How can I extract metadata from a music file?

[Pbaodoge]

Hello, I'm trying to extract metadata from music files so that I can use it for specific applications. I tried to use QMediaPlayer. However, as I'm using Qt 6, some metadata functions have been removed. Therefore, I'm looking for a solution to extract the metadata, so that I can use titles, artist names,... etc, etc.
So this code in Qt 6 is completely failed:

    QMediaPlayer *player = new QMediaPlayer;
    player->setSource(QUrl::fromLocalFile("music.flac"));
    QStringList mdlist = player->availableMetaData(); // No member named 'availableMetaData' in 'QMediaPlayer'

If you know how can fix this, please help me. Thank you!

[jsulm]

@Pbaodoge said in How can I extract metadata from a music file?:

Calling 'metaData' with incomplete return type 'QMediaMetaData'

you have to include QMediaMetaData header file as shown in https://doc-snapshots.qt.io/qt6-dev/qmediametadata.html

[jsulm]

@Pbaodoge What about https://doc.qt.io/qt-6/qmediaplayer.html#metaData ?

[Pbaodoge]

I tried with metaData, but it is still failed:

    QMediaPlayer *player = new QMediaPlayer;
    player->setSource(QUrl::fromLocalFile("music.flac"));
    QStringList mdlist = player->metaData(); //Calling 'metaData' with incomplete return type 'QMediaMetaData'

Maybe my code is wrong or something?

[jsulm]

@Pbaodoge said in How can I extract metadata from a music file?:

Calling 'metaData' with incomplete return type 'QMediaMetaData'

you have to include QMediaMetaData header file as shown in https://doc-snapshots.qt.io/qt6-dev/qmediametadata.html

[J.Hilk]

@Pbaodoge in addition to what @jsulm said,

metaData() returns a QVariant not a QStringList, and expects a key as argument
https://doc.qt.io/qt-5/qmediaobject.html#metaData
and
https://doc.qt.io/qt-5/qmediametadata.html

[Pbaodoge]

@jsulm @J-Hilk
Thanks, that works. However, it returns a blank QString. This means that it can't fetch the metadata information. That seems to be a big problem.
Here's my code:

#include "mainwindow.hpp"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    player = new QMediaPlayer;
    player->setSource(QUrl::fromLocalFile(path));
    connect(player, &QMediaPlayer::mediaStatusChanged, this, &MainWindow::mediaLoaded); //wait until media is loaded, then execute the function
    player->setSource(QUrl::fromLocalFile(path));
};

void MainWindow::mediaLoaded() {
    if(player->mediaStatus() == QMediaPlayer::LoadedMedia)  { // which means that the media is loaded
         QMediaMetaData mdData = player->metaData();
         QVariant var = mdData[QMediaMetaData::Genre];
         qDebug() << var.toString();
    }
}

It outputs nothing. I checked every part of the program with qDebug(). everything works just fine. The result is just nothing.

[JonB]

@Pbaodoge said in How can I extract metadata from a music file?:

     QVariant var = mdData[QMediaMetaData::Genre];
     qDebug() << var.toString();

Please read the docs carefully! :) QMediaMetaData::Genre returns a QStringList. QVariant::toString() does not list that as a type it can convert to a string, and then

Calling QVariant::toString() on an unsupported variant returns an empty string.

Rewrite your code appropriately. You might also try QMediaMetaData::keys() to see what's there and QMediaMetaData::stringValue(QMediaMetaData::Key key) const.