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4349 Serge 1
/*
2
 * AAC encoder psychoacoustic model
3
 * Copyright (C) 2008 Konstantin Shishkov
4
 *
5
 * This file is part of FFmpeg.
6
 *
7
 * FFmpeg is free software; you can redistribute it and/or
8
 * modify it under the terms of the GNU Lesser General Public
9
 * License as published by the Free Software Foundation; either
10
 * version 2.1 of the License, or (at your option) any later version.
11
 *
12
 * FFmpeg is distributed in the hope that it will be useful,
13
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15
 * Lesser General Public License for more details.
16
 *
17
 * You should have received a copy of the GNU Lesser General Public
18
 * License along with FFmpeg; if not, write to the Free Software
19
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20
 */
21
 
22
/**
23
 * @file
24
 * AAC encoder psychoacoustic model
25
 */
26
 
27
#include "libavutil/attributes.h"
28
#include "libavutil/libm.h"
29
 
30
#include "avcodec.h"
31
#include "aactab.h"
32
#include "psymodel.h"
33
 
34
/***********************************
35
 *              TODOs:
36
 * try other bitrate controlling mechanism (maybe use ratecontrol.c?)
37
 * control quality for quality-based output
38
 **********************************/
39
 
40
/**
41
 * constants for 3GPP AAC psychoacoustic model
42
 * @{
43
 */
44
#define PSY_3GPP_THR_SPREAD_HI   1.5f // spreading factor for low-to-hi threshold spreading  (15 dB/Bark)
45
#define PSY_3GPP_THR_SPREAD_LOW  3.0f // spreading factor for hi-to-low threshold spreading  (30 dB/Bark)
46
/* spreading factor for low-to-hi energy spreading, long block, > 22kbps/channel (20dB/Bark) */
47
#define PSY_3GPP_EN_SPREAD_HI_L1 2.0f
48
/* spreading factor for low-to-hi energy spreading, long block, <= 22kbps/channel (15dB/Bark) */
49
#define PSY_3GPP_EN_SPREAD_HI_L2 1.5f
50
/* spreading factor for low-to-hi energy spreading, short block (15 dB/Bark) */
51
#define PSY_3GPP_EN_SPREAD_HI_S  1.5f
52
/* spreading factor for hi-to-low energy spreading, long block (30dB/Bark) */
53
#define PSY_3GPP_EN_SPREAD_LOW_L 3.0f
54
/* spreading factor for hi-to-low energy spreading, short block (20dB/Bark) */
55
#define PSY_3GPP_EN_SPREAD_LOW_S 2.0f
56
 
57
#define PSY_3GPP_RPEMIN      0.01f
58
#define PSY_3GPP_RPELEV      2.0f
59
 
60
#define PSY_3GPP_C1          3.0f           /* log2(8) */
61
#define PSY_3GPP_C2          1.3219281f     /* log2(2.5) */
62
#define PSY_3GPP_C3          0.55935729f    /* 1 - C2 / C1 */
63
 
64
#define PSY_SNR_1DB          7.9432821e-1f  /* -1dB */
65
#define PSY_SNR_25DB         3.1622776e-3f  /* -25dB */
66
 
67
#define PSY_3GPP_SAVE_SLOPE_L  -0.46666667f
68
#define PSY_3GPP_SAVE_SLOPE_S  -0.36363637f
69
#define PSY_3GPP_SAVE_ADD_L    -0.84285712f
70
#define PSY_3GPP_SAVE_ADD_S    -0.75f
71
#define PSY_3GPP_SPEND_SLOPE_L  0.66666669f
72
#define PSY_3GPP_SPEND_SLOPE_S  0.81818181f
73
#define PSY_3GPP_SPEND_ADD_L   -0.35f
74
#define PSY_3GPP_SPEND_ADD_S   -0.26111111f
75
#define PSY_3GPP_CLIP_LO_L      0.2f
76
#define PSY_3GPP_CLIP_LO_S      0.2f
77
#define PSY_3GPP_CLIP_HI_L      0.95f
78
#define PSY_3GPP_CLIP_HI_S      0.75f
79
 
80
#define PSY_3GPP_AH_THR_LONG    0.5f
81
#define PSY_3GPP_AH_THR_SHORT   0.63f
82
 
83
enum {
84
    PSY_3GPP_AH_NONE,
85
    PSY_3GPP_AH_INACTIVE,
86
    PSY_3GPP_AH_ACTIVE
87
};
88
 
89
#define PSY_3GPP_BITS_TO_PE(bits) ((bits) * 1.18f)
90
 
91
/* LAME psy model constants */
92
#define PSY_LAME_FIR_LEN 21         ///< LAME psy model FIR order
93
#define AAC_BLOCK_SIZE_LONG 1024    ///< long block size
94
#define AAC_BLOCK_SIZE_SHORT 128    ///< short block size
95
#define AAC_NUM_BLOCKS_SHORT 8      ///< number of blocks in a short sequence
96
#define PSY_LAME_NUM_SUBBLOCKS 3    ///< Number of sub-blocks in each short block
97
 
98
/**
99
 * @}
100
 */
101
 
102
/**
103
 * information for single band used by 3GPP TS26.403-inspired psychoacoustic model
104
 */
105
typedef struct AacPsyBand{
106
    float energy;       ///< band energy
107
    float thr;          ///< energy threshold
108
    float thr_quiet;    ///< threshold in quiet
109
    float nz_lines;     ///< number of non-zero spectral lines
110
    float active_lines; ///< number of active spectral lines
111
    float pe;           ///< perceptual entropy
112
    float pe_const;     ///< constant part of the PE calculation
113
    float norm_fac;     ///< normalization factor for linearization
114
    int   avoid_holes;  ///< hole avoidance flag
115
}AacPsyBand;
116
 
117
/**
118
 * single/pair channel context for psychoacoustic model
119
 */
120
typedef struct AacPsyChannel{
121
    AacPsyBand band[128];               ///< bands information
122
    AacPsyBand prev_band[128];          ///< bands information from the previous frame
123
 
