Frame

Video is stored in "frames", which are snapshot images of a moving picture. These are typically captured (and shown) at a fixed rate, for example, 24 frames per second (fps). Television in the US, under the NTSC standard, is 29.97 frames per second.[1]

Old-fashioned movies, such as World War I newsreels, were shot at a slower frame rate (such as 16 frames per second). When these are added into a modern 24 fps movie, often they are played at the same frame rate, which speeds everything up noticeably. It is possible, of course, to program a computer to play frames at a variable rate, so that the old 16 fps footage would appear at normal speed, and even 24 fps movies could play at 24 frames per second, but to save money or development time, this is rarely done. It seems to be easier to convert 24 fps to 29.97 fps by playing one frame twice and the next frame 3 times. This is done using a process named 2:3 pulldown.[2]

## References[edit]

1. ↑ Time codes
2. ↑ Pulldown Explained