUG, "%3d: %7d %7.0f\n", i, output[i], output1[i]);
1675
        e = output[i] - output1[i];
1676
        if (e > emax)
1677
            emax = e;
1678
        err += e * e;
1679
    }
1680
    av_log(NULL, AV_LOG_DEBUG, "err2=%f emax=%f\n", err / AC3_MAX_COEFS, emax);
1681
}
1682

    
1683

    
1684
int main(void)
1685
{
1686
    AVLFG lfg;
1687

    
1688
    av_log_set_level(AV_LOG_DEBUG);
1689
    mdct_init(9);
1690

    
1691
    fft_test(&lfg);
1692
    mdct_test(&lfg);
1693

    
1694
    return 0;
1695
}
1696
#endif /* TEST */
1697

    
1698

    
1699
AVCodec ac3_encoder = {
1700
    "ac3",
1701
    AVMEDIA_TYPE_AUDIO,
1702
    CODEC_ID_AC3,
1703
    sizeof(AC3EncodeContext),
1704
    ac3_encode_init,
1705
    ac3_encode_frame,
1706
    ac3_encode_close,
1707
    NULL,
1708
    .sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE},
1709
    .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
1710
    .channel_layouts = (const int64_t[]){
1711
        AV_CH_LAYOUT_MONO,
1712
        AV_CH_LAYOUT_STEREO,
1713
        AV_CH_LAYOUT_2_1,
1714
        AV_CH_LAYOUT_SURROUND,
1715
        AV_CH_LAYOUT_2_2,
1716
        AV_CH_LAYOUT_QUAD,
1717
        AV_CH_LAYOUT_4POINT0,
1718
        AV_CH_LAYOUT_5POINT0,
1719
        AV_CH_LAYOUT_5POINT0_BACK,
1720
       (AV_CH_LAYOUT_MONO     | AV_CH_LOW_FREQUENCY),
1721
       (AV_CH_LAYOUT_STEREO   | AV_CH_LOW_FREQUENCY),
1722
       (AV_CH_LAYOUT_2_1      | AV_CH_LOW_FREQUENCY),
1723
       (AV_CH_LAYOUT_SURROUND | AV_CH_LOW_FREQUENCY),
1724
       (AV_CH_LAYOUT_2_2      | AV_CH_LOW_FREQUENCY),
1725
       (AV_CH_LAYOUT_QUAD     | AV_CH_LOW_FREQUENCY),
1726
       (AV_CH_LAYOUT_4POINT0  | AV_CH_LOW_FREQUENCY),
1727
        AV_CH_LAYOUT_5POINT1,
1728
        AV_CH_LAYOUT_5POINT1_BACK,
1729
        0 },
1730
};