[提问]一段看不懂的QT录音代码 [复制链接]

大家好，最近在研究QT examples录音部分源代码audioinput，以下这个函数看不懂，只知道是往QIODevice写数据，
但是什么原理为什么这么做一点都不明白，望哪位大侠能指点指点，谢谢！
qint64 AudioInfo::writeData(const char *data, qint64 len)
{
     if (m_maxAmplitude) {
         Q_ASSERT(m_format.sampleSize() % 8 == 0);
         const int channelBytes = m_format.sampleSize() / 8;//???
         const int sampleBytes = m_format.channels() * channelBytes;//???
         Q_ASSERT(len % sampleBytes == 0);//???
         const int numSamples = len / sampleBytes;//???

         quint16 maxValue = 0;
         const unsigned char *ptr = reinterpret_cast<const unsigned char *>(data);//???

         for (int i = 0; i < numSamples; ++i) {
             for(int j = 0; j < m_format.channels(); ++j) {
                 quint16 value = 0;

                 if (m_format.sampleSize() == 8 && m_format.sampleType() == QAudioFormat::UnSignedInt) {
                     value = *reinterpret_cast<const quint8*>(ptr);
                 } else if (m_format.sampleSize() == 8 && m_format.sampleType() == QAudioFormat::SignedInt) {
                     value = qAbs(*reinterpret_cast<const qint8*>(ptr));
                 } else if (m_format.sampleSize() == 16 && m_format.sampleType() == QAudioFormat::UnSignedInt) {
                     if (m_format.byteOrder() == QAudioFormat::LittleEndian)
                         value = qFromLittleEndian<quint16>(ptr);
                     else
                         value = qFromBigEndian<quint16>(ptr);
                 } else if (m_format.sampleSize() == 16 && m_format.sampleType() == QAudioFormat::SignedInt) {
                     if (m_format.byteOrder() == QAudioFormat::LittleEndian)
                         value = qAbs(qFromLittleEndian<qint16>(ptr));
                     else
                         value = qAbs(qFromBigEndian<qint16>(ptr));
                 }

                 maxValue = qMax(value, maxValue);//???
                 ptr += channelBytes;
             }
         }

         maxValue = qMin(maxValue, m_maxAmplitude);
         m_level = qreal(maxValue) / m_maxAmplitude;
     }

     emit update();
     return len;
}

实例完整部分代码:
http://doc.qt.nokia.com/stable/multimedia-audioinput-audioinput-cpp.html