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/******************************************************************************
*
* Copyright 2022 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
******************************************************************************/
#include "energy.h"
#include "tables.h"
/**
* Energy estimation per band
*/
bool lc3_energy_compute(
enum lc3_dt dt, enum lc3_srate sr, const float *x, float *e)
{
static const int n1_table[LC3_NUM_DT][LC3_NUM_SRATE] = {
[LC3_DT_7M5] = { 56, 34, 27, 24, 22 },
[LC3_DT_10M] = { 49, 28, 23, 20, 18 },
};
/* First bands are 1 coefficient width */
int n1 = n1_table[dt][sr];
float e_sum[2] = { 0, 0 };
int iband;
for (iband = 0; iband < n1; iband++) {
*e = x[iband] * x[iband];
e_sum[0] += *(e++);
}
/* Mean the square of coefficients within each band,
* note that 7.5ms 8KHz frame has more bands than samples */
int nb = LC3_MIN(LC3_NUM_BANDS, LC3_NS(dt, sr));
int iband_h = nb - 2*(2 - dt);
const int *lim = lc3_band_lim[dt][sr];
for (int i = lim[iband]; iband < nb; iband++) {
int ie = lim[iband+1];
int n = ie - i;
float sx2 = x[i] * x[i];
for (i++; i < ie; i++)
sx2 += x[i] * x[i];
*e = sx2 / n;
e_sum[iband >= iband_h] += *(e++);
}
for (; iband < LC3_NUM_BANDS; iband++)
*(e++) = 0;
/* Return the near nyquist flag */
return e_sum[1] > 30 * e_sum[0];
}
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