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#ifndef POLYPHASE_RESAMPLER_H
#define POLYPHASE_RESAMPLER_H
#include <vector>
using uint = unsigned int;
/* This is a polyphase sinc-filtered resampler. It is built for very high
* quality results, rather than real-time performance.
*
* Upsample Downsample
*
* p/q = 3/2 p/q = 3/5
*
* M-+-+-+-> M-+-+-+->
* -------------------+ ---------------------+
* p s * f f f f|f| | p s * f f f f f |
* | 0 * 0 0 0|0|0 | | 0 * 0 0 0 0|0| |
* v 0 * 0 0|0|0 0 | v 0 * 0 0 0|0|0 |
* s * f|f|f f f | s * f f|f|f f |
* 0 * |0|0 0 0 0 | 0 * 0|0|0 0 0 |
* --------+=+--------+ 0 * |0|0 0 0 0 |
* d . d .|d|. d . d ----------+=+--------+
* d . . . .|d|. . . .
* q->
* q-+-+-+->
*
* P_f(i,j) = q i mod p + pj
* P_s(i,j) = floor(q i / p) - j
* d[i=0..N-1] = sum_{j=0}^{floor((M - 1) / p)} {
* { f[P_f(i,j)] s[P_s(i,j)], P_f(i,j) < M
* { 0, P_f(i,j) >= M. }
*/
struct PPhaseResampler {
void init(const uint srcRate, const uint dstRate);
void process(const uint inN, const double *in, const uint outN, double *out);
explicit operator bool() const noexcept { return !mF.empty(); }
private:
uint mP{}, mQ{}, mM{}, mL{};
std::vector<double> mF;
};
#endif /* POLYPHASE_RESAMPLER_H */
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