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freeaptx.c
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/*
* Open Source implementation of Audio Processing Technology codec (aptX)
* Copyright (C) 2017 Aurelien Jacobs <aurel@gnuage.org>
* Copyright (C) 2018-2020 Pali Rohár <pali.rohar@gmail.com>
* Copyright (C) 2025 Hunter Wardlaw <wardlawhunter@gmail.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <freeaptx.h>
#if (!defined(__STDC_VERSION__) || __STDC_VERSION__ < 199901L) && !defined(inline)
#define inline
#endif
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(*(a)))
#define DIFFSIGN(x,y) (((x)>(y)) - ((x)<(y)))
/*
* Clip a signed integer into the -(2^p),(2^p-1) range.
* @param a value to clip
* @param p bit position to clip at
* @return clipped value
*/
static inline int32_t clip_intp2(int32_t a, unsigned p)
{
if (((uint32_t)a + ((uint32_t)1 << p)) & ~(((uint32_t)2 << p) - 1))
return (a >> 31) ^ ((1 << p) - 1);
else
return a;
}
/*
* Clip a signed integer value into the amin-amax range.
* @param a value to clip
* @param amin minimum value of the clip range
* @param amax maximum value of the clip range
* @return clipped value
*/
static inline int32_t clip(int32_t a, int32_t amin, int32_t amax)
{
if (a < amin) return amin;
else if (a > amax) return amax;
else return a;
}
static inline int32_t sign_extend(int32_t val, unsigned bits)
{
const unsigned shift = 8 * sizeof(val) - bits;
union { uint32_t u; int32_t s; } v;
v.u = (uint32_t)val << shift;
return v.s >> shift;
}
enum channels {
LEFT,
RIGHT,
NB_CHANNELS
};
#define NB_SUBBANDS 4
#define NB_FILTERS 2
#define FILTER_TAPS 16
#define LATENCY_SAMPLES 90
struct aptx_filter_signal {
int32_t buffer[2*FILTER_TAPS];
uint8_t pos;
};
struct aptx_QMF_analysis {
struct aptx_filter_signal outer_filter_signal[NB_FILTERS];
struct aptx_filter_signal inner_filter_signal[NB_FILTERS][NB_FILTERS];
};
struct aptx_quantize {
int32_t quantized_sample;
int32_t quantized_sample_parity_change;
int32_t error;
};
struct aptx_invert_quantize {
int32_t quantization_factor;
int32_t factor_select;
int32_t reconstructed_difference;
};
struct aptx_prediction {
int32_t prev_sign[2];
int32_t s_weight[2];
int32_t d_weight[24];
int32_t pos;
int32_t reconstructed_differences[48];
int32_t previous_reconstructed_sample;
int32_t predicted_difference;
int32_t predicted_sample;
};
struct aptx_channel {
int32_t codeword_history;
int32_t dither_parity;
int32_t dither[NB_SUBBANDS];
struct aptx_QMF_analysis qmf;
struct aptx_quantize quantize[NB_SUBBANDS];
struct aptx_invert_quantize invert_quantize[NB_SUBBANDS];
struct aptx_prediction prediction[NB_SUBBANDS];
};
struct aptx_context {
size_t decode_sync_packets;
size_t decode_dropped;
struct aptx_channel channels[NB_CHANNELS];
uint8_t hd;
uint8_t sync_idx;
uint8_t encode_remaining;
uint8_t decode_skip_leading;
uint8_t decode_sync_buffer_len;
unsigned char decode_sync_buffer[6];
};
static const int32_t quantize_intervals_LF[65] = {
-9948, 9948, 29860, 49808, 69822, 89926, 110144, 130502,
151026, 171738, 192666, 213832, 235264, 256982, 279014, 301384,
324118, 347244, 370790, 394782, 419250, 444226, 469742, 495832,
522536, 549890, 577936, 606720, 636290, 666700, 698006, 730270,
763562, 797958, 833538, 870398, 908640, 948376, 989740, 1032874,
1077948, 1125150, 1174700, 1226850, 1281900, 1340196, 1402156, 1468282,
1539182, 1615610, 1698514, 1789098, 1888944, 2000168, 2125700, 2269750,
2438670, 2642660, 2899462, 3243240, 3746078, 4535138, 5664098, 7102424,
8897462,
};
static const int32_t invert_quantize_dither_factors_LF[65] = {
9948, 9948, 9962, 9988, 10026, 10078, 10142, 10218,
10306, 10408, 10520, 10646, 10784, 10934, 11098, 11274,
11462, 11664, 11880, 12112, 12358, 12618, 12898, 13194,
13510, 13844, 14202, 14582, 14988, 15422, 15884, 16380,
16912, 17484, 18098, 18762, 19480, 20258, 21106, 22030,