124
    float       win_energy;              ///< sliding average of channel energy
125
    float       iir_state[2];            ///< hi-pass IIR filter state
126
    uint8_t     next_grouping;           ///< stored grouping scheme for the next frame (in case of 8 short window sequence)
127
    enum WindowSequence next_window_seq; ///< window sequence to be used in the next frame
128
    /* LAME psy model specific members */
129
    float attack_threshold;              ///< attack threshold for this channel
130
    float prev_energy_subshort[AAC_NUM_BLOCKS_SHORT * PSY_LAME_NUM_SUBBLOCKS];
131
    int   prev_attack;                   ///< attack value for the last short block in the previous sequence
132
}AacPsyChannel;
133
 
134
/**
135
 * psychoacoustic model frame type-dependent coefficients
136
 */
137
typedef struct AacPsyCoeffs{
138
    float ath;           ///< absolute threshold of hearing per bands
139
    float barks;         ///< Bark value for each spectral band in long frame
140
    float spread_low[2]; ///< spreading factor for low-to-high threshold spreading in long frame
141
    float spread_hi [2]; ///< spreading factor for high-to-low threshold spreading in long frame
142
    float min_snr;       ///< minimal SNR
143
}AacPsyCoeffs;
144
 
145
/**
146
 * 3GPP TS26.403-inspired psychoacoustic model specific data
147
 */
148
typedef struct AacPsyContext{
149
    int chan_bitrate;     ///< bitrate per channel
150
    int frame_bits;       ///< average bits per frame
151
    int fill_level;       ///< bit reservoir fill level
152
    struct {
153
        float min;        ///< minimum allowed PE for bit factor calculation
154
        float max;        ///< maximum allowed PE for bit factor calculation
155
        float previous;   ///< allowed PE of the previous frame
156
        float correction; ///< PE correction factor
157
    } pe;
158
    AacPsyCoeffs psy_coef[2][64];
159
    AacPsyChannel *ch;
160
}AacPsyContext;
161
 
162
/**
163
 * LAME psy model preset struct
164
 */
165
typedef struct {
166
    int   quality;  ///< Quality to map the rest of the vaules to.
167
     /* This is overloaded to be both kbps per channel in ABR mode, and
168
      * requested quality in constant quality mode.
169
      */
170
    float st_lrm;   ///< short threshold for L, R, and M channels
171
} PsyLamePreset;
172
 
173
/**
174
 * LAME psy model preset table for ABR
175
 */
176
static const PsyLamePreset psy_abr_map[] = {
177
/* TODO: Tuning. These were taken from LAME. */
178
/* kbps/ch st_lrm   */
179
    {  8,  6.60},
180
    { 16,  6.60},
181
    { 24,  6.60},
182
    { 32,  6.60},
183
    { 40,  6.60},
184
    { 48,  6.60},
185
    { 56,  6.60},
186
    { 64,  6.40},
187
    { 80,  6.00},
188
    { 96,  5.60},
189
    {112,  5.20},
190
    {128,  5.20},
191
    {160,  5.20}
192
};
193
 
194
/**
195
* LAME psy model preset table for constant quality
196
*/
197
static const PsyLamePreset psy_vbr_map[] = {
198
/* vbr_q  st_lrm    */
199
    { 0,  4.20},
200
    { 1,  4.20},
201
    { 2,  4.20},
202
    { 3,  4.20},
203
    { 4,  4.20},
204
    { 5,  4.20},
205
    { 6,  4.20},
206
    { 7,  4.20},
207
    { 8,  4.20},
208
    { 9,  4.20},
209
    {10,  4.20}
210
};
211
 
212
/**
213
 * LAME psy model FIR coefficient table
214
 */
215
static const float psy_fir_coeffs[] = {
216
    -8.65163e-18 * 2, -0.00851586 * 2, -6.74764e-18 * 2, 0.0209036 * 2,
217
    -3.36639e-17 * 2, -0.0438162 * 2,  -1.54175e-17 * 2, 0.0931738 * 2,
218
    -5.52212e-17 * 2, -0.313819 * 2
219
};
220
 
221
#if ARCH_MIPS
222
#   include "mips/aacpsy_mips.h"
223
#endif /* ARCH_MIPS */
224
 
225
/**
226
 * Calculate the ABR attack threshold from the above LAME psymodel table.
227
 */
228
static float lame_calc_attack_threshold(int bitrate)
229
{
230
    /* Assume max bitrate to start with */
231
    int lower_range = 12, upper_range = 12;
232
    int lower_range_kbps = psy_abr_map[12].quality;
233
    int upper_range_kbps = psy_abr_map[12].quality;
234
    int i;
235
 
236
    /* Determine which bitrates the value specified falls between.
237
     * If the loop ends without breaking our above assumption of 320kbps was correct.
238
     */
239
    for (i = 1; i < 13; i++) {
240
        if (FFMAX(bitrate, psy_abr_map[i].quality) != bitrate) {
241
            upper_range = i;
242
            upper_range_kbps = psy_abr_map[i    ].quality;
243
            lower_range = i - 1;
244
            lower_range_kbps = psy_abr_map[i - 1].quality;
245
            break; /* Upper range found */
246
        }
247
    }
248
 
249
    /* Determine which range the value specified is closer to */
250
    if ((upper_range_kbps - bitrate) > (bitrate - lower_range_kbps))
251
        return psy_abr_map[lower_range].st_lrm;
252
    return psy_abr_map[upper_range].st_lrm;
253
}
254
 
255
/**
256
 * LAME psy model specific initialization
257
 */
258
static av_cold void lame_window_init(AacPsyContext *ctx, AVCodecContext *avctx)
259
{
260
    int i, j;
261
 
262
    for (i = 0; i < avctx->channels; i++) {
263
        AacPsyChannel *pch = &ctx->ch[i];
264
 
265
        if (avctx->flags & CODEC_FLAG_QSCALE)
266
            pch->attack_threshold = psy_vbr_map[avctx->global_quality / FF_QP2LAMBDA].st_lrm;
267
        else
268
            pch->attack_threshold = lame_calc_attack_threshold(avctx->bit_rate / avctx->channels / 1000);
269
 
270
        for (j = 0; j < AAC_NUM_BLOCKS_SHORT * PSY_LAME_NUM_SUBBLOCKS; j++)
271
            pch->prev_energy_subshort[j] = 10.0f;
272
    }
273
}
274
 
