portapack-mayhem/firmware/baseband-tx/linear_resampler.hpp

70 lines
1.9 KiB
C++

/*
* Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
*
* This file is part of PortaPack.
*
* 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 2, 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; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#ifndef __LINEAR_RESAMPLER_H__
#define __LINEAR_RESAMPLER_H__
namespace dsp {
namespace interpolation {
class LinearResampler {
public:
void configure(
const float input_rate,
const float output_rate
) {
phase_increment = calculate_increment(input_rate, output_rate);
}
template<typename InterpolatedSampleHandler>
void operator()(
const float sample,
InterpolatedSampleHandler interpolated_sample_handler
) {
const float sample_delta = sample - last_sample;
while( phase < 1.0f ) {
const float interpolated_value = last_sample + phase * sample_delta;
interpolated_sample_handler(interpolated_value);
phase += phase_increment;
}
last_sample = sample;
phase -= 1.0f;
}
void advance(const float fraction) {
phase += (fraction * phase_increment);
}
private:
float last_sample { 0.0f };
float phase { 0.0f };
float phase_increment { 0.0f };
static constexpr float calculate_increment(const float input_rate, const float output_rate) {
return input_rate / output_rate;
}
};
} /* namespace interpolation */
} /* namespace dsp */
#endif/*__LINEAR_RESAMPLER_H__*/