23044, 24158, 25390, 26760, 28290, 30008, 31954, 34172,
36728, 39700, 43202, 47382, 52462, 58762, 66770, 77280,
91642, 112348, 144452, 199326, 303512, 485546, 643414, 794914,
1000124,
};
static const int32_t quantize_dither_factors_LF[65] = {
0, 4, 7, 10, 13, 16, 19, 22,
26, 28, 32, 35, 38, 41, 44, 47,
51, 54, 58, 62, 65, 70, 74, 79,
84, 90, 95, 102, 109, 116, 124, 133,
143, 154, 166, 180, 195, 212, 231, 254,
279, 308, 343, 383, 430, 487, 555, 639,
743, 876, 1045, 1270, 1575, 2002, 2628, 3591,
5177, 8026, 13719, 26047, 45509, 39467, 37875, 51303,
0,
};
static const int16_t quantize_factor_select_offset_LF[65] = {
0, -21, -19, -17, -15, -12, -10, -8,
-6, -4, -1, 1, 3, 6, 8, 10,
13, 15, 18, 20, 23, 26, 29, 31,
34, 37, 40, 43, 47, 50, 53, 57,
60, 64, 68, 72, 76, 80, 85, 89,
94, 99, 105, 110, 116, 123, 129, 136,
144, 152, 161, 171, 182, 194, 207, 223,
241, 263, 291, 328, 382, 467, 522, 522,
522,
};
static const int32_t quantize_intervals_MLF[9] = {
-89806, 89806, 278502, 494338, 759442, 1113112, 1652322, 2720256, 5190186,
};
static const int32_t invert_quantize_dither_factors_MLF[9] = {
89806, 89806, 98890, 116946, 148158, 205512, 333698, 734236, 1735696,
};
static const int32_t quantize_dither_factors_MLF[9] = {
0, 2271, 4514, 7803, 14339, 32047, 100135, 250365, 0,
};
static const int16_t quantize_factor_select_offset_MLF[9] = {
0, -14, 6, 29, 58, 96, 154, 270, 521,
};
static const int32_t quantize_intervals_MHF[3] = {
-194080, 194080, 890562,
};
static const int32_t invert_quantize_dither_factors_MHF[3] = {
194080, 194080, 502402,
};
static const int32_t quantize_dither_factors_MHF[3] = {
0, 77081, 0,
};
static const int16_t quantize_factor_select_offset_MHF[3] = {
0, -33, 136,
};
static const int32_t quantize_intervals_HF[5] = {
-163006, 163006, 542708, 1120554, 2669238,
};
static const int32_t invert_quantize_dither_factors_HF[5] = {
163006, 163006, 216698, 361148, 1187538,
};
static const int32_t quantize_dither_factors_HF[5] = {
0, 13423, 36113, 206598, 0,
};
static const int16_t quantize_factor_select_offset_HF[5] = {
0, -8, 33, 95, 262,
};
static const int32_t hd_quantize_intervals_LF[257] = {
-2436, 2436, 7308, 12180, 17054, 21930, 26806, 31686,
36566, 41450, 46338, 51230, 56124, 61024, 65928, 70836,
75750, 80670, 85598, 90530, 95470, 100418, 105372, 110336,
115308, 120288, 125278, 130276, 135286, 140304, 145334, 150374,
155426, 160490, 165566, 170654, 175756, 180870, 185998, 191138,
196294, 201466, 206650, 211850, 217068, 222300, 227548, 232814,
238096, 243396, 248714, 254050, 259406, 264778, 270172, 275584,
281018, 286470, 291944, 297440, 302956, 308496, 314056, 319640,
325248, 330878, 336532, 342212, 347916, 353644, 359398, 365178,
370986, 376820, 382680, 388568, 394486, 400430, 406404, 412408,
418442, 424506, 430600, 436726, 442884, 449074, 455298, 461554,
467844, 474168, 480528, 486922, 493354, 499820, 506324, 512866,
519446, 526064, 532722, 539420, 546160, 552940, 559760, 566624,
573532, 580482, 587478, 594520, 601606, 608740, 615920, 623148,
630426, 637754, 645132, 652560, 660042, 667576, 675164, 682808,
690506, 698262, 706074, 713946, 721876, 729868, 737920, 746036,
754216, 762460, 770770, 779148, 787594, 796108, 804694, 813354,
822086, 830892, 839774, 848736, 857776, 866896, 876100, 885386,
894758, 904218, 913766, 923406, 933138, 942964, 952886, 962908,
973030, 983254, 993582, 1004020, 1014566, 1025224, 1035996, 1046886,
1057894, 1069026, 1080284, 1091670, 1103186, 1114838, 1126628, 1138558,
1150634, 1162858, 1175236, 1187768, 1200462, 1213320, 1226346, 1239548,
1252928, 1266490, 1280242, 1294188, 1308334, 1322688, 1337252, 1352034,
1367044, 1382284, 1397766, 1413494, 1429478, 1445728, 1462252, 1479058,
1496158, 1513562, 1531280, 1549326, 1567710, 1586446, 1605550, 1625034,
1644914, 1665208, 1685932, 1707108, 1728754, 1750890, 1773542, 1796732,