275
/**
276
 * Calculate Bark value for given line.
277
 */
278
static av_cold float calc_bark(float f)
279
{
280
    return 13.3f * atanf(0.00076f * f) + 3.5f * atanf((f / 7500.0f) * (f / 7500.0f));
281
}
282
 
283
#define ATH_ADD 4
284
/**
285
 * Calculate ATH value for given frequency.
286
 * Borrowed from Lame.
287
 */
288
static av_cold float ath(float f, float add)
289
{
290
    f /= 1000.0f;
291
    return    3.64 * pow(f, -0.8)
292
            - 6.8  * exp(-0.6  * (f - 3.4) * (f - 3.4))
293
            + 6.0  * exp(-0.15 * (f - 8.7) * (f - 8.7))
294
            + (0.6 + 0.04 * add) * 0.001 * f * f * f * f;
295
}
296
 
297
static av_cold int psy_3gpp_init(FFPsyContext *ctx) {
298
    AacPsyContext *pctx;
299
    float bark;
300
    int i, j, g, start;
301
    float prev, minscale, minath, minsnr, pe_min;
302
    const int chan_bitrate = ctx->avctx->bit_rate / ctx->avctx->channels;
303
    const int bandwidth    = ctx->avctx->cutoff ? ctx->avctx->cutoff : AAC_CUTOFF(ctx->avctx);
304
    const float num_bark   = calc_bark((float)bandwidth);
305
 
306
    ctx->model_priv_data = av_mallocz(sizeof(AacPsyContext));
307
    pctx = (AacPsyContext*) ctx->model_priv_data;
308
 
309
    pctx->chan_bitrate = chan_bitrate;
310
    pctx->frame_bits   = chan_bitrate * AAC_BLOCK_SIZE_LONG / ctx->avctx->sample_rate;
311
    pctx->pe.min       =  8.0f * AAC_BLOCK_SIZE_LONG * bandwidth / (ctx->avctx->sample_rate * 2.0f);
312
    pctx->pe.max       = 12.0f * AAC_BLOCK_SIZE_LONG * bandwidth / (ctx->avctx->sample_rate * 2.0f);
313
    ctx->bitres.size   = 6144 - pctx->frame_bits;
314
    ctx->bitres.size  -= ctx->bitres.size % 8;
315
    pctx->fill_level   = ctx->bitres.size;
316
    minath = ath(3410, ATH_ADD);
317
    for (j = 0; j < 2; j++) {
318
        AacPsyCoeffs *coeffs = pctx->psy_coef[j];
319
        const uint8_t *band_sizes = ctx->bands[j];
320
        float line_to_frequency = ctx->avctx->sample_rate / (j ? 256.f : 2048.0f);
321
        float avg_chan_bits = chan_bitrate * (j ? 128.0f : 1024.0f) / ctx->avctx->sample_rate;
322
        /* reference encoder uses 2.4% here instead of 60% like the spec says */
323
        float bark_pe = 0.024f * PSY_3GPP_BITS_TO_PE(avg_chan_bits) / num_bark;
324
        float en_spread_low = j ? PSY_3GPP_EN_SPREAD_LOW_S : PSY_3GPP_EN_SPREAD_LOW_L;
325
        /* High energy spreading for long blocks <= 22kbps/channel and short blocks are the same. */
326
        float en_spread_hi  = (j || (chan_bitrate <= 22.0f)) ? PSY_3GPP_EN_SPREAD_HI_S : PSY_3GPP_EN_SPREAD_HI_L1;
327
 
328
        i = 0;
329
        prev = 0.0;
330
        for (g = 0; g < ctx->num_bands[j]; g++) {
331
            i += band_sizes[g];
332
            bark = calc_bark((i-1) * line_to_frequency);
333
            coeffs[g].barks = (bark + prev) / 2.0;
334
            prev = bark;
335
        }
336
        for (g = 0; g < ctx->num_bands[j] - 1; g++) {
337
            AacPsyCoeffs *coeff = &coeffs[g];
338
            float bark_width = coeffs[g+1].barks - coeffs->barks;
339
            coeff->spread_low[0] = pow(10.0, -bark_width * PSY_3GPP_THR_SPREAD_LOW);
340
            coeff->spread_hi [0] = pow(10.0, -bark_width * PSY_3GPP_THR_SPREAD_HI);
341
            coeff->spread_low[1] = pow(10.0, -bark_width * en_spread_low);
342
            coeff->spread_hi [1] = pow(10.0, -bark_width * en_spread_hi);
343
            pe_min = bark_pe * bark_width;
344
            minsnr = exp2(pe_min / band_sizes[g]) - 1.5f;
345
            coeff->min_snr = av_clipf(1.0f / minsnr, PSY_SNR_25DB, PSY_SNR_1DB);
346
        }
347
        start = 0;
348
        for (g = 0; g < ctx->num_bands[j]; g++) {
349
            minscale = ath(start * line_to_frequency, ATH_ADD);
350
            for (i = 1; i < band_sizes[g]; i++)
351
                minscale = FFMIN(minscale, ath((start + i) * line_to_frequency, ATH_ADD));
352
            coeffs[g].ath = minscale - minath;
353
            start += band_sizes[g];
354
        }
355
    }
356
 
357
    pctx->ch = av_mallocz(sizeof(AacPsyChannel) * ctx->avctx->channels);
358
 
359
    lame_window_init(pctx, ctx->avctx);
360
 
361
    return 0;
362
}
363
 
364
/**
365
 * IIR filter used in block switching decision
366
 */
367
static float iir_filter(int in, float state[2])
368
{
369
    float ret;
370
 
371
    ret = 0.7548f * (in - state[0]) + 0.5095f * state[1];
372
    state[0] = in;
373
    state[1] = ret;
374
    return ret;
375
}
376
 
377
/**
378
 * window grouping information stored as bits (0 - new group, 1 - group continues)
379
 */
380
static const uint8_t window_grouping[9] = {
381
    0xB6, 0x6C, 0xD8, 0xB2, 0x66, 0xC6, 0x96, 0x36, 0x36
382
};
383
 
