Should be possible by passing a parameter into the embedded video URL.
http://code.google.com/apis/youtube/pla ... l#autoplayI'll add this as a feature to v5.1:
http://quest.codeplex.com/workitem/968In the meantime, you can probably fake it by adding this parameter to the video ID, for YouTube at least. I've not tested this, but if your video ID is "abcd1234", you should be able to make it auto play by entering this as the ID instead: abcd1234&autoplay=1