1820488, 1844840, 1869816, 1895452, 1921780, 1948842, 1976680, 2005338,
2034868, 2065322, 2096766, 2129260, 2162880, 2197708, 2233832, 2271352,
2310384, 2351050, 2393498, 2437886, 2484404, 2533262, 2584710, 2639036,
2696578, 2757738, 2822998, 2892940, 2968278, 3049896, 3138912, 3236760,
3345312, 3467068, 3605434, 3765154, 3952904, 4177962, 4452178, 4787134,
5187290, 5647128, 6159120, 6720518, 7332904, 8000032, 8726664, 9518152,
10380372,
};
static const int32_t hd_invert_quantize_dither_factors_LF[257] = {
2436, 2436, 2436, 2436, 2438, 2438, 2438, 2440,
2442, 2442, 2444, 2446, 2448, 2450, 2454, 2456,
2458, 2462, 2464, 2468, 2472, 2476, 2480, 2484,
2488, 2492, 2498, 2502, 2506, 2512, 2518, 2524,
2528, 2534, 2540, 2548, 2554, 2560, 2568, 2574,
2582, 2588, 2596, 2604, 2612, 2620, 2628, 2636,
2646, 2654, 2664, 2672, 2682, 2692, 2702, 2712,
2722, 2732, 2742, 2752, 2764, 2774, 2786, 2798,
2810, 2822, 2834, 2846, 2858, 2870, 2884, 2896,
2910, 2924, 2938, 2952, 2966, 2980, 2994, 3010,
3024, 3040, 3056, 3070, 3086, 3104, 3120, 3136,
3154, 3170, 3188, 3206, 3224, 3242, 3262, 3280,
3300, 3320, 3338, 3360, 3380, 3400, 3422, 3442,
3464, 3486, 3508, 3532, 3554, 3578, 3602, 3626,
3652, 3676, 3702, 3728, 3754, 3780, 3808, 3836,
3864, 3892, 3920, 3950, 3980, 4010, 4042, 4074,
4106, 4138, 4172, 4206, 4240, 4276, 4312, 4348,
4384, 4422, 4460, 4500, 4540, 4580, 4622, 4664,
4708, 4752, 4796, 4842, 4890, 4938, 4986, 5036,
5086, 5138, 5192, 5246, 5300, 5358, 5416, 5474,
5534, 5596, 5660, 5726, 5792, 5860, 5930, 6002,
6074, 6150, 6226, 6306, 6388, 6470, 6556, 6644,
6736, 6828, 6924, 7022, 7124, 7228, 7336, 7448,
7562, 7680, 7802, 7928, 8058, 8192, 8332, 8476,
8624, 8780, 8940, 9106, 9278, 9458, 9644, 9840,
10042, 10252, 10472, 10702, 10942, 11194, 11458, 11734,
12024, 12328, 12648, 12986, 13342, 13720, 14118, 14540,
14990, 15466, 15976, 16520, 17102, 17726, 18398, 19124,
19908, 20760, 21688, 22702, 23816, 25044, 26404, 27922,
29622, 31540, 33720, 36222, 39116, 42502, 46514, 51334,
57218, 64536, 73830, 85890, 101860, 123198, 151020, 183936,
216220, 243618, 268374, 293022, 319362, 347768, 378864, 412626, 449596,
};
static const int32_t hd_quantize_dither_factors_LF[256] = {
0, 0, 0, 1, 0, 0, 1, 1,
0, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 2, 1, 1, 2, 2, 2, 1,
2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 3,
2, 3, 2, 3, 3, 3, 3, 3,
3, 3, 3, 3, 3, 3, 3, 3,
3, 3, 3, 3, 3, 4, 3, 4,
4, 4, 4, 4, 4, 4, 4, 4,
4, 4, 4, 4, 5, 4, 4, 5,
4, 5, 5, 5, 5, 5, 5, 5,
5, 5, 6, 5, 5, 6, 5, 6,
6, 6, 6, 6, 6, 6, 6, 7,
6, 7, 7, 7, 7, 7, 7, 7,
7, 7, 8, 8, 8, 8, 8, 8,
8, 9, 9, 9, 9, 9, 9, 9,
10, 10, 10, 10, 10, 11, 11, 11,
11, 11, 12, 12, 12, 12, 13, 13,
13, 14, 14, 14, 15, 15, 15, 15,
16, 16, 17, 17, 17, 18, 18, 18,
19, 19, 20, 21, 21, 22, 22, 23,
23, 24, 25, 26, 26, 27, 28, 29,
30, 31, 32, 33, 34, 35, 36, 37,
39, 40, 42, 43, 45, 47, 49, 51,
53, 55, 58, 60, 63, 66, 69, 73,
76, 80, 85, 89, 95, 100, 106, 113,
119, 128, 136, 146, 156, 168, 182, 196,
213, 232, 254, 279, 307, 340, 380, 425,
480, 545, 626, 724, 847, 1003, 1205, 1471,
1830, 2324, 3015, 3993, 5335, 6956, 8229, 8071,
6850, 6189, 6162, 6585, 7102, 7774, 8441, 9243,
};
static const int16_t hd_quantize_factor_select_offset_LF[257] = {
0, -22, -21, -21, -20, -20, -19, -19,
-18, -18, -17, -17, -16, -16, -15, -14,
-14, -13, -13, -12, -12, -11, -11, -10,
-10, -9, -9, -8, -7, -7, -6, -6,
-5, -5, -4, -4, -3, -3, -2, -1,
-1, 0, 0, 1, 1, 2, 2, 3,
4, 4, 5, 5, 6, 6, 7, 8,
8, 9, 9, 10, 11, 11, 12, 12,
13, 14, 14, 15, 15, 16, 17, 17,
18, 19, 19, 20, 20, 21, 22, 22,
23, 24, 24, 25, 26, 26, 27, 28,
28, 29, 30, 30, 31, 32, 33, 33,
34, 35, 35, 36, 37, 38, 38, 39,
40, 41, 41, 42, 43, 44, 44, 45,
46, 47, 48, 48, 49, 50, 51, 52,
52, 53, 54, 55, 56, 57, 58, 58,
59, 60, 61, 62, 63, 64, 65, 66,
67, 68, 69, 69, 70, 71, 72, 73,
74, 75, 77, 78, 79, 80, 81, 82,
83, 84, 85, 86, 87, 89, 90, 91,
