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1
/*
2
 * The simplest mpeg audio layer 2 encoder
3
 * Copyright (c) 2000, 2001 Gerard Lantau.
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 *
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 * This program is free software; you can redistribute it and/or modify
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 * it under the terms of the GNU General Public License as published by
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 * the Free Software Foundation; either version 2 of the License, or
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 * (at your option) any later version.
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 *
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 * This program 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
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 * GNU General Public License for more details.
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 *
15
 * You should have received a copy of the GNU General Public License
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 * along with this program; if not, write to the Free Software
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 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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 */
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#include "avcodec.h"
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#include <math.h>
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#include "mpegaudio.h"
22

    
23
/* currently, cannot change these constants (need to modify
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   quantization stage) */
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#define FRAC_BITS 15
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#define WFRAC_BITS  14
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#define MUL(a,b) (((INT64)(a) * (INT64)(b)) >> FRAC_BITS)
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#define FIX(a)   ((int)((a) * (1 << FRAC_BITS)))
29

    
30
#define SAMPLES_BUF_SIZE 4096
31

    
32
typedef struct MpegAudioContext {
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    PutBitContext pb;
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    int nb_channels;
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    int freq, bit_rate;
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    int lsf;           /* 1 if mpeg2 low bitrate selected */
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    int bitrate_index; /* bit rate */
38
    int freq_index;
39
    int frame_size; /* frame size, in bits, without padding */
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    INT64 nb_samples; /* total number of samples encoded */
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    /* padding computation */
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    int frame_frac, frame_frac_incr, do_padding;
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    short samples_buf[MPA_MAX_CHANNELS][SAMPLES_BUF_SIZE]; /* buffer for filter */
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    int samples_offset[MPA_MAX_CHANNELS];       /* offset in samples_buf */
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    int sb_samples[MPA_MAX_CHANNELS][3][12][SBLIMIT];
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    unsigned char scale_factors[MPA_MAX_CHANNELS][SBLIMIT][3]; /* scale factors */
47
    /* code to group 3 scale factors */
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    unsigned char scale_code[MPA_MAX_CHANNELS][SBLIMIT];       
49
    int sblimit; /* number of used subbands */
50
    const unsigned char *alloc_table;
51
} MpegAudioContext;
52

    
53
/* define it to use floats in quantization (I don't like floats !) */
54
//#define USE_FLOATS
55

    
56
#include "mpegaudiotab.h"
57

    
58
int MPA_encode_init(AVCodecContext *avctx)
59
{
60
    MpegAudioContext *s = avctx->priv_data;
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    int freq = avctx->sample_rate;
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    int bitrate = avctx->bit_rate;
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    int channels = avctx->channels;
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    int i, v, table;
65
    float a;
66

    
67
    if (channels > 2)
68
        return -1;
69
    bitrate = bitrate / 1000;
70
    s->nb_channels = channels;
71
    s->freq = freq;
72
    s->bit_rate = bitrate * 1000;
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    avctx->frame_size = MPA_FRAME_SIZE;
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    avctx->key_frame = 1; /* always key frame */
75

    
76
    /* encoding freq */
77
    s->lsf = 0;
78
    for(i=0;i<3;i++) {
79
        if (mpa_freq_tab[i] == freq) 
80
            break;
81
        if ((mpa_freq_tab[i] / 2) == freq) {
82
            s->lsf = 1;
83
            break;
84
        }
85
    }
86
    if (i == 3)
87
        return -1;
88
    s->freq_index = i;
89

    
90
    /* encoding bitrate & frequency */
91
    for(i=0;i<15;i++) {
92
        if (mpa_bitrate_tab[s->lsf][1][i] == bitrate) 
93
            break;
94
    }
95
    if (i == 15)
96
        return -1;
97
    s->bitrate_index = i;
98

    
99
    /* compute total header size & pad bit */
100
    
101
    a = (float)(bitrate * 1000 * MPA_FRAME_SIZE) / (freq * 8.0);
102
    s->frame_size = ((int)a) * 8;
103

    
104
    /* frame fractional size to compute padding */
105
    s->frame_frac = 0;
106
    s->frame_frac_incr = (int)((a - floor(a)) * 65536.0);
107
    
108
    /* select the right allocation table */
109
    table = l2_select_table(bitrate, s->nb_channels, freq, s->lsf);
110

