79 lines
2.6 KiB
C++
79 lines
2.6 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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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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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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/* Initilize 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 bandwith
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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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