summaryrefslogtreecommitdiff
path: root/libavcodec/aacpsy.c (plain)
blob: fca692cb153f17082e3bcb918841b8e2bbbfe2c4
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/ffmath.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#define PSY_PE_FORGET_SLOPE 511
84
85enum {
86 PSY_3GPP_AH_NONE,
87 PSY_3GPP_AH_INACTIVE,
88 PSY_3GPP_AH_ACTIVE
89};
90
91#define PSY_3GPP_BITS_TO_PE(bits) ((bits) * 1.18f)
92#define PSY_3GPP_PE_TO_BITS(bits) ((bits) / 1.18f)
93
94/* LAME psy model constants */
95#define PSY_LAME_FIR_LEN 21 ///< LAME psy model FIR order
96#define AAC_BLOCK_SIZE_LONG 1024 ///< long block size
97#define AAC_BLOCK_SIZE_SHORT 128 ///< short block size
98#define AAC_NUM_BLOCKS_SHORT 8 ///< number of blocks in a short sequence
99#define PSY_LAME_NUM_SUBBLOCKS 3 ///< Number of sub-blocks in each short block
100
101/**
102 * @}
103 */
104
105/**
106 * information for single band used by 3GPP TS26.403-inspired psychoacoustic model
107 */
108typedef struct AacPsyBand{
109 float energy; ///< band energy
110 float thr; ///< energy threshold
111 float thr_quiet; ///< threshold in quiet
112 float nz_lines; ///< number of non-zero spectral lines
113 float active_lines; ///< number of active spectral lines
114 float pe; ///< perceptual entropy
115 float pe_const; ///< constant part of the PE calculation
116 float norm_fac; ///< normalization factor for linearization
117 int avoid_holes; ///< hole avoidance flag
118}AacPsyBand;
119
120/**
121 * single/pair channel context for psychoacoustic model
122 */
123typedef struct AacPsyChannel{
124 AacPsyBand band[128]; ///< bands information
125 AacPsyBand prev_band[128]; ///< bands information from the previous frame
126
127 float win_energy; ///< sliding average of channel energy
128 float iir_state[2]; ///< hi-pass IIR filter state
129 uint8_t next_grouping; ///< stored grouping scheme for the next frame (in case of 8 short window sequence)
130 enum WindowSequence next_window_seq; ///< window sequence to be used in the next frame
131 /* LAME psy model specific members */
132 float attack_threshold; ///< attack threshold for this channel
133 float prev_energy_subshort[AAC_NUM_BLOCKS_SHORT * PSY_LAME_NUM_SUBBLOCKS];
134 int prev_attack; ///< attack value for the last short block in the previous sequence
135}AacPsyChannel;
136
137/**
138 * psychoacoustic model frame type-dependent coefficients
139 */
140typedef struct AacPsyCoeffs{
141 float ath; ///< absolute threshold of hearing per bands
142 float barks; ///< Bark value for each spectral band in long frame
143 float spread_low[2]; ///< spreading factor for low-to-high threshold spreading in long frame
144 float spread_hi [2]; ///< spreading factor for high-to-low threshold spreading in long frame
145 float min_snr; ///< minimal SNR
146}AacPsyCoeffs;
147
148/**
149 * 3GPP TS26.403-inspired psychoacoustic model specific data
150 */
151typedef struct AacPsyContext{
152 int chan_bitrate; ///< bitrate per channel
153 int frame_bits; ///< average bits per frame
154 int fill_level; ///< bit reservoir fill level
155 struct {
156 float min; ///< minimum allowed PE for bit factor calculation
157 float max; ///< maximum allowed PE for bit factor calculation
158 float previous; ///< allowed PE of the previous frame
159 float correction; ///< PE correction factor
160 } pe;
161 AacPsyCoeffs psy_coef[2][64];
162 AacPsyChannel *ch;
163 float global_quality; ///< normalized global quality taken from avctx
164}AacPsyContext;
165
166/**
167 * LAME psy model preset struct
168 */
169typedef struct PsyLamePreset {
170 int quality; ///< Quality to map the rest of the vaules to.
171 /* This is overloaded to be both kbps per channel in ABR mode, and
172 * requested quality in constant quality mode.
173 */
174 float st_lrm; ///< short threshold for L, R, and M channels
175} PsyLamePreset;
176
177/**
178 * LAME psy model preset table for ABR
179 */
180static const PsyLamePreset psy_abr_map[] = {
181/* TODO: Tuning. These were taken from LAME. */
182/* kbps/ch st_lrm */
183 { 8, 6.60},
184 { 16, 6.60},
185 { 24, 6.60},
186 { 32, 6.60},
187 { 40, 6.60},
188 { 48, 6.60},
189 { 56, 6.60},
190 { 64, 6.40},
191 { 80, 6.00},
192 { 96, 5.60},
193 {112, 5.20},
194 {128, 5.20},
195 {160, 5.20}
196};
197
198/**
199* LAME psy model preset table for constant quality
200*/
201static const PsyLamePreset psy_vbr_map[] = {
202/* vbr_q st_lrm */
203 { 0, 4.20},
204 { 1, 4.20},
205 { 2, 4.20},
206 { 3, 4.20},
207 { 4, 4.20},
208 { 5, 4.20},
209 { 6, 4.20},
210 { 7, 4.20},
211 { 8, 4.20},
212 { 9, 4.20},
213 {10, 4.20}
214};
215
216/**
217 * LAME psy model FIR coefficient table
218 */
219static const float psy_fir_coeffs[] = {
220 -8.65163e-18 * 2, -0.00851586 * 2, -6.74764e-18 * 2, 0.0209036 * 2,
221 -3.36639e-17 * 2, -0.0438162 * 2, -1.54175e-17 * 2, 0.0931738 * 2,
222 -5.52212e-17 * 2, -0.313819 * 2
223};
224
225#if ARCH_MIPS
226# include "mips/aacpsy_mips.h"
227#endif /* ARCH_MIPS */
228
229/**
230 * Calculate the ABR attack threshold from the above LAME psymodel table.
