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/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */
/*
QM DSP Library
Centre for Digital Music, Queen Mary, University of London.
This file by Chris Cannam.
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 of the
License, or (at your option) any later version. See the file
COPYING included with this distribution for more information.
*/
#ifndef RESAMPLER_H
#define RESAMPLER_H
#include <vector>
/**
* Resampler resamples a stream from one integer sample rate to
* another (arbitrary) rate, using a kaiser-windowed sinc filter. The
* results and performance are pretty similar to libraries such as
* libsamplerate, though this implementation does not support
* time-varying ratios (the ratio is fixed on construction).
*
* See also Decimator, which is faster and rougher but supports only
* power-of-two downsampling factors.
*/
class Resampler
{
public:
/**
* Construct a Resampler to resample from sourceRate to
* targetRate.
*/
Resampler(int sourceRate, int targetRate);
/**
* Construct a Resampler to resample from sourceRate to
* targetRate, using the given filter parameters.
*/
Resampler(int sourceRate, int targetRate,
double snr, double bandwidth);
virtual ~Resampler();
/**
* Read n input samples from src and write resampled data to
* dst. The return value is the number of samples written, which
* will be no more than ceil((n * targetRate) / sourceRate). The
* caller must ensure the dst buffer has enough space for the
* samples returned.
*/
int process(const double *src, double *dst, int n);
/**
* Read n input samples from src and return resampled data by
* value.
*/
std::vector<double> process(const double *src, int n);
/**
* Return the number of samples of latency at the output due by
* the filter. (That is, the output will be delayed by this number
* of samples relative to the input.)
*/
int getLatency() const { return m_latency; }
/**
* Carry out a one-off resample of a single block of n
* samples. The output is latency-compensated.
*/
static std::vector<double> resample
(int sourceRate, int targetRate, const double *data, int n);
private:
int m_sourceRate;
int m_targetRate;
int m_gcd;
int m_filterLength;
int m_bufferLength;
int m_latency;
double m_peakToPole;
struct Phase {
int nextPhase;
std::vector<double> filter;
int drop;
};
Phase *m_phaseData;
int m_phase;
std::vector<double> m_buffer;
int m_bufferOrigin;
void initialise(double, double);
double reconstructOne();
};
#endif
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