Cover version? I think so. I have a thing about watching ASL/BSL versions of songs, even though I can't understand a word, ever since seeing the version of Cee Lo Green's **** You (amusingly the copyright owners complained about the track of the original so audio is now muted, a funny speeded up version is here
https://www.youtube.com/watch?v=LtQ9lEuEzrc - I would have thought the SL version has similar humour to the audio)
But I really think this version of Gotye's Someone I use to know adds to the original
https://www.youtube.com/watch?v=hUt4W8sE8Ns