Create keyframe in already-encoded XviD for precise split

[Giggity]

Nandub has done a fine job of splittling videos for me when I don't need to extract a precise clip from a movie, as it can only split on keyframes. This time, however, I'm looking to extract just a few funny clips from certain already-encoded XviD movies. Trouble is, the keyframes are often over 10 seconds apart on my encoded vids (used GK original), which can leave a good chunk of time hanging off the beginning or end of the clip, which I don't know how to trim off.

I was hoping to correct this by cutting out the general vicinity of the clip using NanDub, then making keyframes out of the frames on either end of the clip, and then cutting out the precise clip using NanDub.

So... how do I make a keyframe out of a non-keyframe? I hope I've described my dilemma well enough. I'm trying to avoid having to bust out my DVD's again, re-rip the right chapters, then reindex, then reencode.

[mod]

Cut out just the part between 2 consecutive keyframes that contains the frame you want to use, reencode it with max keyframes interval = 1, edit, append.