converting avi to avi transparent

[perfection]

Is there a tool/software that inputs avi and outputs transparent avi (removes say a black backgorund colour) and retains the alpha channel on export for sue in other software that supports it?

[poisondeathray]

most NLE's will have basic chroma or color key plugins (e.g. vegas, premiere pro) , or cinegobs keyer, after effects. You can do it in avisynth as well

you can use uncompressed RGBA export, or lossless RGBA compression (e.g. huffyuv, lagarith, ut video codec support lossless compression of alpha channel)

"black" usually isn't a good idea, because other objects in your video that are black will be keyed out, unless you isolate with masks