If it's just you in the household using the internet at one time then 1 Mbps can stream movies without a problem because I've done it before.
But I found that once I moved my internet speed to 2 Mbps the movies streamed much better than they did on 1 Mbps.
So although 1 Mbps would work it would be best to have at least 1 Mbps for a better streaming experience especially if anyone else is using internet in your house at the same time.