QMediaPlayer positionChanged not precise

UnitScan

In my player I implemented a QLabel which display the progress of the plaiyng file

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    //…
    display = new QLabel(this);
    display->setGeometry(4,4,88,23);
    display->setText("00:00:00");
    //…
    player = new QMediaPlayer;
    connect(player, SIGNAL(positionChanged(qint64)), this, SLOT(playerOnPositionChanged(qint64)));
    //…
}

void MainWindow::playerOnPositionChanged(qint64 position) {
    QTime time(0,0,0);
    time = time.addMSecs(position);
    display->setText(time.toString());
}

The problem is that this method is not very accurate, because it often happens may skip seconds: for example, QLabels throw from 1:05 to 1:07. Is there a more accurate way to display the progress of the playing file?

VRonin

It looks like just a "called too many times" problem.
Since your resolution is seconds try something like this

void MainWindow::playerOnPositionChanged(qint64 position) {
    if(position%1000i64 == 0)
        display->setText(QTime(0,0,0).addMSecs(position).toString());
}

UnitScan

Qt Creator send me this error message:

error: unable to find numeric literal operator 'operator""i64'
if (position%1000i64 == 0)
^

VRonin

Sorry, I didn't realise i64 is MSVC only. corrected:

void MainWindow::playerOnPositionChanged(qint64 position) {
    if(position % static_cast<qint64>(1000) == 0)
        display->setText(QTime(0,0,0).addMSecs(position).toString());
}

UnitScan

Not work: display text is always "00:00:00"

VRonin

this is strange. try this in your main (just as a test):

for (qint64 position = 0; position < 50000; ++position) {
        if ((position % static_cast<qint64>(1000)) == 0)
            qDebug() << QTime(0, 0, 0).addMSecs(position).toString();
    }

it works for me

UnitScan

Yes, this loop works on MainWindow constructor

VRonin

then

void MainWindow::playerOnPositionChanged(qint64 position) {
qDebug() << position;
    if((position % static_cast<qint64>(1000)) == 0)
        display->setText(QTime(0,0,0).addMSecs(position).toString());
}

should work too...

UnitScan

@VRonin tried this:

void MainWindow::playerOnPositionChanged(qint64 position) {
    if((position % static_cast<qint64>(1000)) == 0)
            display->setText(QTime(0,0,0).addMSecs(position).toString());
    qDebug() << position % static_cast<qint64>(1000);
}

This is the output:

0
859
873
887
901
916
930
944
958
972
…

So, the condition

position % static_cast<qint64>(1000)) == 0

is true only once

VRonin

do you have the same if you run this example? http://doc.qt.io/qt-5/qtmultimedia-multimediawidgets-player-example.html

UnitScan

[SOLVED]

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    //…
    display = new QLabel(this);
    display->setGeometry(4,4,88,23);
    display->setText("00:00:00");
    //…
    player = new QMediaPlayer;
    connect(player, SIGNAL(mediaStatusChanged(QMediaPlayer::MediaStatus)), 
        this, SLOT(playerOnMediaStatusChanged(QMediaPlayer::MediaStatus)));
    //…
    timer = new QTimer;
    timer->setTimerType(Qt::PreciseTimer);
    connect(timer, SIGNAL(timeout()), this, SLOT(timerSlot()));
    //…
}

void MainWindow::playerOnMediaStatusChanged(QMediaPlayer::MediaStatus status) {
    if (status == QMediaPlayer::BufferedMedia) {
        pos = -1; //int pos declared on .h file
        timer->start(1000);
    }
}

void MainWindow::timerSlot() {
    pos = pos + 1;
    QTime time((pos/3600)%60, (pos/60)%60, pos%60);
    display->setText(time.toString("hh:mm:ss"));
}