title: Get duration of QMediaPlaylist object
body: <p>I create a player for audiobooks - when you open a folder with mp3 file, whole list of them is added to playlist and List View. And i have a Label, which suppose to show duration of the whole book. But player->duration returns only a duration of current track, and if i go through the loop and do playlist->next() every step, player->duration returns 0. I know about Phonon and file metadata, but i need to do this without using it.</p>