With PAL speed-up, film material (24 frames per second) is expedited slightly to 25 frames per second. The result is a 4 percent reduction in running time and a change in the pitch. The purpose of speed-up us to adjust the image frequency to create a PAL-compatible signal (50Hz).
The 25 frames per second can be segmented very easily. A full frame is divided into exactly two half frames. After this process (2:2 pulldown), 50 half frames per second are present; these can be transmitted or saved to DVD without any difficulty. Since segmentation is linear, the impression of movement is not changed from the original 24 frames per second signal.
PAL- speed-up is also used for transmitting PAL material via HDTV. However speed-up is generally not used for relevant material on HD DVD and Blu-ray.