To insert advanced options for browsers that don't support the source video encoding, click the Advanced tab [1].
To specify an alternative source for the video, enter the URL in the Alternative source field [1]. Alternative source URLs can be used to specify a different video encoding in case the browser doesn't support the initial encoding offered.
To specify an image that displays until the user clicks the play button, enter the URL in the Poster field [2]. If the Poster field is blank, the first frame of the source video will be used as the poster image.
Note: Links from common providers (like YouTube and Vimeo) often link to custom media players and will not recognize any content added to the alternative source and poster options.