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/*
2
 * The simplest AC-3 encoder
3
 * Copyright (c) 2000 Fabrice Bellard
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 *
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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
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 * 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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 */
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22
/**
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 * @file
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 * The simplest AC-3 encoder.
25
 */
26

    
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//#define DEBUG
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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

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

    
40
/** 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)))
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43
/** 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))
45

    
46

    
47
/**
48
 * Compex number.
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 * Used in fixed-point MDCT calculation.
50
 */
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typedef struct IComplex {
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    int16_t re,im;
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} IComplex;
54

    
55
/**
56
 * AC-3 encoder private context.
57
 */
58
typedef struct AC3EncodeContext {
59
    PutBitContext pb;                       ///< bitstream writer context
60

    
61
    int bitstream_id;                       ///< bitstream id                           (bsid)
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    int bitstream_mode;                     ///< bitstream mode                         (bsmod)
63

    
64
    int bit_rate;                           ///< target bit rate, in bits-per-second
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    int sample_rate;                        ///< sampling frequency, in Hz
66

    
67
    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)
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73
    int fbw_channels;                       ///< number of full-bandwidth channels      (nfchans)
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    int channels;                           ///< total number of channels               (nchans)
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    int lfe_on;                             ///< indicates if there is an LFE channel   (lfeon)
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    int lfe_channel;                        ///< channel index of the LFE channel
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    int channel_mode;                       ///< channel mode                           (acmod)
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    const uint8_t *channel_map;             ///< channel map used to reorder channels
79

    
80
    int bandwidth_code[AC3_MAX_CHANNELS];   ///< bandwidth code (0 to 60)               (chbwcod)
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    int nb_coefs[AC3_MAX_CHANNELS];
82

    
83
    /* bitrate allocation control */
84
    int slow_gain_code;                     ///< slow gain code                         (sgaincod)
85
    int slow_decay_code;                    ///< slow decay code                        (sdcycod)
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    int fast_decay_code;                    ///< fast decay code                        (fdcycod)
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    int db_per_bit_code;                    ///< dB/bit code                            (dbpbcod)
88
    int floor_code;                         ///< floor code                             (floorcod)
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    AC3BitAllocParameters bit_alloc;        ///< bit allocation parameters
90
    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)
93

    
94
    /* mantissa encoding */
95
    int mant1_cnt, mant2_cnt, mant4_cnt;    ///< mantissa counts for bap=1,2,4
96

    
97
    int16_t last_samples[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE]; ///< last 256 samples from previous frame
98
} AC3EncodeContext;
99

    
100

    
101
/** MDCT and FFT tables */
102
static int16_t costab[64];
103
static int16_t sintab[64];
104
static int16_t xcos1[128];
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static int16_t xsin1[128];
106

    
107

    
108
/**
109
 * Adjust the frame size to make the average bit rate match the target bit rate.
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 * This is only needed for 11025, 22050, and 44100 sample rates.
111
 */
112
static void adjust_frame_size(AC3EncodeContext *s)
113
{
114
    while (s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
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        s->bits_written    -= s->bit_rate;
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        s->samples_written -= s->sample_rate;
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    }
118
    s->frame_size = s->frame_size_min + 2 * (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
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    s->bits_written    += s->frame_size * 8;
120
    s->samples_written += AC3_FRAME_SIZE;
121
}
122

    
123

    
124
/**
125
 * Deinterleave input samples.
126
 * Channels are reordered from FFmpeg's default order to AC-3 order.
127
 */
128
static void deinterleave_input_samples(AC3EncodeContext *s,
129
                                       const int16_t *samples,
130
                                       int16_t planar_samples[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE+AC3_FRAME_SIZE])
131
{
132
    int ch, i;
133

    
134
    /* deinterleave and remap input samples */
135
    for (ch = 0; ch < s->channels; ch++) {
136
        const int16_t *sptr;
137
        int sinc;
138

    
139
        /* copy last 256 samples of previous frame to the start of the current frame */
140
        memcpy(&planar_samples[ch][0], s->last_samples[ch],
141
               AC3_BLOCK_SIZE * sizeof(planar_samples[0][0]));
142

    
143
        /* deinterleave */
144
        sinc = s->channels;
145
        sptr = samples + s->channel_map[ch];
146
        for (i = AC3_BLOCK_SIZE; i < AC3_FRAME_SIZE+AC3_BLOCK_SIZE; i++) {
147
            planar_samples[ch][i] = *sptr;
148
            sptr += sinc;
149
        }
150

    
151
        /* save last 256 samples for next frame */
152
        memcpy(s->last_samples[ch], &planar_samples[ch][6* AC3_BLOCK_SIZE],
153
               AC3_BLOCK_SIZE * sizeof(planar_samples[0][0]));
154
    }
155
}
156

    
157

    
158
/**
159
 * Initialize FFT tables.
160
 * @param ln log2(FFT size)
161
 */
162
static av_cold void fft_init(int ln)
163
{
164
    int i, n, n2;
165
    float alpha;
166

    
167
    n  = 1 << ln;
168
    n2 = n >> 1;
169

    
170
    for (i = 0; i < n2; i++) {
171
        alpha     = 2.0 * M_PI * i / n;
172
        costab[i] = FIX15(cos(alpha));
173
        sintab[i] = FIX15(sin(alpha));
174
    }
175
}
176

    
177

    
178
/**
179
 * Initialize MDCT tables.
180
 * @param nbits log2(MDCT size)
181
 */
182
static av_cold void mdct_init(int nbits)
183
{
184
    int i, n, n4;
185

    
186
    n  = 1 << nbits;
187
    n4 = n >> 2;
188

    
189
    fft_init(nbits - 2);
190

    
191
    for (i = 0; i < n4; i++) {
192
        float alpha = 2.0 * M_PI * (i + 1.0 / 8.0) / n;
193
        xcos1[i] = FIX15(-cos(alpha));
194
        xsin1[i] = FIX15(-sin(alpha));
195
    }
196
}
197

    
198

    
199
/** Butterfly op */
200
#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1)  \
201
{                                                       \
202
  int ax, ay, bx, by;                                   \
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  bx  = pre1;                                           \
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  by  = pim1;                                           \
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  ax  = qre1;                                           \
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  ay  = qim1;                                           \
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  pre = (bx + ax) >> 1;                                 \
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  pim = (by + ay) >> 1;                                 \
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  qre = (bx - ax) >> 1;                                 \
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  qim = (by - ay) >> 1;                                 \
211
}
212

    
213

    
214
/** Complex multiply */
215
#define CMUL(pre, pim, are, aim, bre, bim)              \
216
{                                                       \
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   pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15;     \
218
   pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;     \
219
}
220

    
221

    
222
/**
223
 * Calculate a 2^n point complex FFT on 2^ln points.
224
 * @param z  complex input/output samples
225
 * @param ln log2(FFT size)
226
 */
227
static void fft(IComplex *z, int ln)
228
{
229
    int j, l, np, np2;
230
    int nblocks, nloops;
231
    register IComplex *p,*q;
232
    int tmp_re, tmp_im;
233

    
234
    np = 1 << ln;
235

    
236
    /* reverse */
237
    for (j = 0; j < np; j++) {
238
        int k = av_reverse[j] >> (8 - ln);
239
        if (k < j)
240
            FFSWAP(IComplex, z[k], z[j]);
241
    }
242

    
243
    /* pass 0 */
244

    
245
    p = &z[0];
246
    j = np >> 1;
247
    do {
248
        BF(p[0].re, p[0].im, p[1].re, p[1].im,
249
           p[0].re, p[0].im, p[1].re, p[1].im);
250
        p += 2;
251
    } while (--j);
252

