MST3K video layers

[krg765]

I am an old MST3k nerd. Some of the old cast have a relatively new project called "Rifftrax" going. It's audio commentary you can download from their site, but no video effects like the bots in the theater at the bottom of the screen. For kicks, I was thinking about attempting to pull the black matte of Mike and the bots out of a video file and lay it over one of the Rifftrax movies. I know I can accomplish this by re encoding the movie, but I was curious if there was another way to do it in layers. If the intended output is mkv, mp4, or something along those lines, is there a way to render an alpha channel matte that can be muxed into an existing video file without re encoding the file completely? I remember the old Ghostbusters DVD had an effect like this for their commentary with Harold Ramis and a couple of other people.

[poisondeathray]

is there a way to render an alpha channel matte that can be muxed into an existing video file without re encoding the file completely?

Not really.

You might be able to do something with overlayed soft subtitles, like ssa

[krg765]

Thanks for the help. I'll look into that. It has to be possible, because they did it on the Ghostbusters DVD. I just have no idea how they did it.

[poisondeathray]

Was it like an overlay ? If so, it was probably a different track (different encoding, not an actual separate overlay)