qtmultimedia/examples/spectrum/app/wavfile.cpp

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#include <QtCore/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.setChannels(qFromLittleEndian<quint16>(header.wave.numChannels));
            m_fileFormat.setCodec("audio/pcm");
            m_fileFormat.setFrequency(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;
}