Qt 5.8 | Qt Multimedia | Spectrum Example | wavfile.cpp Example File

Qt 5.8.0 Reference Documentation

# wavfile.cpp Example File

multimedia/spectrum/app/wavfile.cpp

      /****************************************************************************
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      ** This file is part of the examples of the Qt Toolkit.
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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;
      }