384
/**
385
 * Tell encoder which window types to use.
386
 * @see 3GPP TS26.403 5.4.1 "Blockswitching"
387
 */
388
static av_unused FFPsyWindowInfo psy_3gpp_window(FFPsyContext *ctx,
389
                                                 const int16_t *audio,
390
                                                 const int16_t *la,
391
                                                 int channel, int prev_type)
392
{
393
    int i, j;
394
    int br               = ctx->avctx->bit_rate / ctx->avctx->channels;
395
    int attack_ratio     = br <= 16000 ? 18 : 10;
396
    AacPsyContext *pctx = (AacPsyContext*) ctx->model_priv_data;
397
    AacPsyChannel *pch  = &pctx->ch[channel];
398
    uint8_t grouping     = 0;
399
    int next_type        = pch->next_window_seq;
400
    FFPsyWindowInfo wi  = { { 0 } };
401
 
402
    if (la) {
403
        float s[8], v;
404
        int switch_to_eight = 0;
405
        float sum = 0.0, sum2 = 0.0;
406
        int attack_n = 0;
407
        int stay_short = 0;
408
        for (i = 0; i < 8; i++) {
409
            for (j = 0; j < 128; j++) {
410
                v = iir_filter(la[i*128+j], pch->iir_state);
411
                sum += v*v;
412
            }
413
            s[i]  = sum;
414
            sum2 += sum;
415
        }
416
        for (i = 0; i < 8; i++) {
417
            if (s[i] > pch->win_energy * attack_ratio) {
418
                attack_n        = i + 1;
419
                switch_to_eight = 1;
420
                break;
421
            }
422
        }
423
        pch->win_energy = pch->win_energy*7/8 + sum2/64;
424
 
425
        wi.window_type[1] = prev_type;
426
        switch (prev_type) {
427
        case ONLY_LONG_SEQUENCE:
428
            wi.window_type[0] = switch_to_eight ? LONG_START_SEQUENCE : ONLY_LONG_SEQUENCE;
429
            next_type = switch_to_eight ? EIGHT_SHORT_SEQUENCE : ONLY_LONG_SEQUENCE;
430
            break;
431
        case LONG_START_SEQUENCE:
432
            wi.window_type[0] = EIGHT_SHORT_SEQUENCE;
433
            grouping = pch->next_grouping;
434
            next_type = switch_to_eight ? EIGHT_SHORT_SEQUENCE : LONG_STOP_SEQUENCE;
435
            break;
436
        case LONG_STOP_SEQUENCE:
437
            wi.window_type[0] = switch_to_eight ? LONG_START_SEQUENCE : ONLY_LONG_SEQUENCE;
438
            next_type = switch_to_eight ? EIGHT_SHORT_SEQUENCE : ONLY_LONG_SEQUENCE;
439
            break;
440
        case EIGHT_SHORT_SEQUENCE:
441
            stay_short = next_type == EIGHT_SHORT_SEQUENCE || switch_to_eight;
442
            wi.window_type[0] = stay_short ? EIGHT_SHORT_SEQUENCE : LONG_STOP_SEQUENCE;
443
            grouping = next_type == EIGHT_SHORT_SEQUENCE ? pch->next_grouping : 0;
444
            next_type = switch_to_eight ? EIGHT_SHORT_SEQUENCE : LONG_STOP_SEQUENCE;
445
            break;
446
        }
447
 
448
        pch->next_grouping = window_grouping[attack_n];
449
        pch->next_window_seq = next_type;
450
    } else {
451
        for (i = 0; i < 3; i++)
452
            wi.window_type[i] = prev_type;
453
        grouping = (prev_type == EIGHT_SHORT_SEQUENCE) ? window_grouping[0] : 0;
454
    }
455
 
456
    wi.window_shape   = 1;
457
    if (wi.window_type[0] != EIGHT_SHORT_SEQUENCE) {
458
        wi.num_windows = 1;
459
        wi.grouping[0] = 1;
460
    } else {
461
        int lastgrp = 0;
462
        wi.num_windows = 8;
463
        for (i = 0; i < 8; i++) {
464
            if (!((grouping >> i) & 1))
465
                lastgrp = i;
466
            wi.grouping[lastgrp]++;
467
        }
468
    }
469
 
470
    return wi;
471
}
472
 
473
/* 5.6.1.2 "Calculation of Bit Demand" */
474
static int calc_bit_demand(AacPsyContext *ctx, float pe, int bits, int size,
475
                           int short_window)
476
{
477
    const float bitsave_slope  = short_window ? PSY_3GPP_SAVE_SLOPE_S  : PSY_3GPP_SAVE_SLOPE_L;
478
    const float bitsave_add    = short_window ? PSY_3GPP_SAVE_ADD_S    : PSY_3GPP_SAVE_ADD_L;
479
    const float bitspend_slope = short_window ? PSY_3GPP_SPEND_SLOPE_S : PSY_3GPP_SPEND_SLOPE_L;
480
    const float bitspend_add   = short_window ? PSY_3GPP_SPEND_ADD_S   : PSY_3GPP_SPEND_ADD_L;
481
    const float clip_low       = short_window ? PSY_3GPP_CLIP_LO_S     : PSY_3GPP_CLIP_LO_L;
482
    const float clip_high      = short_window ? PSY_3GPP_CLIP_HI_S     : PSY_3GPP_CLIP_HI_L;
483
    float clipped_pe, bit_save, bit_spend, bit_factor, fill_level;
484
 
485
    ctx->fill_level += ctx->frame_bits - bits;
486
    ctx->fill_level  = av_clip(ctx->fill_level, 0, size);
487
    fill_level = av_clipf((float)ctx->fill_level / size, clip_low, clip_high);
488
    clipped_pe = av_clipf(pe, ctx->pe.min, ctx->pe.max);
489
    bit_save   = (fill_level + bitsave_add) * bitsave_slope;
490
    assert(bit_save <= 0.3f && bit_save >= -0.05000001f);
491
    bit_spend  = (fill_level + bitspend_add) * bitspend_slope;
492
    assert(bit_spend <= 0.5f && bit_spend >= -0.1f);
493
    /* The bit factor graph in the spec is obviously incorrect.
494
     *      bit_spend + ((bit_spend - bit_spend))...
495
     * The reference encoder subtracts everything from 1, but also seems incorrect.
496
     *      1 - bit_save + ((bit_spend + bit_save))...
497
     * Hopefully below is correct.
498
     */
499
    bit_factor = 1.0f - bit_save + ((bit_spend - bit_save) / (ctx->pe.max - ctx->pe.min)) * (clipped_pe - ctx->pe.min);
500
    /* NOTE: The reference encoder attempts to center pe max/min around the current pe. */
501
    ctx->pe.max = FFMAX(pe, ctx->pe.max);
502
    ctx->pe.min = FFMIN(pe, ctx->pe.min);
503
 
