Fake. Video cuts @ just over a second in but audio streams seamlessly. More obvious in the slo-mo.
Besides, the video is of a plane in seeming level flight...not the attitude of the Germanwings aircraft based on speed of descent. The altitude is a bit higher than the 6800 feet at which they lost radar contact as well.
.02
It does look like somebody’s video of flying over the alps with a soundtrack added.
Besides, the real thing — if it exists- will most likely be of the inside of the passenger compartment.