Digital video is a representation of moving visual images in the form of encoded digital data. This is in contrast to analog video, which represents moving visual images with analog signals. Digital video comprises a series digital images displayed in rapid succession. In contrast, one of the key analog video methods, motion picture film, uses a series of photographs which are projected in rapid succession. Standard film stocks such as 16 mm and 35 mm record at 24 frames per second. For video, there are two frame rate standards: NTSC, at about 30 frames per second, and PAL at 25 frames per second.