231 */
232static float lame_calc_attack_threshold(int bitrate)
233{
234 /* Assume max bitrate to start with */
235 int lower_range = 12, upper_range = 12;
236 int lower_range_kbps = psy_abr_map[12].quality;
237 int upper_range_kbps = psy_abr_map[12].quality;
238 int i;
239
240 /* Determine which bitrates the value specified falls between.
241 * If the loop ends without breaking our above assumption of 320kbps was correct.
242 */
243 for (i = 1; i < 13; i++) {
244 if (FFMAX(bitrate, psy_abr_map[i].quality) != bitrate) {
245 upper_range = i;
246 upper_range_kbps = psy_abr_map[i ].quality;
247 lower_range = i - 1;
248 lower_range_kbps = psy_abr_map[i - 1].quality;
249 break; /* Upper range found */
250 }
251 }
252
253 /* Determine which range the value specified is closer to */
254 if ((upper_range_kbps - bitrate) > (bitrate - lower_range_kbps))
255 return psy_abr_map[lower_range].st_lrm;
256 return psy_abr_map[upper_range].st_lrm;
257}
258
259/**
260 * LAME psy model specific initialization
261 */
262static av_cold void lame_window_init(AacPsyContext *ctx, AVCodecContext *avctx)
263{
264 int i, j;
265
266 for (i = 0; i < avctx->channels; i++) {
267 AacPsyChannel *pch = &ctx->ch[i];
268
269 if (avctx->flags & AV_CODEC_FLAG_QSCALE)
270 pch->attack_threshold = psy_vbr_map[avctx->global_quality / FF_QP2LAMBDA].st_lrm;
271 else
272 pch->attack_threshold = lame_calc_attack_threshold(avctx->bit_rate / avctx->channels / 1000);
273
274 for (j = 0; j < AAC_NUM_BLOCKS_SHORT * PSY_LAME_NUM_SUBBLOCKS; j++)
275 pch->prev_energy_subshort[j] = 10.0f;
276 }
277}
278
279/**
280 * Calculate Bark value for given line.
281 */
282static av_cold float calc_bark(float f)
283{
284 return 13.3f * atanf(0.00076f * f) + 3.5f * atanf((f / 7500.0f) * (f / 7500.0f));
285}
286
287#define ATH_ADD 4
288/**
289 * Calculate ATH value for given frequency.
290 * Borrowed from Lame.
291 */
292static av_cold float ath(float f, float add)
293{
294 f /= 1000.0f;
295 return 3.64 * pow(f, -0.8)
296 - 6.8 * exp(-0.6 * (f - 3.4) * (f - 3.4))
297 + 6.0 * exp(-0.15 * (f - 8.7) * (f - 8.7))
298 + (0.6 + 0.04 * add) * 0.001 * f * f * f * f;
299}
300
301static av_cold int psy_3gpp_init(FFPsyContext *ctx) {
302 AacPsyContext *pctx;
303 float bark;
304 int i, j, g, start;
305 float prev, minscale, minath, minsnr, pe_min;
306 int chan_bitrate = ctx->avctx->bit_rate / ((ctx->avctx->flags & AV_CODEC_FLAG_QSCALE) ? 2.0f : ctx->avctx->channels);
307
308 const int bandwidth = ctx->cutoff ? ctx->cutoff : AAC_CUTOFF(ctx->avctx);
309 const float num_bark = calc_bark((float)bandwidth);
310
311 ctx->model_priv_data = av_mallocz(sizeof(AacPsyContext));
312 if (!ctx->model_priv_data)
313 return AVERROR(ENOMEM);
314 pctx = ctx->model_priv_data;
315 pctx->global_quality = (ctx->avctx->global_quality ? ctx->avctx->global_quality : 120) * 0.01f;
316
317 if (ctx->avctx->flags & AV_CODEC_FLAG_QSCALE) {
318 /* Use the target average bitrate to compute spread parameters */
319 chan_bitrate = (int)(chan_bitrate / 120.0 * (ctx->avctx->global_quality ? ctx->avctx->global_quality : 120));
320 }
321
322 pctx->chan_bitrate = chan_bitrate;
323 pctx->frame_bits = FFMIN(2560, chan_bitrate * AAC_BLOCK_SIZE_LONG / ctx->avctx->sample_rate);
324 pctx->pe.min = 8.0f * AAC_BLOCK_SIZE_LONG * bandwidth / (ctx->avctx->sample_rate * 2.0f);
325 pctx->pe.max = 12.0f * AAC_BLOCK_SIZE_LONG * bandwidth / (ctx->avctx->sample_rate * 2.0f);
326 ctx->bitres.size = 6144 - pctx->frame_bits;
327 ctx->bitres.size -= ctx->bitres.size % 8;
328 pctx->fill_level = ctx->bitres.size;
329 minath = ath(3410 - 0.733 * ATH_ADD, ATH_ADD);
330 for (j = 0; j < 2; j++) {
331 AacPsyCoeffs *coeffs = pctx->psy_coef[j];
332 const uint8_t *band_sizes = ctx->bands[j];
333 float line_to_frequency = ctx->avctx->sample_rate / (j ? 256.f : 2048.0f);
334 float avg_chan_bits = chan_bitrate * (j ? 128.0f : 1024.0f) / ctx->avctx->sample_rate;
335 /* reference encoder uses 2.4% here instead of 60% like the spec says */
336 float bark_pe = 0.024f * PSY_3GPP_BITS_TO_PE(avg_chan_bits) / num_bark;
337 float en_spread_low = j ? PSY_3GPP_EN_SPREAD_LOW_S : PSY_3GPP_EN_SPREAD_LOW_L;
338 /* High energy spreading for long blocks <= 22kbps/channel and short blocks are the same. */
