需要 metaDataChanged 信号触发响应

{
    connect(player, SIGNAL(metaDataChanged()), this, SLOT(metaDataChange()));
}

void MainWindow::metaDataChange()
{
    ui->menu_audioTrack->clear();
    QList<QMediaMetaData> list_MMD = player->audioTracks();
    qDebug() << "audioTracks" << list_MMD.length();
    QActionGroup *actionGroup_audioTrack = new QActionGroup(this);
    actionGroup_audioTrack->setExclusive(true);
    for (int i=0; i<list_MMD.length(); i++) {
        QAction *action = new QAction(QString::number(i));
        action->setCheckable(true);
        if (i == 0)
            action->setChecked(true);
        ui->menu_audioTrack->addAction(action);
        actionGroup_audioTrack->addAction(action);
        connect(action, &QAction::triggered, [=](){
            action->setChecked(true);
            int index = ui->menu_audioTrack->actions().indexOf(action);
            player->setActiveAudioTrack(index);
        });
    }
}