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aacpsy.c
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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 {
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
131  int prev_attack; ///< attack value for the last short block in the previous sequence
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;
161 
162 /**
163  * LAME psy model preset struct
164  */
165 typedef struct PsyLamePreset {
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  */
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 
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_array(ctx->avctx->channels, sizeof(AacPsyChannel));
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  */
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;
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;
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 
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);
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 {
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)
667  else
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 
798 {
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) {
809  blocktype = LONG_STOP_SEQUENCE;
810  } else {
811  blocktype = 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 {
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 
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 };