Transparent background in PNG, but MP4 background is black I've managed to render PNGs which have my machine on a transparent background, but I want to have a video of it.  I've tried lots of settings to no avail....the film/transparent setting doesn't seem to do anything.

Every vid I've rendered, whether it be straight from Blender Render or Cycles Render or via creating a film strip from the PNGs via Video Editor and creating a vid from there, turns up with a black background from my scene.

Whats the trick?

Thanks!
Mp4 does not support alpha channel. You need to encode using a codec that does.