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*******************************************************************************
* @file OpenPDMFilter.c
* @author CL
* @version V1.0.0
* @date 9-September-2015
* @brief Open PDM audio software decoding Library.
* This Library is used to decode and reconstruct the audio signal
* produced by ST MEMS microphone (MP45Dxxx, MP34Dxxx).
*******************************************************************************
* @attention
*
* <h2><center>© COPYRIGHT 2018 STMicroelectronics</center></h2>
*
* 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.
*******************************************************************************
*/
/* Includes ------------------------------------------------------------------*/
#include "OpenPDMFilter.h"
/* Variables -----------------------------------------------------------------*/
uint32_t div_const = 0;
int64_t sub_const = 0;
uint32_t sinc[DECIMATION_MAX * SINCN];
uint32_t sinc1[DECIMATION_MAX];
uint32_t sinc2[DECIMATION_MAX * 2];
uint32_t coef[SINCN][DECIMATION_MAX];
#ifdef USE_LUT
int32_t lut[256][DECIMATION_MAX / 8][SINCN];
#endif
/* Functions -----------------------------------------------------------------*/
#ifdef USE_LUT
int32_t filter_table_mono_64(uint8_t *data, uint8_t sincn)
{
return (int32_t)
lut[data[0]][0][sincn] +
lut[data[1]][1][sincn] +
lut[data[2]][2][sincn] +
lut[data[3]][3][sincn] +
lut[data[4]][4][sincn] +
lut[data[5]][5][sincn] +
lut[data[6]][6][sincn] +
lut[data[7]][7][sincn];
}
int32_t filter_table_stereo_64(uint8_t *data, uint8_t sincn)
{
return (int32_t)
lut[data[0]][0][sincn] +
lut[data[2]][1][sincn] +
lut[data[4]][2][sincn] +
lut[data[6]][3][sincn] +
lut[data[8]][4][sincn] +
lut[data[10]][5][sincn] +
lut[data[12]][6][sincn] +
lut[data[14]][7][sincn];
}
int32_t filter_table_mono_128(uint8_t *data, uint8_t sincn)
{
return (int32_t)
lut[data[0]][0][sincn] +
lut[data[1]][1][sincn] +
lut[data[2]][2][sincn] +
lut[data[3]][3][sincn] +
lut[data[4]][4][sincn] +
lut[data[5]][5][sincn] +
lut[data[6]][6][sincn] +
lut[data[7]][7][sincn] +
lut[data[8]][8][sincn] +
lut[data[9]][9][sincn] +
lut[data[10]][10][sincn] +
lut[data[11]][11][sincn] +
lut[data[12]][12][sincn] +
lut[data[13]][13][sincn] +
lut[data[14]][14][sincn] +
lut[data[15]][15][sincn];
}
int32_t filter_table_stereo_128(uint8_t *data, uint8_t sincn)
{
return (int32_t)
lut[data[0]][0][sincn] +
lut[data[2]][1][sincn] +
lut[data[4]][2][sincn] +
lut[data[6]][3][sincn] +
lut[data[8]][4][sincn] +
lut[data[10]][5][sincn] +
lut[data[12]][6][sincn] +
lut[data[14]][7][sincn] +
lut[data[16]][8][sincn] +
lut[data[18]][9][sincn] +
lut[data[20]][10][sincn] +
lut[data[22]][11][sincn] +
lut[data[24]][12][sincn] +
lut[data[26]][13][sincn] +
lut[data[28]][14][sincn] +
lut[data[30]][15][sincn];
}
int32_t (* filter_tables_64[2]) (uint8_t *data, uint8_t sincn) = {filter_table_mono_64, filter_table_stereo_64};
int32_t (* filter_tables_128[2]) (uint8_t *data, uint8_t sincn) = {filter_table_mono_128, filter_table_stereo_128};
#else
int32_t filter_table(uint8_t *data, uint8_t sincn, TPDMFilter_InitStruct *param)
{
uint8_t c, i;
uint16_t data_index = 0;
uint32_t *coef_p = &coef[sincn][0];
int32_t F = 0;
uint8_t decimation = param->Decimation;
uint8_t channels = param->In_MicChannels;
for (i = 0; i < decimation; i += 8) {
c = data[data_index];
F += ((c >> 7) ) * coef_p[i ] +
((c >> 6) & 0x01) * coef_p[i + 1] +
((c >> 5) & 0x01) * coef_p[i + 2] +
((c >> 4) & 0x01) * coef_p[i + 3] +
((c >> 3) & 0x01) * coef_p[i + 4] +
((c >> 2) & 0x01) * coef_p[i + 5] +
((c >> 1) & 0x01) * coef_p[i + 6] +
((c ) & 0x01) * coef_p[i + 7];
data_index += channels;
}
return F;
}
#endif
void convolve(uint32_t Signal[/* SignalLen */], unsigned short SignalLen,
uint32_t Kernel[/* KernelLen */], unsigned short KernelLen,
uint32_t Result[/* SignalLen + KernelLen - 1 */])
{
uint16_t n;
for (n = 0; n < SignalLen + KernelLen - 1; n++)
{
unsigned short kmin, kmax, k;
Result[n] = 0;
kmin = (n >= KernelLen - 1) ? n - (KernelLen - 1) : 0;