    
253
    /* pass 1 */
254

    
255
    p = &z[0];
256
    j = np >> 2;
257
    do {
258
        BF(p[0].re, p[0].im, p[2].re,  p[2].im,
259
           p[0].re, p[0].im, p[2].re,  p[2].im);
260
        BF(p[1].re, p[1].im, p[3].re,  p[3].im,
261
           p[1].re, p[1].im, p[3].im, -p[3].re);
262
        p+=4;
263
    } while (--j);
264

    
265
    /* pass 2 .. ln-1 */
266

    
267
    nblocks = np >> 3;
268
    nloops  =  1 << 2;
269
    np2     = np >> 1;
270
    do {
271
        p = z;
272
        q = z + nloops;
273
        for (j = 0; j < nblocks; j++) {
274
            BF(p->re, p->im, q->re, q->im,
275
               p->re, p->im, q->re, q->im);
276
            p++;
277
            q++;
278
            for(l = nblocks; l < np2; l += nblocks) {
279
                CMUL(tmp_re, tmp_im, costab[l], -sintab[l], q->re, q->im);
280
                BF(p->re, p->im, q->re,  q->im,
281
                   p->re, p->im, tmp_re, tmp_im);
282
                p++;
283
                q++;
284
            }
285
            p += nloops;
286
            q += nloops;
287
        }
288
        nblocks = nblocks >> 1;
289
        nloops  = nloops  << 1;
290
    } while (nblocks);
291
}
292

    
293

    
294
/**
295
 * Calculate a 512-point MDCT
296
 * @param out 256 output frequency coefficients
297
 * @param in  512 windowed input audio samples
298
 */
299
static void mdct512(int32_t *out, int16_t *in)
300
{
301
    int i, re, im, re1, im1;
302
    int16_t rot[MDCT_SAMPLES];
303
    IComplex x[MDCT_SAMPLES/4];
304

    
305
    /* shift to simplify computations */
306
    for (i = 0; i < MDCT_SAMPLES/4; i++)
307
        rot[i] = -in[i + 3*MDCT_SAMPLES/4];
308
    for (;i < MDCT_SAMPLES; i++)
309
        rot[i] =  in[i -   MDCT_SAMPLES/4];
310

    
311
    /* pre rotation */
312
    for (i = 0; i < MDCT_SAMPLES/4; i++) {
313
        re =  ((int)rot[               2*i] - (int)rot[MDCT_SAMPLES  -1-2*i]) >> 1;
314
        im = -((int)rot[MDCT_SAMPLES/2+2*i] - (int)rot[MDCT_SAMPLES/2-1-2*i]) >> 1;
315
        CMUL(x[i].re, x[i].im, re, im, -xcos1[i], xsin1[i]);
316
    }
317

    
318
    fft(x, MDCT_NBITS - 2);
319

    
320
    /* post rotation */
321
    for (i = 0; i < MDCT_SAMPLES/4; i++) {
322
        re = x[i].re;
323
        im = x[i].im;
324
        CMUL(re1, im1, re, im, xsin1[i], xcos1[i]);
325
        out[                 2*i] = im1;
326
        out[MDCT_SAMPLES/2-1-2*i] = re1;
327
    }
328
}
329

    
330

    
331
/**
332
 * Apply KBD window to input samples prior to MDCT.
333
 */
334
static void apply_window(int16_t *output, const int16_t *input,
335
                         const int16_t *window, int n)
336
{
337
    int i;
338
    int n2 = n >> 1;
339

    
340
    for (i = 0; i < n2; i++) {
341
        output[i]     = MUL16(input[i],     window[i]) >> 15;
342
        output[n-i-1] = MUL16(input[n-i-1], window[i]) >> 15;
343
    }
344
}
345

    
346

    
347
/**
348
 * Calculate the log2() of the maximum absolute value in an array.
349
 * @param tab input array
350
 * @param n   number of values in the array
351
 * @return    log2(max(abs(tab[])))
352
 */
353
static int log2_tab(int16_t *tab, int n)
354
{
355
    int i, v;
356

    
357
    v = 0;
358
    for (i = 0; i < n; i++)
359
        v |= abs(tab[i]);
360

    
361
    return av_log2(v);
362
}
363

    
364

    
365
/**
366
 * Left-shift each value in an array by a specified amount.
367
 * @param tab    input array
368
 * @param n      number of values in the array
369
 * @param lshift left shift amount. a negative value means right shift.
370
 */
371
static void lshift_tab(int16_t *tab, int n, int lshift)
372
{
373
    int i;
374

    
375
    if (lshift > 0) {
376
        for(i = 0; i < n; i++)
377
            tab[i] <<= lshift;
378
    } else if (lshift < 0) {
379
        lshift = -lshift;
380
        for (i = 0; i < n; i++)
381
            tab[i] >>= lshift;
382
    }
383
}
384

    
385

    
386
/**
387
 * Normalize the input samples to use the maximum available precision.
388
 * This assumes signed 16-bit input samples. Exponents are reduced by 9 to
389
 * match the 24-bit internal precision for MDCT coefficients.
390
 *
391
 * @return exponent shift
392
 */
393
static int normalize_samples(AC3EncodeContext *s,
394
                             int16_t windowed_samples[AC3_WINDOW_SIZE])
395
{
396
    int v = 14 - log2_tab(windowed_samples, AC3_WINDOW_SIZE);
397
    v = FFMAX(0, v);
398
    lshift_tab(windowed_samples, AC3_WINDOW_SIZE, v);
399
    return v - 9;
400
}
401

    
402

    
403
/**
404
 * Apply the MDCT to input samples to generate frequency coefficients.
405
 * This applies the KBD window and normalizes the input to reduce precision
406
 * loss due to fixed-point calculations.
407
 */
408
static void apply_mdct(AC3EncodeContext *s,
409
                       int16_t planar_samples[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE+AC3_FRAME_SIZE],
410
                       int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
411
                       int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
412
{
413
    int blk, ch;
414
    int16_t windowed_samples[AC3_WINDOW_SIZE];
415

    
416
    for (ch = 0; ch < s->channels; ch++) {
417
        for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
418
            const int16_t *input_samples = &planar_samples[ch][blk * AC3_BLOCK_SIZE];
419

    
420
            apply_window(windowed_samples, input_samples, ff_ac3_window, AC3_WINDOW_SIZE);
421

    
422
            exp_shift[blk][ch] = normalize_samples(s, windowed_samples);
423

    
424
            mdct512(mdct_coef[blk][ch], windowed_samples);
425
        }
426
    }
427
}
428

    
429

    
430
/**
431
 * Extract exponents from the MDCT coefficients.
432
 * This takes into account the normalization that was done to the input samples
433
 * by adjusting the exponents by the exponent shift values.
434
 */
435
static void extract_exponents(AC3EncodeContext *s,
436
                              int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
437
                              int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
438
                              uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
439
{
440
    int blk, ch, i;
441

    
442
    /* extract exponents */
443
    for (ch = 0; ch < s->channels; ch++) {
444
        for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
445
            /* compute "exponents". We take into account the normalization there */
446
            for (i = 0; i < AC3_MAX_COEFS; i++) {
447
                int e;
448
                int v = abs(mdct_coef[blk][ch][i]);
449
                if (v == 0)
450
                    e = 24;
451
                else {
452
                    e = 23 - av_log2(v) + exp_shift[blk][ch];
453
                    if (e >= 24) {
454
                        e = 24;
455
                        mdct_coef[blk][ch][i] = 0;
456
                    }
457
                }
458
                exp[blk][ch][i] = e;
459
            }
460
        }
461
    }
462
}
463

    
464

    
465
/**
466
 * Calculate the sum of absolute differences (SAD) between 2 sets of exponents.
467
 */
468
static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n)
469
{
470
    int sum, i;
471
    sum = 0;
472
    for (i = 0; i < n; i++)
473
        sum += abs(exp1[i] - exp2[i]);
474
    return sum;
475
}
476