    
111
    /* number of used subbands */
112
    s->sblimit = sblimit_table[table];
113
    s->alloc_table = alloc_tables[table];
114

    
115
#ifdef DEBUG
116
    printf("%d kb/s, %d Hz, frame_size=%d bits, table=%d, padincr=%x\n", 
117
           bitrate, freq, s->frame_size, table, s->frame_frac_incr);
118
#endif
119

    
120
    for(i=0;i<s->nb_channels;i++)
121
        s->samples_offset[i] = 0;
122

    
123
    for(i=0;i<257;i++) {
124
        int v;
125
        v = mpa_enwindow[i];
126
#if WFRAC_BITS != 16
127
        v = (v + (1 << (16 - WFRAC_BITS - 1))) >> (16 - WFRAC_BITS);
128
#endif
129
        filter_bank[i] = v;
130
        if ((i & 63) != 0)
131
            v = -v;
132
        if (i != 0)
133
            filter_bank[512 - i] = v;
134
    }
135

    
136
    for(i=0;i<64;i++) {
137
        v = (int)(pow(2.0, (3 - i) / 3.0) * (1 << 20));
138
        if (v <= 0)
139
            v = 1;
140
        scale_factor_table[i] = v;
141
#ifdef USE_FLOATS
142
        scale_factor_inv_table[i] = pow(2.0, -(3 - i) / 3.0) / (float)(1 << 20);
143
#else
144
#define P 15
145
        scale_factor_shift[i] = 21 - P - (i / 3);
146
        scale_factor_mult[i] = (1 << P) * pow(2.0, (i % 3) / 3.0);
147
#endif
148
    }
149
    for(i=0;i<128;i++) {
150
        v = i - 64;
151
        if (v <= -3)
152
            v = 0;
153
        else if (v < 0)
154
            v = 1;
155
        else if (v == 0)
156
            v = 2;
157
        else if (v < 3)
158
            v = 3;
159
        else 
160
            v = 4;
161
        scale_diff_table[i] = v;
162
    }
163

    
164
    for(i=0;i<17;i++) {
165
        v = quant_bits[i];
166
        if (v < 0) 
167
            v = -v;
168
        else
169
            v = v * 3;
170
        total_quant_bits[i] = 12 * v;
171
    }
172

    
173
    return 0;
174
}
175

    
176
/* 32 point floating point IDCT without 1/sqrt(2) coef zero scaling */
177
static void idct32(int *out, int *tab)
178
{
179
    int i, j;
180
    int *t, *t1, xr;
181
    const int *xp = costab32;
182

    
183
    for(j=31;j>=3;j-=2) tab[j] += tab[j - 2];
184
    
185
    t = tab + 30;
186
    t1 = tab + 2;
187
    do {
188
        t[0] += t[-4];
189
        t[1] += t[1 - 4];
190
        t -= 4;
191
    } while (t != t1);
192

    
193
    t = tab + 28;
194
    t1 = tab + 4;
195
    do {
196
        t[0] += t[-8];
197
        t[1] += t[1-8];
198
        t[2] += t[2-8];
199
        t[3] += t[3-8];
200
        t -= 8;
201
    } while (t != t1);
202
    
203
    t = tab;
204
    t1 = tab + 32;
205
    do {
206
        t[ 3] = -t[ 3];    
207
        t[ 6] = -t[ 6];    
208
        
209
        t[11] = -t[11];    
210
        t[12] = -t[12];    
211
        t[13] = -t[13];    
212
        t[15] = -t[15]; 
213
        t += 16;
214
    } while (t != t1);
215

    
216
    
217
    t = tab;
218
    t1 = tab + 8;
219
    do {
220
        int x1, x2, x3, x4;
221
        
222
        x3 = MUL(t[16], FIX(SQRT2*0.5));
223
        x4 = t[0] - x3;
224
        x3 = t[0] + x3;
225
        
226
        x2 = MUL(-(t[24] + t[8]), FIX(SQRT2*0.5));
227
        x1 = MUL((t[8] - x2), xp[0]);
228
        x2 = MUL((t[8] + x2), xp[1]);
229