92, 93, 94, 96, 97, 98, 99, 101,
102, 103, 105, 106, 107, 109, 110, 112,
113, 115, 116, 118, 119, 121, 122, 124,
125, 127, 129, 130, 132, 134, 136, 137,
139, 141, 143, 145, 147, 149, 151, 153,
155, 158, 160, 162, 164, 167, 169, 172,
174, 177, 180, 182, 185, 188, 191, 194,
197, 201, 204, 208, 211, 215, 219, 223,
227, 232, 236, 241, 246, 251, 257, 263,
269, 275, 283, 290, 298, 307, 317, 327,
339, 352, 367, 384, 404, 429, 458, 494,
522, 522, 522, 522, 522, 522, 522, 522, 522,
};
static const int32_t hd_quantize_intervals_MLF[33] = {
-21236, 21236, 63830, 106798, 150386, 194832, 240376, 287258,
335726, 386034, 438460, 493308, 550924, 611696, 676082, 744626,
817986, 896968, 982580, 1076118, 1179278, 1294344, 1424504, 1574386,
1751090, 1966260, 2240868, 2617662, 3196432, 4176450, 5658260, 7671068,
10380372,
};
static const int32_t hd_invert_quantize_dither_factors_MLF[33] = {
21236, 21236, 21360, 21608, 21978, 22468, 23076, 23806,
24660, 25648, 26778, 28070, 29544, 31228, 33158, 35386,
37974, 41008, 44606, 48934, 54226, 60840, 69320, 80564,
96140, 119032, 155576, 221218, 357552, 622468, 859344, 1153464, 1555840,
};
static const int32_t hd_quantize_dither_factors_MLF[32] = {
0, 31, 62, 93, 123, 152, 183, 214,
247, 283, 323, 369, 421, 483, 557, 647,
759, 900, 1082, 1323, 1654, 2120, 2811, 3894,
5723, 9136, 16411, 34084, 66229, 59219, 73530, 100594,
};
static const int16_t hd_quantize_factor_select_offset_MLF[33] = {
0, -21, -16, -12, -7, -2, 3, 8,
13, 19, 24, 30, 36, 43, 50, 57,
65, 74, 83, 93, 104, 117, 131, 147,
166, 189, 219, 259, 322, 427, 521, 521, 521,
};
static const int32_t hd_quantize_intervals_MHF[9] = {
-95044, 95044, 295844, 528780, 821332, 1226438, 1890540, 3344850, 6450664,
};
static const int32_t hd_invert_quantize_dither_factors_MHF[9] = {
95044, 95044, 105754, 127180, 165372, 39736, 424366, 1029946, 2075866,
};
static const int32_t hd_quantize_dither_factors_MHF[8] = {
0, 2678, 5357, 9548, -31409, 96158, 151395, 261480,
};
static const int16_t hd_quantize_factor_select_offset_MHF[9] = {
0, -17, 5, 30, 62, 105, 177, 334, 518,
};
static const int32_t hd_quantize_intervals_HF[17] = {
-45754, 45754, 138496, 234896, 337336, 448310, 570738, 708380,
866534, 1053262, 1281958, 1577438, 1993050, 2665984, 3900982, 5902844,
8897462,
};
static const int32_t hd_invert_quantize_dither_factors_HF[17] = {
45754, 45754, 46988, 49412, 53026, 57950, 64478, 73164,
84988, 101740, 126958, 168522, 247092, 425842, 809154, 1192708, 1801910,
};
static const int32_t hd_quantize_dither_factors_HF[16] = {
0, 309, 606, 904, 1231, 1632, 2172, 2956,
4188, 6305, 10391, 19643, 44688, 95828, 95889, 152301,
};
static const int16_t hd_quantize_factor_select_offset_HF[17] = {
0, -18, -8, 2, 13, 25, 38, 53,
70, 90, 115, 147, 192, 264, 398, 521, 521,
};
struct aptx_tables {
const int32_t *quantize_intervals;
const int32_t *invert_quantize_dither_factors;
const int32_t *quantize_dither_factors;
const int16_t *quantize_factor_select_offset;
int tables_size;
int32_t factor_max;
int prediction_order;
};
static const struct aptx_tables all_tables[2][NB_SUBBANDS] = {
{
{
/* Low Frequency (0-5.5 kHz) */
quantize_intervals_LF,
invert_quantize_dither_factors_LF,
quantize_dither_factors_LF,
quantize_factor_select_offset_LF,
ARRAY_SIZE(quantize_intervals_LF),
0x11FF,
24
},
{
/* Medium-Low Frequency (5.5-11kHz) */
quantize_intervals_MLF,
invert_quantize_dither_factors_MLF,
quantize_dither_factors_MLF,
quantize_factor_select_offset_MLF,
ARRAY_SIZE(quantize_intervals_MLF),
0x14FF,
12
},
{
/* Medium-High Frequency (11-16.5kHz) */
quantize_intervals_MHF,
invert_quantize_dither_factors_MHF,
quantize_dither_factors_MHF,
quantize_factor_select_offset_MHF,
ARRAY_SIZE(quantize_intervals_MHF),
0x16FF,
6
},
{
/* High Frequency (16.5-22kHz) */
quantize_intervals_HF,
invert_quantize_dither_factors_HF,
quantize_dither_factors_HF,
