feature-functions.cc (1604B)
1 /** 2 * Copyright (c) 2022 Xiaomi Corporation (authors: Fangjun Kuang) 3 * 4 * See LICENSE for clarification regarding multiple authors 5 * 6 * Licensed under the Apache License, Version 2.0 (the "License"); 7 * you may not use this file except in compliance with the License. 8 * You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 19 // This file is copied/modified from kaldi/src/feat/feature-functions.cc 20 21 #include "kaldi-native-fbank/csrc/feature-functions.h" 22 23 #include <cstdint> 24 #include <vector> 25 26 namespace knf { 27 28 void ComputePowerSpectrum(std::vector<float> *complex_fft) { 29 int32_t dim = complex_fft->size(); 30 31 // now we have in complex_fft, first half of complex spectrum 32 // it's stored as [real0, realN/2, real1, im1, real2, im2, ...] 33 34 float *p = complex_fft->data(); 35 int32_t half_dim = dim / 2; 36 float first_energy = p[0] * p[0]; 37 float last_energy = p[1] * p[1]; // handle this special case 38 39 for (int32_t i = 1; i < half_dim; ++i) { 40 float real = p[i * 2]; 41 float im = p[i * 2 + 1]; 42 p[i] = real * real + im * im; 43 } 44 p[0] = first_energy; 45 p[half_dim] = last_energy; // Will actually never be used, and anyway 46 // if the signal has been bandlimited sensibly this should be zero. 47 } 48 49 } // namespace knf