How to port QAudioOutput device(QAudioDeviceInfo::defaultOutputDevice()); to Qt6?

Cobra91151

@Christian-Ehrlicher is right, you need to know at least basic C++ to create your projects. @Urbi in your case your local QFile effect; variable gets out of scope (gets deleted) after the bracket, so no audio will be outputed. You must have it as a pointer and keep in mind to remove it later after you no longer need it to prevent a memory leak. You can use delete or deleteLater(). Please, check out my test code below.

Code:

   if (play) {
       QFile *effectFile = new QFile(this);
       effectFile->setFileName(QString("%1/%2").arg(homePath, "sounds/1.wav"));
       qDebug() << "Is file exists: " << effectFile->exists() << " | " << effectFile->fileName();
       effectFile->open(QIODevice::ReadOnly);
       audio->start(effectFile);
       effectFile->close();
       effectFile->deleteLater(); //removes the QFile object, or call - delete effectFile
   }

Also, you can use the qDebug() to check the console output for example to see if the file exists and other useful stuff. By the way, what Qt 6 version are you using for this project?

Urbi

@Cobra91151 It gives this compilation error: 'audio' was not declared in this scope; did you mean 'QAudio'?

Urbi

@Cobra91151 Sorry, I forgot that I had already deleted the lines

QAudioFormat format;
 format.setSampleRate(8000);
 format.setChannelCount(1);
 format.setSampleFormat(QAudioFormat::UInt8);
 QAudioSink* audio = new QAudioSink(format, this);

Now it compiles and sends "something" to the default audio device. However, I just hear a crackle, and the program crashes afterwards. But at least one step ahead ...

Cobra91151

@Urbi

It's audio object from your code above: QAudioSink *audio = new QAudioSink(format, this);
What Qt 6 version do you use? Because I got qt.multimedia.audiooutput: Failed to set up resampler issue, which is well known bug: https://bugreports.qt.io/browse/QTBUG-108383. This issue has been fixed in Qt 6.4.3.
So, I recommend check out the console output for the same issue?

Cobra91151

@Urbi

Then check out your program using the debugger to find out what causes the crash (debug mode only). It should point you to the right code section.

By the way, include this code in main function:

#ifdef QT_DEBUG
    qputenv("QT_FATAL_WARNINGS", "1");
    qputenv("QT_MESSAGE_PATTERN",
            "Type: %{type}\nProduct Name: %{appname}\nFile: %{file}\nLine: %{line}\nMethod: %{function}\nThreadID: %{threadid}\nThreadPtr: %{qthreadptr}\nMessage: %{message}");
#endif

Then run the debugger. It should provide more details about this issue.

Urbi

@Cobra91151 With these parameters, the wav file is correctly played. However, the program still crashes immediately after playing is finished.

#include <QSoundEffect>
#include <QAudioOutput>
#include <QMediaDevices>
#include <QAudioDevice>
#include <QAudioSink>
#include <QCoreApplication>
#include <QDir>

{
  QAudioDevice info(QMediaDevices::defaultAudioOutput());
  QString homePath = QDir::homePath();
  QAudioFormat format;
  format.setSampleRate(48000);
  format.setChannelCount(1);
  format.setSampleFormat(QAudioFormat::Int16);
  QAudioSink* audio = new QAudioSink(format, this);
  connect(audio, SIGNAL(stateChanged(QAudio::State)), this, SLOT(handleStateChanged(QAudio::State)));

  if (play_) {
      QFile *effectFile = new QFile(this);
      effectFile->setFileName(QString("%1/%2").arg(homePath, "/sounds/1.wav"));
      qDebug() << "Is file exists: " << effectFile->exists() << " | " << effectFile->fileName();
      effectFile->open(QIODevice::ReadOnly);
      audio->start(effectFile);
      effectFile->close();
      effectFile->deleteLater(); //removes the QFile object, or call - delete effectFile
  }
}

Cobra91151

@Urbi

I see your QAudioSink *audio is initialized but never deleted, this could be a memory leak which could lead to crash.

Code:

if (play_)  {
    QFile *effectFile = new QFile(this);
    effectFile->setFileName(QString("%1/%2").arg(homePath, "/sounds/1.wav"));
    qDebug() << "Is file exists: " << effectFile->exists() << " | " << effectFile->fileName();
    effectFile->open(QIODevice::ReadOnly);
    audio->start(effectFile);
    effectFile->close();
    effectFile->deleteLater(); //removes the QFile object, or call - delete effectFile
}

audio->deleteLater(); // removes QAudioSink object

Please, check out my post above regarding using the debugger.

Urbi

@Cobra91151 Ok, the last two lines are breaking it.

effectFile->close();

leads to an abrupt end of the played sound. And this line causes the program crashs:

effectFile->deleteLater(); //removes the QFile object, or call - delete effectFile

I will now try to consolidate my code. (It was just a simplified example I presented here.) Let's see if I can put the entire definition of audio device, format and so on somewhere else where it is only called once after program start.

Anyway, many thanks for your help, Cobra91151!

Cobra91151

@Urbi

It could close the file when audio is still running. It was just an example how to work with QFile. So, I recommend you to close and delete the file after the audio is finished. Happy coding!

Urbi

@Cobra91151 Yes, that seems to be necessary. Because in reality there are up to 12 such wav files played in time cascade under certain conditions. I've set a command to close the audio sink at the end of this cascade to prevent a memory leak. Meanwhile, this is working pretty well.
However, I noticed, that the virtual memory slightly increases each time a wav file is loaded. Please tell me: what is the right command to close and delete such a played file? Because as written before, the two lines

effectFile->close();
effectFile->deleteLater();

do not work in my case.

Urbi

@Urbi I have now put all the close and delete commands at the end of the cascade and all the

QFile *effect123 = new QFile(this);

definitions at the beginning. This way the program doesn't crash anymore with the two lines from above. BUT: The observed memory leak effect is still the same. Why?

audio->deleteLater();

is set, and also for each effect file

effect123->close();
effect123->deleteLater();

I have found a number of similar reports on the Internet, but so far I've not seen any solution. Any idea?

Cobra91151

@Urbi

Hello!

The issue with memory leak could be that you create multiple QFile objects on the heap and remove only some of them. Or you have other objects which are still not deleted. You need a better object management depending on your current project or use the smart pointers (https://wiki.qt.io/Smart_Pointers). As for deleteLater() method it does not remove it immediately, it's only schedules this object for deletion, which is recommended by Qt to use deleteLater() instead of delete. You can use for example: delete someFileObj; to clear the resources immediately. Also, you can make some objects as class member variables and remove them in the destructor, you can reuse one object for several files etc. Additionally, please, check out the docs for more details about deleteLater() method: https://doc.qt.io/qt-6/qobject.html#deleteLater