Movie as texture with white color as alpha - blender cycles

I have question how to do movie as texture with white color as alpha.
I’m trying to create scene with smoke. All textures are baked. I’m using clip with smoke on white background to put smoke where i want.
I’ve tried to do this like with image alpha texture using mix shader(emission with transparency) but results was not satisfying me see attached screens. Smoke has hard edges and visible image frame. Can anyone help me to solve this issue?
I’m using movie clip from site: