yup, that's an extremely common format.
Basically you have three types of material, all three of which have been posted in this thread in fact. Firstly, is 4:3... bonified, either sourced like that (ie. old tv cameras, old cinema before ws) or open matte (the master before cropping to widescreen) or pan scan, that is cropped further from open matte. In the example of the first post that's pan scan *spit*
Next up is the joy to work with that is anamorphic. anamorphic is 16:9 content encoded at 4:3 because its much less wasteful than using black matting. In these cases your dvd player does the resizing for you on the fly, but because mpeg4 has the concept of encode resolution, that being the ability to store the AR in the headers properally without the need for black borders, you must appropriately setup your rip to be 16:9. Usually you
must uncheck the follow ITU button found on the gknot dash, as if you don't you will have an AR that is slightly off, as was the case with Dr P. rip.
Next up is your material, this is 16:9 material but encoded non-anamorphically, meaning that black matting is required to maintain AR with MPEG2... you need to crop this as MPEG4 doesn't need black matte to maintain AR (infact black matte is a big waste of space for mpeg4).
In terms of quality, anamorphic is the best because of a number of reasons, but mostly the largest part of the resolution is spent on the
real picture and not the borders amongst other things. anamorphic is what happens with higher quality masters, and with newer films.
Cheaper dvds opt for non-anamorphic encoding. You shouldn't be surprised, non-anamorphic DVDs are extremely common. i suspect if you own several widescreen dvds you'll find a lot of them are in non-anamorphic (it will say on the back of most dvd in fact). and the bottom of the barrel is usually 4:3.
