I wonder which capabilities are required to allow the use of the QMediaPlayer and QMediaPlayerControl classes.

According to the player example ( http://doc.qt.nokia.com/qtmobility-1.0/player-player-pro.html ) , the following set is good enough :
UserEnvironment WriteDeviceData ReadDeviceData NetworkServices SwEvent

However the application does not startup, because of the following line:

new QMediaPlayer(this, QMediaPlayer::LowLatency)

PS : I am using Open Signed Online