I want to do the arithmetic mean of values of a buffer which I wanna to fill with QAudioInput.

I declare these objects:
Qt Code: 
  1. QAudioFormat audioformat;
  2. QAudioInput *input;
  3. QIODevice *intermediario;
  4. QByteArray buffer;
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I wrote this function for formatting audioformat:
Qt Code: 
  1. void formatta_audio (QAudioFormat *formato)
  2. {
  3.     formato->setFrequency(1000);
  4.     formato->setSampleSize(8);
  5.     formato->setCodec("audio/pcm");
  6.     formato->setByteOrder(QAudioFormat::LittleEndian);
  7.     formato->setSampleType(QAudioFormat::UnSignedInt);
  8.     formato->setChannels(1);
  9. }
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In the MainWindow costructor I wrote this:
Qt Code: 
  1. QAudioDeviceInfo info =  QAudioDeviceInfo::defaultInputDevice();
  2.  
  3. formatta_audio(&audioformat);
  4.  
  5. if (!info.isFormatSupported(audioformat))
  6.     audioformat = info.nearestFormat(audioformat);
  7.  
  8. input= new QAudioInput (audioformat);
  9.  
  10.  ui->setupUi(this);
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I start the QaudioInput in this way:
Qt Code: 
  1. intermediario = input->start();
  2.        connect (intermediario,SIGNAL(readyRead()),this,SLOT(cattura()));
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And stop the QaudioInput in this way:
Qt Code: 
  1. input->stop();
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"cattura()" function is this:
Qt Code: 
  1. void MainWindow::cattura()
  2. {
  3.  
  4.     qint64 Nbytesletti;
  5.     qint64 i;
  6.     qint64 media=0;
  7.     qint64 bytescatturati;
  8.  
  9.  
  10.     bytescatturati= intermediario->bytesAvailable();
  11.  
  12.     if (bytescatturati>0)
  13.     {
  14.  
  15.         Nbytesletti= intermediario->read(buffer.data(),bytescatturati);
  16.  
  17.         for (i=0;i<Nbytesletti;i++)
  18.         {
  19.             media+=(qint64)buffer.at(i);
  20.         }
  21.  
  22.         media/=Nbytesletti;
  23.  
  24.         ui->label->setText(QString("%1").arg(media));
  25.     }
  26.  
  27.  
  28. }
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I've tried a lot of times but "intermediario->bytesAvailable()" return ever "0"

Why? What is the problem?