    
230
        t[ 0] = x3 + x1;
231
        t[ 8] = x4 - x2;
232
        t[16] = x4 + x2;
233
        t[24] = x3 - x1;
234
        t++;
235
    } while (t != t1);
236

    
237
    xp += 2;
238
    t = tab;
239
    t1 = tab + 4;
240
    do {
241
        xr = MUL(t[28],xp[0]);
242
        t[28] = (t[0] - xr);
243
        t[0] = (t[0] + xr);
244

    
245
        xr = MUL(t[4],xp[1]);
246
        t[ 4] = (t[24] - xr);
247
        t[24] = (t[24] + xr);
248
        
249
        xr = MUL(t[20],xp[2]);
250
        t[20] = (t[8] - xr);
251
        t[ 8] = (t[8] + xr);
252
            
253
        xr = MUL(t[12],xp[3]);
254
        t[12] = (t[16] - xr);
255
        t[16] = (t[16] + xr);
256
        t++;
257
    } while (t != t1);
258
    xp += 4;
259

    
260
    for (i = 0; i < 4; i++) {
261
        xr = MUL(tab[30-i*4],xp[0]);
262
        tab[30-i*4] = (tab[i*4] - xr);
263
        tab[   i*4] = (tab[i*4] + xr);
264
        
265
        xr = MUL(tab[ 2+i*4],xp[1]);
266
        tab[ 2+i*4] = (tab[28-i*4] - xr);
267
        tab[28-i*4] = (tab[28-i*4] + xr);
268
        
269
        xr = MUL(tab[31-i*4],xp[0]);
270
        tab[31-i*4] = (tab[1+i*4] - xr);
271
        tab[ 1+i*4] = (tab[1+i*4] + xr);
272
        
273
        xr = MUL(tab[ 3+i*4],xp[1]);
274
        tab[ 3+i*4] = (tab[29-i*4] - xr);
275
        tab[29-i*4] = (tab[29-i*4] + xr);
276
        
277
        xp += 2;
278
    }
279

    
280
    t = tab + 30;
281
    t1 = tab + 1;
282
    do {
283
        xr = MUL(t1[0], *xp);
284
        t1[0] = (t[0] - xr);
285
        t[0] = (t[0] + xr);
286
        t -= 2;
287
        t1 += 2;
288
        xp++;
289
    } while (t >= tab);
290

    
291
    for(i=0;i<32;i++) {
292
        out[i] = tab[bitinv32[i]];
293
    }
294
}
295

    
296
#define WSHIFT (WFRAC_BITS + 15 - FRAC_BITS)
297

    
298
static void filter(MpegAudioContext *s, int ch, short *samples, int incr)
299
{
300
    short *p, *q;
301
    int sum, offset, i, j;
302
    int tmp[64];
303
    int tmp1[32];
304
    int *out;
305

    
306
    //    print_pow1(samples, 1152);
307

    
308
    offset = s->samples_offset[ch];
309
    out = &s->sb_samples[ch][0][0][0];
310
    for(j=0;j<36;j++) {
311
        /* 32 samples at once */
312
        for(i=0;i<32;i++) {
313
            s->samples_buf[ch][offset + (31 - i)] = samples[0];
314
            samples += incr;
315
        }
316

    
317
        /* filter */
318
        p = s->samples_buf[ch] + offset;
319
        q = filter_bank;
320
        /* maxsum = 23169 */
321
        for(i=0;i<64;i++) {
322
            sum = p[0*64] * q[0*64];
323
            sum += p[1*64] * q[1*64];
324
            sum += p[2*64] * q[2*64];
325
            sum += p[3*64] * q[3*64];
326
            sum += p[4*64] * q[4*64];
327
            sum += p[5*64] * q[5*64];
328
            sum += p[6*64] * q[6*64];
329
            sum += p[7*64] * q[7*64];
330
            tmp[i] = sum;
331
            p++;
332
            q++;
333
        }
334
        tmp1[0] = tmp[16] >> WSHIFT;
335
        for( i=1; i<=16; i++ ) tmp1[i] = (tmp[i+16]+tmp[16-i]) >> WSHIFT;
336
        for( i=17; i<=31; i++ ) tmp1[i] = (tmp[i+16]-tmp[80-i]) >> WSHIFT;
337

