Hey, concerning those who, in the last weeks, asked for solutions concerning 16:9 shot with 4:3 format, I just found a mask you just have to drop on your top track on this site: http://www.indigipix.com/videotips.htm
Could be useful for those of you who don't have Photoshop or other alpha channel program to make one...

Here's the mask:
http://www.indigipix.com/images/letterbox.png

Hope this helps. Otherwise, some interesting info on this site...