mirror of
https://github.com/aicodix/dsp.git
synced 2026-04-27 14:30:36 +00:00
56 lines
1.2 KiB
C++
56 lines
1.2 KiB
C++
/*
|
|
Resampling by an arbitrary rate difference
|
|
|
|
Copyright 2018 Ahmet Inan <inan@aicodix.de>
|
|
*/
|
|
|
|
|
|
#ifndef RESAMPLER_HH
|
|
#define RESAMPLER_HH
|
|
|
|
#include "window.hh"
|
|
#include "spline.hh"
|
|
#include "utils.hh"
|
|
#include "const.hh"
|
|
|
|
namespace DSP {
|
|
|
|
template <typename TYPE, int RATE, int TAPS, int OVER>
|
|
class Resampler
|
|
{
|
|
typedef DSP::UniformNaturalCubicSpline<TAPS * OVER, TYPE, TYPE> spline_type;
|
|
spline_type lpf;
|
|
public:
|
|
Resampler(TYPE cutoff, TYPE alpha)
|
|
{
|
|
TYPE tmp[TAPS * OVER];
|
|
DSP::Kaiser<TYPE> window(alpha);
|
|
for (int n = 0; n < TAPS * OVER; ++n) {
|
|
TYPE x = TYPE(n) / TYPE(OVER) - TYPE(TAPS - 1) / TYPE(2);
|
|
TYPE y = TYPE(2) * cutoff / TYPE(RATE) * sinc(TYPE(2) * cutoff / TYPE(RATE) * x);
|
|
tmp[n] = y * window(n, TAPS * OVER);
|
|
}
|
|
lpf = spline_type(tmp, 0, 1.0 / OVER);
|
|
}
|
|
template <typename IO>
|
|
void operator ()(IO *output, IO *input, TYPE diff, int samples, int stride = 1)
|
|
{
|
|
TYPE ratio = (RATE + diff) / RATE;
|
|
TYPE recip = RATE / (RATE + diff);
|
|
for (int i = 0; i < samples - TAPS; ++i) {
|
|
IO sum = 0;
|
|
int s0 = nearbyint(i * ratio);
|
|
int s1 = s0 + TAPS;
|
|
for (int s = s0; s < s1; ++s) {
|
|
TYPE k = s * recip - i;
|
|
sum += lpf(k) * input[s * stride];
|
|
}
|
|
output[(i + (TAPS - 1) / 2) * stride] = sum;
|
|
}
|
|
}
|
|
};
|
|
|
|
}
|
|
|
|
#endif
|
|
|