How to render Alpha background I downloaded a file from blend swap edit it and I tried to render it with alpha channel but whenever I does this happens

It look like it is rendering with alpha channel but it doesn't after when the rendering is completed this happends



You see when the render is completed there is a black background, what should I do.
The problem was caused because of the compositing pipeline what I did was just unchecked the use nodes checkbox and boom, Finally the render I desired.

If uses these render setting for transparent video render

  

Blender Version: 2.79c

Render Engine: Cycles

Render Format: .mov (quicktime)