    
338
        idct32(out, tmp1);
339

    
340
        /* advance of 32 samples */
341
        offset -= 32;
342
        out += 32;
343
        /* handle the wrap around */
344
        if (offset < 0) {
345
            memmove(s->samples_buf[ch] + SAMPLES_BUF_SIZE - (512 - 32), 
346
                    s->samples_buf[ch], (512 - 32) * 2);
347
            offset = SAMPLES_BUF_SIZE - 512;
348
        }
349
    }
350
    s->samples_offset[ch] = offset;
351

    
352
    //    print_pow(s->sb_samples, 1152);
353
}
354

    
355
static void compute_scale_factors(unsigned char scale_code[SBLIMIT],
356
                                  unsigned char scale_factors[SBLIMIT][3], 
357
                                  int sb_samples[3][12][SBLIMIT],
358
                                  int sblimit)
359
{
360
    int *p, vmax, v, n, i, j, k, code;
361
    int index, d1, d2;
362
    unsigned char *sf = &scale_factors[0][0];
363
    
364
    for(j=0;j<sblimit;j++) {
365
        for(i=0;i<3;i++) {
366
            /* find the max absolute value */
367
            p = &sb_samples[i][0][j];
368
            vmax = abs(*p);
369
            for(k=1;k<12;k++) {
370
                p += SBLIMIT;
371
                v = abs(*p);
372
                if (v > vmax)
373
                    vmax = v;
374
            }
375
            /* compute the scale factor index using log 2 computations */
376
            if (vmax > 0) {
377
                n = av_log2(vmax);
378
                /* n is the position of the MSB of vmax. now 
379
                   use at most 2 compares to find the index */
380
                index = (21 - n) * 3 - 3;
381
                if (index >= 0) {
382
                    while (vmax <= scale_factor_table[index+1])
383
                        index++;
384
                } else {
385
                    index = 0; /* very unlikely case of overflow */
386
                }
387
            } else {
388
                index = 62; /* value 63 is not allowed */
389
            }
390

    
391
#if 0
392
            printf("%2d:%d in=%x %x %d\n", 
393
                   j, i, vmax, scale_factor_table[index], index);
394
#endif
395
            /* store the scale factor */
396
            assert(index >=0 && index <= 63);
397
            sf[i] = index;
398
        }
399

    
400
        /* compute the transmission factor : look if the scale factors
401
           are close enough to each other */
402
        d1 = scale_diff_table[sf[0] - sf[1] + 64];
403
        d2 = scale_diff_table[sf[1] - sf[2] + 64];
404
        
405
        /* handle the 25 cases */
406
        switch(d1 * 5 + d2) {
407
        case 0*5+0:
408
        case 0*5+4:
409
        case 3*5+4:
410
        case 4*5+0:
411
        case 4*5+4:
412
            code = 0;
413
            break;
414
        case 0*5+1:
415
        case 0*5+2:
416
        case 4*5+1:
417
        case 4*5+2:
418
            code = 3;
419
            sf[2] = sf[1];
420
            break;
421
        case 0*5+3:
422
        case 4*5+3:
423
            code = 3;
424
            sf[1] = sf[2];
425
            break;
426
        case 1*5+0:
427
        case 1*5+4:
428
        case 2*5+4:
429
            code = 1;
430
            sf[1] = sf[0];
431
            break;
432
        case 1*5+1:
433
        case 1*5+2:
434
        case 2*5+0:
435
        case 2*5+1:
436
        case 2*5+2:
437
            code = 2;
438
            sf[1] = sf[2] = sf[0];
439
            break;
440
        case 2*5+3:
441
        case 3*5+3:
442
            code = 2;
443
            sf[0] = sf[1] = sf[2];
444
            break;
445
        case 3*5+0:
446
        case 3*5+1:
447
        case 3*5+2:
448
            code = 2;
449
            sf[0] = sf[2] = sf[1];
450
            break;
451
        case 1*5+3:
452
            code = 2;
453
            if (sf[0] > sf[2])
454
              sf[0] = sf[2];
455
            sf[1] = sf[2] = sf[0];
456
            break;
457
        default:
458
            abort();
459
        }
460
        
461
#if 0
462
        printf("%d: %2d %2d %2d %d %d -> %d\n", j, 
463
               sf[0], sf[1], sf[2], d1, d2, code);
464
#endif
465
        scale_code[j] = code;
466
        sf += 3;
467
    }
468
}
469

    
470
/* The most important function : psycho acoustic module. In this
471
   encoder there is basically none, so this is the worst you can do,
472
   but also this is the simpler. */
473
static void psycho_acoustic_model(MpegAudioContext *s, short smr[SBLIMIT])
474
{
475
    int i;
476

    
477
    for(i=0;i<s->sblimit;i++) {
478
        smr[i] = (int)(fixed_smr[i] * 10);
479
    }
480
}
481

    
482

    
483
#define SB_NOTALLOCATED  0
484
#define SB_ALLOCATED     1
485
#define SB_NOMORE        2
486

    
487
/* Try to maximize the smr while using a number of bits inferior to
488
   the frame size. I tried to make the code simpler, faster and
489
   smaller than other encoders :-) */
490
static void compute_bit_allocation(MpegAudioContext *s, 
491
                                   short smr1[MPA_MAX_CHANNELS][SBLIMIT],
492
                                   unsigned char bit_alloc[MPA_MAX_CHANNELS][SBLIMIT],
493
                                   int *padding)
494
{
495
    int i, ch, b, max_smr, max_ch, max_sb, current_frame_size, max_frame_size;
496
    int incr;
497
    short smr[MPA_MAX_CHANNELS][SBLIMIT];
498
    unsigned char subband_status[MPA_MAX_CHANNELS][SBLIMIT];
499
    const unsigned char *alloc;
500

    
501
    memcpy(smr, smr1, s->nb_channels * sizeof(short) * SBLIMIT);
502
    memset(subband_status, SB_NOTALLOCATED, s->nb_channels * SBLIMIT);
503
    memset(bit_alloc, 0, s->nb_channels * SBLIMIT);
504
    
505
    /* compute frame size and padding */
506
    max_frame_size = s->frame_size;
507
    s->frame_frac += s->frame_frac_incr;
508
    if (s->frame_frac >= 65536) {
509
        s->frame_frac -= 65536;
510
        s->do_padding = 1;
511
        max_frame_size += 8;
512
    } else {
513
        s->do_padding = 0;
514
    }
515

    
516
    /* compute the header + bit alloc size */
517
    current_frame_size = 32;
518
    alloc = s->alloc_table;
519
    for(i=0;i<s->sblimit;i++) {
520
        incr = alloc[0];
521
        current_frame_size += incr * s->nb_channels;
522
        alloc += 1 << incr;
523
    }
524
    for(;;) {
525
        /* look for the subband with the largest signal to mask ratio */
526
        max_sb = -1;
527
        max_ch = -1;
528
        max_smr = 0x80000000;
529
        for(ch=0;ch<s->nb_channels;ch++) {
530
            for(i=0;i<s->sblimit;i++) {
531
                if (smr[ch][i] > max_smr && subband_status[ch][i] != SB_NOMORE) {
532
                    max_smr = smr[ch][i];
533
                    max_sb = i;
534
                    max_ch = ch;
535
                }
536
            }
537
        }
538
#if 0
539
        printf("current=%d max=%d max_sb=%d alloc=%d\n", 
540
               current_frame_size, max_frame_size, max_sb,
541
               bit_alloc[max_sb]);
542
#endif        
543
        if (max_sb < 0)
544
            break;
545
        
546
        /* find alloc table entry (XXX: not optimal, should use
547
           pointer table) */
548
        alloc = s->alloc_table;
549
        for(i=0;i<max_sb;i++) {
550
            alloc += 1 << alloc[0];
551
        }
552

    
553
        if (subband_status[max_ch][max_sb] == SB_NOTALLOCATED) {
554
            /* nothing was coded for this band: add the necessary bits */
555
            incr = 2 + nb_scale_factors[s->scale_code[max_ch][max_sb]] * 6;
556
            incr += total_quant_bits[alloc[1]];
557
        } else {
558
            /* increments bit allocation */
559
            b = bit_alloc[max_ch][max_sb];
560
            incr = total_quant_bits[alloc[b + 1]] - 
561
                total_quant_bits[alloc[b]];
562
        }
563

