- Qt 5.5
- Qt Multimedia
- Spectrum Example
- wavfile.cpp Example File
- Qt 5.5.1 Reference Documentation

# wavfile.cpp Example File

spectrum/app/wavfile.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** 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.
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    **     the documentation and/or other materials provided with the
    **     distribution.
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    **     contributors may be used to endorse or promote products derived
    **     from this software without specific prior written permission.
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    #include <qendian.h>
    #include <QVector>
    #include <QDebug>
    #include "utils.h"
    #include "wavfile.h"

    struct chunk
    {
        char        id[4];
        quint32     size;
    };

    struct RIFFHeader
    {
        chunk       descriptor;     // "RIFF"
        char        type[4];        // "WAVE"
    };

    struct WAVEHeader
    {
        chunk       descriptor;
        quint16     audioFormat;
        quint16     numChannels;
        quint32     sampleRate;
        quint32     byteRate;
        quint16     blockAlign;
        quint16     bitsPerSample;
    };

    struct DATAHeader
    {
        chunk       descriptor;
    };

    struct CombinedHeader
    {
        RIFFHeader  riff;
        WAVEHeader  wave;
    };

    WavFile::WavFile(QObject *parent)
        : QFile(parent)
        , m_headerLength(0)
    {

    }

    bool WavFile::open(const QString &fileName)
    {
        close();
        setFileName(fileName);
        return QFile::open(QIODevice::ReadOnly) && readHeader();
    }

    const QAudioFormat &WavFile::fileFormat() const
    {
        return m_fileFormat;
    }

    qint64 WavFile::headerLength() const
    {
    return m_headerLength;
    }

    bool WavFile::readHeader()
    {
        seek(0);
        CombinedHeader header;
        bool result = read(reinterpret_cast<char *>(&header), sizeof(CombinedHeader)) == sizeof(CombinedHeader);
        if (result) {
            if ((memcmp(&header.riff.descriptor.id, "RIFF", 4) == 0
                || memcmp(&header.riff.descriptor.id, "RIFX", 4) == 0)
                && memcmp(&header.riff.type, "WAVE", 4) == 0
                && memcmp(&header.wave.descriptor.id, "fmt ", 4) == 0
                && (header.wave.audioFormat == 1 || header.wave.audioFormat == 0)) {

                // Read off remaining header information
                DATAHeader dataHeader;

                if (qFromLittleEndian<quint32>(header.wave.descriptor.size) > sizeof(WAVEHeader)) {
                    // Extended data available
                    quint16 extraFormatBytes;
                    if (peek((char*)&extraFormatBytes, sizeof(quint16)) != sizeof(quint16))
                        return false;
                    const qint64 throwAwayBytes = sizeof(quint16) + qFromLittleEndian<quint16>(extraFormatBytes);
                    if (read(throwAwayBytes).size() != throwAwayBytes)
                        return false;
                }

                if (read((char*)&dataHeader, sizeof(DATAHeader)) != sizeof(DATAHeader))
                    return false;

                // Establish format
                if (memcmp(&header.riff.descriptor.id, "RIFF", 4) == 0)
                    m_fileFormat.setByteOrder(QAudioFormat::LittleEndian);
                else
                    m_fileFormat.setByteOrder(QAudioFormat::BigEndian);

                int bps = qFromLittleEndian<quint16>(header.wave.bitsPerSample);
                m_fileFormat.setChannelCount(qFromLittleEndian<quint16>(header.wave.numChannels));
                m_fileFormat.setCodec("audio/pcm");
                m_fileFormat.setSampleRate(qFromLittleEndian<quint32>(header.wave.sampleRate));
                m_fileFormat.setSampleSize(qFromLittleEndian<quint16>(header.wave.bitsPerSample));
                m_fileFormat.setSampleType(bps == 8 ? QAudioFormat::UnSignedInt : QAudioFormat::SignedInt);
            } else {
                result = false;
            }
        }
        m_headerLength = pos();
        return result;
    }