Three-two pull down

3:2 pull-down is a process for the conversion of a film signal in an NTSC television signal.

Since the NTSC standard operates at 29.97 frames per second ( fps), movies are shot at 24 fps but, the conversion of a film signal into an NTSC television signal in two steps must be performed. First, the film signal must be slowed to about 0.1 % (more precisely: the 1001 seconds, 1000 seconds of original footage playing). This difference is so small that it is unnoticeable to a viewer. This produces for the film signal is now a speed of 23,976 frames per second and thus are 4 frames in the film signal 5 frames in the NTSC signal over:

The four individual images will be stretched in the second step with the aid of the interlaced method to five images. A full image is decomposed into fields. The second frame, the first frame is shown two fields long, three fields long, the third frame again two fields long, etc. This results in the desired 59.94 fields ( = 29.97: For every cinema screen two or three fields are generated alternately images) per second for NTSC. For settings with a fixed camera or on fast pans, this is as good as not seen in slow panning shots, however, results in a noticeable judder in motion.

For digital reception or playback devices ( digital TV, DVD, Video CD ), the 3:2 pull-down usually performed only in the terminal, the actual digital data stream contains 23,976 frames per second and a flag which the pull-down in the terminal causes. This is because they must be in two from different origin - frames "mixed" frames (both 3rd and 4th picture the group of five ), which result from the pull-down in any full-screen group of five, compress well. In the reverse case, the storage of a video signal that is caused by pull-down, so the pull-down an Inverse Telecine should therefore in the interest of good data compression be performed first, be undone. Most digital video recorder for NTSC signals detect pull-down automatically and then run before storage (eg on an integrated hard drive ) an inverse telecine by.