Process that takes place when a film is being transferred to NTSC video. Cinema film is in 24 frames per second (fps) format worldwide; NTSC works with 30 half frames, or 30 fps. A PAL picture has 25 half frames, or 25 fps. As a result, the video transfer process is different for both norms.
With NTSC, two or three half frames are created from every cinema frame. The result is then slowed slightly to form the 60 half frames that make up the NTSC norm. This causes motion errors to arise in the video version, but these are not noticed by viewers unless they have been taught how to see them.
With PAL, the process is different and rather takes the form of a "2/2 pulldown": here, the film is sped up by about 4%, so that the material runs at 25 instead of 24 frames per second. The expedited images are broken down into two half frames each ("2/2 pulldown"), or 50 per second. The video version is therefore about 5 minutes shorter than the original depending on the length of the film. The compression raises the frequencies of dialogue and music slightly, but in such a small measure that it could only be noticed by a viewer with a very trained ear.
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