quantize_factor_select_offset_HF,
ARRAY_SIZE(quantize_intervals_HF),
0x15FF,
12
},
},
{
{
/* Low Frequency (0-5.5 kHz) */
hd_quantize_intervals_LF,
hd_invert_quantize_dither_factors_LF,
hd_quantize_dither_factors_LF,
hd_quantize_factor_select_offset_LF,
ARRAY_SIZE(hd_quantize_intervals_LF),
0x11FF,
24
},
{
/* Medium-Low Frequency (5.5-11kHz) */
hd_quantize_intervals_MLF,
hd_invert_quantize_dither_factors_MLF,
hd_quantize_dither_factors_MLF,
hd_quantize_factor_select_offset_MLF,
ARRAY_SIZE(hd_quantize_intervals_MLF),
0x14FF,
12
},
{
/* Medium-High Frequency (11-16.5kHz) */
hd_quantize_intervals_MHF,
hd_invert_quantize_dither_factors_MHF,
hd_quantize_dither_factors_MHF,
hd_quantize_factor_select_offset_MHF,
ARRAY_SIZE(hd_quantize_intervals_MHF),
0x16FF,
6
},
{
/* High Frequency (16.5-22kHz) */
hd_quantize_intervals_HF,
hd_invert_quantize_dither_factors_HF,
hd_quantize_dither_factors_HF,
hd_quantize_factor_select_offset_HF,
ARRAY_SIZE(hd_quantize_intervals_HF),
0x15FF,
12
},
}
};
static const int16_t quantization_factors[32] = {
2048, 2093, 2139, 2186, 2233, 2282, 2332, 2383,
2435, 2489, 2543, 2599, 2656, 2714, 2774, 2834,
2896, 2960, 3025, 3091, 3158, 3228, 3298, 3371,
3444, 3520, 3597, 3676, 3756, 3838, 3922, 4008,
};
/* Rounded right shift with optional clipping */
#define RSHIFT_SIZE(size) \
static inline int##size##_t rshift##size(int##size##_t value, unsigned shift) \
{ \
const int##size##_t rounding = (int##size##_t)1 << (shift - 1); \
const int##size##_t mask = ((int##size##_t)1 << (shift + 1)) - 1; \
return ((value + rounding) >> shift) - ((value & mask) == rounding); \
} \
static inline int32_t rshift##size##_clip24(int##size##_t value, unsigned shift) \
{ \
return clip_intp2((int32_t)rshift##size(value, shift), 23); \
}
RSHIFT_SIZE(32)
RSHIFT_SIZE(64)
static inline void aptx_update_codeword_history(struct aptx_channel *channel)
{
const int32_t cw = ((channel->quantize[0].quantized_sample & 3) << 0) +
((channel->quantize[1].quantized_sample & 2) << 1) +
((channel->quantize[2].quantized_sample & 1) << 3);
channel->codeword_history = (cw << 8) + (int32_t)((uint32_t)channel->codeword_history << 4);
}
static void aptx_generate_dither(struct aptx_channel *channel)
{
unsigned subband;
int64_t m;
int32_t d;
aptx_update_codeword_history(channel);
m = (int64_t)5184443 * (channel->codeword_history >> 7);
d = (int32_t)((m * 4) + (m >> 22));
for (subband = 0; subband < NB_SUBBANDS; subband++)
channel->dither[subband] = (int32_t)((uint32_t)d << (23 - 5*subband));
channel->dither_parity = (d >> 25) & 1;
}
/*
* Convolution filter coefficients for the outer QMF of the QMF tree.
* The 2 sets are a mirror of each other.
*/
static const int32_t aptx_qmf_outer_coeffs[NB_FILTERS][FILTER_TAPS] = {
{
730, -413, -9611, 43626, -121026, 269973, -585547, 2801966,
697128, -160481, 27611, 8478, -10043, 3511, 688, -897,
},
{
-897, 688, 3511, -10043, 8478, 27611, -160481, 697128,
2801966, -585547, 269973, -121026, 43626, -9611, -413, 730,
},
};
/*
* Convolution filter coefficients for the inner QMF of the QMF tree.
* The 2 sets are a mirror of each other.
*/
static const int32_t aptx_qmf_inner_coeffs[NB_FILTERS][FILTER_TAPS] = {
{
1033, -584, -13592, 61697, -171156, 381799, -828088, 3962579,
985888, -226954, 39048, 11990, -14203, 4966, 973, -1268,
},
{
-1268, 973, 4966, -14203, 11990, 39048, -226954, 985888,
3962579, -828088, 381799, -171156, 61697, -13592, -584, 1033,
},
};
/*
* Push one sample into a circular signal buffer.
*/
static inline void aptx_qmf_filter_signal_push(struct aptx_filter_signal *signal,
int32_t sample)
{
signal->buffer[signal->pos ] = sample;
signal->buffer[signal->pos+FILTER_TAPS] = sample;
signal->pos = (signal->pos + 1) & (FILTER_TAPS - 1);
}
/*
* Compute the convolution of the signal with the coefficients, and reduce
* to 24 bits by applying the specified right shifting.
