PAL Speed-up
Motion pictures are typically shot on film at 24 frames per second. When telecined and played back at PAL's standard of 25 frames per second, films run 4% faster. This also applies to most TV series that are shot on film or digital 24p. Unlike NTSC's telecine system, which uses 3:2 pulldown to convert the 24 frames per second to the 30 fps frame rate, PAL speed-up results in the telecined video running 4% shorter than the original film as well as the equivalent NTSC telecined video.
Depending on the sound system in use, it also slightly increases the pitch of the soundtrack by 70.67 cents (0.7067 of a semitone). More recently, digital conversion methods have used algorithms which preserve the original pitch of the soundtrack, although the frame rate conversion still results in faster playback.
Conversion methods exist that can convert 24 frames per second video to 25 frames per second with no speed increase, however image quality suffers when conversions of this type are used. This method is most commonly employed through conversions done digitally (i.e. using a computer and software like VirtualDub), and is employed in situations where the importance of preserving the speed of the video outweighs the need for image quality.
Many movie enthusiasts prefer PAL over NTSC despite the former's speed-up, because the latter results in telecine judder, a visual distortion not present in PAL sped-up video. This is not an issue on modern upconverting DVD players and PCs, as they play back 23.97 frame/s–encoded video at its true frame rate, without 3:2 pulldown.
Naturally, PAL speed-up does not occur on native 25 fps video, such as European TV-series or movies that are shot on video instead of film.
Software which corrects the speed-up is available for those viewing 576i DVD films on their computers, WinDVD's "PAL TruSpeed" being the most ubiquitous. However, this method involves resampling the soundtrack(s), which results in a slight decrease in audio quality. The echo/audio balance issue can be resolved by re-adjusting the playback pitch (located in the Audio Effect tab) from normal to low and back to normal again.
Read more about this topic: 576i
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