A good easy to follow guide for changing the menu aspect ratio in the IFO files so a menu generated at 4:3 aspect displays at 16:9. The technique has been discussed several times, most recently in http://forums.vso-software.fr/menu-sizi ... 11541.html
The background does have to have a 16:9 = 1.778 aspect though or distortion will be introduced
There is a way to change the aspect ratio (AR) of a menu from 4:3 to 16:9 so that a 16:9 background picture or video can be used without distortion or the need to crop, pad, or edit the picture or video.
, there is no way around that.
A snapshot of a menu using a 2.25 AR background and with the aspect changed to 16:9 in the IFO, is shown below. Note that the menu does display in 16:9, but the rectangle and ellipses in the midlle are supposed to be a square and circles as shown in the small thumbnail at upper left. Preparing the background, as discussed in the first post above, so it has a 16:9 aspect, will prevent that distortion.
Changing the menu AR in the IFO is sufficient for many standalone DVD players, but may not be enough for some as pointed out by toaddub in the above thread link.