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/*
* Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
// MSVC++ requires this to be set before any other includes to get M_PI.
#define _USE_MATH_DEFINES
#include "webrtc/common_audio/resampler/sinusoidal_linear_chirp_source.h"
#include <math.h>
namespace webrtc {
SinusoidalLinearChirpSource::SinusoidalLinearChirpSource(int sample_rate,
size_t samples,
double max_frequency,
double delay_samples)
: sample_rate_(sample_rate),
total_samples_(samples),
max_frequency_(max_frequency),
current_index_(0),
delay_samples_(delay_samples) {
// Chirp rate.
double duration = static_cast<double>(total_samples_) / sample_rate_;
k_ = (max_frequency_ - kMinFrequency) / duration;
}
void SinusoidalLinearChirpSource::Run(size_t frames, float* destination) {
for (size_t i = 0; i < frames; ++i, ++current_index_) {
// Filter out frequencies higher than Nyquist.
if (Frequency(current_index_) > 0.5 * sample_rate_) {
destination[i] = 0;
} else {
// Calculate time in seconds.
if (current_index_ < delay_samples_) {
destination[i] = 0;
} else {
// Sinusoidal linear chirp.
double t = (current_index_ - delay_samples_) / sample_rate_;
destination[i] =
sin(2 * M_PI * (kMinFrequency * t + (k_ / 2) * t * t));
}
}
}
}
double SinusoidalLinearChirpSource::Frequency(size_t position) {
return kMinFrequency + (position - delay_samples_) *
(max_frequency_ - kMinFrequency) / total_samples_;
}
} // namespace webrtc
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