/**
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* Copyright (c) 2022 Xiaomi Corporation (authors: Fangjun Kuang)
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*
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* See LICENSE for clarification regarding multiple authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef KALDI_NATIVE_FBANK_CSRC_RFFT_H_
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#define KALDI_NATIVE_FBANK_CSRC_RFFT_H_
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#include <memory>
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namespace knf {
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// n-point Real discrete Fourier transform
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// where n is a power of 2. n >= 2
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//
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// R[k] = sum_j=0^n-1 in[j]*cos(2*pi*j*k/n), 0<=k<=n/2
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// I[k] = sum_j=0^n-1 in[j]*sin(2*pi*j*k/n), 0<k<n/2
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class Rfft {
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public:
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// @param n Number of fft bins. it should be a power of 2.
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explicit Rfft(int32_t n);
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~Rfft();
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/** @param in_out A 1-D array of size n.
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* On return:
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* in_out[0] = R[0]
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* in_out[1] = R[n/2]
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* for 1 < k < n/2,
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* in_out[2*k] = R[k]
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* in_out[2*k+1] = I[k]
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*
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*/
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void Compute(float *in_out);
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void Compute(double *in_out);
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private:
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class RfftImpl;
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std::unique_ptr<RfftImpl> impl_;
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};
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} // namespace knf
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#endif // KALDI_NATIVE_FBANK_CSRC_RFFT_H_
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