    
477

    
478
/**
479
 * Exponent Difference Threshold.
480
 * New exponents are sent if their SAD exceed this number.
481
 */
482
#define EXP_DIFF_THRESHOLD 1000
483

    
484

    
485
/**
486
 * Calculate exponent strategies for all blocks in a single channel.
487
 */
488
static void compute_exp_strategy_ch(uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
489
                                    uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
490
                                    int ch, int is_lfe)
491
{
492
    int blk, blk1;
493
    int exp_diff;
494

    
495
    /* estimate if the exponent variation & decide if they should be
496
       reused in the next frame */
497
    exp_strategy[0][ch] = EXP_NEW;
498
    for (blk = 1; blk < AC3_MAX_BLOCKS; blk++) {
499
        exp_diff = calc_exp_diff(exp[blk][ch], exp[blk-1][ch], AC3_MAX_COEFS);
500
        if (exp_diff > EXP_DIFF_THRESHOLD)
501
            exp_strategy[blk][ch] = EXP_NEW;
502
        else
503
            exp_strategy[blk][ch] = EXP_REUSE;
504
    }
505
    if (is_lfe)
506
        return;
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][ch] == EXP_REUSE)
514
            blk1++;
515
        switch (blk1 - blk) {
516
        case 1:  exp_strategy[blk][ch] = EXP_D45; break;
517
        case 2:
518
        case 3:  exp_strategy[blk][ch] = EXP_D25; break;
519
        default: exp_strategy[blk][ch] = EXP_D15; break;
520
        }
521
        blk = blk1;
522
    }
523
}
524

    
525

    
526
/**
527
 * Calculate exponent strategies for all channels.
528
 */
529
static void compute_exp_strategy(AC3EncodeContext *s,
530
                                 uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
531
                                 uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
532
{
533
    int ch;
534

    
535
    for (ch = 0; ch < s->channels; ch++) {
536
        compute_exp_strategy_ch(exp_strategy, exp, ch, ch == s->lfe_channel);
537
    }
538
}
539

    
540

    
541
/**
542
 * Set each encoded exponent in a block to the minimum of itself and the
543
 * exponent in the same frequency bin of a following block.
544
 * exp[i] = min(exp[i], exp1[i]
545
 */
546
static void exponent_min(uint8_t exp[AC3_MAX_COEFS], uint8_t exp1[AC3_MAX_COEFS], int n)
547
{
548
    int i;
549
    for (i = 0; i < n; i++) {
550
        if (exp1[i] < exp[i])
551
            exp[i] = exp1[i];
552
    }
553
}
554

    
555

    
556
/**
557
 * Update the exponents so that they are the ones the decoder will decode.
558
 * @return the number of bits used to encode the exponents.
559
 */
560
static int encode_exponents_blk_ch(uint8_t encoded_exp[AC3_MAX_COEFS],
561
                                   uint8_t exp[AC3_MAX_COEFS],
562
                                   int nb_exps, int exp_strategy)
563
{
564
    int group_size, nb_groups, i, j, k, exp_min;
565
    uint8_t exp1[AC3_MAX_COEFS];
566

    
567
    group_size = exp_strategy + (exp_strategy == EXP_D45);
568
    nb_groups = ((nb_exps + (group_size * 3) - 4) / (3 * group_size)) * 3;
569

    
570
    /* for each group, compute the minimum exponent */
571
    exp1[0] = exp[0]; /* DC exponent is handled separately */
572
    k = 1;
573
    for (i = 1; i <= nb_groups; i++) {
574
        exp_min = exp[k];
575
        assert(exp_min >= 0 && exp_min <= 24);
576
        for (j = 1; j < group_size; j++) {
577
            if (exp[k+j] < exp_min)
578
                exp_min = exp[k+j];
579
        }
580
        exp1[i] = exp_min;
581
        k += group_size;
582
    }
583

    
584
    /* constraint for DC exponent */
585
    if (exp1[0] > 15)
586
        exp1[0] = 15;
587

    
588
    /* decrease the delta between each groups to within 2 so that they can be
589
       differentially encoded */
590
    for (i = 1; i <= nb_groups; i++)
591
        exp1[i] = FFMIN(exp1[i], exp1[i-1] + 2);
592
    for (i = nb_groups-1; i >= 0; i--)
593
        exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2);
594

    
595
    /* now we have the exponent values the decoder will see */
596
    encoded_exp[0] = exp1[0];
597
    k = 1;
598
    for (i = 1; i <= nb_groups; i++) {
599
        for (j = 0; j < group_size; j++)
600
            encoded_exp[k+j] = exp1[i];
601
        k += group_size;
602
    }
603

    
604
    return 4 + (nb_groups / 3) * 7;
605
}
606

    
607

    
608
/**
609
 * Encode exponents from original extracted form to what the decoder will see.
610
 * This copies and groups exponents based on exponent strategy and reduces
611
 * deltas between adjacent exponent groups so that they can be differentially
612
 * encoded.
613
 * @return bits needed to encode the exponents
614
 */
615
static int encode_exponents(AC3EncodeContext *s,
616
                            uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
617
                            uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
618
                            uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
619
{
620
    int blk, blk1, blk2, ch;
621
    int frame_bits;
622

    
623
    frame_bits = 0;
624
    for (ch = 0; ch < s->channels; ch++) {
625
        /* for the EXP_REUSE case we select the min of the exponents */
626
        blk = 0;
627
        while (blk < AC3_MAX_BLOCKS) {
628
            blk1 = blk + 1;
629
            while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1][ch] == EXP_REUSE) {
630
                exponent_min(exp[blk][ch], exp[blk1][ch], s->nb_coefs[ch]);
631
                blk1++;
632
            }
633
            frame_bits += encode_exponents_blk_ch(encoded_exp[blk][ch],
634
                                                  exp[blk][ch], s->nb_coefs[ch],
635
                                                  exp_strategy[blk][ch]);
636
            /* copy encoded exponents for reuse case */
637
            for (blk2 = blk+1; blk2 < blk1; blk2++) {
638
                memcpy(encoded_exp[blk2][ch], encoded_exp[blk][ch],
639
                       s->nb_coefs[ch] * sizeof(uint8_t));
640
            }
641
            blk = blk1;
642
        }
643
    }
644

    
645
    return frame_bits;
646
}
647

    
648

    
649
/**
650
 * Calculate final exponents from the supplied MDCT coefficients and exponent shift.
651
 * Extract exponents from MDCT coefficients, calculate exponent strategies,
652
 * and encode final exponents.
653
 * @return bits needed to encode the exponents
654
 */
655
static int process_exponents(AC3EncodeContext *s,
656
                             int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
657
                             int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
658
                             uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
659
                             uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
660
                             uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
661
{
662
    extract_exponents(s, mdct_coef, exp_shift, exp);
663

    
664
    compute_exp_strategy(s, exp_strategy, exp);
665

    
666
    return encode_exponents(s, exp, exp_strategy, encoded_exp);
667
}
668

    
669

    
670
/**
671
 * Calculate the number of bits needed to encode a set of mantissas.
672
 */
673
static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs)
674
{
675
    int bits, mant, i;
676

