Qt Reference Documentation

# utils.cpp Example File

demos/spectrum/app/utils.cpp

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     #include <QtMultimedia/QAudioFormat>
     #include "utils.h"

     qint64 audioDuration(const QAudioFormat &format, qint64 bytes)
     {
         return (bytes * 1000000) /
             (format.frequency() * format.channels() * (format.sampleSize() / 8));
     }

     qint64 audioLength(const QAudioFormat &format, qint64 microSeconds)
     {
        qint64 result = (format.frequency() * format.channels() * (format.sampleSize() / 8))
            * microSeconds / 1000000;
        result -= result % (format.channelCount() * format.sampleSize());
        return result;
     }

     qreal nyquistFrequency(const QAudioFormat &format)
     {
         return format.frequency() / 2;
     }

     QString formatToString(const QAudioFormat &format)
     {
         QString result;

         if (QAudioFormat() != format) {
             if (format.codec() == "audio/pcm") {
                 Q_ASSERT(format.sampleType() == QAudioFormat::SignedInt);

                 const QString formatEndian = (format.byteOrder() == QAudioFormat::LittleEndian)
                     ?   QString("LE") : QString("BE");

                 QString formatType;
                 switch(format.sampleType()) {
                 case QAudioFormat::SignedInt:
                     formatType = "signed";
                     break;
                 case QAudioFormat::UnSignedInt:
                     formatType = "unsigned";
                     break;
                 case QAudioFormat::Float:
                     formatType = "float";
                     break;
                 case QAudioFormat::Unknown:
                     formatType = "unknown";
                     break;
                 }

                 QString formatChannels = QString("%1 channels").arg(format.channels());
                 switch (format.channels()) {
                 case 1:
                     formatChannels = "mono";
                     break;
                 case 2:
                     formatChannels = "stereo";
                     break;
                 }

                 result = QString("%1 Hz %2 bit %3 %4 %5")
                     .arg(format.frequency())
                     .arg(format.sampleSize())
                     .arg(formatType)
                     .arg(formatEndian)
                     .arg(formatChannels);
             } else {
                 result = format.codec();
             }
         }

         return result;
     }

     bool isPCM(const QAudioFormat &format)
     {
         return (format.codec() == "audio/pcm");
     }

     bool isPCMS16LE(const QAudioFormat &format)
     {
         return (isPCM(format) &&
                 format.sampleType() == QAudioFormat::SignedInt &&
                 format.sampleSize() == 16 &&
                 format.byteOrder() == QAudioFormat::LittleEndian);
     }

     const qint16  PCMS16MaxValue     =  32767;
     const quint16 PCMS16MaxAmplitude =  32768; // because minimum is -32768

     qreal pcmToReal(qint16 pcm)
     {
         return qreal(pcm) / PCMS16MaxAmplitude;
     }

     qint16 realToPcm(qreal real)
     {
         return real * PCMS16MaxValue;
     }