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 "bwdet.h" 20 21 22 /** 23 * Bandwidth detector 24 */ 25 enum lc3_bandwidth lc3_bwdet_run( 26 enum lc3_dt dt, enum lc3_srate sr, const float *e) 27 { 28 /* Bandwidth regions */ 29 30 struct region { int is : 8; int ie : 8; }; 31 32 #if LC3_PLUS 33 34 static const struct region bws_table_2m5[][LC3_BANDWIDTH_SWB+1] = { 35 { { 24, 34+1 } }, 36 { { 24, 32+1 }, { 35, 39+1 } }, 37 { { 24, 31+1 }, { 33, 38+1 }, { 39, 42+1 } }, 38 { { 22, 29+1 }, { 31, 35+1 }, { 37, 40+1 }, { 41, 43+1 } }, 39 }; 40 41 static const struct region bws_table_5m[][LC3_BANDWIDTH_SWB+1] = { 42 { { 39, 49+1 } }, 43 { { 35, 44+1 }, { 47, 51+1 } }, 44 { { 34, 42+1 }, { 44, 49+1 }, { 50, 53+1 } }, 45 { { 32, 40+1 }, { 42, 46+1 }, { 48, 51+1 }, { 52, 54+1 } }, 46 }; 47 48 #endif /* LC3_PLUS */ 49 50 static const struct region bws_table_7m5[][LC3_BANDWIDTH_SWB+1] = { 51 { { 51, 63+1 } }, 52 { { 45, 55+1 }, { 58, 63+1 } }, 53 { { 42, 51+1 }, { 53, 58+1 }, { 60, 63+1 } }, 54 { { 40, 48+1 }, { 51, 55+1 }, { 57, 60+1 }, { 61, 63+1 } }, 55 }; 56 57 static const struct region bws_table_10m[][LC3_BANDWIDTH_SWB+1] = { 58 { { 53, 63+1 } }, 59 { { 47, 56+1 }, { 59, 63+1 } }, 60 { { 44, 52+1 }, { 54, 59+1 }, { 60, 63+1 } }, 61 { { 41, 49+1 }, { 51, 55+1 }, { 57, 60+1 }, { 61, 63+1 } }, 62 }; 63 64 static const struct region (*bws_table[])[LC3_BANDWIDTH_SWB+1] = { 65 [LC3_DT_2M5] = LC3_IF_PLUS(bws_table_2m5, NULL), 66 [LC3_DT_5M ] = LC3_IF_PLUS(bws_table_5m , NULL), 67 [LC3_DT_7M5] = bws_table_7m5, 68 [LC3_DT_10M] = bws_table_10m, 69 }; 70 71 static const int l_table[LC3_NUM_DT][LC3_BANDWIDTH_SWB+1] = { 72 [LC3_DT_2M5] = { 4, 4, 3, 1 }, 73 [LC3_DT_5M ] = { 4, 4, 3, 1 }, 74 [LC3_DT_7M5] = { 4, 4, 3, 2 }, 75 [LC3_DT_10M] = { 4, 4, 3, 1 }, 76 }; 77 78 /* --- Stage 1 --- 79 * Determine bw0 candidate */ 80 81 enum lc3_bandwidth bw0 = LC3_BANDWIDTH_NB; 82 enum lc3_bandwidth bwn = (enum lc3_bandwidth)sr; 83 84 if (bwn <= bw0 || lc3_hr(sr)) 85 return bwn; 86 87 const struct region *bwr = bws_table[dt][bwn-1]; 88 89 for (enum lc3_bandwidth bw = bw0; bw < bwn; bw++) { 90 int i = bwr[bw].is, ie = bwr[bw].ie; 91 int n = ie - i; 92 93 float se = e[i]; 94 for (i++; i < ie; i++) 95 se += e[i]; 96 97 if (se >= (10 << (bw == LC3_BANDWIDTH_NB)) * n) 98 bw0 = bw + 1; 99 } 100 101 /* --- Stage 2 --- 102 * Detect drop above cut-off frequency. 103 * The Tc condition (13) is precalculated, as 104 * Tc[] = 10 ^ (n / 10) , n = { 15, 23, 20, 20 } */ 105 106 int hold = bw0 >= bwn; 107 108 if (!hold) { 109 int i0 = bwr[bw0].is, l = l_table[dt][bw0]; 110 float tc = (const float []){ 111 31.62277660, 199.52623150, 100, 100 }[bw0]; 112 113 for (int i = i0 - l + 1; !hold && i <= i0 + 1; i++) { 114 hold = e[i-l] > tc * e[i]; 115 } 116 117 } 118 119 return hold ? bw0 : bwn; 120 } 121 122 /** 123 * Return number of bits coding the bandwidth value 124 */ 125 int lc3_bwdet_get_nbits(enum lc3_srate sr) 126 { 127 return lc3_hr(sr) ? 0 : (sr > 0) + (sr > 1) + (sr > 3); 128 } 129 130 /** 131 * Put bandwidth indication 132 */ 133 void lc3_bwdet_put_bw(lc3_bits_t *bits, 134 enum lc3_srate sr, enum lc3_bandwidth bw) 135 { 136 int nbits_bw = lc3_bwdet_get_nbits(sr); 137 if (nbits_bw > 0) 138 lc3_put_bits(bits, bw, nbits_bw); 139 } 140 141 /** 142 * Get bandwidth indication 143 */ 144 int lc3_bwdet_get_bw(lc3_bits_t *bits, 145 enum lc3_srate sr, enum lc3_bandwidth *bw) 146 { 147 enum lc3_bandwidth max_bw = (enum lc3_bandwidth)sr; 148 int nbits_bw = lc3_bwdet_get_nbits(sr); 149 150 *bw = nbits_bw <= 0 ? max_bw : 151 (enum lc3_bandwidth)lc3_get_bits(bits, nbits_bw); 152 153 return *bw > max_bw ? (*bw = max_bw), -1 : 0; 154 } 155