Playing audio using thread

goshantry

Is there any way to free up memory after an object has been created in Qt or does it automatically frees up memory after the function has been completed?

jsulm

@goshantry Variables allocated on the stack are freed automatically when the function/method finishes.
If a variable was allocated on the heap (new) then it is either freed when the parent is deleted (if you're using Qt parent/child feature) or you have to delete it at some point.
As @SGaist pointed out your mutex is useless the way you're using it...

goshantry

@jsulm I removed that part of my code and created a new function to play audio without thread. Everything works fine and I left to test it for 2 days. Now when I run the free -m command in the terminal it shows only around 250-300 mb remaining out of my 8Gb. The swap memory is also used to a great extent.

Is this memory because of those objects which I declared with new() or with any object that has been created?

Also do I use the delete later with every object that i created at the end of the function to release the memory?

My application is supposed to run for long hours without having to shutdown or restart the system.

jsulm

@goshantry You release the memory when you don't need it anymore.
"Also do I use the delete later with every object that i created at the end of the function to release the memory?" - do you mean deleteLater() method?
You should use Valgrind to analyse where your app is consuming memory.
"Is this memory because of those objects which I declared with new() or with any object that has been created?" - any of course. Everything in use by your app.
Can you show the code you're currently using?

goshantry

@jsulm I tried using valgrind in Qt and this is the output which I get everytime

11:40:37: valgrind --child-silent-after-fork=yes --xml-socket=127.0.0.1:43171 --log-socket=127.0.0.1:46593 --xml=yes --smc-check=stack --tool=memcheck --gen-suppressions=all --track-origins=yes --leak-check=summary --num-callers=25 /home/fiem/workspace/build-PAPIS-Desktop_Qt_5_12_1_GCC_64bit-Debug/PAPIS
11:41:11: The program has unexpectedly finished.
11:41:11: Process exited with return value Process crashed
11:41:11: Analyzing finished.

Also I changed the Audio Playing function to

// Constructor for class
pisUser::pisUser(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::pisUser)
{
    ui->setupUi(this);
    player = new QMediaPlayer(this);
}

// Function to play audio
void pisUser::playAudioDirect()
{
//    player->deleteLater();
    player->setMedia(QUrl::fromLocalFile(path));
    player->play();               // Play the audio sounds
}

also player->deleteLater(); always crashes the application no matter where i put it

jsulm

@goshantry said in Playing audio using thread:

also player->deleteLater(); always crashes the application no matter where i put it

That's because player has a parent and parent deletes its children when it is deleted, so you have a double delete. Do not pass "this" to player as parent (or do not call delete later).
And why do you try to call deleteLater BEFORE you actually use it?! You should do it when you don't need it anymore.
See https://doc.qt.io/qt-5/objecttrees.html

kuzulis

AFAIK, QtMM is not designed to use in separate threads (look to QMediaPlayer source code).

goshantry

I was reading about QPointers and I tried the following

QPointer<QMediaPlayer> player = new QMediaPlayer(this);

    //player = new QMediaPlayer(this);

the part which I wrote in comments works fine
The part with QPointer crashes my application

It comes in the following function

void QMediaPlayer::setMedia(const QMediaContent &media, QIODevice *stream)
{
    Q_D(QMediaPlayer);
    stop();

    QMediaContent oldMedia = d->rootMedia;
    d->disconnectPlaylist();
    d->playlist = 0;
    d->rootMedia = media;
    d->nestedPlaylists = 0;

    if (oldMedia != media)
        emit mediaChanged(d->rootMedia);

    if (media.playlist()) {
        // reset playlist to the 1st item
        media.playlist()->setCurrentIndex(0);
        d->setPlaylist(media.playlist());
    } else {
        d->setMedia(media, stream);
    }
}

I get the segmentation fault error and the program crashes

jsulm

@goshantry said in Playing audio using thread:

I get the segmentation fault error

Where exactly?

goshantry

@jsulm the current debugger location is on the starting brackets of the setmedia function.