*/
static inline int32_t aptx_qmf_convolution(const struct aptx_filter_signal *signal,
const int32_t coeffs[FILTER_TAPS],
unsigned shift)
{
const int32_t *sig = &signal->buffer[signal->pos];
int64_t e = 0;
unsigned i;
for (i = 0; i < FILTER_TAPS; i++)
e += (int64_t)sig[i] * (int64_t)coeffs[i];
return rshift64_clip24(e, shift);
}
/*
* Half-band QMF analysis filter realized with a polyphase FIR filter.
* Split into 2 subbands and downsample by 2.
* So for each pair of samples that goes in, one sample goes out,
* split into 2 separate subbands.
*/
static inline void aptx_qmf_polyphase_analysis(struct aptx_filter_signal signal[NB_FILTERS],
const int32_t coeffs[NB_FILTERS][FILTER_TAPS],
unsigned shift,
const int32_t samples[NB_FILTERS],
int32_t *low_subband_output,
int32_t *high_subband_output)
{
int32_t subbands[NB_FILTERS];
unsigned i;
for (i = 0; i < NB_FILTERS; i++) {
aptx_qmf_filter_signal_push(&signal[i], samples[NB_FILTERS-1-i]);
subbands[i] = aptx_qmf_convolution(&signal[i], coeffs[i], shift);
}
*low_subband_output = clip_intp2(subbands[0] + subbands[1], 23);
*high_subband_output = clip_intp2(subbands[0] - subbands[1], 23);
}
/*
* Two stage QMF analysis tree.
* Split 4 input samples into 4 subbands and downsample by 4.
* So for each group of 4 samples that goes in, one sample goes out,
* split into 4 separate subbands.
*/
static void aptx_qmf_tree_analysis(struct aptx_QMF_analysis *qmf,
const int32_t samples[4],
int32_t subband_samples[NB_SUBBANDS])
{
int32_t intermediate_samples[4];
unsigned i;
/* Split 4 input samples into 2 intermediate subbands downsampled to 2 samples */
for (i = 0; i < 2; i++)
aptx_qmf_polyphase_analysis(qmf->outer_filter_signal,
aptx_qmf_outer_coeffs, 23,
&samples[2*i],
&intermediate_samples[0+i],
&intermediate_samples[2+i]);
/* Split 2 intermediate subband samples into 4 final subbands downsampled to 1 sample */
for (i = 0; i < 2; i++)
aptx_qmf_polyphase_analysis(qmf->inner_filter_signal[i],
aptx_qmf_inner_coeffs, 23,
&intermediate_samples[2*i],
&subband_samples[2*i+0],
&subband_samples[2*i+1]);
}
/*
* Half-band QMF synthesis filter realized with a polyphase FIR filter.
* Join 2 subbands and upsample by 2.
* So for each 2 subbands sample that goes in, a pair of samples goes out.
*/
static inline void aptx_qmf_polyphase_synthesis(struct aptx_filter_signal signal[NB_FILTERS],
const int32_t coeffs[NB_FILTERS][FILTER_TAPS],
unsigned shift,
int32_t low_subband_input,
int32_t high_subband_input,
int32_t samples[NB_FILTERS])
{
int32_t subbands[NB_FILTERS];
unsigned i;
subbands[0] = low_subband_input + high_subband_input;
subbands[1] = low_subband_input - high_subband_input;
for (i = 0; i < NB_FILTERS; i++) {
aptx_qmf_filter_signal_push(&signal[i], subbands[1-i]);
samples[i] = aptx_qmf_convolution(&signal[i], coeffs[i], shift);
}
}
/*
* Two stage QMF synthesis tree.
* Join 4 subbands and upsample by 4.
* So for each 4 subbands sample that goes in, a group of 4 samples goes out.
