If you are trying to upload a video which is not 16:9 or 4:3 ratio you will get the below error:
Use this online tool to convert your video to 16:9 or 4:3. For videos that are 16:9 use width = 1280 and height = 720. For videos that are 4:3 use width = 1280 and height = 960.
For a video you wish to resize to 4:3 using the following settings: