Extract media duration from metadata

[UnitScan]

Since duration is available only while media is playing, there is another way to retrieve the media duration? I'm creating a TableWidget to display all the files in the playlist, and beyond the filename would obtain the duration.

Can you help me?

[A Former User]

Hi! QAudioDecoder can do this for you.

void MainWindow::on_pushButton_clicked()
{
    QAudioDecoder *ad = new QAudioDecoder(this);
    ad->setSourceFilename("/home/user/file.mp3");
    connect(ad, &QAudioDecoder::durationChanged, this, &MainWindow::onDurationChanged);
    ad->start();
}

void MainWindow::onDurationChanged(qint64 d)
{
    QTime t(0,0,0,0);
    t = t.addMSecs(d); 
    ui->label->setText( t.toString("hh:mm:ss") );
}

Edit: Removed code that deleted ad to early.

[UnitScan]

I have already tried the QAudioDecoder class, but Qt sends me this error:

defaultServiceProvider::requestService(): no service found for - "org.qt-project.qt.audiodecode"

[A Former User]

Depending on your platform, audio decoding might not be provided by the backend. See: http://wiki.qt.io/Qt_5.7_Multimedia_Backends#Audio_plugins

[UnitScan]

I'm running Qt 5.7 on Window 7. msvc2013 installed, but QAudioDecoder still not work

[Devopia53]

@UnitScan

Hi.

Do you want this?

qlonglong duration = mediaPlayer->metaData("Duration");

[UnitScan]

@Devopia53

void MainWindow::playerOnMediaStatusChanged(QMediaPlayer::MediaStatus status) {
    if (status == QMediaPlayer::BufferedMedia) {
        QVariant duration = player->metaData("Duration");
        qDebug() << duration.toLongLong();
    }
}

returns 0

Yes, I know, there is player->duration(), but as I mentioned early works only for the current media

[Devopia53]

@UnitScan

Yeah, you're right.
However, it is possible resolved by using a few tricks.
like this:

    auto    playlist = new QMediaPlaylist;
    playlist->addMedia(QUrl::fromLocalFile("/Sample/Music/1.mp3"));
    playlist->addMedia(QUrl::fromLocalFile("/Sample/Music/2.mp3"));
    playlist->addMedia(QUrl::fromLocalFile("/Sample/Music/3.mp3"));
    player->setPlaylist(playlist);
    playlist->setCurrentIndex(0);
    //player->play();

    static bool     isExtractMode = true;
    connect(player, &QMediaPlayer::mediaStatusChanged,
            [&, playlist](QMediaPlayer::MediaStatus status){
        if (isExtractMode) {
            if (status == QMediaPlayer::LoadedMedia) {
                qDebug() << "Duration: " << player->metaData("Duration");

                int     index = playlist->nextIndex();
                if (index < 0) {
                    isExtractMode = false;
                    playlist->setCurrentIndex(0);
                }
                else
                    playlist->setCurrentIndex(index);
            }
        }
    });

[UnitScan]

[SOLVED]

I had to resort to the help of TagLibs library. And since the documentation available how to build this library to make it interact with Qt are very confusing and outdated, I proceeded to make available the library that I managed, with great difficulty, to compile by my hand:

http://www.unitscan.org/archives/301

I hope will be usefull