*/
static void aptx_qmf_tree_synthesis(struct aptx_QMF_analysis *qmf,
const int32_t subband_samples[NB_SUBBANDS],
int32_t samples[4])
{
int32_t intermediate_samples[4];
unsigned i;
/* Join 4 subbands into 2 intermediate subbands upsampled to 2 samples. */
for (i = 0; i < 2; i++)
aptx_qmf_polyphase_synthesis(qmf->inner_filter_signal[i],
aptx_qmf_inner_coeffs, 22,
subband_samples[2*i+0],
subband_samples[2*i+1],
&intermediate_samples[2*i]);
/* Join 2 samples from intermediate subbands upsampled to 4 samples. */
for (i = 0; i < 2; i++)
aptx_qmf_polyphase_synthesis(qmf->outer_filter_signal,
aptx_qmf_outer_coeffs, 21,
intermediate_samples[0+i],
intermediate_samples[2+i],
&samples[2*i]);
}
static inline int32_t aptx_bin_search(int32_t value, int32_t factor,
const int32_t *intervals, int nb_intervals)
{
int32_t idx = 0;
int i;
for (i = nb_intervals >> 1; i > 0; i >>= 1)
if ((int64_t)factor * (int64_t)intervals[idx + i] <= ((int64_t)value << 24))
idx += i;
return idx;
}
static void aptx_quantize_difference(struct aptx_quantize *quantize,
int32_t sample_difference,
int32_t dither,
int32_t quantization_factor,
const struct aptx_tables *tables)
{
const int32_t *intervals = tables->quantize_intervals;
int32_t quantized_sample, dithered_sample, parity_change;
int32_t d, mean, interval, inv, sample_difference_abs;
int64_t error;
sample_difference_abs = sample_difference;
if (sample_difference_abs < 0)
sample_difference_abs = -sample_difference_abs;
if (sample_difference_abs > ((int32_t)1 << 23) - 1)
sample_difference_abs = ((int32_t)1 << 23) - 1;
quantized_sample = aptx_bin_search(sample_difference_abs >> 4,
quantization_factor,
intervals, tables->tables_size);
d = rshift32_clip24((int32_t)(((int64_t)dither * (int64_t)dither) >> 32), 7) - ((int32_t)1 << 23);
d = (int32_t)rshift64((int64_t)d * (int64_t)tables->quantize_dither_factors[quantized_sample], 23);
intervals += quantized_sample;
mean = (intervals[1] + intervals[0]) / 2;
interval = (intervals[1] - intervals[0]) * (-(sample_difference < 0) | 1);
dithered_sample = rshift64_clip24((int64_t)dither * (int64_t)interval + ((int64_t)clip_intp2(mean + d, 23) << 32), 32);
error = ((int64_t)sample_difference_abs << 20) - (int64_t)dithered_sample * (int64_t)quantization_factor;
quantize->error = (int32_t)rshift64(error, 23);
if (quantize->error < 0)
quantize->error = -quantize->error;
parity_change = quantized_sample;
if (error < 0)
quantized_sample--;
else
parity_change--;
inv = -(sample_difference < 0);
quantize->quantized_sample = quantized_sample ^ inv;
quantize->quantized_sample_parity_change = parity_change ^ inv;
}
static void aptx_encode_channel(struct aptx_channel *channel, const int32_t samples[4], int hd)
{
int32_t subband_samples[NB_SUBBANDS];
int32_t diff;
unsigned subband;
aptx_qmf_tree_analysis(&channel->qmf, samples, subband_samples);
aptx_generate_dither(channel);
for (subband = 0; subband < NB_SUBBANDS; subband++) {
diff = clip_intp2(subband_samples[subband] - channel->prediction[subband].predicted_sample, 23);
aptx_quantize_difference(&channel->quantize[subband], diff,
channel->dither[subband],
channel->invert_quantize[subband].quantization_factor,
&all_tables[hd][subband]);
}
}
static void aptx_decode_channel(struct aptx_channel *channel, int32_t samples[4])
{
int32_t subband_samples[NB_SUBBANDS];
unsigned subband;
for (subband = 0; subband < NB_SUBBANDS; subband++)
subband_samples[subband] = channel->prediction[subband].previous_reconstructed_sample;
aptx_qmf_tree_synthesis(&channel->qmf, subband_samples, samples);
}
static void aptx_invert_quantization(struct aptx_invert_quantize *invert_quantize,
int32_t quantized_sample, int32_t dither,
const struct aptx_tables *tables)
{
int32_t qr, idx, shift, factor_select;
idx = (quantized_sample ^ -(quantized_sample < 0)) + 1;
qr = tables->quantize_intervals[idx] / 2;
if (quantized_sample < 0)
qr = -qr;
qr = rshift64_clip24(((int64_t)qr * ((int64_t)1<<32)) + (int64_t)dither * (int64_t)tables->invert_quantize_dither_factors[idx], 32);
invert_quantize->reconstructed_difference = (int32_t)(((int64_t)invert_quantize->quantization_factor * (int64_t)qr) >> 19);
/* update factor_select */
factor_select = 32620 * invert_quantize->factor_select;
factor_select = rshift32(factor_select + (tables->quantize_factor_select_offset[idx] * (1 << 15)), 15);
invert_quantize->factor_select = clip(factor_select, 0, tables->factor_max);
/* update quantization factor */
idx = (invert_quantize->factor_select & 0xFF) >> 3;
shift = (tables->factor_max - invert_quantize->factor_select) >> 8;
invert_quantize->quantization_factor = (quantization_factors[idx] << 11) >> shift;
}
static int32_t *aptx_reconstructed_differences_update(struct aptx_prediction *prediction,
int32_t reconstructed_difference,
int order)
{
int32_t *rd1 = prediction->reconstructed_differences, *rd2 = rd1 + order;
int p = prediction->pos;
rd1[p] = rd2[p];
prediction->pos = p = (p + 1) % order;
rd2[p] = reconstructed_difference;
return &rd2[p];
}
static void aptx_prediction_filtering(struct aptx_prediction *prediction,
int32_t reconstructed_difference,
int order)
{
