Cropping, commonly known as black-bar removal is used to remove black borders from DVD video content.
Because DVDs were invented when Wide screen was not commonplace, the official DVD standard did not account for the different screen size of the video content in this format. To produce wide-screen content that conforms to the official square-screen DVD standard, black padding is added to top and bottom of the video, which effectively makes the movie screen size the proper size. Recent DVD players are capable to detect these black borders, and if they are set up to display content on a wide-screen TV, they can remove these borders to fill the screen.
When you convert a movie, these black borders are, because they are part of the video, actually converted as well. When we remove these black borders, the video section itself ends up smaller, and thus the quality is improved throughout the section that is left. What many people do not realize is that if you have a file that does not have black borders, but you play it on a device that uses a different screen kind (wide screen movie on a square screen device for example) the video player itself actually adds black borders to the video to fill the screen. Because of this, DVD Catalyst offers a couple of different kinds of black bar removal options.
*No cropping. This leaves the video section unmodified. If there are black borders as actual part of the video, they will also end up in the created video file.
*Remove black bars from file. This removes the video padding from the original file during conversion, but leaves the actual video section of the video unmodified. When watched on a device with a different screen kind, it will still have black borders (unless you use the Zoom function on the player itself)
*Remove black bars from device. This removes the video padding from the original file during conversion, but will also cut of parts of the sides of the actual video part based on the selected screen size. This setting makes any kind of movie full screen on the selected screen size in the device profile, regardless of the screen kind. A wide-screen movie on a square-screen device, or a square-screen movie on a wide-screen device, it will always end up full screen.
*Fullscreen stretch. This removes the black borders from the original file during conversion, and then stretches the video to make it full screen on the selected device profile. You will not loose anything from the actual video content, but the video will look different, and depending on the selected device even distorted. A widescreen movie on a square screen device will have people appear longer and thinner, and a square screen movie on a wide screen device will have people look short and stubby. This setting is only recommended if you are converting video content of the same kind as the device screen.
*Add black bars to fit resolution. Required for PlayStation 3 and PlayStation Portable HQ profiles. This setting adds black padding the the video to make it fit the exact selected resolution. Some devices (PS3, PSP) can only play content of a very specific screen size, and will not play it otherwise. The normal PSP profiles work fine with every crop-setting, however the HQ profile can only be played if it is exactly 720×480. anything bigger than 480×272 and different from 720×480 will not play.
More info, including screenshots, can be found in the User Guide of DVD Catalyst 3