Image Processing Reference
In-Depth Information
24 FPS film
30 FPS (60 field) NTSC video
Figure 33-6 Telecine pulldown.
Inverse Telecine to Remove Extra Frames
This technique is relevant to those situations when you are removing the interlaced arti-
facts from footage that was originated on film. Note that this is relevant only to NTSC
525i30 and it is not required on PAL 625i25 versions of movie film footage.
When converting 24-fps movie film to the near 30 fps used on NTSC TV broadcasts,
some frames are scanned more than others to increase the number of fields.
This is easiest if two media are viewed side by side, as shown in Figure 33-6.
The first frame of the film is imposed on two fields of video while the second frame
is imposed on three fields. This 2-3 pattern is repeated in a cycling pattern of five fields,
distributing them uniformly across an odd and even field structure. The two formats
are in synchronization every 10 fields, during which time only 4 frames of movie film have
passed through the gate. This cyclic pattern is called the cadence, and it is illustrated in
Figure 33-7.
One frame of cadence
Figure 33-7 Telecine cadence.
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