fake news network:compositing

Maybe I am missing something, but I can’t find for the life of me how to output an alpha video frame. I would lick to put my news logo on the bottom right hand corner of the video frame,but would like to do that in a dedicated video editor outside of blender. Is it possible to output an alpha channel video frame from blender? I googled and search the forums,but can not find a solid solution. In blender I clicked on the animation tab and set the resolution to that of the video footage I’m using,then I position my logo at the bottom right hand corner and set the world material to not render. Should I just green screen it?(i.e. world material to a solid green texture) Thanks for reading.

I’d figured it out,from reading another post thats similar( yea, I must be blind as a bat today) All I have to do is output all the frames separately in png RGBA format and then string them together in my dedicated video editor(or ffmpeg)

manual has a nice section on explaining the output options:
http://wiki.blender.org/index.php/Doc:Manual/Render/Output_Formats