339 float en_spread_hi = (j || (chan_bitrate <= 22.0f)) ? PSY_3GPP_EN_SPREAD_HI_S : PSY_3GPP_EN_SPREAD_HI_L1;
340
341 i = 0;
342 prev = 0.0;
343 for (g = 0; g < ctx->num_bands[j]; g++) {
344 i += band_sizes[g];
345 bark = calc_bark((i-1) * line_to_frequency);
346 coeffs[g].barks = (bark + prev) / 2.0;
347 prev = bark;
348 }
349 for (g = 0; g < ctx->num_bands[j] - 1; g++) {
350 AacPsyCoeffs *coeff = &coeffs[g];
351 float bark_width = coeffs[g+1].barks - coeffs->barks;
352 coeff->spread_low[0] = ff_exp10(-bark_width * PSY_3GPP_THR_SPREAD_LOW);
353 coeff->spread_hi [0] = ff_exp10(-bark_width * PSY_3GPP_THR_SPREAD_HI);
354 coeff->spread_low[1] = ff_exp10(-bark_width * en_spread_low);
355 coeff->spread_hi [1] = ff_exp10(-bark_width * en_spread_hi);
356 pe_min = bark_pe * bark_width;
357 minsnr = exp2(pe_min / band_sizes[g]) - 1.5f;
358 coeff->min_snr = av_clipf(1.0f / minsnr, PSY_SNR_25DB, PSY_SNR_1DB);
359 }
360 start = 0;
361 for (g = 0; g < ctx->num_bands[j]; g++) {
362 minscale = ath(start * line_to_frequency, ATH_ADD);
363 for (i = 1; i < band_sizes[g]; i++)
364 minscale = FFMIN(minscale, ath((start + i) * line_to_frequency, ATH_ADD));
365 coeffs[g].ath = minscale - minath;
366 start += band_sizes[g];
367 }
368 }
369
370 pctx->ch = av_mallocz_array(ctx->avctx->channels, sizeof(AacPsyChannel));
371 if (!pctx->ch) {
372 av_freep(&ctx->model_priv_data);
373 return AVERROR(ENOMEM);
374 }
375
376 lame_window_init(pctx, ctx->avctx);
377
378 return 0;
379}
380
381/**
382 * IIR filter used in block switching decision
383 */
384static float iir_filter(int in, float state[2])
385{
386 float ret;
387
388 ret = 0.7548f * (in - state[0]) + 0.5095f * state[1];
389 state[0] = in;
390 state[1] = ret;
391 return ret;
392}
393
394/**
395 * window grouping information stored as bits (0 - new group, 1 - group continues)
396 */
397static const uint8_t window_grouping[9] = {
398 0xB6, 0x6C, 0xD8, 0xB2, 0x66, 0xC6, 0x96, 0x36, 0x36
399};
400
401/**
402 * Tell encoder which window types to use.
403 * @see 3GPP TS26.403 5.4.1 "Blockswitching"
404 */
405static av_unused FFPsyWindowInfo psy_3gpp_window(FFPsyContext *ctx,
406 const int16_t *audio,
407 const int16_t *la,
408 int channel, int prev_type)
409{
410 int i, j;
411 int br = ((AacPsyContext*)ctx->model_priv_data)->chan_bitrate;
412 int attack_ratio = br <= 16000 ? 18 : 10;
413 AacPsyContext *pctx = (AacPsyContext*) ctx->model_priv_data;
414 AacPsyChannel *pch = &pctx->ch[channel];
415 uint8_t grouping = 0;
416 int next_type = pch->next_window_seq;
417 FFPsyWindowInfo wi = { { 0 } };
418
419 if (la) {
420 float s[8], v;
421 int switch_to_eight = 0;
422 float sum = 0.0, sum2 = 0.0;
423 int attack_n = 0;
424 int stay_short = 0;
425 for (i = 0; i < 8; i++) {
426 for (j = 0; j < 128; j++) {
427 v = iir_filter(la[i*128+j], pch->iir_state);
428 sum += v*v;
429 }
430 s[i] = sum;
431 sum2 += sum;
432 }
433 for (i = 0; i < 8; i++) {
434 if (s[i] > pch->win_energy * attack_ratio) {
435 attack_n = i + 1;
436 switch_to_eight = 1;
437 break;
438 }
439 }
440 pch->win_energy = pch->win_energy*7/8 + sum2/64;
441
442 wi.window_type[1] = prev_type;
443 switch (prev_type) {
444 case ONLY_LONG_SEQUENCE:
445 wi.window_type[0] = switch_to_eight ? LONG_START_SEQUENCE : ONLY_LONG_SEQUENCE;
446 next_type = switch_to_eight ? EIGHT_SHORT_SEQUENCE : ONLY_LONG_SEQUENCE;
447 break;
448 case LONG_START_SEQUENCE:
449 wi.window_type[0] = EIGHT_SHORT_SEQUENCE;
450 grouping = pch->next_grouping;
451 next_type = switch_to_eight ? EIGHT_SHORT_SEQUENCE : LONG_STOP_SEQUENCE;
452 break;
453 case LONG_STOP_SEQUENCE:
454 wi.window_type[0] = switch_to_eight ? LONG_START_SEQUENCE : ONLY_LONG_SEQUENCE;
455 next_type = switch_to_eight ? EIGHT_SHORT_SEQUENCE : ONLY_LONG_SEQUENCE;
456 break;
457 case EIGHT_SHORT_SEQUENCE:
458 stay_short = next_type == EIGHT_SHORT_SEQUENCE || switch_to_eight;
459 wi.window_type[0] = stay_short ? EIGHT_SHORT_SEQUENCE : LONG_STOP_SEQUENCE;
460 grouping = next_type == EIGHT_SHORT_SEQUENCE ? pch->next_grouping : 0;
461 next_type = switch_to_eight ? EIGHT_SHORT_SEQUENCE : LONG_STOP_SEQUENCE;
462 break;
463 }
464