    
677
    bits = 0;
678
    for (i = 0; i < nb_coefs; i++) {
679
        mant = m[i];
680
        switch (mant) {
681
        case 0:
682
            /* nothing */
683
            break;
684
        case 1:
685
            /* 3 mantissa in 5 bits */
686
            if (s->mant1_cnt == 0)
687
                bits += 5;
688
            if (++s->mant1_cnt == 3)
689
                s->mant1_cnt = 0;
690
            break;
691
        case 2:
692
            /* 3 mantissa in 7 bits */
693
            if (s->mant2_cnt == 0)
694
                bits += 7;
695
            if (++s->mant2_cnt == 3)
696
                s->mant2_cnt = 0;
697
            break;
698
        case 3:
699
            bits += 3;
700
            break;
701
        case 4:
702
            /* 2 mantissa in 7 bits */
703
            if (s->mant4_cnt == 0)
704
                bits += 7;
705
            if (++s->mant4_cnt == 2)
706
                s->mant4_cnt = 0;
707
            break;
708
        case 14:
709
            bits += 14;
710
            break;
711
        case 15:
712
            bits += 16;
713
            break;
714
        default:
715
            bits += mant - 1;
716
            break;
717
        }
718
    }
719
    return bits;
720
}
721

    
722

    
723
/**
724
 * Calculate masking curve based on the final exponents.
725
 * Also calculate the power spectral densities to use in future calculations.
726
 */
727
static void bit_alloc_masking(AC3EncodeContext *s,
728
                              uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
729
                              uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
730
                              int16_t psd[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
731
                              int16_t mask[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS])
732
{
733
    int blk, ch;
734
    int16_t band_psd[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS];
735

    
736
    for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
737
        for (ch = 0; ch < s->channels; ch++) {
738
            if(exp_strategy[blk][ch] == EXP_REUSE) {
739
                memcpy(psd[blk][ch],  psd[blk-1][ch],  AC3_MAX_COEFS*sizeof(psd[0][0][0]));
740
                memcpy(mask[blk][ch], mask[blk-1][ch], AC3_CRITICAL_BANDS*sizeof(mask[0][0][0]));
741
            } else {
742
                ff_ac3_bit_alloc_calc_psd(encoded_exp[blk][ch], 0,
743
                                          s->nb_coefs[ch],
744
                                          psd[blk][ch], band_psd[blk][ch]);
745
                ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, band_psd[blk][ch],
746
                                           0, s->nb_coefs[ch],
747
                                           ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
748
                                           ch == s->lfe_channel,
749
                                           DBA_NONE, 0, NULL, NULL, NULL,
750
                                           mask[blk][ch]);
751
            }
752
        }
753
    }
754
}
755

    
756

    
757
/**
758
 * Run the bit allocation with a given SNR offset.
759
 * This calculates the bit allocation pointers that will be used to determine
760
 * the quantization of each mantissa.
761
 * @return the number of remaining bits (positive or negative) if the given
762
 *         SNR offset is used to quantize the mantissas.
763
 */
764
static int bit_alloc(AC3EncodeContext *s,
765
                     int16_t mask[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS],
766
                     int16_t psd[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
767
                     uint8_t bap[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
768
                     int frame_bits, int coarse_snr_offset, int fine_snr_offset)
769
{
770
    int blk, ch;
771
    int snr_offset;
772

    
773
    snr_offset = (((coarse_snr_offset - 15) << 4) + fine_snr_offset) << 2;
774

    
775
    for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
776
        s->mant1_cnt = 0;
777
        s->mant2_cnt = 0;
778
        s->mant4_cnt = 0;
779
        for (ch = 0; ch < s->channels; ch++) {
780
            ff_ac3_bit_alloc_calc_bap(mask[blk][ch], psd[blk][ch], 0,
781
                                      s->nb_coefs[ch], snr_offset,
782
                                      s->bit_alloc.floor, ff_ac3_bap_tab,
783
                                      bap[blk][ch]);
784
            frame_bits += compute_mantissa_size(s, bap[blk][ch], s->nb_coefs[ch]);
785
        }
786
    }
787
    return 8 * s->frame_size - frame_bits;
788
}
789

    
790

    
791
#define SNR_INC1 4
792

    
793
/**
794
 * Perform bit allocation search.
795
 * Finds the SNR offset value that maximizes quality and fits in the specified
796
 * frame size.  Output is the SNR offset and a set of bit allocation pointers
797
 * used to quantize the mantissas.
798
 */
799
static int compute_bit_allocation(AC3EncodeContext *s,
800
                                  uint8_t bap[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
801
                                  uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
802
                                  uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
803
                                  int frame_bits)
804
{
805
    int blk, ch;
806
    int coarse_snr_offset, fine_snr_offset;
807
    uint8_t bap1[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
808
    int16_t psd[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
809
    int16_t mask[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS];
810
    static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
811

    
812
    /* init default parameters */
813
    s->slow_decay_code = 2;
814
    s->fast_decay_code = 1;
815
    s->slow_gain_code  = 1;
816
    s->db_per_bit_code = 2;
817
    s->floor_code      = 4;
818
    for (ch = 0; ch < s->channels; ch++)
819
        s->fast_gain_code[ch] = 4;
820

    
821
    /* compute real values */
822
    s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->bit_alloc.sr_shift;
823
    s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->bit_alloc.sr_shift;
824
    s->bit_alloc.slow_gain  = ff_ac3_slow_gain_tab[s->slow_gain_code];
825
    s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
826
    s->bit_alloc.floor      = ff_ac3_floor_tab[s->floor_code];
827

    
828
    /* header size */
829
    frame_bits += 65;
830
    // if (s->channel_mode == 2)
831
    //    frame_bits += 2;
832
    frame_bits += frame_bits_inc[s->channel_mode];
833

    
834
    /* audio blocks */
835
    for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
836
        frame_bits += s->fbw_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
837
        if (s->channel_mode == AC3_CHMODE_STEREO) {
838
            frame_bits++; /* rematstr */
839
            if (!blk)
840
                frame_bits += 4;
841
        }
842
        frame_bits += 2 * s->fbw_channels; /* chexpstr[2] * c */
843
        if (s->lfe_on)
844
            frame_bits++; /* lfeexpstr */
845
        for (ch = 0; ch < s->fbw_channels; ch++) {
846
            if (exp_strategy[blk][ch] != EXP_REUSE)
847
                frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
848
        }
849
        frame_bits++; /* baie */
850
        frame_bits++; /* snr */
851
        frame_bits += 2; /* delta / skip */
852
    }
853
    frame_bits++; /* cplinu for block 0 */
854
    /* bit alloc info */
855
    /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
856
    /* csnroffset[6] */
857
    /* (fsnoffset[4] + fgaincod[4]) * c */
858
    frame_bits += 2*4 + 3 + 6 + s->channels * (4 + 3);
859

    
860
    /* auxdatae, crcrsv */
861
    frame_bits += 2;
862

    
863
    /* CRC */
864
    frame_bits += 16;
865

    
866
    /* calculate psd and masking curve before doing bit allocation */
867
    bit_alloc_masking(s, encoded_exp, exp_strategy, psd, mask);
868

    
869
    /* now the big work begins : do the bit allocation. Modify the snr
870
       offset until we can pack everything in the requested frame size */
871

    
872
    coarse_snr_offset = s->coarse_snr_offset;
873
    while (coarse_snr_offset >= 0 &&
874
           bit_alloc(s, mask, psd, bap, frame_bits, coarse_snr_offset, 0) < 0)
875
        coarse_snr_offset -= SNR_INC1;
876
    if (coarse_snr_offset < 0) {
877
        av_log(NULL, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
878
        return -1;
879
    }
880
    while (coarse_snr_offset + SNR_INC1 <= 63 &&
881
           bit_alloc(s, mask, psd, bap1, frame_bits,
882
                     coarse_snr_offset + SNR_INC1, 0) >= 0) {
883
        coarse_snr_offset += SNR_INC1;
884
        memcpy(bap, bap1, sizeof(bap1));
885
    }
886
    while (coarse_snr_offset + 1 <= 63 &&
887
           bit_alloc(s, mask, psd, bap1, frame_bits, coarse_snr_offset + 1, 0) >= 0) {
888
        coarse_snr_offset++;
889
        memcpy(bap, bap1, sizeof(bap1));
890
    }
891

