Optional ReadonlyaspectThe frame's width over its height, for a video whose child is a carousel: the app encodes the child inside the carousel's square frame, a centred crop of the source (a 1280×720 video becomes 720×720). The whole picture when left out; every side of the crop is even, as 4:2:0 requires.
ReadonlydirectiveReadonlyvideoThe developer's file: an MP4 with one H.264 video track.
What the encode reads: the developer's file and the server's directive.