Not quite! I run it through Streamclip using the export to other formats option. For the frame size I choose "Other" the values you enter here depend on how much you need to crop off.

I start by working out how wide the frame should be. In the case of my '97SE LD captures there was 5 square pixels of analogue blanking on each side so you do the following:

768 (PAL resolution in square pixels rather then CCIR.601)
-5 (Left Hand Side)
-5 (Right Hand Side)
= 758 square pixels

So we have determined that the width of our frame will be 758 so to work out what the height should be we do:

758/16 = 47.375
47.375 x 9 = 426.375 (Round this down to 426)

So our final frame should be 426 square pixels heigh, to work out how much to crop off you do 576 (original height) - 426 = 150

So we need to crop of 150 pixels which is 75 off the top and 75 off the bottom. I enter the crop values in the crop section of the export window, choosing to crop the source from the drop down menu. I then enter the width and height values I have worked out and away you go.

I find trial and error using the preview button in the export window is the best way to work out how much cropping is needed on the left and right hand sides. You can also use the preview button to check the crop settings for the top/bottom edges, as the picture is not always perfectly central and so you might need to take more off the top then bottom and vice versa.

I apologise if this seems really complicated, I am the first to admit I am rubbish at explaining how to do things over the web! :(