Qt MediaPlayer doesn't play audio

ABouncyMi

I am trying to make an application where there is a looping background music. I have added the bgm m4a file into the project via CMake. The code in MainWindow is below.

ui->setupUi(this);
screamer = new QMediaPlayer(this);
audioOutput = new QAudioOutput(this);
screamer->setAudioOutput(audioOutput);
QString filePath = "bgm.m4a";
qDebug() << QUrl::fromLocalFile(filePath).toString();
screamer->setSource(QUrl::fromLocalFile(filePath));
audioOutput->setVolume(40);
screamer->play();
qDebug() << screamer->errorString();

Now I am quite sure that the bgm.m4a file was correctly named, the errorString() returns "", and all the codes are executed in the correct order, but there is no sound coming out of my speakers. What am I doing wrong here?

SGaist

Hi and welcome to devnet,

You are using a relative path to your file. Is it located beside your application executable ?

ABouncyMi

@SGaist said in Qt MediaPlayer doesn't play audio:

Is it located beside your application executable ?

Yes, I have also tried to use qt resource files but the sound still doesn't play

Ronel_qtmaster

@ABouncyMi When you remove set AudioOuptut does it play?
Is there any message in the application output?
You can check this as well https://evileg.com/en/post/155/

ABouncyMi

@Ronel_qtmaster
I've changed that, unfortunately it has the same output as before.

Error 20 (this feature has not been implemented yet) in function AVolute::GetProductInfoT::<lambda_3920e95365a48b95dd51020986e9e351>::operator ()
Error 20 (this feature has not been implemented yet) in function AVolute::GetProductInfoT::<lambda_3920e95365a48b95dd51020986e9e351>::operator ()
Error 20 (this feature has not been implemented yet) in function AVolute::GetProductInfoT::<lambda_3920e95365a48b95dd51020986e9e351>::operator ()
Error 20 (this feature has not been implemented yet) in function AVolute::GetProductInfoT::<lambda_3920e95365a48b95dd51020986e9e351>::operator ()
Error 20 (this feature has not been implemented yet) in function AVolute::GetProductInfoT::<lambda_3920e95365a48b95dd51020986e9e351>::operator ()
Error 20 (this feature has not been implemented yet) in function AVolute::GetProductInfoT::<lambda_3920e95365a48b95dd51020986e9e351>::operator ()
Error 20 (this feature has not been implemented yet) in function AVolute::GetProductInfoT::<lambda_3920e95365a48b95dd51020986e9e351>::operator ()
Error 20 (this feature has not been implemented yet) in function AVolute::GetProductInfoT::<lambda_3920e95365a48b95dd51020986e9e351>::operator ()
Error 20 (this feature has not been implemented yet) in function AVolute::GetProductInfoT::<lambda_3920e95365a48b95dd51020986e9e351>::operator ()
Error 20 (this feature has not been implemented yet) in function AVolute::GetProductInfoT::<lambda_3920e95365a48b95dd51020986e9e351>::operator ()
Error 20 (this feature has not been implemented yet) in function AVolute::GetProductInfoT::<lambda_3920e95365a48b95dd51020986e9e351>::operator ()
Error 20 (this feature has not been implemented yet) in function AVolute::GetProductInfoT::<lambda_3920e95365a48b95dd51020986e9e351>::operator ()
"file::/audio/bgm.m4a"
""

Ronel_qtmaster

@ABouncyMi then you have a bug https://bugreports.qt.io/browse/QTBUG-79799

Did you try with Qmake?or simple qt exemple with qmake?It could be a problem with cmake

ABouncyMi

@Ronel_qtmaster said in Qt MediaPlayer doesn't play audio:

@ABouncyMi then you have a bug https://bugreports.qt.io/browse/QTBUG-79799

Did you try with Qmake?or simple qt exemple with qmake?It could be a problem with cmake

I tried Qmake, the same bug, but strangely the qt mediaplayer example in qt creator examples is working well, also I do not have an alien computer or msi sonic radar installed on my computer

Ronel_qtmaster

@ABouncyMi then it is an error in your code.Now try to open your file from QFileDialog.
QString video = QFileDialog::getOpenFileName(this);
Then set that string as the url of your video and remove Audio output

ABouncyMi

@Ronel_qtmaster said in Qt MediaPlayer doesn't play audio:

@ABouncyMi then it is an error in your code.Now try to open your file from QFileDialog.
QString video = QFileDialog::getOpenFileName(this);
Then set that string as the url of your video and remove Audio output

Thanks for the code but it still doesn't play the audio. I'm beginning to think if it's a problem with windows or my audio driver.
P.S. why is it video when I am trying to play an audio?

Ronel_qtmaster

@ABouncyMi did you install klitecodec for audios and videos codecs?

ABouncyMi

@Ronel_qtmaster
No, I only installed the extra Multimedia package from qt maintenance tool

JonB

@ABouncyMi
As @Ronel_qtmaster said, I think you have to download/install any required codes, I don't think the Qt multimedia package supplies those, it expects to find them installed!

Ronel_qtmaster

@ABouncyMi https://codecguide.com/

ABouncyMi

@Ronel_qtmaster
Successfully installed k-lite codecs standard with default options, is there anything else I can do? There still isn't any sound

Ronel_qtmaster

@ABouncyMi is it at least playing? Try to create mediaplayer when a button is pressed for example, not in the constructor

ABouncyMi

@Ronel_qtmaster Unfortunately I can hear no sound from the application, the installation exited with no errors and I tried restarting.

I then tried using a pushbutton like this:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFileDialog>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    screamer = new QMediaPlayer(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_pushButton_clicked()
{
    QString video = QFileDialog::getOpenFileName(this);
    qDebug() << QUrl::fromLocalFile(video).toString();
    screamer->setSource(QUrl::fromLocalFile(video));
    screamer->play();
    qDebug() << screamer->errorString();
}

No sound :(
This is surely the hardest problem I had experienced with qt

Ronel_qtmaster

@ABouncyMi could you try this?
void MainWindow::on_pushButton_clicked()
{
screamer = new QMediaPlayer(this);
QString video = QFileDialog::getOpenFileName(this);
qDebug() << QUrl::fromLocalFile(video).toString();
screamer->setSource(QUrl::fromLocalFile(video));
screamer->play();
qDebug() << screamer->errorString();
}

Ronel_qtmaster

@ABouncyMi remove screamer line in the constructor

SGaist

One thing: QMediaPlayer is asynchronous so checking the error string right after calling play is useless.

Use the error signal and stateChanged.

ABouncyMi

@SGaist I tried using the https://doc.qt.io/qt-5/qmediaplayer.html#error-1 method, it gives out the error:

mainwindow.cpp:25:23: No matching function for call to 'of'
qoverload.h:44:27: candidate template ignored: failed template argument deduction
qoverload.h:32:27: candidate template ignored: could not match 'R (QMediaPlayer::Error)' against 'Error () const'
qoverload.h:61:27: candidate template ignored: could not match 'R (*)(QMediaPlayer::Error)' against 'Error (QMediaPlayer::*)() const'