qt-everywhere-src-5.14.1/qtmultimedia/examples/multimedia/spectrum/app/tonegenerator.cpp

/****************************************************************************
**
** Copyright (C) 2017 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the examples of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:BSD$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** BSD License Usage
** Alternatively, you may use this file under the terms of the BSD license
** as follows:
**
** "Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are
** met:
**   * Redistributions of source code must retain the above copyright
**     notice, this list of conditions and the following disclaimer.
**   * Redistributions in binary form must reproduce the above copyright
**     notice, this list of conditions and the following disclaimer in
**     the documentation and/or other materials provided with the
**     distribution.
**   * Neither the name of The Qt Company Ltd nor the names of its
**     contributors may be used to endorse or promote products derived
**     from this software without specific prior written permission.
**
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
**
** $QT_END_LICENSE$
**
****************************************************************************/

#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(isPCMS16LE(format));

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