I've been set the task of editting a video, however most of it is people talking over a powerpoint.

I was thinking of cutting a frame, then streaching it across the blank video areas, with just the audio.

Then cut back to actual video when some is on screen.

Would this reduce file size?

also any insight on flv or mp4 format would be helpful. What kind of length of video for mp4 (ipod) video would be standard?