504
    return FFMIN(ctx->frame_bits * bit_factor, ctx->frame_bits + size - bits);
505
}
506
 
507
static float calc_pe_3gpp(AacPsyBand *band)
508
{
509
    float pe, a;
510
 
511
    band->pe           = 0.0f;
512
    band->pe_const     = 0.0f;
513
    band->active_lines = 0.0f;
514
    if (band->energy > band->thr) {
515
        a  = log2f(band->energy);
516
        pe = a - log2f(band->thr);
517
        band->active_lines = band->nz_lines;
518
        if (pe < PSY_3GPP_C1) {
519
            pe = pe * PSY_3GPP_C3 + PSY_3GPP_C2;
520
            a  = a  * PSY_3GPP_C3 + PSY_3GPP_C2;
521
            band->active_lines *= PSY_3GPP_C3;
522
        }
523
        band->pe       = pe * band->nz_lines;
524
        band->pe_const = a  * band->nz_lines;
525
    }
526
 
527
    return band->pe;
528
}
529
 
530
static float calc_reduction_3gpp(float a, float desired_pe, float pe,
531
                                 float active_lines)
532
{
533
    float thr_avg, reduction;
534
 
535
    if(active_lines == 0.0)
536
        return 0;
537
 
538
    thr_avg   = exp2f((a - pe) / (4.0f * active_lines));
539
    reduction = exp2f((a - desired_pe) / (4.0f * active_lines)) - thr_avg;
540
 
541
    return FFMAX(reduction, 0.0f);
542
}
543
 
544
static float calc_reduced_thr_3gpp(AacPsyBand *band, float min_snr,
545
                                   float reduction)
546
{
547
    float thr = band->thr;
548
 
549
    if (band->energy > thr) {
550
        thr = sqrtf(thr);
551
        thr = sqrtf(thr) + reduction;
552
        thr *= thr;
553
        thr *= thr;
554
 
555
        /* This deviates from the 3GPP spec to match the reference encoder.
556
         * It performs min(thr_reduced, max(thr, energy/min_snr)) only for bands
557
         * that have hole avoidance on (active or inactive). It always reduces the
558
         * threshold of bands with hole avoidance off.
559
         */
560
        if (thr > band->energy * min_snr && band->avoid_holes != PSY_3GPP_AH_NONE) {
561
            thr = FFMAX(band->thr, band->energy * min_snr);
562
            band->avoid_holes = PSY_3GPP_AH_ACTIVE;
563
        }
564
    }
565
 
566
    return thr;
567
}
568
 
569
#ifndef calc_thr_3gpp
570
static void calc_thr_3gpp(const FFPsyWindowInfo *wi, const int num_bands, AacPsyChannel *pch,
571
                          const uint8_t *band_sizes, const float *coefs)
572
{
573
    int i, w, g;
574
    int start = 0;
575
    for (w = 0; w < wi->num_windows*16; w += 16) {
576
        for (g = 0; g < num_bands; g++) {
577
            AacPsyBand *band = &pch->band[w+g];
578
 
579
            float form_factor = 0.0f;
580
            float Temp;
581
            band->energy = 0.0f;
582
            for (i = 0; i < band_sizes[g]; i++) {
583
                band->energy += coefs[start+i] * coefs[start+i];
584
                form_factor  += sqrtf(fabs(coefs[start+i]));
585
            }
586
            Temp = band->energy > 0 ? sqrtf((float)band_sizes[g] / band->energy) : 0;
587
            band->thr      = band->energy * 0.001258925f;
588
            band->nz_lines = form_factor * sqrtf(Temp);
589
 
590
            start += band_sizes[g];
591
        }
592
    }
593
}
594
#endif /* calc_thr_3gpp */
595
 
596
#ifndef psy_hp_filter
597
static void psy_hp_filter(const float *firbuf, float *hpfsmpl, const float *psy_fir_coeffs)
598
{
599
    int i, j;
600
    for (i = 0; i < AAC_BLOCK_SIZE_LONG; i++) {
601
        float sum1, sum2;
602
        sum1 = firbuf[i + (PSY_LAME_FIR_LEN - 1) / 2];
603
        sum2 = 0.0;
604
        for (j = 0; j < ((PSY_LAME_FIR_LEN - 1) / 2) - 1; j += 2) {
605
            sum1 += psy_fir_coeffs[j] * (firbuf[i + j] + firbuf[i + PSY_LAME_FIR_LEN - j]);
606
            sum2 += psy_fir_coeffs[j + 1] * (firbuf[i + j + 1] + firbuf[i + PSY_LAME_FIR_LEN - j - 1]);
607
        }
608
        /* NOTE: The LAME psymodel expects it's input in the range -32768 to 32768.
609
         *       Tuning this for normalized floats would be difficult. */
610
        hpfsmpl[i] = (sum1 + sum2) * 32768.0f;
611
    }
612
}
613
#endif /* psy_hp_filter */
614
 
