Undistorting a distorted source

[yukichigai]

Okay, say I have some video that shows an image in a trapezoidal arrangement. (e.g. bottom and top parallel, but sides are non-parallel) Now let's suppose I want to undistort this video so that it is instead shown in a more rectangular arrangement. Clear on the concept so far? Good.

Now, if I were an avisynth filter that could take a set of four coordinates and resize the area defined by those coordinates into any rectangular shape, where would I live?

Annnnnnnnnnnnnnnnnnnnnnnnnnnnd go!

[foxyshadis]

ffdshow has a perspective/skew filter, which can be activated with its avisynth plugin, ffavisynth (presumably using a custom profile).

[vcmohan]

you can try my Reform plugin.