1 /******************************************************************************
2 *
3 * Copyright 2022 Google LLC
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at:
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 ******************************************************************************/
18
19 #include "attdet.h"
20
21
22 /**
23 * Time domain attack detector
24 */
lc3_attdet_run(enum lc3_dt dt,enum lc3_srate sr,int nbytes,struct lc3_attdet_analysis * attdet,const int16_t * x)25 bool lc3_attdet_run(enum lc3_dt dt, enum lc3_srate sr,
26 int nbytes, struct lc3_attdet_analysis *attdet, const int16_t *x)
27 {
28 /* --- Check enabling --- */
29
30 const int nbytes_ranges[LC3_NUM_DT][LC3_NUM_SRATE - LC3_SRATE_32K][2] = {
31 [LC3_DT_7M5] = { { 61, 149 }, { 75, 149 } },
32 [LC3_DT_10M] = { { 81, INT_MAX }, { 100, INT_MAX } },
33 };
34
35 if (sr < LC3_SRATE_32K ||
36 nbytes < nbytes_ranges[dt][sr - LC3_SRATE_32K][0] ||
37 nbytes > nbytes_ranges[dt][sr - LC3_SRATE_32K][1] )
38 return 0;
39
40 /* --- Filtering & Energy calculation --- */
41
42 int nblk = 4 - (dt == LC3_DT_7M5);
43 int32_t e[4];
44
45 for (int i = 0; i < nblk; i++) {
46 e[i] = 0;
47
48 if (sr == LC3_SRATE_32K) {
49 int16_t xn2 = (x[-4] + x[-3]) >> 1;
50 int16_t xn1 = (x[-2] + x[-1]) >> 1;
51 int16_t xn, xf;
52
53 for (int j = 0; j < 40; j++, x += 2, xn2 = xn1, xn1 = xn) {
54 xn = (x[0] + x[1]) >> 1;
55 xf = (3 * xn - 4 * xn1 + 1 * xn2) >> 3;
56 e[i] += (xf * xf) >> 5;
57 }
58 }
59
60 else {
61 int16_t xn2 = (x[-6] + x[-5] + x[-4]) >> 2;
62 int16_t xn1 = (x[-3] + x[-2] + x[-1]) >> 2;
63 int16_t xn, xf;
64
65 for (int j = 0; j < 40; j++, x += 3, xn2 = xn1, xn1 = xn) {
66 xn = (x[0] + x[1] + x[2]) >> 2;
67 xf = (3 * xn - 4 * xn1 + 1 * xn2) >> 3;
68 e[i] += (xf * xf) >> 5;
69 }
70 }
71 }
72
73 /* --- Attack detection ---
74 * The attack block `p_att` is defined as the normative value + 1,
75 * in such way, it will be initialized to 0 */
76
77 int p_att = 0;
78 int32_t a[4];
79
80 for (int i = 0; i < nblk; i++) {
81 a[i] = LC3_MAX(attdet->an1 >> 2, attdet->en1);
82 attdet->en1 = e[i], attdet->an1 = a[i];
83
84 if ((e[i] >> 3) > a[i] + (a[i] >> 4))
85 p_att = i + 1;
86 }
87
88 int att = attdet->p_att >= 1 + (nblk >> 1) || p_att > 0;
89 attdet->p_att = p_att;
90
91 return att;
92 }
93