    
564
        if (current_frame_size + incr <= max_frame_size) {
565
            /* can increase size */
566
            b = ++bit_alloc[max_ch][max_sb];
567
            current_frame_size += incr;
568
            /* decrease smr by the resolution we added */
569
            smr[max_ch][max_sb] = smr1[max_ch][max_sb] - quant_snr[alloc[b]];
570
            /* max allocation size reached ? */
571
            if (b == ((1 << alloc[0]) - 1))
572
                subband_status[max_ch][max_sb] = SB_NOMORE;
573
            else
574
                subband_status[max_ch][max_sb] = SB_ALLOCATED;
575
        } else {
576
            /* cannot increase the size of this subband */
577
            subband_status[max_ch][max_sb] = SB_NOMORE;
578
        }
579
    }
580
    *padding = max_frame_size - current_frame_size;
581
    assert(*padding >= 0);
582

    
583
#if 0
584
    for(i=0;i<s->sblimit;i++) {
585
        printf("%d ", bit_alloc[i]);
586
    }
587
    printf("\n");
588
#endif
589
}
590

    
591
/*
592
 * Output the mpeg audio layer 2 frame. Note how the code is small
593
 * compared to other encoders :-)
594
 */
595
static void encode_frame(MpegAudioContext *s,
596
                         unsigned char bit_alloc[MPA_MAX_CHANNELS][SBLIMIT],
597
                         int padding)
598
{
599
    int i, j, k, l, bit_alloc_bits, b, ch;
600
    unsigned char *sf;
601
    int q[3];
602
    PutBitContext *p = &s->pb;
603

    
604
    /* header */
605

    
606
    put_bits(p, 12, 0xfff);
607
    put_bits(p, 1, 1 - s->lsf); /* 1 = mpeg1 ID, 0 = mpeg2 lsf ID */
608
    put_bits(p, 2, 4-2);  /* layer 2 */
609
    put_bits(p, 1, 1); /* no error protection */
610
    put_bits(p, 4, s->bitrate_index);
611
    put_bits(p, 2, s->freq_index);
612
    put_bits(p, 1, s->do_padding); /* use padding */
613
    put_bits(p, 1, 0);             /* private_bit */
614
    put_bits(p, 2, s->nb_channels == 2 ? MPA_STEREO : MPA_MONO);
615
    put_bits(p, 2, 0); /* mode_ext */
616
    put_bits(p, 1, 0); /* no copyright */
617
    put_bits(p, 1, 1); /* original */
618
    put_bits(p, 2, 0); /* no emphasis */
619

    
620
    /* bit allocation */
621
    j = 0;
622
    for(i=0;i<s->sblimit;i++) {
623
        bit_alloc_bits = s->alloc_table[j];
624
        for(ch=0;ch<s->nb_channels;ch++) {
625
            put_bits(p, bit_alloc_bits, bit_alloc[ch][i]);
626
        }
627
        j += 1 << bit_alloc_bits;
628
    }
629
    
630
    /* scale codes */
631
    for(i=0;i<s->sblimit;i++) {
632
        for(ch=0;ch<s->nb_channels;ch++) {
633
            if (bit_alloc[ch][i]) 
634
                put_bits(p, 2, s->scale_code[ch][i]);
635
        }
636
    }
637

    
638
    /* scale factors */
639
    for(i=0;i<s->sblimit;i++) {
640
        for(ch=0;ch<s->nb_channels;ch++) {
641
            if (bit_alloc[ch][i]) {
642
                sf = &s->scale_factors[ch][i][0];
643
                switch(s->scale_code[ch][i]) {
644
                case 0:
645
                    put_bits(p, 6, sf[0]);
646
                    put_bits(p, 6, sf[1]);
647
                    put_bits(p, 6, sf[2]);
648
                    break;
649
                case 3:
650
                case 1:
651
                    put_bits(p, 6, sf[0]);
652
                    put_bits(p, 6, sf[2]);
653
                    break;
654
                case 2:
655
                    put_bits(p, 6, sf[0]);
656
                    break;
657
                }
658
            }
659
        }
660
    }
661
    
