In the REF Menu you can set your video mode -- i.e. 576, 50 hz and then you can set either 4x3 or 16x9.
Note that the switcher is not "aspectizing" the video. In SD both 16x9 and 4x3 use the same number of pixels its just that they are treated as non-square. Your devices like cameras and content playback need to be set for 16x9. The switcher just processes the pixels. What we need to be aware of the format for is the shape of wipe patterns to make sure a circle is a circle and not an oval. ;)
If you do have some sources that are SD 4x3 you can use the FCFS as an aspect conversion tool. just turn one on for the source and set it's aspect to Zoom or Pillar -- if you want to have it stretch don't bother using and FCFS as it will look the same as just letting the input get processed normally.
Les
#Carbonite