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 */ 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