Media sources dialog
You can use the media sources dialog to set the Sources property of the Video player and the Audio player controls at designtime. You can specify one or more media source files, and, optionally, the type / codecs to be used by every media file. If you leave the media type / code without specify, the browser or platform try to identify it and act accordingly.
There is an Audio and Video sample apps included with the installation of DecSoft App Builder. Take a look to see the above dialog in action!