You will need to transfer your video from from your mobile device to a computer to upload via Kaltura into a Canvas Assignment. See :Transferring Media from a Mobile Device to a Computer for more information.
Note: If your assignment requires you to upload a Video along with another file. You must submitted each file separately for both to be successfully uploaded to the Assignment. If you upload a video file and another file to a Canvas assignment, when you submit, only the last file uploaded will be submitted to Canvas.
Uploading and submitting an video via Kaltura
Viewing multiple Canvas Assignment Submissions on a mobile device (iOS)
Note: If you have trouble viewing Kaltura videos try going to Safari/Preferences/Privacy, try unchecking Prevent cross-site tracking to see if that helps.