kmax = (n < SignalLen - 1) ? n : SignalLen - 1;
for (k = kmin; k <= kmax; k++) {
Result[n] += Signal[k] * Kernel[n - k];
}
}
}
void Open_PDM_Filter_Init(TPDMFilter_InitStruct *Param)
{
uint16_t i, j;
int64_t sum = 0;
uint8_t decimation = Param->Decimation;
for (i = 0; i < SINCN; i++) {
Param->Coef[i] = 0;
Param->bit[i] = 0;
}
for (i = 0; i < decimation; i++) {
sinc1[i] = 1;
}
Param->OldOut = Param->OldIn = Param->OldZ = 0;
Param->LP_ALFA = (Param->LP_HZ != 0 ? (uint16_t) (Param->LP_HZ * 256 / (Param->LP_HZ + Param->Fs / (2 * 3.14159))) : 0);
Param->HP_ALFA = (Param->HP_HZ != 0 ? (uint16_t) (Param->Fs * 256 / (2 * 3.14159 * Param->HP_HZ + Param->Fs)) : 0);
Param->FilterLen = decimation * SINCN;
sinc[0] = 0;
sinc[decimation * SINCN - 1] = 0;
convolve(sinc1, decimation, sinc1, decimation, sinc2);
convolve(sinc2, decimation * 2 - 1, sinc1, decimation, &sinc[1]);
for(j = 0; j < SINCN; j++) {
for (i = 0; i < decimation; i++) {
coef[j][i] = sinc[j * decimation + i];
sum += sinc[j * decimation + i];
}
}
sub_const = sum >> 1;
div_const = sub_const * Param->MaxVolume / 32768 / FILTER_GAIN;
div_const = (div_const == 0 ? 1 : div_const);
#ifdef USE_LUT
/* Look-Up Table. */
uint16_t c, d, s;
for (s = 0; s < SINCN; s++)
{
uint32_t *coef_p = &coef[s][0];
for (c = 0; c < 256; c++)
for (d = 0; d < decimation / 8; d++)
lut[c][d][s] = ((c >> 7) ) * coef_p[d * 8 ] +
((c >> 6) & 0x01) * coef_p[d * 8 + 1] +
((c >> 5) & 0x01) * coef_p[d * 8 + 2] +
((c >> 4) & 0x01) * coef_p[d * 8 + 3] +
((c >> 3) & 0x01) * coef_p[d * 8 + 4] +
((c >> 2) & 0x01) * coef_p[d * 8 + 5] +
((c >> 1) & 0x01) * coef_p[d * 8 + 6] +
((c ) & 0x01) * coef_p[d * 8 + 7];
}
#endif
}
void Open_PDM_Filter_64(uint8_t* data, uint16_t* dataOut, uint16_t volume, TPDMFilter_InitStruct *Param)
{
uint8_t i, data_out_index;
uint8_t channels = Param->In_MicChannels;
uint8_t data_inc = ((DECIMATION_MAX >> 4) * channels);
int64_t Z, Z0, Z1, Z2;
int64_t OldOut, OldIn, OldZ;
OldOut = Param->OldOut;
OldIn = Param->OldIn;
OldZ = Param->OldZ;
#ifdef USE_LUT
uint8_t j = channels - 1;
#endif
for (i = 0, data_out_index = 0; i < Param->Fs / 1000; i++, data_out_index += channels) {
#ifdef USE_LUT
Z0 = filter_tables_64[j](data, 0);
Z1 = filter_tables_64[j](data, 1);
Z2 = filter_tables_64[j](data, 2);
#else
Z0 = filter_table(data, 0, Param);
Z1 = filter_table(data, 1, Param);
Z2 = filter_table(data, 2, Param);
#endif
Z = Param->Coef[1] + Z2 - sub_const;
Param->Coef[1] = Param->Coef[0] + Z1;
Param->Coef[0] = Z0;
OldOut = (Param->HP_ALFA * (OldOut + Z - OldIn)) >> 8;
OldIn = Z;
OldZ = ((256 - Param->LP_ALFA) * OldZ + Param->LP_ALFA * OldOut) >> 8;
Z = OldZ * volume;
Z = RoundDiv(Z, div_const);
Z = SaturaLH(Z, -32700, 32700);
dataOut[data_out_index] = Z;
data += data_inc;
}
Param->OldOut = OldOut;
Param->OldIn = OldIn;
Param->OldZ = OldZ;
}
void Open_PDM_Filter_128(uint8_t* data, uint16_t* dataOut, uint16_t volume, TPDMFilter_InitStruct *Param)
{
uint8_t i, data_out_index;
uint8_t channels = Param->In_MicChannels;
uint8_t data_inc = ((DECIMATION_MAX >> 3) * channels);
int64_t Z, Z0, Z1, Z2;
int64_t OldOut, OldIn, OldZ;
OldOut = Param->OldOut;
OldIn = Param->OldIn;
OldZ = Param->OldZ;
#ifdef USE_LUT
uint8_t j = channels - 1;
#endif
for (i = 0, data_out_index = 0; i < Param->Fs / 1000; i++, data_out_index += channels) {
#ifdef USE_LUT
Z0 = filter_tables_128[j](data, 0);
Z1 = filter_tables_128[j](data, 1);
Z2 = filter_tables_128[j](data, 2);
#else
Z0 = filter_table(data, 0, Param);
Z1 = filter_table(data, 1, Param);
Z2 = filter_table(data, 2, Param);
#endif
Z = Param->Coef[1] + Z2 - sub_const;
Param->Coef[1] = Param->Coef[0] + Z1;
Param->Coef[0] = Z0;
OldOut = (Param->HP_ALFA * (OldOut + Z - OldIn)) >> 8;
OldIn = Z;
OldZ = ((256 - Param->LP_ALFA) * OldZ + Param->LP_ALFA * OldOut) >> 8;
Z = OldZ * volume;
Z = RoundDiv(Z, div_const);
Z = SaturaLH(Z, -32700, 32700);
dataOut[data_out_index] = Z;
data += data_inc;
}
Param->OldOut = OldOut;
Param->OldIn = OldIn;
Param->OldZ = OldZ;
}
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