615
/**
616
 * Calculate band thresholds as suggested in 3GPP TS26.403
617
 */
618
static void psy_3gpp_analyze_channel(FFPsyContext *ctx, int channel,
619
                                     const float *coefs, const FFPsyWindowInfo *wi)
620
{
621
    AacPsyContext *pctx = (AacPsyContext*) ctx->model_priv_data;
622
    AacPsyChannel *pch  = &pctx->ch[channel];
623
    int i, w, g;
624
    float desired_bits, desired_pe, delta_pe, reduction= NAN, spread_en[128] = {0};
625
    float a = 0.0f, active_lines = 0.0f, norm_fac = 0.0f;
626
    float pe = pctx->chan_bitrate > 32000 ? 0.0f : FFMAX(50.0f, 100.0f - pctx->chan_bitrate * 100.0f / 32000.0f);
627
    const int      num_bands   = ctx->num_bands[wi->num_windows == 8];
628
    const uint8_t *band_sizes  = ctx->bands[wi->num_windows == 8];
629
    AacPsyCoeffs  *coeffs      = pctx->psy_coef[wi->num_windows == 8];
630
    const float avoid_hole_thr = wi->num_windows == 8 ? PSY_3GPP_AH_THR_SHORT : PSY_3GPP_AH_THR_LONG;
631
 
632
    //calculate energies, initial thresholds and related values - 5.4.2 "Threshold Calculation"
633
    calc_thr_3gpp(wi, num_bands, pch, band_sizes, coefs);
634
 
635
    //modify thresholds and energies - spread, threshold in quiet, pre-echo control
636
    for (w = 0; w < wi->num_windows*16; w += 16) {
637
        AacPsyBand *bands = &pch->band[w];
638
 
639
        /* 5.4.2.3 "Spreading" & 5.4.3 "Spread Energy Calculation" */
640
        spread_en[0] = bands[0].energy;
641
        for (g = 1; g < num_bands; g++) {
642
            bands[g].thr   = FFMAX(bands[g].thr,    bands[g-1].thr * coeffs[g].spread_hi[0]);
643
            spread_en[w+g] = FFMAX(bands[g].energy, spread_en[w+g-1] * coeffs[g].spread_hi[1]);
644
        }
645
        for (g = num_bands - 2; g >= 0; g--) {
646
            bands[g].thr   = FFMAX(bands[g].thr,   bands[g+1].thr * coeffs[g].spread_low[0]);
647
            spread_en[w+g] = FFMAX(spread_en[w+g], spread_en[w+g+1] * coeffs[g].spread_low[1]);
648
        }
649
        //5.4.2.4 "Threshold in quiet"
650
        for (g = 0; g < num_bands; g++) {
651
            AacPsyBand *band = &bands[g];
652
 
653
            band->thr_quiet = band->thr = FFMAX(band->thr, coeffs[g].ath);
654
            //5.4.2.5 "Pre-echo control"
655
            if (!(wi->window_type[0] == LONG_STOP_SEQUENCE || (wi->window_type[1] == LONG_START_SEQUENCE && !w)))
656
                band->thr = FFMAX(PSY_3GPP_RPEMIN*band->thr, FFMIN(band->thr,
657
                                  PSY_3GPP_RPELEV*pch->prev_band[w+g].thr_quiet));
658
 
659
            /* 5.6.1.3.1 "Preparatory steps of the perceptual entropy calculation" */
660
            pe += calc_pe_3gpp(band);
661
            a  += band->pe_const;
662
            active_lines += band->active_lines;
663
 
664
            /* 5.6.1.3.3 "Selection of the bands for avoidance of holes" */
665
            if (spread_en[w+g] * avoid_hole_thr > band->energy || coeffs[g].min_snr > 1.0f)
666
                band->avoid_holes = PSY_3GPP_AH_NONE;
667
            else
668
                band->avoid_holes = PSY_3GPP_AH_INACTIVE;
669
        }
670
    }
671
 
672
    /* 5.6.1.3.2 "Calculation of the desired perceptual entropy" */
673
    ctx->ch[channel].entropy = pe;
674
    desired_bits = calc_bit_demand(pctx, pe, ctx->bitres.bits, ctx->bitres.size, wi->num_windows == 8);
675
    desired_pe = PSY_3GPP_BITS_TO_PE(desired_bits);
676
    /* NOTE: PE correction is kept simple. During initial testing it had very
677
     *       little effect on the final bitrate. Probably a good idea to come
678
     *       back and do more testing later.
679
     */
680
    if (ctx->bitres.bits > 0)
681
        desired_pe *= av_clipf(pctx->pe.previous / PSY_3GPP_BITS_TO_PE(ctx->bitres.bits),
682
                               0.85f, 1.15f);
683
    pctx->pe.previous = PSY_3GPP_BITS_TO_PE(desired_bits);
684
 
685
    if (desired_pe < pe) {
686
        /* 5.6.1.3.4 "First Estimation of the reduction value" */
687
        for (w = 0; w < wi->num_windows*16; w += 16) {
688
            reduction = calc_reduction_3gpp(a, desired_pe, pe, active_lines);
689
            pe = 0.0f;
690
            a  = 0.0f;
691
            active_lines = 0.0f;
692
            for (g = 0; g < num_bands; g++) {
693
                AacPsyBand *band = &pch->band[w+g];
694
 
695
                band->thr = calc_reduced_thr_3gpp(band, coeffs[g].min_snr, reduction);
696
                /* recalculate PE */
697
                pe += calc_pe_3gpp(band);
698
                a  += band->pe_const;
699
                active_lines += band->active_lines;
700
            }
701
        }
702
 
703
        /* 5.6.1.3.5 "Second Estimation of the reduction value" */
704
        for (i = 0; i < 2; i++) {
705
            float pe_no_ah = 0.0f, desired_pe_no_ah;
706
            active_lines = a = 0.0f;
707
            for (w = 0; w < wi->num_windows*16; w += 16) {
708
                for (g = 0; g < num_bands; g++) {
709
                    AacPsyBand *band = &pch->band[w+g];
710
 
711
                    if (band->avoid_holes != PSY_3GPP_AH_ACTIVE) {
712
                        pe_no_ah += band->pe;
713
                        a        += band->pe_const;
714
                        active_lines += band->active_lines;
715
                    }
716
                }
717
            }
718
            desired_pe_no_ah = FFMAX(desired_pe - (pe - pe_no_ah), 0.0f);
719
            if (active_lines > 0.0f)
720
                reduction += calc_reduction_3gpp(a, desired_pe_no_ah, pe_no_ah, active_lines);
721
 
722
            pe = 0.0f;
723
            for (w = 0; w < wi->num_windows*16; w += 16) {
724
                for (g = 0; g < num_bands; g++) {
725
                    AacPsyBand *band = &pch->band[w+g];
726
 