465 pch->next_grouping = window_grouping[attack_n];
466 pch->next_window_seq = next_type;
467 } else {
468 for (i = 0; i < 3; i++)
469 wi.window_type[i] = prev_type;
470 grouping = (prev_type == EIGHT_SHORT_SEQUENCE) ? window_grouping[0] : 0;
471 }
472
473 wi.window_shape = 1;
474 if (wi.window_type[0] != EIGHT_SHORT_SEQUENCE) {
475 wi.num_windows = 1;
476 wi.grouping[0] = 1;
477 } else {
478 int lastgrp = 0;
479 wi.num_windows = 8;
480 for (i = 0; i < 8; i++) {
481 if (!((grouping >> i) & 1))
482 lastgrp = i;
483 wi.grouping[lastgrp]++;
484 }
485 }
486
487 return wi;
488}
489
490/* 5.6.1.2 "Calculation of Bit Demand" */
491static int calc_bit_demand(AacPsyContext *ctx, float pe, int bits, int size,
492 int short_window)
493{
494 const float bitsave_slope = short_window ? PSY_3GPP_SAVE_SLOPE_S : PSY_3GPP_SAVE_SLOPE_L;
495 const float bitsave_add = short_window ? PSY_3GPP_SAVE_ADD_S : PSY_3GPP_SAVE_ADD_L;
496 const float bitspend_slope = short_window ? PSY_3GPP_SPEND_SLOPE_S : PSY_3GPP_SPEND_SLOPE_L;
497 const float bitspend_add = short_window ? PSY_3GPP_SPEND_ADD_S : PSY_3GPP_SPEND_ADD_L;
498 const float clip_low = short_window ? PSY_3GPP_CLIP_LO_S : PSY_3GPP_CLIP_LO_L;
499 const float clip_high = short_window ? PSY_3GPP_CLIP_HI_S : PSY_3GPP_CLIP_HI_L;
500 float clipped_pe, bit_save, bit_spend, bit_factor, fill_level, forgetful_min_pe;
501
502 ctx->fill_level += ctx->frame_bits - bits;
503 ctx->fill_level = av_clip(ctx->fill_level, 0, size);
504 fill_level = av_clipf((float)ctx->fill_level / size, clip_low, clip_high);
505 clipped_pe = av_clipf(pe, ctx->pe.min, ctx->pe.max);
506 bit_save = (fill_level + bitsave_add) * bitsave_slope;
507 assert(bit_save <= 0.3f && bit_save >= -0.05000001f);
508 bit_spend = (fill_level + bitspend_add) * bitspend_slope;
509 assert(bit_spend <= 0.5f && bit_spend >= -0.1f);
510 /* The bit factor graph in the spec is obviously incorrect.
511 * bit_spend + ((bit_spend - bit_spend))...
512 * The reference encoder subtracts everything from 1, but also seems incorrect.
513 * 1 - bit_save + ((bit_spend + bit_save))...
514 * Hopefully below is correct.
515 */
516 bit_factor = 1.0f - bit_save + ((bit_spend - bit_save) / (ctx->pe.max - ctx->pe.min)) * (clipped_pe - ctx->pe.min);
517 /* NOTE: The reference encoder attempts to center pe max/min around the current pe.
518 * Here we do that by slowly forgetting pe.min when pe stays in a range that makes
519 * it unlikely (ie: above the mean)
520 */
521 ctx->pe.max = FFMAX(pe, ctx->pe.max);
522 forgetful_min_pe = ((ctx->pe.min * PSY_PE_FORGET_SLOPE)
523 + FFMAX(ctx->pe.min, pe * (pe / ctx->pe.max))) / (PSY_PE_FORGET_SLOPE + 1);
524 ctx->pe.min = FFMIN(pe, forgetful_min_pe);
525
526 /* NOTE: allocate a minimum of 1/8th average frame bits, to avoid
527 * reservoir starvation from producing zero-bit frames
528 */
529 return FFMIN(
530 ctx->frame_bits * bit_factor,
531 FFMAX(ctx->frame_bits + size - bits, ctx->frame_bits / 8));
532}
533
534static float calc_pe_3gpp(AacPsyBand *band)
535{
536 float pe, a;
537
538 band->pe = 0.0f;
539 band->pe_const = 0.0f;
540 band->active_lines = 0.0f;
541 if (band->energy > band->thr) {
542 a = log2f(band->energy);
543 pe = a - log2f(band->thr);
544 band->active_lines = band->nz_lines;
545 if (pe < PSY_3GPP_C1) {
546 pe = pe * PSY_3GPP_C3 + PSY_3GPP_C2;
547 a = a * PSY_3GPP_C3 + PSY_3GPP_C2;
548 band->active_lines *= PSY_3GPP_C3;
549 }
550 band->pe = pe * band->nz_lines;
551 band->pe_const = a * band->nz_lines;
552 }
553
554 return band->pe;
555}
556
557static float calc_reduction_3gpp(float a, float desired_pe, float pe,
558 float active_lines)
559{
560 float thr_avg, reduction;
561
562 if(active_lines == 0.0)
563 return 0;
564
565 thr_avg = exp2f((a - pe) / (4.0f * active_lines));
566 reduction = exp2f((a - desired_pe) / (4.0f * active_lines)) - thr_avg;
567
568 return FFMAX(reduction, 0.0f);
569}
570
571static float calc_reduced_thr_3gpp(AacPsyBand *band, float min_snr,
572 float reduction)
573{
574 float thr = band->thr;
575
576 if (band->energy > thr) {
577 thr = sqrtf(thr);
578 thr = sqrtf(thr) + reduction;
579 thr *= thr;
580 thr *= thr;
581
582 /* This deviates from the 3GPP spec to match the reference encoder.
