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45 lines
970 B
C++
45 lines
970 B
C++
/*
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Frequency-domain zero padding
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Copyright 2019 Ahmet Inan <inan@aicodix.de>
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*/
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#pragma once
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#include "fft.hh"
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namespace DSP {
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template <int BINS, int FACT, typename CMPLX>
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class FDZP
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{
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typedef typename CMPLX::value_type VALUE;
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FastFourierTransform<BINS, CMPLX, -1> fwd;
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FastFourierTransform<BINS * FACT, CMPLX, 1> bwd;
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CMPLX tmp[BINS * FACT];
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static constexpr VALUE SCALE = VALUE(1) / VALUE(BINS);
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public:
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void operator ()(CMPLX *output, const CMPLX *input)
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{
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fwd(tmp, input);
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if (BINS&1) {
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for (int i = 1; i < BINS/2; ++i)
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tmp[BINS*FACT-BINS/2+i] = tmp[BINS/2+1+i];
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for (int i = 1; i < BINS/2; ++i)
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tmp[BINS/2+1+i] = 0;
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} else {
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tmp[BINS/2] *= VALUE(0.5);
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tmp[BINS*FACT-BINS/2] = tmp[BINS/2];
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for (int i = 1; i < BINS/2; ++i)
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tmp[BINS*FACT-BINS/2+i] = tmp[BINS/2+i];
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for (int i = 1; i < BINS/2; ++i)
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tmp[BINS/2+i] = 0;
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}
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bwd(output, tmp);
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for (int i = 0; i < BINS * FACT; ++i)
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output[i] *= SCALE;
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}
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};
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}
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