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