583 * It performs min(thr_reduced, max(thr, energy/min_snr)) only for bands
584 * that have hole avoidance on (active or inactive). It always reduces the
585 * threshold of bands with hole avoidance off.
586 */
587 if (thr > band->energy * min_snr && band->avoid_holes != PSY_3GPP_AH_NONE) {
588 thr = FFMAX(band->thr, band->energy * min_snr);
589 band->avoid_holes = PSY_3GPP_AH_ACTIVE;
590 }
591 }
592
593 return thr;
594}
595
596#ifndef calc_thr_3gpp
597static void calc_thr_3gpp(const FFPsyWindowInfo *wi, const int num_bands, AacPsyChannel *pch,
598 const uint8_t *band_sizes, const float *coefs, const int cutoff)
599{
600 int i, w, g;
601 int start = 0, wstart = 0;
602 for (w = 0; w < wi->num_windows*16; w += 16) {
603 wstart = 0;
604 for (g = 0; g < num_bands; g++) {
605 AacPsyBand *band = &pch->band[w+g];
606
607 float form_factor = 0.0f;
608 float Temp;
609 band->energy = 0.0f;
610 if (wstart < cutoff) {
611 for (i = 0; i < band_sizes[g]; i++) {
612 band->energy += coefs[start+i] * coefs[start+i];
613 form_factor += sqrtf(fabs(coefs[start+i]));
614 }
615 }
616 Temp = band->energy > 0 ? sqrtf((float)band_sizes[g] / band->energy) : 0;
617 band->thr = band->energy * 0.001258925f;
618 band->nz_lines = form_factor * sqrtf(Temp);
619
620 start += band_sizes[g];
621 wstart += band_sizes[g];
622 }
623 }
624}
625#endif /* calc_thr_3gpp */
626
627#ifndef psy_hp_filter
628static void psy_hp_filter(const float *firbuf, float *hpfsmpl, const float *psy_fir_coeffs)
629{
630 int i, j;
631 for (i = 0; i < AAC_BLOCK_SIZE_LONG; i++) {
632 float sum1, sum2;
633 sum1 = firbuf[i + (PSY_LAME_FIR_LEN - 1) / 2];
634 sum2 = 0.0;
635 for (j = 0; j < ((PSY_LAME_FIR_LEN - 1) / 2) - 1; j += 2) {
636 sum1 += psy_fir_coeffs[j] * (firbuf[i + j] + firbuf[i + PSY_LAME_FIR_LEN - j]);
637 sum2 += psy_fir_coeffs[j + 1] * (firbuf[i + j + 1] + firbuf[i + PSY_LAME_FIR_LEN - j - 1]);
638 }
639 /* NOTE: The LAME psymodel expects it's input in the range -32768 to 32768.
640 * Tuning this for normalized floats would be difficult. */
641 hpfsmpl[i] = (sum1 + sum2) * 32768.0f;
642 }
643}
644#endif /* psy_hp_filter */
645
646/**
647 * Calculate band thresholds as suggested in 3GPP TS26.403
648 */
649static void psy_3gpp_analyze_channel(FFPsyContext *ctx, int channel,
650 const float *coefs, const FFPsyWindowInfo *wi)
651{
652 AacPsyContext *pctx = (AacPsyContext*) ctx->model_priv_data;
653 AacPsyChannel *pch = &pctx->ch[channel];
654 int i, w, g;
655 float desired_bits, desired_pe, delta_pe, reduction= NAN, spread_en[128] = {0};
656 float a = 0.0f, active_lines = 0.0f, norm_fac = 0.0f;
657 float pe = pctx->chan_bitrate > 32000 ? 0.0f : FFMAX(50.0f, 100.0f - pctx->chan_bitrate * 100.0f / 32000.0f);
658 const int num_bands = ctx->num_bands[wi->num_windows == 8];
659 const uint8_t *band_sizes = ctx->bands[wi->num_windows == 8];
660 AacPsyCoeffs *coeffs = pctx->psy_coef[wi->num_windows == 8];
661 const float avoid_hole_thr = wi->num_windows == 8 ? PSY_3GPP_AH_THR_SHORT : PSY_3GPP_AH_THR_LONG;
662 const int bandwidth = ctx->cutoff ? ctx->cutoff : AAC_CUTOFF(ctx->avctx);
663 const int cutoff = bandwidth * 2048 / wi->num_windows / ctx->avctx->sample_rate;
664
665 //calculate energies, initial thresholds and related values - 5.4.2 "Threshold Calculation"
666 calc_thr_3gpp(wi, num_bands, pch, band_sizes, coefs, cutoff);
667
668 //modify thresholds and energies - spread, threshold in quiet, pre-echo control
669 for (w = 0; w < wi->num_windows*16; w += 16) {
670 AacPsyBand *bands = &pch->band[w];
671
672 /* 5.4.2.3 "Spreading" & 5.4.3 "Spread Energy Calculation" */
673 spread_en[0] = bands[0].energy;
674 for (g = 1; g < num_bands; g++) {
675 bands[g].thr = FFMAX(bands[g].thr, bands[g-1].thr * coeffs[g].spread_hi[0]);
676 spread_en[w+g] = FFMAX(bands[g].energy, spread_en[w+g-1] * coeffs[g].spread_hi[1]);
677 }
678 for (g = num_bands - 2; g >= 0; g--) {
679 bands[g].thr = FFMAX(bands[g].thr, bands[g+1].thr * coeffs[g].spread_low[0]);
680 spread_en[w+g] = FFMAX(spread_en[w+g], spread_en[w+g+1] * coeffs[g].spread_low[1]);
681 }
682 //5.4.2.4 "Threshold in quiet"
683 for (g = 0; g < num_bands; g++) {
684 AacPsyBand *band = &bands[g];
685
686 band->thr_quiet = band->thr = FFMAX(band->thr, coeffs[g].ath);
687 //5.4.2.5 "Pre-echo control"
