QAudioOutput Unable to setVolume

Banshee10000

Currently I'm struggling to set the volume for a QAudioOutput object...
In the documentation its noted that ::setVolume takes a qreal

I have a horizontal slider with value 0 to 100.
Then I convert the incoming horizontal Slider value like this:

output is a QAudioOutput

void SoundSystem::SetVolume(int volume)
{
    if(output->state() ==  QAudio::ActiveState)
    {
        //qreal linearVolume = QAudio::convertVolume(volume / qreal(100.0),
                                                        //QAudio::LogarithmicVolumeScale,
                                                        //QAudio::LinearVolumeScale);
        //output->setVolume(qRound(linearVolume * 100));

        qreal newVol =  (qreal)volume / 100;
        qDebug() << "Volume  Value: "  << newVol;
        output->setVolume(newVol);
        qDebug() << "Check Value: "  << output->volume();
    }
}

The debugging output:

Exec::playSound
handleAudioStateChanged ActiveState
Volume Value: 0.99
Check Value: 0.99
Volume Value: 0.98
Check Value: 0.98
Volume Value: 0.97
Check Value: 0.97
Volume Value: 0.96
Check Value: 0.96
Volume Value: 0.95
Check Value: 0.95
Volume Value: 0.7
Check Value: 0.7
handleAudioStateChanged StoppedState
sound stopped

It seems like the value is set currently and even when I query the objects current volume using ::volume() member I get the correct values. However the volume doesn't change. Only when it get to max or min does the stream either mute or play at full volume.

So basically when I move the slider it goes from 0 (Min value from the Slider) to 100 (MAX value from the slider.)
converting that to a range between 0 and 1. All which works when I move the slider the audio either plays or if the slider is low the audio is muted, everything in between doesn't do anything to the volume of the QAudioOutput output.
I have also tried to do it like its stated in the Qt Documentation on how to set the volume and that too didn't work.

My setup:
Windows 10 Pro x64
Qt 5.9.3
MinGW32 Compiler.

Any idea's?

Ratzz

@Banshee10000

Can you setVolume directly with qreal values which you get from QAudio::convertVolume ?
https://doc.qt.io/qt-5/qtmultimedia-multimedia-audiooutput-audiooutput-cpp.html

Banshee10000

Hello @Ratzz I have tried to set the value directly, with qreal values as suggested but same results. Volume doesn't change unless slider is at 0 then the audio mutes otherwise its playing at max. so either 0 or 1. even though I feed it a range between 0 and 1 its ignored
Debug from qreal values set directly using QAudio::convertVolume

Exec::playSound
handleAudioStateChanged ActiveState
Check Value: 1
Check Value: 0.849485
Check Value: 0.761439
Check Value: 0.69897
Check Value: 0.650515
Check Value: 0.610924
Check Value: 0.577451
Check Value: 0.548455
Check Value: 0.522879
Check Value: 0.5
Check Value: 0
handleAudioStateChanged StoppedState
sound stopped

I have also tried to use doubles and floats instead of qreal and I have downloaded the latest version of Qt 5.11.1 to see if that address the issue but the same issue remains. No idea however why though.

Pradeep P N

Hi @Banshee10000

Did you check the example code available in Qt ?
the link suggested by @Ratzz

https://doc.qt.io/qt-5/qtmultimedia-multimedia-audiooutput-example.html
Can you run this example and check the volume ?

Banshee10000

I was just testing with the example on my system which works. The volume can be set correctly and behaves as expected in the example. Could it maybe be PCM data that I'm sending to QAudioOutput that is preventing correct volume change ?

I'm also using QAudioOutput in a thread. the slider is on the mainWindow UI sending the int value to the thread via signals and slots. I know that the value from the slider is received and converted in the thread correctly as per debug output. As well as when I move the slider it does mute the audio when its at its lowest point but moving it instantly goes from mute to max vol.

Banshee10000

After a lot of trial and error I managed to solve this. It was indeed the way I create the PCM data.
I used a unSignedInt as the sampleType and it should be SignedInt. Then setVolume works.