MediaPlayerInterfacePlayVideoMessage

Play a base64 encoded video on the endpoint's screen, replacing what the endpoint's own player plays and repeating it while loop is true. Requires a supportedVideoMimeTypes entry for the video's mimeType. A SUCCEEDED result means the command was delivered, not that the video is playing; confirm with endpoint_query expand media-player and forceDeviceAttributeQuery true; playback-state reads LOADING while the endpoint fetches the file, then PLAYING, so poll until it leaves LOADING. A pause while LOADING starts the video paused at its beginning.