    
892
    fine_snr_offset = 0;
893
    while (fine_snr_offset + SNR_INC1 <= 15 &&
894
           bit_alloc(s, mask, psd, bap1, frame_bits,
895
                     coarse_snr_offset, fine_snr_offset + SNR_INC1) >= 0) {
896
        fine_snr_offset += SNR_INC1;
897
        memcpy(bap, bap1, sizeof(bap1));
898
    }
899
    while (fine_snr_offset + 1 <= 15 &&
900
           bit_alloc(s, mask, psd, bap1, frame_bits,
901
                     coarse_snr_offset, fine_snr_offset + 1) >= 0) {
902
        fine_snr_offset++;
903
        memcpy(bap, bap1, sizeof(bap1));
904
    }
905

    
906
    s->coarse_snr_offset = coarse_snr_offset;
907
    for (ch = 0; ch < s->channels; ch++)
908
        s->fine_snr_offset[ch] = fine_snr_offset;
909

    
910
    return 0;
911
}
912

    
913

    
914
/**
915
 * Write the AC-3 frame header to the output bitstream.
916
 */
917
static void output_frame_header(AC3EncodeContext *s)
918
{
919
    put_bits(&s->pb, 16, 0x0b77);   /* frame header */
920
    put_bits(&s->pb, 16, 0);        /* crc1: will be filled later */
921
    put_bits(&s->pb, 2,  s->bit_alloc.sr_code);
922
    put_bits(&s->pb, 6,  s->frame_size_code + (s->frame_size - s->frame_size_min) / 2);
923
    put_bits(&s->pb, 5,  s->bitstream_id);
924
    put_bits(&s->pb, 3,  s->bitstream_mode);
925
    put_bits(&s->pb, 3,  s->channel_mode);
926
    if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)
927
        put_bits(&s->pb, 2, 1);     /* XXX -4.5 dB */
928
    if (s->channel_mode & 0x04)
929
        put_bits(&s->pb, 2, 1);     /* XXX -6 dB */
930
    if (s->channel_mode == AC3_CHMODE_STEREO)
931
        put_bits(&s->pb, 2, 0);     /* surround not indicated */
932
    put_bits(&s->pb, 1, s->lfe_on); /* LFE */
933
    put_bits(&s->pb, 5, 31);        /* dialog norm: -31 db */
934
    put_bits(&s->pb, 1, 0);         /* no compression control word */
935
    put_bits(&s->pb, 1, 0);         /* no lang code */
936
    put_bits(&s->pb, 1, 0);         /* no audio production info */
937
    put_bits(&s->pb, 1, 0);         /* no copyright */
938
    put_bits(&s->pb, 1, 1);         /* original bitstream */
939
    put_bits(&s->pb, 1, 0);         /* no time code 1 */
940
    put_bits(&s->pb, 1, 0);         /* no time code 2 */
941
    put_bits(&s->pb, 1, 0);         /* no additional bit stream info */
942
}
943

    
944

    
945
/**
946
 * Symmetric quantization on 'levels' levels.
947
 */
948
static inline int sym_quant(int c, int e, int levels)
949
{
950
    int v;
951

    
952
    if (c >= 0) {
953
        v = (levels * (c << e)) >> 24;
954
        v = (v + 1) >> 1;
955
        v = (levels >> 1) + v;
956
    } else {
957
        v = (levels * ((-c) << e)) >> 24;
958
        v = (v + 1) >> 1;
959
        v = (levels >> 1) - v;
960
    }
961
    assert (v >= 0 && v < levels);
962
    return v;
963
}
964

    
965

    
966
/**
967
 * Asymmetric quantization on 2^qbits levels.
968
 */
969
static inline int asym_quant(int c, int e, int qbits)
970
{
971
    int lshift, m, v;
972

    
973
    lshift = e + qbits - 24;
974
    if (lshift >= 0)
975
        v = c << lshift;
976
    else
977
        v = c >> (-lshift);
978
    /* rounding */
979
    v = (v + 1) >> 1;
980
    m = (1 << (qbits-1));
981
    if (v >= m)
982
        v = m - 1;
983
    assert(v >= -m);
984
    return v & ((1 << qbits)-1);
985
}
986

    
987

    
988
/**
989
 * Write one audio block to the output bitstream.
990
 */
991
static void output_audio_block(AC3EncodeContext *s,
992
                               uint8_t exp_strategy[AC3_MAX_CHANNELS],
993
                               uint8_t encoded_exp[AC3_MAX_CHANNELS][AC3_MAX_COEFS],
994
                               uint8_t bap[AC3_MAX_CHANNELS][AC3_MAX_COEFS],
995
                               int32_t mdct_coef[AC3_MAX_CHANNELS][AC3_MAX_COEFS],
996
                               int8_t exp_shift[AC3_MAX_CHANNELS],
997
                               int block_num)
998
{
999
    int ch, nb_groups, group_size, i, baie, rbnd;
1000
    uint8_t *p;
1001
    uint16_t qmant[AC3_MAX_CHANNELS][AC3_MAX_COEFS];
1002
    int exp0, exp1;
1003
    int mant1_cnt, mant2_cnt, mant4_cnt;
1004
    uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr;
1005
    int delta0, delta1, delta2;
1006

    
1007
    for (ch = 0; ch < s->fbw_channels; ch++)
1008
        put_bits(&s->pb, 1, 0); /* no block switching */
1009
    for (ch = 0; ch < s->fbw_channels; ch++)
1010
        put_bits(&s->pb, 1, 1); /* no dither */
1011
    put_bits(&s->pb, 1, 0);     /* no dynamic range */
1012
    if (!block_num) {
1013
        put_bits(&s->pb, 1, 1); /* coupling strategy present */
1014
        put_bits(&s->pb, 1, 0); /* no coupling strategy */
1015
    } else {
1016
        put_bits(&s->pb, 1, 0); /* no new coupling strategy */
1017
    }
1018

    
1019
    if (s->channel_mode == AC3_CHMODE_STEREO) {
1020
        if (!block_num) {
1021
            /* first block must define rematrixing (rematstr) */
1022
            put_bits(&s->pb, 1, 1);
1023

    
1024
            /* dummy rematrixing rematflg(1:4)=0 */
1025
            for (rbnd = 0; rbnd < 4; rbnd++)
1026
                put_bits(&s->pb, 1, 0);
1027
        } else {
1028
            /* no matrixing (but should be used in the future) */
1029
            put_bits(&s->pb, 1, 0);
1030
        }
1031
    }
1032

    
1033
    /* exponent strategy */
1034
    for (ch = 0; ch < s->fbw_channels; ch++)
1035
        put_bits(&s->pb, 2, exp_strategy[ch]);
1036

    
1037
    if (s->lfe_on)
1038
        put_bits(&s->pb, 1, exp_strategy[s->lfe_channel]);
1039

    
1040
    /* bandwidth */
1041
    for (ch = 0; ch < s->fbw_channels; ch++) {
1042
        if (exp_strategy[ch] != EXP_REUSE)
1043
            put_bits(&s->pb, 6, s->bandwidth_code[ch]);
1044
    }
1045

    
1046
    /* exponents */
1047
    for (ch = 0; ch < s->channels; ch++) {
1048
        if (exp_strategy[ch] == EXP_REUSE)
1049
            continue;
1050
        group_size = exp_strategy[ch] + (exp_strategy[ch] == EXP_D45);
1051
        nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
1052
        p = encoded_exp[ch];
1053

    
1054
        /* first exponent */
1055
        exp1 = *p++;
1056
        put_bits(&s->pb, 4, exp1);
1057

