mirror of
https://github.com/OpenRTX/OpenRTX
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90 lines
2.3 KiB
C
90 lines
2.3 KiB
C
/*
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* SPDX-FileCopyrightText: Copyright 2020-2026 OpenRTX Contributors
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*
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* SPDX-License-Identifier: GPL-3.0-or-later
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*/
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#ifndef DSP_H
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#define DSP_H
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#include <stdbool.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <string.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*
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* This header contains various DSP utilities which can be used to condition
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* input or output signals when implementing digital modes on OpenRTX.
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*/
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/**
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* Reset the state variables of a DSP object.
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*
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* @param state: state variable.
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*/
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#define dsp_resetState(state) memset(&state, 0x00, sizeof(state))
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/**
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* Data structure holding the internal state of a DC blocking filter.
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*/
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struct dcBlock {
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int32_t accum;
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int32_t prevIn;
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int32_t prevOut;
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};
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/**
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* Run a single step of the DC blocking filter.
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*
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* @param dcb: pointer to DC filter state.
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* @param sample: input sample.
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* @return filtered sample
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*/
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int16_t dsp_dcBlockFilter(struct dcBlock *dcb, int16_t sample);
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/**
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* Remove the DC offset from a collection of samples, processing data in-place.
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*
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* @param state: pointer to the data structure containing the filter state.
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* @param buffer: buffer containing the audio samples.
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* @param length: number of samples contained in the buffer.
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*/
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static inline void dsp_removeDcOffset(struct dcBlock *dcb, int16_t *buffer,
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const size_t length)
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{
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for (size_t i = 0; i < length; i++)
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buffer[i] = dsp_dcBlockFilter(dcb, buffer[i]);
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}
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/**
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* Data structure holding the internal state of a decimation block.
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*/
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struct decimatorState {
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int32_t accumulator;
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uint32_t count;
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};
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/**
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* @brief Run a single step of the oversampling decimation filter.
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*
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* Accumulates input samples and returns their truncated integer average
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* once the oversampling factor number of samples have been collected.
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*
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* @param state: pointer to the decimator state.
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* @param sample: pointer to the audio sample. Contains the value of the
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* decimated output when the function returns true.
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* @param ratio: sample decimation ratio.
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* @return true when a decimated sample is ready, false otherwise.
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*/
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bool dsp_decimator(struct decimatorState *state, int16_t *sample,
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uint16_t ratio);
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#ifdef __cplusplus
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}
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#endif // __cplusplus
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#endif /* DSP_H */
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