662
    /* quantization & write sub band samples */
663

    
664
    for(k=0;k<3;k++) {
665
        for(l=0;l<12;l+=3) {
666
            j = 0;
667
            for(i=0;i<s->sblimit;i++) {
668
                bit_alloc_bits = s->alloc_table[j];
669
                for(ch=0;ch<s->nb_channels;ch++) {
670
                    b = bit_alloc[ch][i];
671
                    if (b) {
672
                        int qindex, steps, m, sample, bits;
673
                        /* we encode 3 sub band samples of the same sub band at a time */
674
                        qindex = s->alloc_table[j+b];
675
                        steps = quant_steps[qindex];
676
                        for(m=0;m<3;m++) {
677
                            sample = s->sb_samples[ch][k][l + m][i];
678
                            /* divide by scale factor */
679
#ifdef USE_FLOATS
680
                            {
681
                                float a;
682
                                a = (float)sample * scale_factor_inv_table[s->scale_factors[ch][i][k]];
683
                                q[m] = (int)((a + 1.0) * steps * 0.5);
684
                            }
685
#else
686
                            {
687
                                int q1, e, shift, mult;
688
                                e = s->scale_factors[ch][i][k];
689
                                shift = scale_factor_shift[e];
690
                                mult = scale_factor_mult[e];
691
                                
692
                                /* normalize to P bits */
693
                                if (shift < 0)
694
                                    q1 = sample << (-shift);
695
                                else
696
                                    q1 = sample >> shift;
697
                                q1 = (q1 * mult) >> P;
698
                                q[m] = ((q1 + (1 << P)) * steps) >> (P + 1);
699
                            }
700
#endif
701
                            if (q[m] >= steps)
702
                                q[m] = steps - 1;
703
                            assert(q[m] >= 0 && q[m] < steps);
704
                        }
705
                        bits = quant_bits[qindex];
706
                        if (bits < 0) {
707
                            /* group the 3 values to save bits */
708
                            put_bits(p, -bits, 
709
                                     q[0] + steps * (q[1] + steps * q[2]));
710
#if 0
711
                            printf("%d: gr1 %d\n", 
712
                                   i, q[0] + steps * (q[1] + steps * q[2]));
713
#endif
714
                        } else {
715
#if 0
716
                            printf("%d: gr3 %d %d %d\n", 
717
                                   i, q[0], q[1], q[2]);
718
#endif                               
719
                            put_bits(p, bits, q[0]);
720
                            put_bits(p, bits, q[1]);
721
                            put_bits(p, bits, q[2]);
722
                        }
723
                    }
724
                }
725
                /* next subband in alloc table */
726
                j += 1 << bit_alloc_bits; 
727
            }
728
        }
729
    }
730

    
731
    /* padding */
732
    for(i=0;i<padding;i++)
733
        put_bits(p, 1, 0);
734

    
735
    /* flush */
736
    flush_put_bits(p);
737
}
738

    
739
int MPA_encode_frame(AVCodecContext *avctx,
740
                     unsigned char *frame, int buf_size, void *data)
741
{
742
    MpegAudioContext *s = avctx->priv_data;
743
    short *samples = data;
744
    short smr[MPA_MAX_CHANNELS][SBLIMIT];
745
    unsigned char bit_alloc[MPA_MAX_CHANNELS][SBLIMIT];
746
    int padding, i;
747

    
748
    for(i=0;i<s->nb_channels;i++) {
749
        filter(s, i, samples + i, s->nb_channels);
750
    }
751

    
752
    for(i=0;i<s->nb_channels;i++) {
753
        compute_scale_factors(s->scale_code[i], s->scale_factors[i], 
754
                              s->sb_samples[i], s->sblimit);
755
    }
756
    for(i=0;i<s->nb_channels;i++) {
757
        psycho_acoustic_model(s, smr[i]);
758
    }
759
    compute_bit_allocation(s, smr, bit_alloc, &padding);
760

    
761
    init_put_bits(&s->pb, frame, MPA_MAX_CODED_FRAME_SIZE, NULL, NULL);
762

    
763
    encode_frame(s, bit_alloc, padding);
764
    
765
    s->nb_samples += MPA_FRAME_SIZE;
766
    return pbBufPtr(&s->pb) - s->pb.buf;
767
}
768

    
769

    
770
AVCodec mp2_encoder = {
771
    "mp2",
772
    CODEC_TYPE_AUDIO,
773
    CODEC_ID_MP2,
774
    sizeof(MpegAudioContext),
775
    MPA_encode_init,
776
    MPA_encode_frame,
777
    NULL,
778
};