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424c74d006
Remove the paragraph about writing to the Free Software Foundation's mailing address. The FSF has changed addresses in the past, and may do so again. In 2021 this is not useful, let's rather have a bit less boilerplate at the start of source files. Change-Id: I8ba71ab9ccde4ba25151ecbeb2a323f706b57d43
75 lines
2.4 KiB
C++
75 lines
2.4 KiB
C++
/*
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* Rational Sample Rate Conversion
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* Copyright (C) 2012, 2013 Thomas Tsou <tom@tsou.cc>
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*
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* SPDX-License-Identifier: LGPL-2.1+
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*/
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#ifndef _RESAMPLER_H_
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#define _RESAMPLER_H_
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#include <vector>
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#include <complex>
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class Resampler {
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public:
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/* Constructor for rational sample rate conversion
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* @param p numerator of resampling ratio
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* @param q denominator of resampling ratio
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* @param filt_len length of each polyphase subfilter
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*/
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Resampler(size_t p, size_t q, size_t filt_len = 16);
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~Resampler();
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/* Initialize resampler filterbank.
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* @param bw bandwidth factor on filter generation (pre-window)
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* @return false on error, zero otherwise
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*
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* Automatic setting is to compute the filter to prevent aliasing with
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* a Blackman-Harris window. Adjustment is made through a bandwidth
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* factor to shift the cutoff and/or the constituent filter lengths.
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* Calculation of specific rolloff factors or 3-dB cutoff points is
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* left as an excersize for the reader.
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*/
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bool init(float bw = 1.0f);
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/* Rotate "commutator" and drive samples through filterbank
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* @param in continuous buffer of input complex float values
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* @param in_len input buffer length
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* @param out continuous buffer of output complex float values
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* @param out_len output buffer length
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* @return number of samples outputted, negative on error
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*
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* Input and output vector lengths must of be equal multiples of the
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* rational conversion rate denominator and numerator respectively.
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*/
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int rotate(const float *in, size_t in_len, float *out, size_t out_len);
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/* Get filter length
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* @return number of taps in each filter partition
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*/
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size_t len();
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private:
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size_t p;
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size_t q;
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size_t filt_len;
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std::vector<size_t> in_index;
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std::vector<size_t> out_path;
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std::vector<std::complex<float> *> partitions;
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void initFilters(float bw);
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};
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#endif /* _RESAMPLER_H_ */
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