Select your viewing speed based on your internet connection. If you have a slower connection you may be better listening to the audio while viewing the slides. To change your viewing speed Select Video or Audio from the dropdown and the click "Change"
iPod, iPhone and iPad implementation
For iPods, iPhones and iPads the slides are always shown without the video because iPhones and iPods will always show the video in their native viewer and so to have all the functionality such as seeing slides and subtitles. At present the iPad is implemented in the same manner.
iPods, iPhones and iPads will not show flv videos. Earlier talks are encoded in this format. If this is the case the the audio will be played.