688 if (!(wi->window_type[0] == LONG_STOP_SEQUENCE || (!w && wi->window_type[1] == LONG_START_SEQUENCE)))
689 band->thr = FFMAX(PSY_3GPP_RPEMIN*band->thr, FFMIN(band->thr,
690 PSY_3GPP_RPELEV*pch->prev_band[w+g].thr_quiet));
691
692 /* 5.6.1.3.1 "Preparatory steps of the perceptual entropy calculation" */
693 pe += calc_pe_3gpp(band);
694 a += band->pe_const;
695 active_lines += band->active_lines;
696
697 /* 5.6.1.3.3 "Selection of the bands for avoidance of holes" */
698 if (spread_en[w+g] * avoid_hole_thr > band->energy || coeffs[g].min_snr > 1.0f)
699 band->avoid_holes = PSY_3GPP_AH_NONE;
700 else
701 band->avoid_holes = PSY_3GPP_AH_INACTIVE;
702 }
703 }
704
705 /* 5.6.1.3.2 "Calculation of the desired perceptual entropy" */
706 ctx->ch[channel].entropy = pe;
707 if (ctx->avctx->flags & AV_CODEC_FLAG_QSCALE) {
708 /* (2.5 * 120) achieves almost transparent rate, and we want to give
709 * ample room downwards, so we make that equivalent to QSCALE=2.4
710 */
711 desired_pe = pe * (ctx->avctx->global_quality ? ctx->avctx->global_quality : 120) / (2 * 2.5f * 120.0f);
712 desired_bits = FFMIN(2560, PSY_3GPP_PE_TO_BITS(desired_pe));
713 desired_pe = PSY_3GPP_BITS_TO_PE(desired_bits); // reflect clipping
714
715 /* PE slope smoothing */
716 if (ctx->bitres.bits > 0) {
717 desired_bits = FFMIN(2560, PSY_3GPP_PE_TO_BITS(desired_pe));
718 desired_pe = PSY_3GPP_BITS_TO_PE(desired_bits); // reflect clipping
719 }
720
721 pctx->pe.max = FFMAX(pe, pctx->pe.max);
722 pctx->pe.min = FFMIN(pe, pctx->pe.min);
723 } else {
724 desired_bits = calc_bit_demand(pctx, pe, ctx->bitres.bits, ctx->bitres.size, wi->num_windows == 8);
725 desired_pe = PSY_3GPP_BITS_TO_PE(desired_bits);
726
727 /* NOTE: PE correction is kept simple. During initial testing it had very
728 * little effect on the final bitrate. Probably a good idea to come
729 * back and do more testing later.
730 */
731 if (ctx->bitres.bits > 0)
732 desired_pe *= av_clipf(pctx->pe.previous / PSY_3GPP_BITS_TO_PE(ctx->bitres.bits),
733 0.85f, 1.15f);
734 }
735 pctx->pe.previous = PSY_3GPP_BITS_TO_PE(desired_bits);
736 ctx->bitres.alloc = desired_bits;
737
738 if (desired_pe < pe) {
739 /* 5.6.1.3.4 "First Estimation of the reduction value" */
740 for (w = 0; w < wi->num_windows*16; w += 16) {
741 reduction = calc_reduction_3gpp(a, desired_pe, pe, active_lines);
742 pe = 0.0f;
743 a = 0.0f;
744 active_lines = 0.0f;
745 for (g = 0; g < num_bands; g++) {
746 AacPsyBand *band = &pch->band[w+g];
747
748 band->thr = calc_reduced_thr_3gpp(band, coeffs[g].min_snr, reduction);
749 /* recalculate PE */
750 pe += calc_pe_3gpp(band);
751 a += band->pe_const;
752 active_lines += band->active_lines;
753 }
754 }
755
756 /* 5.6.1.3.5 "Second Estimation of the reduction value" */
757 for (i = 0; i < 2; i++) {
758 float pe_no_ah = 0.0f, desired_pe_no_ah;
759 active_lines = a = 0.0f;
760 for (w = 0; w < wi->num_windows*16; w += 16) {
761 for (g = 0; g < num_bands; g++) {
762 AacPsyBand *band = &pch->band[w+g];
763
764 if (band->avoid_holes != PSY_3GPP_AH_ACTIVE) {
765 pe_no_ah += band->pe;
766 a += band->pe_const;
767 active_lines += band->active_lines;
768 }
769 }
770 }
771 desired_pe_no_ah = FFMAX(desired_pe - (pe - pe_no_ah), 0.0f);
772 if (active_lines > 0.0f)
773 reduction = calc_reduction_3gpp(a, desired_pe_no_ah, pe_no_ah, active_lines);
774
775 pe = 0.0f;
776 for (w = 0; w < wi->num_windows*16; w += 16) {
777 for (g = 0; g < num_bands; g++) {
778 AacPsyBand *band = &pch->band[w+g];
779
780 if (active_lines > 0.0f)
781 band->thr = calc_reduced_thr_3gpp(band, coeffs[g].min_snr, reduction);
782 pe += calc_pe_3gpp(band);
783 if (band->thr > 0.0f)
784 band->norm_fac = band->active_lines / band->thr;
785 else
786 band->norm_fac = 0.0f;
787 norm_fac += band->norm_fac;
788 }
789 }
790 delta_pe = desired_pe - pe;
791 if (fabs(delta_pe) > 0.05f * desired_pe)
792 break;
793 }
794
795 if (pe < 1.15f * desired_pe) {
796 /* 6.6.1.3.6 "Final threshold modification by linearization" */
797 norm_fac = 1.0f / norm_fac;
798 for (w = 0; w < wi->num_windows*16; w += 16) {
799 for (g = 0; g < num_bands; g++) {
800 AacPsyBand *band = &pch->band[w+g];
801
802 if (band->active_lines > 0.5f) {
803 float delta_sfb_pe = band->norm_fac * norm_fac * delta_pe;
804 float thr = band->thr;
