40 lines
2.1 KiB
C++
40 lines
2.1 KiB
C++
/***************************************************************************
|
|
* Copyright (C) 2020 - 2025 by Federico Amedeo Izzo IU2NUO, *
|
|
* Niccolò Izzo IU2KIN, *
|
|
* Silvano Seva IU2KWO, *
|
|
* Frederik Saraci IU2NRO *
|
|
* *
|
|
* This program is free software; you can redistribute it and/or modify *
|
|
* it under the terms of the GNU General Public License as published by *
|
|
* the Free Software Foundation; either version 3 of the License, or *
|
|
* (at your option) any later version. *
|
|
* *
|
|
* This program is distributed in the hope that it will be useful, *
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of *
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
|
|
* GNU General Public License for more details. *
|
|
* *
|
|
* You should have received a copy of the GNU General Public License *
|
|
* along with this program; if not, see <http://www.gnu.org/licenses/> *
|
|
***************************************************************************/
|
|
|
|
#include "core/dsp.h"
|
|
|
|
int16_t dsp_dcBlockFilter(struct dcBlock *dcb, int16_t sample)
|
|
{
|
|
/*
|
|
* Implementation of a fixed-point DC block filter with noise shaping,
|
|
* ensuring zero DC component at the output.
|
|
* Filter pole set at 0.995
|
|
*
|
|
* Code adapted from https://dspguru.com/dsp/tricks/fixed-point-dc-blocking-filter-with-noise-shaping/
|
|
*/
|
|
dcb->accum -= dcb->prevIn;
|
|
dcb->prevIn = static_cast<int32_t>(sample) << 15;
|
|
dcb->accum += dcb->prevIn;
|
|
dcb->accum -= 164 * dcb->prevOut; // 32768.0 * (1.0 - pole)
|
|
dcb->prevOut = dcb->accum >> 15;
|
|
|
|
return static_cast<int16_t>(dcb->prevOut);
|
|
}
|