Ok I've been getting my head around this and if someone could confirm or deny my findings I would be really appreciative.
From FCP6 I am sending to compressor to create an mpeg1 & mpeg2 muxed file.
With mpeg1 I've found the only way inside of compressor to create the 16 by 9 look is to add padding top and bottom under the geometry tab in the inspector. This works but I would prefer a true 16 by 9 output without the letterboxing is this possible.
There is no way I can find of adjusting the dimensions (encoded pixels) or the Pixel Aspect which defaults to 4 by 3.
With mpeg2 I'm using a program stream to mux the audio. Under the Video Format tab of the inspector I can set the pixel aspect to 16 by 9 (sweet this I want). looking in the Geometry Tab of the inspector the dimensions are greyed out but it looks more like what I want with 720 wide and 576 high as the frame size, with Pixel Aspect as PAL CCIR (Animorphic).
This to me looks like the correct settings but after it has rendered I open it in Quicktime and it is 720 Wide and 404 pixels high. I have sent this to our distributer who releases them to station and he feed back was that it was correct, I found an article saying there were issues with quicktime and mpeg2 playback which looks like my file is correct but it isn't displaying at the full pixel size I would expect.
Really sorry if this is babbling if anyone could clarify this I'd be really appreciative.