805
806 thr *= exp2f(delta_sfb_pe / band->active_lines);
807 if (thr > coeffs[g].min_snr * band->energy && band->avoid_holes == PSY_3GPP_AH_INACTIVE)
808 thr = FFMAX(band->thr, coeffs[g].min_snr * band->energy);
809 band->thr = thr;
810 }
811 }
812 }
813 } else {
814 /* 5.6.1.3.7 "Further perceptual entropy reduction" */
815 g = num_bands;
816 while (pe > desired_pe && g--) {
817 for (w = 0; w < wi->num_windows*16; w+= 16) {
818 AacPsyBand *band = &pch->band[w+g];
819 if (band->avoid_holes != PSY_3GPP_AH_NONE && coeffs[g].min_snr < PSY_SNR_1DB) {
820 coeffs[g].min_snr = PSY_SNR_1DB;
821 band->thr = band->energy * PSY_SNR_1DB;
822 pe += band->active_lines * 1.5f - band->pe;
823 }
824 }
825 }
826 /* TODO: allow more holes (unused without mid/side) */
827 }
828 }
829
830 for (w = 0; w < wi->num_windows*16; w += 16) {
831 for (g = 0; g < num_bands; g++) {
832 AacPsyBand *band = &pch->band[w+g];
833 FFPsyBand *psy_band = &ctx->ch[channel].psy_bands[w+g];
834
835 psy_band->threshold = band->thr;
836 psy_band->energy = band->energy;
837 psy_band->spread = band->active_lines * 2.0f / band_sizes[g];
838 psy_band->bits = PSY_3GPP_PE_TO_BITS(band->pe);
839 }
840 }
841
842 memcpy(pch->prev_band, pch->band, sizeof(pch->band));
843}
844
845static void psy_3gpp_analyze(FFPsyContext *ctx, int channel,
846 const float **coeffs, const FFPsyWindowInfo *wi)
847{
848 int ch;
849 FFPsyChannelGroup *group = ff_psy_find_group(ctx, channel);
850
851 for (ch = 0; ch < group->num_ch; ch++)
852 psy_3gpp_analyze_channel(ctx, channel + ch, coeffs[ch], &wi[ch]);
853}
854
855static av_cold void psy_3gpp_end(FFPsyContext *apc)
856{
857 AacPsyContext *pctx = (AacPsyContext*) apc->model_priv_data;
858 av_freep(&pctx->ch);
859 av_freep(&apc->model_priv_data);
860}
861
862static void lame_apply_block_type(AacPsyChannel *ctx, FFPsyWindowInfo *wi, int uselongblock)
863{
864 int blocktype = ONLY_LONG_SEQUENCE;
865 if (uselongblock) {
866 if (ctx->next_window_seq == EIGHT_SHORT_SEQUENCE)
867 blocktype = LONG_STOP_SEQUENCE;
868 } else {
869 blocktype = EIGHT_SHORT_SEQUENCE;
870 if (ctx->next_window_seq == ONLY_LONG_SEQUENCE)
871 ctx->next_window_seq = LONG_START_SEQUENCE;
872 if (ctx->next_window_seq == LONG_STOP_SEQUENCE)
873 ctx->next_window_seq = EIGHT_SHORT_SEQUENCE;
874 }
875
876 wi->window_type[0] = ctx->next_window_seq;
877 ctx->next_window_seq = blocktype;
878}
879
880static FFPsyWindowInfo psy_lame_window(FFPsyContext *ctx, const float *audio,
881 const float *la, int channel, int prev_type)
882{
883 AacPsyContext *pctx = (AacPsyContext*) ctx->model_priv_data;
884 AacPsyChannel *pch = &pctx->ch[channel];
885 int grouping = 0;
886 int uselongblock = 1;
887 int attacks[AAC_NUM_BLOCKS_SHORT + 1] = { 0 };
888 int i;
889 FFPsyWindowInfo wi = { { 0 } };
890
891 if (la) {
892 float hpfsmpl[AAC_BLOCK_SIZE_LONG];
893 const float *pf = hpfsmpl;
894 float attack_intensity[(AAC_NUM_BLOCKS_SHORT + 1) * PSY_LAME_NUM_SUBBLOCKS];
895 float energy_subshort[(AAC_NUM_BLOCKS_SHORT + 1) * PSY_LAME_NUM_SUBBLOCKS];
896 float energy_short[AAC_NUM_BLOCKS_SHORT + 1] = { 0 };
897 const float *firbuf = la + (AAC_BLOCK_SIZE_SHORT/4 - PSY_LAME_FIR_LEN);
898 int att_sum = 0;
899
900 /* LAME comment: apply high pass filter of fs/4 */
901 psy_hp_filter(firbuf, hpfsmpl, psy_fir_coeffs);
902
903 /* Calculate the energies of each sub-shortblock */
904 for (i = 0; i < PSY_LAME_NUM_SUBBLOCKS; i++) {
905 energy_subshort[i] = pch->prev_energy_subshort[i + ((AAC_NUM_BLOCKS_SHORT - 1) * PSY_LAME_NUM_SUBBLOCKS)];
906 assert(pch->prev_energy_subshort[i + ((AAC_NUM_BLOCKS_SHORT - 2) * PSY_LAME_NUM_SUBBLOCKS + 1)] > 0);
907 attack_intensity[i] = energy_subshort[i] / pch->prev_energy_subshort[i + ((AAC_NUM_BLOCKS_SHORT - 2) * PSY_LAME_NUM_SUBBLOCKS + 1)];
908 energy_short[0] += energy_subshort[i];
909 }
910
911 for (i = 0; i < AAC_NUM_BLOCKS_SHORT * PSY_LAME_NUM_SUBBLOCKS; i++) {
912 const float *const pfe = pf + AAC_BLOCK_SIZE_LONG / (AAC_NUM_BLOCKS_SHORT * PSY_LAME_NUM_SUBBLOCKS);
913 float p = 1.0f;
914 for (; pf < pfe; pf++)
915 p = FFMAX(p, fabsf(*pf));
916 pch->prev_energy_subshort[i] = energy_subshort[i + PSY_LAME_NUM_SUBBLOCKS] = p;
917 energy_short[1 + i / PSY_LAME_NUM_SUBBLOCKS] += p;
918 /* NOTE: The indexes below are [i + 3 - 2] in the LAME source.
