Capturing burned subtitles

There's something I have been trying with no results.

What I would like to do is capture some subtitles that are already burned on some films I have and convert them into text subtitles, already time-coded to the video images.

The program I tried was Subrip 1.30.

It has an option they call "Hard Subbed Video Files", where you can open avi video files, then make a window where the program will OCR any eventual subtitles and convert them.

When doing so it opens another screen where the film will show through. You then select the window to OCR, which should be as small as possible, and then run the program.

What I don't seem to get is the avi file to show. This avi file is not compressed. I did try with some Divx compressed avi files and it does show on the window, so I wonder if the program only accepts Dvixed files. Can that be so?

Any experience with this program or other capturing types?