    
1058
        /* next ones are delta encoded */
1059
        for (i = 0; i < nb_groups; i++) {
1060
            /* merge three delta in one code */
1061
            exp0   = exp1;
1062
            exp1   = p[0];
1063
            p     += group_size;
1064
            delta0 = exp1 - exp0 + 2;
1065

    
1066
            exp0   = exp1;
1067
            exp1   = p[0];
1068
            p     += group_size;
1069
            delta1 = exp1 - exp0 + 2;
1070

    
1071
            exp0   = exp1;
1072
            exp1   = p[0];
1073
            p     += group_size;
1074
            delta2 = exp1 - exp0 + 2;
1075

    
1076
            put_bits(&s->pb, 7, ((delta0 * 5 + delta1) * 5) + delta2);
1077
        }
1078

    
1079
        if (ch != s->lfe_channel)
1080
            put_bits(&s->pb, 2, 0); /* no gain range info */
1081
    }
1082

    
1083
    /* bit allocation info */
1084
    baie = (block_num == 0);
1085
    put_bits(&s->pb, 1, baie);
1086
    if (baie) {
1087
        put_bits(&s->pb, 2, s->slow_decay_code);
1088
        put_bits(&s->pb, 2, s->fast_decay_code);
1089
        put_bits(&s->pb, 2, s->slow_gain_code);
1090
        put_bits(&s->pb, 2, s->db_per_bit_code);
1091
        put_bits(&s->pb, 3, s->floor_code);
1092
    }
1093

    
1094
    /* snr offset */
1095
    put_bits(&s->pb, 1, baie);
1096
    if (baie) {
1097
        put_bits(&s->pb, 6, s->coarse_snr_offset);
1098
        for (ch = 0; ch < s->channels; ch++) {
1099
            put_bits(&s->pb, 4, s->fine_snr_offset[ch]);
1100
            put_bits(&s->pb, 3, s->fast_gain_code[ch]);
1101
        }
1102
    }
1103

    
1104
    put_bits(&s->pb, 1, 0); /* no delta bit allocation */
1105
    put_bits(&s->pb, 1, 0); /* no data to skip */
1106

    
1107
    /* mantissa encoding : we use two passes to handle the grouping. A
1108
       one pass method may be faster, but it would necessitate to
1109
       modify the output stream. */
1110

    
1111
    /* first pass: quantize */
1112
    mant1_cnt = mant2_cnt = mant4_cnt = 0;
1113
    qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;
1114

    
1115
    for (ch = 0; ch < s->channels; ch++) {
1116
        int b, c, e, v;
1117

    
1118
        for (i = 0; i < s->nb_coefs[ch]; i++) {
1119
            c = mdct_coef[ch][i];
1120
            e = encoded_exp[ch][i] - exp_shift[ch];
1121
            b = bap[ch][i];
1122
            switch (b) {
1123
            case 0:
1124
                v = 0;
1125
                break;
1126
            case 1:
1127
                v = sym_quant(c, e, 3);
1128
                switch (mant1_cnt) {
1129
                case 0:
1130
                    qmant1_ptr = &qmant[ch][i];
1131
                    v = 9 * v;
1132
                    mant1_cnt = 1;
1133
                    break;
1134
                case 1:
1135
                    *qmant1_ptr += 3 * v;
1136
                    mant1_cnt = 2;
1137
                    v = 128;
1138
                    break;
1139
                default:
1140
                    *qmant1_ptr += v;
1141
                    mant1_cnt = 0;
1142
                    v = 128;
1143
                    break;
1144
                }
1145
                break;
1146
            case 2:
1147
                v = sym_quant(c, e, 5);
1148
                switch (mant2_cnt) {
1149
                case 0:
1150
                    qmant2_ptr = &qmant[ch][i];
1151
                    v = 25 * v;
1152
                    mant2_cnt = 1;
1153
                    break;
1154
                case 1:
1155
                    *qmant2_ptr += 5 * v;
1156
                    mant2_cnt = 2;
1157
                    v = 128;
1158
                    break;
1159
                default:
1160
                    *qmant2_ptr += v;
1161
                    mant2_cnt = 0;
1162
                    v = 128;
1163
                    break;
1164
                }
1165
                break;
1166
            case 3:
1167
                v = sym_quant(c, e, 7);
1168
                break;
1169
            case 4:
1170
                v = sym_quant(c, e, 11);
1171
                switch (mant4_cnt) {
1172
                case 0:
1173
                    qmant4_ptr = &qmant[ch][i];
1174
                    v = 11 * v;
1175
                    mant4_cnt = 1;
1176
                    break;
1177
                default:
1178
                    *qmant4_ptr += v;
1179
                    mant4_cnt = 0;
1180
                    v = 128;
1181
                    break;
1182
                }
1183
                break;
1184
            case 5:
1185
                v = sym_quant(c, e, 15);
1186
                break;
1187
            case 14:
1188
                v = asym_quant(c, e, 14);
1189
                break;
1190
            case 15:
1191
                v = asym_quant(c, e, 16);
1192
                break;
1193
            default:
1194
                v = asym_quant(c, e, b - 1);
1195
                break;
1196
            }
1197
            qmant[ch][i] = v;
1198
        }
1199
    }
1200

    
1201
    /* second pass : output the values */
1202
    for (ch = 0; ch < s->channels; ch++) {
1203
        int b, q;
1204

    
1205
        for (i = 0; i < s->nb_coefs[ch]; i++) {
1206
            q = qmant[ch][i];
1207
            b = bap[ch][i];
1208
            switch (b) {
1209
            case 0:                                         break;
1210
            case 1: if (q != 128) put_bits(&s->pb,   5, q); break;
1211
            case 2: if (q != 128) put_bits(&s->pb,   7, q); break;
1212
            case 3:               put_bits(&s->pb,   3, q); break;
1213
            case 4: if (q != 128) put_bits(&s->pb,   7, q); break;
1214
            case 14:              put_bits(&s->pb,  14, q); break;
1215
            case 15:              put_bits(&s->pb,  16, q); break;
1216
            default:              put_bits(&s->pb, b-1, q); break;
1217
            }
1218
        }
1219
    }
1220
}
1221

    
1222

    
1223
/** CRC-16 Polynomial */
1224
#define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
1225

    
1226

    
1227
static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
1228
{
1229
    unsigned int c;
1230

    
1231
    c = 0;
1232
    while (a) {
1233
        if (a & 1)
1234
            c ^= b;
1235
        a = a >> 1;
1236
        b = b << 1;
1237
        if (b & (1 << 16))
1238
            b ^= poly;
1239
    }
1240
    return c;
1241
}
1242

    
1243

    
1244
static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
1245
{
1246
    unsigned int r;
1247
    r = 1;
1248
    while (n) {
1249
        if (n & 1)
1250
            r = mul_poly(r, a, poly);
1251
        a = mul_poly(a, a, poly);
1252
        n >>= 1;
1253
    }
1254
    return r;
1255
}
1256

    
1257

    
1258
/**
1259
 * Fill the end of the frame with 0's and compute the two CRCs.
1260
 */
1261
static void output_frame_end(AC3EncodeContext *s)
1262
{
1263
    int frame_size, frame_size_58, pad_bytes, crc1, crc2, crc_inv;
1264
    uint8_t *frame;
1265

    
1266
    frame_size = s->frame_size; /* frame size in words */
1267
    /* align to 8 bits */
1268
    flush_put_bits(&s->pb);
1269
    /* add zero bytes to reach the frame size */
1270
    frame = s->pb.buf;
1271
    pad_bytes = s->frame_size - (put_bits_ptr(&s->pb) - frame) - 2;
1272
    assert(pad_bytes >= 0);
1273
    if (pad_bytes > 0)
1274
        memset(put_bits_ptr(&s->pb), 0, pad_bytes);
1275

