When attempting to retrieve a library url with the parameter Category=62, the page is said to not be found.
In the documentation, there doesn’t appear to be a way to retrieve videos using this field. assetType=62 brings no avail either.
I assume this is because videos are new and still being fully added to roblox, just give it some time and if it doesn’t come in a few weeks head over to #platform-feedback and create a feature request for the json api to add support for videos. Not really anything you can do but wait