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/*
Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011 Her Majesty
the Queen in Right of Canada (Communications Research Center Canada)
Copyright (C) 2017
Matthias P. Braendli, matthias.braendli@mpb.li
http://opendigitalradio.org
*/
/*
This file is part of ODR-DabMod.
ODR-DabMod 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.
ODR-DabMod 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 ODR-DabMod. If not, see <http://www.gnu.org/licenses/>.
*/
#pragma once
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#include <cstddef>
#include <deque>
#include <complex>
/* Helper class to calculate Peak-to-average-power ratio.
* Definition of PAPR:
*
* PAPR_dB = 10 * log_10 ( abs(x_peak)^2 / x_rms^2 )
*
* with abs(x_peak) the peak amplitude of the signal, and
* x_rms the Root Mean Squared.
*
* x_rms^2 = 1/n * Sum abs(x_n)^2
* = 1/n * Sum norm(x_n)
*
* Given that peaks are rare in a DAB signal, we want to accumulate
* several seconds worth of samples to do our calculation.
*/
class PAPRStats
{
typedef std::complex<float> complexf;
public:
PAPRStats(size_t num_blocks_to_accumulate);
/* Push in a new block of samples to measure. calculate_papr()
* assumes all blocks have the same size.
*/
void process_block(const complexf* data, size_t data_len);
/* Returns PAPR in dB if enough blocks were processed, or
* 0 otherwise.
*/
double calculate_papr(void) const;
void clear(void);
private:
size_t m_num_blocks_to_accumulate;
std::deque<double> m_squared_peaks;
std::deque<double> m_squared_mean;
};
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