    
1276
    /* Now we must compute both crcs : this is not so easy for crc1
1277
       because it is at the beginning of the data... */
1278
    frame_size_58 = ((frame_size >> 2) + (frame_size >> 4)) << 1;
1279

    
1280
    crc1 = av_bswap16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
1281
                             frame + 4, frame_size_58 - 4));
1282

    
1283
    /* XXX: could precompute crc_inv */
1284
    crc_inv = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
1285
    crc1    = mul_poly(crc_inv, crc1, CRC16_POLY);
1286
    AV_WB16(frame + 2, crc1);
1287

    
1288
    crc2 = av_bswap16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
1289
                             frame + frame_size_58,
1290
                             frame_size - frame_size_58 - 2));
1291
    AV_WB16(frame + frame_size - 2, crc2);
1292
}
1293

    
1294

    
1295
/**
1296
 * Write the frame to the output bitstream.
1297
 */
1298
static void output_frame(AC3EncodeContext *s,
1299
                         unsigned char *frame,
1300
                         uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
1301
                         uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
1302
                         uint8_t bap[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
1303
                         int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
1304
                         int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS])
1305
{
1306
    int blk;
1307

    
1308
    init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
1309

    
1310
    output_frame_header(s);
1311

    
1312
    for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1313
        output_audio_block(s, exp_strategy[blk], encoded_exp[blk],
1314
                           bap[blk], mdct_coef[blk], exp_shift[blk], blk);
1315
    }
1316

    
1317
    output_frame_end(s);
1318
}
1319

    
1320

    
1321
/**
1322
 * Encode a single AC-3 frame.
1323
 */
1324
static int ac3_encode_frame(AVCodecContext *avctx,
1325
                            unsigned char *frame, int buf_size, void *data)
1326
{
1327
    AC3EncodeContext *s = avctx->priv_data;
1328
    const int16_t *samples = data;
1329
    int16_t planar_samples[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE+AC3_FRAME_SIZE];
1330
    int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
1331
    uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
1332
    uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS];
1333
    uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
1334
    uint8_t bap[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
1335
    int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS];
1336
    int frame_bits;
1337

    
1338
    if (s->bit_alloc.sr_code == 1)
1339
        adjust_frame_size(s);
1340

    
1341
    deinterleave_input_samples(s, samples, planar_samples);
1342

    
1343
    apply_mdct(s, planar_samples, exp_shift, mdct_coef);
1344

    
1345
    frame_bits = process_exponents(s, mdct_coef, exp_shift, exp, exp_strategy, encoded_exp);
1346

    
1347
    compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);
1348

    
1349
    output_frame(s, frame, exp_strategy, encoded_exp, bap, mdct_coef, exp_shift);
1350

    
1351
    return s->frame_size;
1352
}
1353

    
1354

    
1355
/**
1356
 * Finalize encoding and free any memory allocated by the encoder.
1357
 */
1358
static av_cold int ac3_encode_close(AVCodecContext *avctx)
1359
{
1360
    av_freep(&avctx->coded_frame);
1361
    return 0;
1362
}
1363

    
1364

    
1365
/**
1366
 * Set channel information during initialization.
1367
 */
1368
static av_cold int set_channel_info(AC3EncodeContext *s, int channels,
1369
                                    int64_t *channel_layout)
1370
{
1371
    int ch_layout;
1372

    
1373
    if (channels < 1 || channels > AC3_MAX_CHANNELS)
1374
        return AVERROR(EINVAL);
1375
    if ((uint64_t)*channel_layout > 0x7FF)
1376
        return AVERROR(EINVAL);
1377
    ch_layout = *channel_layout;
1378
    if (!ch_layout)
1379
        ch_layout = avcodec_guess_channel_layout(channels, CODEC_ID_AC3, NULL);
1380
    if (av_get_channel_layout_nb_channels(ch_layout) != channels)
1381
        return AVERROR(EINVAL);
1382

    
1383
    s->lfe_on       = !!(ch_layout & AV_CH_LOW_FREQUENCY);
1384
    s->channels     = channels;
1385
    s->fbw_channels = channels - s->lfe_on;
1386
    s->lfe_channel  = s->lfe_on ? s->fbw_channels : -1;
1387
    if (s->lfe_on)
1388
        ch_layout -= AV_CH_LOW_FREQUENCY;
1389

    
1390
    switch (ch_layout) {
1391
    case AV_CH_LAYOUT_MONO:           s->channel_mode = AC3_CHMODE_MONO;   break;
1392
    case AV_CH_LAYOUT_STEREO:         s->channel_mode = AC3_CHMODE_STEREO; break;
1393
    case AV_CH_LAYOUT_SURROUND:       s->channel_mode = AC3_CHMODE_3F;     break;
1394
    case AV_CH_LAYOUT_2_1:            s->channel_mode = AC3_CHMODE_2F1R;   break;
1395
    case AV_CH_LAYOUT_4POINT0:        s->channel_mode = AC3_CHMODE_3F1R;   break;
1396
    case AV_CH_LAYOUT_QUAD:
1397
    case AV_CH_LAYOUT_2_2:            s->channel_mode = AC3_CHMODE_2F2R;   break;
1398
    case AV_CH_LAYOUT_5POINT0:
1399
    case AV_CH_LAYOUT_5POINT0_BACK:   s->channel_mode = AC3_CHMODE_3F2R;   break;
1400
    default:
1401
        return AVERROR(EINVAL);
1402
    }
1403

    
1404
    s->channel_map  = ff_ac3_enc_channel_map[s->channel_mode][s->lfe_on];
1405
    *channel_layout = ch_layout;
1406
    if (s->lfe_on)
1407
        *channel_layout |= AV_CH_LOW_FREQUENCY;
1408

    
1409
    return 0;
1410
}
1411

    
1412

    
1413
static av_cold int validate_options(AVCodecContext *avctx, AC3EncodeContext *s)
1414
{
1415
    int i, ret;
1416

    
1417
    /* validate channel layout */
1418
    if (!avctx->channel_layout) {
1419
        av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The "
1420
                                      "encoder will guess the layout, but it "
1421
                                      "might be incorrect.\n");
1422
    }
1423
    ret = set_channel_info(s, avctx->channels, &avctx->channel_layout);
1424
    if (ret) {
1425
        av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n");
1426
        return ret;
1427
    }
1428

    
1429
    /* validate sample rate */
1430
    for (i = 0; i < 9; i++) {
1431
        if ((ff_ac3_sample_rate_tab[i / 3] >> (i % 3)) == avctx->sample_rate)
1432
            break;
1433
    }
1434
    if (i == 9) {
1435
        av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1436
        return AVERROR(EINVAL);
1437
    }
1438
    s->sample_rate        = avctx->sample_rate;
1439
    s->bit_alloc.sr_shift = i % 3;
1440
    s->bit_alloc.sr_code  = i / 3;
1441

    
1442
    /* validate bit rate */
1443
    for (i = 0; i < 19; i++) {
1444
        if ((ff_ac3_bitrate_tab[i] >> s->bit_alloc.sr_shift)*1000 == avctx->bit_rate)
1445
            break;
1446
    }
1447
    if (i == 19) {
1448
        av_log(avctx, AV_LOG_ERROR, "invalid bit rate\n");
1449
        return AVERROR(EINVAL);
1450
    }
1451
    s->bit_rate        = avctx->bit_rate;
1452
    s->frame_size_code = i << 1;
1453

    
1454
    return 0;
1455
}
1456

    
1457

    
1458
/**
1459
 * Set bandwidth for all channels.
1460
 * The user can optionally supply a cutoff frequency. Otherwise an appropriate
1461
 * default value will be used.
1462
 */
1463
static av_cold void set_bandwidth(AC3EncodeContext *s, int cutoff)
1464
{
1465
    int ch, bw_code;
1466

