The QML video component provides an easy way to display a QMediaPlayer in a QML scene. QMediaPlayer in turn uses gstreamer. The bug is in QMediaPlayer. Audio files work, video files do not (hence the QML audio component works fine). I have tried using Phonon (which also uses gstreamer) rather than QMediaPlayer, and it works, but performance is poor. There are a lot of dropped frames when playing on the N900. The poor performance is probably down to attempting to wrap a Phonon VideoPlayer in a QGraphicsProxyWidget. QGraphicsProxyWidget is (I think) intended for simple QWidgets, rather that a video player. So, it looks like I'm back to using KMPlayer to play video files for the Maemo 5 version.