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// MSVC++ requires this to be set before any other includes to get M_PI. 12#define _USE_MATH_DEFINES 13 14#include "webrtc/common_audio/resampler/sinusoidal_linear_chirp_source.h" 15 16#include <math.h> 17 18namespace webrtc { 19 20SinusoidalLinearChirpSource::SinusoidalLinearChirpSource(int sample_rate, 21 size_t samples, 22 double max_frequency, 23 double delay_samples) 24 : sample_rate_(sample_rate), 25 total_samples_(samples), 26 max_frequency_(max_frequency), 27 current_index_(0), 28 delay_samples_(delay_samples) { 29 // Chirp rate. 30 double duration = static_cast<double>(total_samples_) / sample_rate_; 31 k_ = (max_frequency_ - kMinFrequency) / duration; 32} 33 34void SinusoidalLinearChirpSource::Run(size_t frames, float* destination) { 35 for (size_t i = 0; i < frames; ++i, ++current_index_) { 36 // Filter out frequencies higher than Nyquist. 37 if (Frequency(current_index_) > 0.5 * sample_rate_) { 38 destination[i] = 0; 39 } else { 40 // Calculate time in seconds. 41 if (current_index_ < delay_samples_) { 42 destination[i] = 0; 43 } else { 44 // Sinusoidal linear chirp. 45 double t = (current_index_ - delay_samples_) / sample_rate_; 46 destination[i] = 47 sin(2 * M_PI * (kMinFrequency * t + (k_ / 2) * t * t)); 48 } 49 } 50 } 51} 52 53double SinusoidalLinearChirpSource::Frequency(size_t position) { 54 return kMinFrequency + (position - delay_samples_) * 55 (max_frequency_ - kMinFrequency) / total_samples_; 56} 57 58} // namespace webrtc 59