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#include "spectrum.h"

#include "utils.h"

#include <QByteArray>

#include <QtMultimedia/QAudioFormat>

#include <QtCore/qmath.h>

#include <QtCore/qendian.h>

void generateTone(const SweptTone &tone, const QAudioFormat &format, QByteArray &buffer)

{

    Q_ASSERT(isPCMS16LE(format));

    const int channelBytes = format.sampleSize() / 8;

    const int sampleBytes = format.channels() * 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.frequency();

    // 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.channels(); ++i) {

            qToLittleEndian<qint16>(value, ptr);

            ptr += channelBytes;

            length -= channelBytes;

        }

        phase += phaseStep;

        while (phase > 2 * M_PI)

            phase -= 2 * M_PI;

        phaseStep += phaseStepStep;

    }

}