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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef SINEWAVEGENERATOR_H_
#define SINEWAVEGENERATOR_H_
#include "MediaSegment.h"
#include "prtime.h"
namespace mozilla {
// generate 1k sine wave per second
template <typename Sample>
class SineWaveGenerator {
static_assert(std::is_same<Sample, int16_t>::value ||
std::is_same<Sample, float>::value);
public:
static const int bytesPerSample = sizeof(Sample);
static const int millisecondsPerSecond = PR_MSEC_PER_SEC;
static constexpr float twopi = 2 * M_PI;
/* If more than 1 channel, generated samples are interleaved. */
SineWaveGenerator(uint32_t aSampleRate, uint32_t aFrequency)
: mPhase(0.), mPhaseIncrement(twopi * aFrequency / aSampleRate) {}
// NOTE: only safely called from a single thread (MTG callback)
void generate(Sample* aBuffer, TrackTicks aFrameCount,
uint32_t aChannelCount = 1) {
while (aFrameCount--) {
Sample value = sin(mPhase) * Amplitude();
for (uint32_t channel = 0; channel < aChannelCount; channel++) {
*aBuffer++ = value;
}
mPhase += mPhaseIncrement;
if (mPhase > twopi) {
mPhase -= twopi;
}
}
}
static float Amplitude() {
// Set volume to -20db.
if (std::is_same<Sample, int16_t>::value) {
return 3276.8; // 32768.0 * 10^(-20/20) = 3276.8
}
return 0.1f; // 1.0 * 10^(-20/20) = 0.1
}
private:
double mPhase;
const double mPhaseIncrement;
};
} // namespace mozilla
#endif /* SINEWAVEGENERATOR_H_ */