Why do some DVD discs require side flipping?
The basic types of DVD are referred to by a rough approximation of their capacity in gigabytes. In draft versions of the specification, DVD-5 indeed held five gigabytes, but some parameters had to be changed later on to address technical challenges, so the capacity decreased.
The 12 cm type is a standard DVD, and the 8 cm variety is known as a mini-DVD. The capacity by surface (MiB/cm²) varies from 6.92MiB/cm² in the DVD-1 to 18.0 MiB/cm² in the DVD-18.
Although DVD dual-layer technology allows more than four hours of 3.3 for broadcast from single side, some films are split over two sides of a disc, requiring that the disc be flipped partway through. Most "flipper" discs exist because of producers who are too lazy to optimize the compression or make a dual-layer disc.
Better picture quality is a cheap excuse for increasing the data rate; in many cases the video will look better if carefully encoded at a lower bit rate. Quite few players can switch sides automatically, but it's not required because most movies are less than four hours and can easily adapt to a dual-layer (RSDL).
Note: A flipper is not the same as a disc with a widescreen version on one side and a pan & scan version or supplements on the other.
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