int32_t reconstructed_sample, predictor, srd0, srd;
int32_t *reconstructed_differences;
int64_t predicted_difference = 0;
int i;
reconstructed_sample = clip_intp2(reconstructed_difference + prediction->predicted_sample, 23);
predictor = clip_intp2((int32_t)(((int64_t)prediction->s_weight[0] * (int64_t)prediction->previous_reconstructed_sample
+ (int64_t)prediction->s_weight[1] * (int64_t)reconstructed_sample) >> 22), 23);
prediction->previous_reconstructed_sample = reconstructed_sample;
reconstructed_differences = aptx_reconstructed_differences_update(prediction, reconstructed_difference, order);
srd0 = (int32_t)DIFFSIGN(reconstructed_difference, 0) * ((int32_t)1 << 23);
for (i = 0; i < order; i++) {
srd = (reconstructed_differences[-i-1] >> 31) | 1;
prediction->d_weight[i] -= rshift32(prediction->d_weight[i] - srd*srd0, 8);
predicted_difference += (int64_t)reconstructed_differences[-i] * (int64_t)prediction->d_weight[i];
}
prediction->predicted_difference = clip_intp2((int32_t)(predicted_difference >> 22), 23);
prediction->predicted_sample = clip_intp2(predictor + prediction->predicted_difference, 23);
}
static void aptx_process_subband(struct aptx_invert_quantize *invert_quantize,
struct aptx_prediction *prediction,
int32_t quantized_sample, int32_t dither,
const struct aptx_tables *tables)
{
int32_t sign, same_sign[2], weight[2], sw1, range;
aptx_invert_quantization(invert_quantize, quantized_sample, dither, tables);
sign = DIFFSIGN(invert_quantize->reconstructed_difference,
-prediction->predicted_difference);
same_sign[0] = sign * prediction->prev_sign[0];
same_sign[1] = sign * prediction->prev_sign[1];
prediction->prev_sign[0] = prediction->prev_sign[1];
prediction->prev_sign[1] = sign | 1;
range = 0x100000;
sw1 = rshift32(-same_sign[1] * prediction->s_weight[1], 1);
sw1 = (clip(sw1, -range, range) & ~0xF) * 16;
range = 0x300000;
weight[0] = 254 * prediction->s_weight[0] + 0x800000*same_sign[0] + sw1;
prediction->s_weight[0] = clip(rshift32(weight[0], 8), -range, range);
range = 0x3C0000 - prediction->s_weight[0];
weight[1] = 255 * prediction->s_weight[1] + 0xC00000*same_sign[1];
prediction->s_weight[1] = clip(rshift32(weight[1], 8), -range, range);
aptx_prediction_filtering(prediction,
invert_quantize->reconstructed_difference,
tables->prediction_order);
}
static void aptx_invert_quantize_and_prediction(struct aptx_channel *channel, int hd)
{
unsigned subband;
for (subband = 0; subband < NB_SUBBANDS; subband++)
aptx_process_subband(&channel->invert_quantize[subband],
&channel->prediction[subband],
channel->quantize[subband].quantized_sample,
channel->dither[subband],
&all_tables[hd][subband]);
}
static int32_t aptx_quantized_parity(const struct aptx_channel *channel)
{
int32_t parity = channel->dither_parity;
unsigned subband;
for (subband = 0; subband < NB_SUBBANDS; subband++)
parity ^= channel->quantize[subband].quantized_sample;
return parity & 1;
}
/*
* For each sample, ensure that the parity of all subbands of all channels
* is 0 except once every 8 samples where the parity is forced to 1.
*/
static int aptx_check_parity(const struct aptx_channel channels[NB_CHANNELS], uint8_t *sync_idx)
{
const int32_t parity = aptx_quantized_parity(&channels[LEFT])
^ aptx_quantized_parity(&channels[RIGHT]);
const int32_t eighth = *sync_idx == 7;
*sync_idx = (*sync_idx + 1) & 7;
return parity ^ eighth;
}
static void aptx_insert_sync(struct aptx_channel channels[NB_CHANNELS], uint8_t *sync_idx)
{
unsigned i;
struct aptx_channel *c;
static const unsigned map[] = { 1, 2, 0, 3 };
struct aptx_quantize *min = &channels[NB_CHANNELS-1].quantize[map[0]];
if (aptx_check_parity(channels, sync_idx)) {
for (c = &channels[NB_CHANNELS-1]; c >= channels; c--)
for (i = 0; i < NB_SUBBANDS; i++)
if (c->quantize[map[i]].error < min->error)
min = &c->quantize[map[i]];
/*
* Forcing the desired parity is done by offsetting by 1 the quantized
* sample from the subband featuring the smallest quantization error.
*/
min->quantized_sample = min->quantized_sample_parity_change;
}
}
static uint16_t aptx_pack_codeword(const struct aptx_channel *channel)
{
const int32_t parity = aptx_quantized_parity(channel);
return (uint16_t)((((channel->quantize[3].quantized_sample & 0x06) | parity) << 13)
| (((channel->quantize[2].quantized_sample & 0x03) ) << 11)
| (((channel->quantize[1].quantized_sample & 0x0F) ) << 7)
| (((channel->quantize[0].quantized_sample & 0x7F) ) << 0));
}
static uint32_t aptxhd_pack_codeword(const struct aptx_channel *channel)
{
const int32_t parity = aptx_quantized_parity(channel);
return (uint32_t)((((channel->quantize[3].quantized_sample & 0x01E) | parity) << 19)
| (((channel->quantize[2].quantized_sample & 0x00F) ) << 15)
| (((channel->quantize[1].quantized_sample & 0x03F) ) << 9)
| (((channel->quantize[0].quantized_sample & 0x1FF) ) << 0));
}
static void aptx_unpack_codeword(struct aptx_channel *channel, uint16_t codeword)
{
channel->quantize[0].quantized_sample = sign_extend(codeword >> 0, 7);
channel->quantize[1].quantized_sample = sign_extend(codeword >> 7, 4);
channel->quantize[2].quantized_sample = sign_extend(codeword >> 11, 2);