919 * Obviously the 3 and 2 have some significance, or this would be just [i + 1]
920 * (which is what we use here). What the 3 stands for is ambiguous, as it is both
921 * number of short blocks, and the number of sub-short blocks.
922 * It seems that LAME is comparing each sub-block to sub-block + 1 in the
923 * previous block.
924 */
925 if (p > energy_subshort[i + 1])
926 p = p / energy_subshort[i + 1];
927 else if (energy_subshort[i + 1] > p * 10.0f)
928 p = energy_subshort[i + 1] / (p * 10.0f);
929 else
930 p = 0.0;
931 attack_intensity[i + PSY_LAME_NUM_SUBBLOCKS] = p;
932 }
933
934 /* compare energy between sub-short blocks */
935 for (i = 0; i < (AAC_NUM_BLOCKS_SHORT + 1) * PSY_LAME_NUM_SUBBLOCKS; i++)
936 if (!attacks[i / PSY_LAME_NUM_SUBBLOCKS])
937 if (attack_intensity[i] > pch->attack_threshold)
938 attacks[i / PSY_LAME_NUM_SUBBLOCKS] = (i % PSY_LAME_NUM_SUBBLOCKS) + 1;
939
940 /* should have energy change between short blocks, in order to avoid periodic signals */
941 /* Good samples to show the effect are Trumpet test songs */
942 /* GB: tuned (1) to avoid too many short blocks for test sample TRUMPET */
943 /* RH: tuned (2) to let enough short blocks through for test sample FSOL and SNAPS */
944 for (i = 1; i < AAC_NUM_BLOCKS_SHORT + 1; i++) {
945 const float u = energy_short[i - 1];
946 const float v = energy_short[i];
947 const float m = FFMAX(u, v);
948 if (m < 40000) { /* (2) */
949 if (u < 1.7f * v && v < 1.7f * u) { /* (1) */
950 if (i == 1 && attacks[0] < attacks[i])
951 attacks[0] = 0;
952 attacks[i] = 0;
953 }
954 }
955 att_sum += attacks[i];
956 }
957
958 if (attacks[0] <= pch->prev_attack)
959 attacks[0] = 0;
960
961 att_sum += attacks[0];
962 /* 3 below indicates the previous attack happened in the last sub-block of the previous sequence */
963 if (pch->prev_attack == 3 || att_sum) {
964 uselongblock = 0;
965
966 for (i = 1; i < AAC_NUM_BLOCKS_SHORT + 1; i++)
967 if (attacks[i] && attacks[i-1])
968 attacks[i] = 0;
969 }
970 } else {
971 /* We have no lookahead info, so just use same type as the previous sequence. */
972 uselongblock = !(prev_type == EIGHT_SHORT_SEQUENCE);
973 }
974
975 lame_apply_block_type(pch, &wi, uselongblock);
976
977 wi.window_type[1] = prev_type;
978 if (wi.window_type[0] != EIGHT_SHORT_SEQUENCE) {
979
980 wi.num_windows = 1;
981 wi.grouping[0] = 1;
982 if (wi.window_type[0] == LONG_START_SEQUENCE)
983 wi.window_shape = 0;
984 else
985 wi.window_shape = 1;
986
987 } else {
988 int lastgrp = 0;
989
990 wi.num_windows = 8;
991 wi.window_shape = 0;
992 for (i = 0; i < 8; i++) {
993 if (!((pch->next_grouping >> i) & 1))
994 lastgrp = i;
995 wi.grouping[lastgrp]++;
996 }
997 }
998
999 /* Determine grouping, based on the location of the first attack, and save for
1000 * the next frame.
1001 * FIXME: Move this to analysis.
1002 * TODO: Tune groupings depending on attack location
1003 * TODO: Handle more than one attack in a group
1004 */
1005 for (i = 0; i < 9; i++) {
1006 if (attacks[i]) {
1007 grouping = i;
1008 break;
1009 }
1010 }
1011 pch->next_grouping = window_grouping[grouping];
1012
1013 pch->prev_attack = attacks[8];
1014
1015 return wi;
1016}
1017
1018const FFPsyModel ff_aac_psy_model =
1019{
1020 .name = "3GPP TS 26.403-inspired model",
1021 .init = psy_3gpp_init,
1022 .window = psy_lame_window,
1023 .analyze = psy_3gpp_analyze,
1024 .end = psy_3gpp_end,
1025};
1026
generated by cgit at 2024-05-17 05:04:18 (GMT)