    
1467
    if (cutoff) {
1468
        /* calculate bandwidth based on user-specified cutoff frequency */
1469
        int fbw_coeffs;
1470
        cutoff         = av_clip(cutoff, 1, s->sample_rate >> 1);
1471
        fbw_coeffs     = cutoff * 2 * AC3_MAX_COEFS / s->sample_rate;
1472
        bw_code        = av_clip((fbw_coeffs - 73) / 3, 0, 60);
1473
    } else {
1474
        /* use default bandwidth setting */
1475
        /* XXX: should compute the bandwidth according to the frame
1476
           size, so that we avoid annoying high frequency artifacts */
1477
        bw_code = 50;
1478
    }
1479

    
1480
    /* set number of coefficients for each channel */
1481
    for (ch = 0; ch < s->fbw_channels; ch++) {
1482
        s->bandwidth_code[ch] = bw_code;
1483
        s->nb_coefs[ch]       = bw_code * 3 + 73;
1484
    }
1485
    if (s->lfe_on)
1486
        s->nb_coefs[s->lfe_channel] = 7; /* LFE channel always has 7 coefs */
1487
}
1488

    
1489

    
1490
/**
1491
 * Initialize the encoder.
1492
 */
1493
static av_cold int ac3_encode_init(AVCodecContext *avctx)
1494
{
1495
    AC3EncodeContext *s = avctx->priv_data;
1496
    int ret;
1497

    
1498
    avctx->frame_size = AC3_FRAME_SIZE;
1499

    
1500
    ac3_common_init();
1501

    
1502
    ret = validate_options(avctx, s);
1503
    if (ret)
1504
        return ret;
1505

    
1506
    s->bitstream_id   = 8 + s->bit_alloc.sr_shift;
1507
    s->bitstream_mode = 0; /* complete main audio service */
1508

    
1509
    s->frame_size_min  = 2 * ff_ac3_frame_size_tab[s->frame_size_code][s->bit_alloc.sr_code];
1510
    s->bits_written    = 0;
1511
    s->samples_written = 0;
1512
    s->frame_size      = s->frame_size_min;
1513

    
1514
    set_bandwidth(s, avctx->cutoff);
1515

    
1516
    /* initial snr offset */
1517
    s->coarse_snr_offset = 40;
1518

    
1519
    mdct_init(9);
1520

    
1521
    avctx->coded_frame= avcodec_alloc_frame();
1522
    avctx->coded_frame->key_frame= 1;
1523

    
1524
    return 0;
1525
}
1526

    
1527

    
1528
#ifdef TEST
1529
/*************************************************************************/
1530
/* TEST */
1531

    
1532
#include "libavutil/lfg.h"
1533

    
1534
#define FN (MDCT_SAMPLES/4)
1535

    
1536

    
1537
static void fft_test(AVLFG *lfg)
1538
{
1539
    IComplex in[FN], in1[FN];
1540
    int k, n, i;
1541
    float sum_re, sum_im, a;
1542

    
1543
    for (i = 0; i < FN; i++) {
1544
        in[i].re = av_lfg_get(lfg) % 65535 - 32767;
1545
        in[i].im = av_lfg_get(lfg) % 65535 - 32767;
1546
        in1[i]   = in[i];
1547
    }
1548
    fft(in, 7);
1549

    
1550
    /* do it by hand */
1551
    for (k = 0; k < FN; k++) {
1552
        sum_re = 0;
1553
        sum_im = 0;
1554
        for (n = 0; n < FN; n++) {
1555
            a = -2 * M_PI * (n * k) / FN;
1556
            sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);
1557
            sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);
1558
        }
1559
        av_log(NULL, AV_LOG_DEBUG, "%3d: %6d,%6d %6.0f,%6.0f\n",
1560
               k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);
1561
    }
1562
}
1563

    
1564

    
1565
static void mdct_test(AVLFG *lfg)
1566
{
1567
    int16_t input[MDCT_SAMPLES];
1568
    int32_t output[AC3_MAX_COEFS];
1569
    float input1[MDCT_SAMPLES];
1570
    float output1[AC3_MAX_COEFS];
1571
    float s, a, err, e, emax;
1572
    int i, k, n;
1573

    
1574
    for (i = 0; i < MDCT_SAMPLES; i++) {
1575
        input[i]  = (av_lfg_get(lfg) % 65535 - 32767) * 9 / 10;
1576
        input1[i] = input[i];
1577
    }
1578

    
1579
    mdct512(output, input);
1580

    
1581
    /* do it by hand */
1582
    for (k = 0; k < AC3_MAX_COEFS; k++) {
1583
        s = 0;
1584
        for (n = 0; n < MDCT_SAMPLES; n++) {
1585
            a = (2*M_PI*(2*n+1+MDCT_SAMPLES/2)*(2*k+1) / (4 * MDCT_SAMPLES));
1586
            s += input1[n] * cos(a);
1587
        }
1588
        output1[k] = -2 * s / MDCT_SAMPLES;
1589
    }
1590

    
1591
    err  = 0;
1592
    emax = 0;
1593
    for (i = 0; i < AC3_MAX_COEFS; i++) {
1594
        av_log(NULL, AV_LOG_DEBUG, "%3d: %7d %7.0f\n", i, output[i], output1[i]);
1595
        e = output[i] - output1[i];
1596
        if (e > emax)
1597
            emax = e;
1598
        err += e * e;
1599
    }
1600
    av_log(NULL, AV_LOG_DEBUG, "err2=%f emax=%f\n", err / AC3_MAX_COEFS, emax);
1601
}
1602

    
1603

    
1604
int main(void)
1605
{
1606
    AVLFG lfg;
1607

    
1608
    av_log_set_level(AV_LOG_DEBUG);
1609
    mdct_init(9);
1610

    
1611
    fft_test(&lfg);
1612
    mdct_test(&lfg);
1613

    
1614
    return 0;
1615
}
1616
#endif /* TEST */
1617

    
1618

    
1619
AVCodec ac3_encoder = {
1620
    "ac3",
1621
    AVMEDIA_TYPE_AUDIO,
1622
    CODEC_ID_AC3,
1623
    sizeof(AC3EncodeContext),
1624
    ac3_encode_init,
1625
    ac3_encode_frame,
1626
    ac3_encode_close,
1627
    NULL,
1628
    .sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE},
1629
    .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
1630
    .channel_layouts = (const int64_t[]){
1631
        AV_CH_LAYOUT_MONO,
1632
        AV_CH_LAYOUT_STEREO,
1633
        AV_CH_LAYOUT_2_1,
1634
        AV_CH_LAYOUT_SURROUND,
1635
        AV_CH_LAYOUT_2_2,
1636
        AV_CH_LAYOUT_QUAD,
1637
        AV_CH_LAYOUT_4POINT0,
1638
        AV_CH_LAYOUT_5POINT0,
1639
        AV_CH_LAYOUT_5POINT0_BACK,
1640
       (AV_CH_LAYOUT_MONO     | AV_CH_LOW_FREQUENCY),
1641
       (AV_CH_LAYOUT_STEREO   | AV_CH_LOW_FREQUENCY),
1642
       (AV_CH_LAYOUT_2_1      | AV_CH_LOW_FREQUENCY),
1643
       (AV_CH_LAYOUT_SURROUND | AV_CH_LOW_FREQUENCY),
1644
       (AV_CH_LAYOUT_2_2      | AV_CH_LOW_FREQUENCY),
1645
       (AV_CH_LAYOUT_QUAD     | AV_CH_LOW_FREQUENCY),
1646
       (AV_CH_LAYOUT_4POINT0  | AV_CH_LOW_FREQUENCY),
1647
        AV_CH_LAYOUT_5POINT1,
1648
        AV_CH_LAYOUT_5POINT1_BACK,
1649
        0 },
1650
};