[Interest] QAudioOutput and ALSA crashs with I/O Possible.

[Hugo Drumond Jacob]

Hi folks!

I'm using QtMultimedia (Qt 4.8.3) framework to play some sound on my
application but I'm experiencing some problems when using ALSA interface.

The scenario is something like this:

     QFile inputFile;           // class member.
     QAudioOutput *audioOutput; // class member.
     ...
     void startPlaying()
     {
         inputFile.setFileName("/tmp/test.raw");
         inputFile.open(QIODevice::ReadOnly);

         QAudioFormat format;
         // Set up the format, eg.
         format.setFrequency(8000);
         format.setChannels(1);
         format.setSampleSize(8);
         format.setCodec("audio/pcm");
         format.setByteOrder(QAudioFormat::LittleEndian);
         format.setSampleType(QAudioFormat::UnSignedInt);

         QAudioDeviceInfo info(QAudioDeviceInfo::defaultOutputDevice());
         if (!info.isFormatSupported(format)) {
             qWarning()<<"raw audio format not supported by backend, cannot
play audio.";
             return;
         }

         audioOutput = new QAudioOutput(format, this);

 connect(audioOutput,SIGNAL(stateChanged(QAudio::State)),SLOT(finishedPlaying(QAudio::State)));
         audioOutput->start(&inputFile);
     }

     void finishedPlaying(QAudio::State state)
     {
         if (state == QAudio::IdleState) {
             audioOutput->stop();
             inputFile.close();
         }
     }

The problem:
When the application runs with QtMultimedia using pulseaudio to sink the
audio stream, everything occurs like expected. Actually, the problem is
when pulseaudio isn't present. The application crash with a message (from
ALSA!?) "I/O Possible".
Browsing the internet I found [1], that suggests to block SIGIO with
sigprocmask. Ok, this works, but, isn't too 'hardcore'?

Any suggests? Thanks!

Hugo Drumond Jacob

[1]
https://www.mail-archive.com/alsa-user@lists.sourceforge.net/msg21681.html
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