telecine(redirected from pull-down sequence)
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telecineAn umbrella term for converting movie content to TV/video. Pronounced "tel-uh-sin-ee" and "tel-uh-scene," the process was used offline to convert countless movies to videotape for ultimate distribution via TV, cable and satellite networks. The original telecine process dealt only with film to video conversion, but when digital TVs emerged in the late 1990s, telecine algorithms were built into DVD players and TVs and include frame rate conversion, deinterlacing and upconversion.
Frame Rate Conversion
Movies are shot at 24 frames per second (fps), and although advanced digital TVs support 24 fps and can display movies natively, analog TVs and many digital TVs cannot. As a result, movie material must be converted to either 30 interlaced frames or 60 progressive frames by the DVD player or TV. Since 24 does not divide evenly into 60, four progressive movie frames are converted to five interlaced or 10 progressive frames. The process, known as "3:2 pulldown" or "2:3 pulldown," cannot create a flawless copy of the original movie because 24 does not divide evenly into 30 or 60 (see below).
Reverse the Pulldown
Although new movies on DVD are in the progressive 24 fps format (24p), older movies on videotape, which have previously undergone the telecine process and contain the 3:2 conversion, are sometimes recorded on DVDs. If a DVD player or digital TV supports "cadence correction," it reverses any 3:2 cadences it finds back to full film frames before it applies any telecine processes (see cadence correction). See deinterlace, upconvert, 120 Hz and DCDi.
|Convert to Interlaced Video|
|When converting to interlaced video, each movie frame is turned into two or three video fields, which creates an uneven distribution. In addition, a movie frame may get split into odd and even video frames (note red asterisks above "*"). As a result, unwanted artifacts are created if there is a dramatic change of color, brightness or motion from one movie frame to another. See 120 Hz.|
|Movies to Progressive Video|
|When converting to progressive scan at 60 fps (60p), each movie frame is turned into four or six video frames, creating an uneven distribution. However, unlike conversion to interlaced video, there is no chance of odd/even splitting in the final frames. Converting 24p to 60p is essentially a 6:4 pulldown process.|
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