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 "energy.h" 20 #include "tables.h" 21 22 23 /** 24 * Energy estimation per band 25 */ 26 bool lc3_energy_compute( 27 enum lc3_dt dt, enum lc3_srate sr, const float *x, float *e) 28 { 29 int nb = lc3_num_bands[dt][sr]; 30 const int *lim = lc3_band_lim[dt][sr]; 31 32 /* Mean the square of coefficients within each band */ 33 34 float e_sum[2] = { 0, 0 }; 35 int iband_h = nb - (const int []){ 36 [LC3_DT_2M5] = 2, [LC3_DT_5M ] = 3, 37 [LC3_DT_7M5] = 4, [LC3_DT_10M] = 2 }[dt]; 38 39 for (int iband = 0, i = lim[iband]; iband < nb; iband++) { 40 int ie = lim[iband+1]; 41 int n = ie - i; 42 43 float sx2 = x[i] * x[i]; 44 for (i++; i < ie; i++) 45 sx2 += x[i] * x[i]; 46 47 *e = sx2 / n; 48 e_sum[iband >= iband_h] += *(e++); 49 } 50 51 /* Return the near nyquist flag */ 52 53 return e_sum[1] > 30 * e_sum[0]; 54 } 55