Qt Reference Documentation

wavfile.cpp Example File

demos/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;
     DATAHeader  data;
 };

 static const int HeaderLength = sizeof(CombinedHeader);

 WavFile::WavFile(const QAudioFormat &format, qint64 dataLength)
     :   m_format(format)
     ,   m_dataLength(dataLength)
 {

 }

 bool WavFile::readHeader(QIODevice &device)
 {
     bool result = true;

     if (!device.isSequential())
         result = device.seek(0);
     // else, assume that current position is the start of the header

     if (result) {
         CombinedHeader header;
         result = (device.read(reinterpret_cast<char *>(&header), HeaderLength) == HeaderLength);
         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 // PCM
             ) {
                 if (memcmp(&header.riff.descriptor.id, "RIFF", 4) == 0)
                     m_format.setByteOrder(QAudioFormat::LittleEndian);
                 else
                     m_format.setByteOrder(QAudioFormat::BigEndian);

                 m_format.setChannels(qFromLittleEndian<quint16>(header.wave.numChannels));
                 m_format.setCodec("audio/pcm");
                 m_format.setFrequency(qFromLittleEndian<quint32>(header.wave.sampleRate));
                 m_format.setSampleSize(qFromLittleEndian<quint16>(header.wave.bitsPerSample));

                 switch(header.wave.bitsPerSample) {
                 case 8:
                     m_format.setSampleType(QAudioFormat::UnSignedInt);
                     break;
                 case 16:
                     m_format.setSampleType(QAudioFormat::SignedInt);
                     break;
                 default:
                     result = false;
                 }

                 m_dataLength = device.size() - HeaderLength;
             } else {
                 result = false;
             }
         }
     }

     return result;
 }

 bool WavFile::writeHeader(QIODevice &device)
 {
     CombinedHeader header;

     memset(&header, 0, HeaderLength);

     // RIFF header
     if (m_format.byteOrder() == QAudioFormat::LittleEndian)
         strncpy(&header.riff.descriptor.id[0], "RIFF", 4);
     else
         strncpy(&header.riff.descriptor.id[0], "RIFX", 4);
     qToLittleEndian<quint32>(quint32(m_dataLength + HeaderLength - 8),
                              reinterpret_cast<unsigned char*>(&header.riff.descriptor.size));
     strncpy(&header.riff.type[0], "WAVE", 4);

     // WAVE header
     strncpy(&header.wave.descriptor.id[0], "fmt ", 4);
     qToLittleEndian<quint32>(quint32(16),
                              reinterpret_cast<unsigned char*>(&header.wave.descriptor.size));
     qToLittleEndian<quint16>(quint16(1),
                              reinterpret_cast<unsigned char*>(&header.wave.audioFormat));
     qToLittleEndian<quint16>(quint16(m_format.channels()),
                              reinterpret_cast<unsigned char*>(&header.wave.numChannels));
     qToLittleEndian<quint32>(quint32(m_format.frequency()),
                              reinterpret_cast<unsigned char*>(&header.wave.sampleRate));
     qToLittleEndian<quint32>(quint32(m_format.frequency() * m_format.channels() * m_format.sampleSize() / 8),
                              reinterpret_cast<unsigned char*>(&header.wave.byteRate));
     qToLittleEndian<quint16>(quint16(m_format.channels() * m_format.sampleSize() / 8),
                              reinterpret_cast<unsigned char*>(&header.wave.blockAlign));
     qToLittleEndian<quint16>(quint16(m_format.sampleSize()),
                              reinterpret_cast<unsigned char*>(&header.wave.bitsPerSample));

     // DATA header
     strncpy(&header.data.descriptor.id[0], "data", 4);
     qToLittleEndian<quint32>(quint32(m_dataLength),
                              reinterpret_cast<unsigned char*>(&header.data.descriptor.size));

     return (device.write(reinterpret_cast<const char *>(&header), HeaderLength) == HeaderLength);
 }

 const QAudioFormat& WavFile::format() const
 {
     return m_format;
 }

 qint64 WavFile::dataLength() const
 {
     return m_dataLength;
 }

 qint64 WavFile::headerLength()
 {
     return HeaderLength;
 }

 bool WavFile::writeDataLength(QIODevice &device, qint64 dataLength)
 {
     bool result = false;
     if (!device.isSequential()) {
         device.seek(40);
         unsigned char dataLengthLE[4];
         qToLittleEndian<quint32>(quint32(dataLength), dataLengthLE);
         result = (device.write(reinterpret_cast<const char *>(dataLengthLE), 4) == 4);
     }
     return result;
 }

 #include <QFile>
 #include <QTextStream>

 qint64 WavFile::readData(QIODevice &device, QByteArray &buffer,
                          QAudioFormat outputFormat)
 {
     if (QAudioFormat() == outputFormat)
         outputFormat = m_format;

     qint64 result = 0;

     QFile file("wav.txt");
     file.open(QIODevice::WriteOnly | QIODevice::Text);
     QTextStream stream;
     stream.setDevice(&file);

     if (isPCMS16LE(outputFormat) && isPCMS16LE(m_format)) {
         QVector<char> inputSample(2 * m_format.channels());

         qint16 *output = reinterpret_cast<qint16*>(buffer.data());

         while (result < buffer.size()) {
             if (device.read(inputSample.data(), inputSample.count())) {
                 int inputIdx = 0;
                 for (int outputIdx = 0; outputIdx < outputFormat.channels(); ++outputIdx) {
                     const qint16* input = reinterpret_cast<const qint16*>(inputSample.data() + 2 * inputIdx);
                     *output++ = qFromLittleEndian<qint16>(*input);
                     result += 2;
                     if (inputIdx < m_format.channels())
                         ++inputIdx;
                 }
             } else {
                 break;
             }
         }
     }
     return result;
 }
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