Base resource for video streams. Base resource type for all video streams. Classes that derive from [VideoStream] can all be used as resource types to play back videos in [VideoStreamPlayer]. $DOCS_URL/tutorials/animation/playing_videos.html Called when the video starts playing, to initialize and return a subclass of [VideoStreamPlayback]. The video file path or URI that this [VideoStream] resource handles. For [VideoStreamTheora], this filename should be an Ogg Theora video file with the [code].ogv[/code] extension.