727
                    if (active_lines > 0.0f)
728
                        band->thr = calc_reduced_thr_3gpp(band, coeffs[g].min_snr, reduction);
729
                    pe += calc_pe_3gpp(band);
730
                    band->norm_fac = band->active_lines / band->thr;
731
                    norm_fac += band->norm_fac;
732
                }
733
            }
734
            delta_pe = desired_pe - pe;
735
            if (fabs(delta_pe) > 0.05f * desired_pe)
736
                break;
737
        }
738
 
739
        if (pe < 1.15f * desired_pe) {
740
            /* 6.6.1.3.6 "Final threshold modification by linearization" */
741
            norm_fac = 1.0f / norm_fac;
742
            for (w = 0; w < wi->num_windows*16; w += 16) {
743
                for (g = 0; g < num_bands; g++) {
744
                    AacPsyBand *band = &pch->band[w+g];
745
 
746
                    if (band->active_lines > 0.5f) {
747
                        float delta_sfb_pe = band->norm_fac * norm_fac * delta_pe;
748
                        float thr = band->thr;
749
 
750
                        thr *= exp2f(delta_sfb_pe / band->active_lines);
751
                        if (thr > coeffs[g].min_snr * band->energy && band->avoid_holes == PSY_3GPP_AH_INACTIVE)
752
                            thr = FFMAX(band->thr, coeffs[g].min_snr * band->energy);
753
                        band->thr = thr;
754
                    }
755
                }
756
            }
757
        } else {
758
            /* 5.6.1.3.7 "Further perceptual entropy reduction" */
759
            g = num_bands;
760
            while (pe > desired_pe && g--) {
761
                for (w = 0; w < wi->num_windows*16; w+= 16) {
762
                    AacPsyBand *band = &pch->band[w+g];
763
                    if (band->avoid_holes != PSY_3GPP_AH_NONE && coeffs[g].min_snr < PSY_SNR_1DB) {
764
                        coeffs[g].min_snr = PSY_SNR_1DB;
765
                        band->thr = band->energy * PSY_SNR_1DB;
766
                        pe += band->active_lines * 1.5f - band->pe;
767
                    }
768
                }
769
            }
770
            /* TODO: allow more holes (unused without mid/side) */
771
        }
772
    }
773
 
774
    for (w = 0; w < wi->num_windows*16; w += 16) {
775
        for (g = 0; g < num_bands; g++) {
776
            AacPsyBand *band     = &pch->band[w+g];
777
            FFPsyBand  *psy_band = &ctx->ch[channel].psy_bands[w+g];
778
 
779
            psy_band->threshold = band->thr;
780
            psy_band->energy    = band->energy;
781
        }
782
    }
783
 
784
    memcpy(pch->prev_band, pch->band, sizeof(pch->band));
785
}
786
 
787
static void psy_3gpp_analyze(FFPsyContext *ctx, int channel,
788
                                   const float **coeffs, const FFPsyWindowInfo *wi)
789
{
790
    int ch;
791
    FFPsyChannelGroup *group = ff_psy_find_group(ctx, channel);
792
 
793
    for (ch = 0; ch < group->num_ch; ch++)
794
        psy_3gpp_analyze_channel(ctx, channel + ch, coeffs[ch], &wi[ch]);
795
}
796
 
797
static av_cold void psy_3gpp_end(FFPsyContext *apc)
798
{
799
    AacPsyContext *pctx = (AacPsyContext*) apc->model_priv_data;
800
    av_freep(&pctx->ch);
801
    av_freep(&apc->model_priv_data);
802
}
803
 
804
static void lame_apply_block_type(AacPsyChannel *ctx, FFPsyWindowInfo *wi, int uselongblock)
805
{
806
    int blocktype = ONLY_LONG_SEQUENCE;
807
    if (uselongblock) {
808
        if (ctx->next_window_seq == EIGHT_SHORT_SEQUENCE)
809
            blocktype = LONG_STOP_SEQUENCE;
810
    } else {
811
        blocktype = EIGHT_SHORT_SEQUENCE;
812
        if (ctx->next_window_seq == ONLY_LONG_SEQUENCE)
813
            ctx->next_window_seq = LONG_START_SEQUENCE;
814
        if (ctx->next_window_seq == LONG_STOP_SEQUENCE)
815
            ctx->next_window_seq = EIGHT_SHORT_SEQUENCE;
816
    }
817
 
818
    wi->window_type[0] = ctx->next_window_seq;
819
    ctx->next_window_seq = blocktype;
820
}
821
 
822
static FFPsyWindowInfo psy_lame_window(FFPsyContext *ctx, const float *audio,
823
                                       const float *la, int channel, int prev_type)
824
{
825
    AacPsyContext *pctx = (AacPsyContext*) ctx->model_priv_data;
826
    AacPsyChannel *pch  = &pctx->ch[channel];
827
    int grouping     = 0;
828
    int uselongblock = 1;
829
    int attacks[AAC_NUM_BLOCKS_SHORT + 1] = { 0 };
830
    int i;
831
    FFPsyWindowInfo wi = { { 0 } };
832
 
833
    if (la) {
834
        float hpfsmpl[AAC_BLOCK_SIZE_LONG];
835
        float const *pf = hpfsmpl;
836
        float attack_intensity[(AAC_NUM_BLOCKS_SHORT + 1) * PSY_LAME_NUM_SUBBLOCKS];
837
        float energy_subshort[(AAC_NUM_BLOCKS_SHORT + 1) * PSY_LAME_NUM_SUBBLOCKS];
838
        float energy_short[AAC_NUM_BLOCKS_SHORT + 1] = { 0 };
839
        const float *firbuf = la + (AAC_BLOCK_SIZE_SHORT/4 - PSY_LAME_FIR_LEN);
840
        int att_sum = 0;
841
 
842
        /* LAME comment: apply high pass filter of fs/4 */
843
        psy_hp_filter(firbuf, hpfsmpl, psy_fir_coeffs);
844
 
