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// Copyright (C) 2017 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
#include "spectrum.h"
#include "utils.h"
#include <QByteArray>
#include <QAudioFormat>
#include <qmath.h>
#include <qendian.h>
void generateTone(const SweptTone &tone, const QAudioFormat &format, QByteArray &buffer)
{
Q_ASSERT(format.sampleFormat() == QAudioFormat::Int16);
const int channelBytes = format.bytesPerSample();
const int sampleBytes = format.channelCount() * channelBytes;
int length = buffer.size();
const int numSamples = buffer.size() / sampleBytes;
Q_ASSERT(length % sampleBytes == 0);
Q_UNUSED(sampleBytes); // suppress warning in release builds
unsigned char *ptr = reinterpret_cast<unsigned char *>(buffer.data());
qreal phase = 0.0;
const qreal d = 2 * M_PI / format.sampleRate();
// We can't generate a zero-frequency sine wave
const qreal startFreq = tone.startFreq ? tone.startFreq : 1.0;
// Amount by which phase increases on each sample
qreal phaseStep = d * startFreq;
// Amount by which phaseStep increases on each sample
// If this is non-zero, the output is a frequency-swept tone
const qreal phaseStepStep = d * (tone.endFreq - startFreq) / numSamples;
while (length) {
const qreal x = tone.amplitude * qSin(phase);
const qint16 value = realToPcm(x);
for (int i=0; i<format.channelCount(); ++i) {
qToLittleEndian<qint16>(value, ptr);
ptr += channelBytes;
length -= channelBytes;
}
phase += phaseStep;
while (phase > 2 * M_PI)
phase -= 2 * M_PI;
phaseStep += phaseStepStep;
}
}
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