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 */
lc3_energy_compute(enum lc3_dt dt,enum lc3_srate sr,const float * x,float * e)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