845
        /* Calculate the energies of each sub-shortblock */
846
        for (i = 0; i < PSY_LAME_NUM_SUBBLOCKS; i++) {
847
            energy_subshort[i] = pch->prev_energy_subshort[i + ((AAC_NUM_BLOCKS_SHORT - 1) * PSY_LAME_NUM_SUBBLOCKS)];
848
            assert(pch->prev_energy_subshort[i + ((AAC_NUM_BLOCKS_SHORT - 2) * PSY_LAME_NUM_SUBBLOCKS + 1)] > 0);
849
            attack_intensity[i] = energy_subshort[i] / pch->prev_energy_subshort[i + ((AAC_NUM_BLOCKS_SHORT - 2) * PSY_LAME_NUM_SUBBLOCKS + 1)];
850
            energy_short[0] += energy_subshort[i];
851
        }
852
 
853
        for (i = 0; i < AAC_NUM_BLOCKS_SHORT * PSY_LAME_NUM_SUBBLOCKS; i++) {
854
            float const *const pfe = pf + AAC_BLOCK_SIZE_LONG / (AAC_NUM_BLOCKS_SHORT * PSY_LAME_NUM_SUBBLOCKS);
855
            float p = 1.0f;
856
            for (; pf < pfe; pf++)
857
                p = FFMAX(p, fabsf(*pf));
858
            pch->prev_energy_subshort[i] = energy_subshort[i + PSY_LAME_NUM_SUBBLOCKS] = p;
859
            energy_short[1 + i / PSY_LAME_NUM_SUBBLOCKS] += p;
860
            /* NOTE: The indexes below are [i + 3 - 2] in the LAME source.
861
             *       Obviously the 3 and 2 have some significance, or this would be just [i + 1]
862
             *       (which is what we use here). What the 3 stands for is ambiguous, as it is both
863
             *       number of short blocks, and the number of sub-short blocks.
864
             *       It seems that LAME is comparing each sub-block to sub-block + 1 in the
865
             *       previous block.
866
             */
867
            if (p > energy_subshort[i + 1])
868
                p = p / energy_subshort[i + 1];
869
            else if (energy_subshort[i + 1] > p * 10.0f)
870
                p = energy_subshort[i + 1] / (p * 10.0f);
871
            else
872
                p = 0.0;
873
            attack_intensity[i + PSY_LAME_NUM_SUBBLOCKS] = p;
874
        }
875
 
876
        /* compare energy between sub-short blocks */
877
        for (i = 0; i < (AAC_NUM_BLOCKS_SHORT + 1) * PSY_LAME_NUM_SUBBLOCKS; i++)
878
            if (!attacks[i / PSY_LAME_NUM_SUBBLOCKS])
879
                if (attack_intensity[i] > pch->attack_threshold)
880
                    attacks[i / PSY_LAME_NUM_SUBBLOCKS] = (i % PSY_LAME_NUM_SUBBLOCKS) + 1;
881
 
882
        /* should have energy change between short blocks, in order to avoid periodic signals */
883
        /* Good samples to show the effect are Trumpet test songs */
884
        /* GB: tuned (1) to avoid too many short blocks for test sample TRUMPET */
885
        /* RH: tuned (2) to let enough short blocks through for test sample FSOL and SNAPS */
886
        for (i = 1; i < AAC_NUM_BLOCKS_SHORT + 1; i++) {
887
            float const u = energy_short[i - 1];
888
            float const v = energy_short[i];
889
            float const m = FFMAX(u, v);
890
            if (m < 40000) {                          /* (2) */
891
                if (u < 1.7f * v && v < 1.7f * u) {   /* (1) */
892
                    if (i == 1 && attacks[0] < attacks[i])
893
                        attacks[0] = 0;
894
                    attacks[i] = 0;
895
                }
896
            }
897
            att_sum += attacks[i];
898
        }
899
 
900
        if (attacks[0] <= pch->prev_attack)
901
            attacks[0] = 0;
902
 
903
        att_sum += attacks[0];
904
        /* 3 below indicates the previous attack happened in the last sub-block of the previous sequence */
905
        if (pch->prev_attack == 3 || att_sum) {
906
            uselongblock = 0;
907
 
908
            for (i = 1; i < AAC_NUM_BLOCKS_SHORT + 1; i++)
909
                if (attacks[i] && attacks[i-1])
910
                    attacks[i] = 0;
911
        }
912
    } else {
913
        /* We have no lookahead info, so just use same type as the previous sequence. */
914
        uselongblock = !(prev_type == EIGHT_SHORT_SEQUENCE);
915
    }
916
 
917
    lame_apply_block_type(pch, &wi, uselongblock);
918
 
919
    wi.window_type[1] = prev_type;
920
    if (wi.window_type[0] != EIGHT_SHORT_SEQUENCE) {
921
        wi.num_windows  = 1;
922
        wi.grouping[0]  = 1;
923
        if (wi.window_type[0] == LONG_START_SEQUENCE)
924
            wi.window_shape = 0;
925
        else
926
            wi.window_shape = 1;
927
    } else {
928
        int lastgrp = 0;
929
 
930
        wi.num_windows = 8;
931
        wi.window_shape = 0;
932
        for (i = 0; i < 8; i++) {
933
            if (!((pch->next_grouping >> i) & 1))
934
                lastgrp = i;
935
            wi.grouping[lastgrp]++;
936
        }
937
    }
938
 
939
    /* Determine grouping, based on the location of the first attack, and save for
940
     * the next frame.
941
     * FIXME: Move this to analysis.
942
     * TODO: Tune groupings depending on attack location
943
     * TODO: Handle more than one attack in a group
944
     */
945
    for (i = 0; i < 9; i++) {
946
        if (attacks[i]) {
947
            grouping = i;
948
            break;
949
        }
950
    }
951
    pch->next_grouping = window_grouping[grouping];
952
 
953
    pch->prev_attack = attacks[8];
954
 
955
    return wi;
956
}
957
 
958
const FFPsyModel ff_aac_psy_model =
959
{
960
    .name    = "3GPP TS 26.403-inspired model",
961
    .init    = psy_3gpp_init,
962
    .window  = psy_lame_window,
963
    .analyze = psy_3gpp_analyze,
964
    .end     = psy_3gpp_end,
965
};