Hi all

I have a video project in vegas that runs for 2 mins 48 seconds at 25fps. When I export as an AVI (div-x encoded) it runs for 2 mins 48 seconds. Now when I export it as an Mpeg 1 file at 25 fps it comes out as 2 mins 20 seconds long. Why is it speeding up? However, when I render it as an mpeg 1 at 30 fps it comes out at the right length of 2mins 48secs. Why is this so?