How can I embed mp4-videos in LibreOffice Impress?

I am making a presentation which I would ‘decorate’ with sounds and videos, but somehow I cannot seem to embed these audio or video files. The insert function always replies that the format is not recognized, even if I try mainstream formats like MP3 or MP4, AVI, WMV, MPEG, etc.

Thanx,
Klaas

Please edit the question to indicate operating system, LO version, and audio/video stream codec.

Refer this related question.