sinusoidal_linear_chirp_source.cc (2033B)
1 /* 2 * Copyright (c) 2013 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #include "common_audio/resampler/sinusoidal_linear_chirp_source.h" 12 13 #include <cmath> 14 #include <cstddef> 15 #include <numbers> 16 17 namespace webrtc { 18 19 SinusoidalLinearChirpSource::SinusoidalLinearChirpSource(int sample_rate, 20 size_t samples, 21 double max_frequency, 22 double delay_samples) 23 : sample_rate_(sample_rate), 24 total_samples_(samples), 25 max_frequency_(max_frequency), 26 current_index_(0), 27 delay_samples_(delay_samples) { 28 // Chirp rate. 29 double duration = static_cast<double>(total_samples_) / sample_rate_; 30 k_ = (max_frequency_ - kMinFrequency) / duration; 31 } 32 33 void SinusoidalLinearChirpSource::Run(size_t frames, float* destination) { 34 for (size_t i = 0; i < frames; ++i, ++current_index_) { 35 // Filter out frequencies higher than Nyquist. 36 if (Frequency(current_index_) > 0.5 * sample_rate_) { 37 destination[i] = 0; 38 } else { 39 // Calculate time in seconds. 40 if (current_index_ < delay_samples_) { 41 destination[i] = 0; 42 } else { 43 // Sinusoidal linear chirp. 44 double t = (current_index_ - delay_samples_) / sample_rate_; 45 destination[i] = 46 sin(2 * std::numbers::pi * (kMinFrequency * t + (k_ / 2) * t * t)); 47 } 48 } 49 } 50 } 51 52 double SinusoidalLinearChirpSource::Frequency(size_t position) { 53 return kMinFrequency + (position - delay_samples_) * 54 (max_frequency_ - kMinFrequency) / total_samples_; 55 } 56 57 } // namespace webrtc