telecine (redirected from Ivtc)

The technique for converting movie film to TV/video. Pronounced "tel-uh-sin-ee," "tel-uh-sin-uh" or "tel-uh-scene." Because film runs at 24 frames per second (fps), and NTSC video runs at 30 fps, telecine inserts duplicate frames into the video to make up the difference. Telecine has been used to convert countless movies to videotape for ultimate distribution via TV, cable and satellite networks.

In the video editing studio, when a TV monitor is used to observe the changes being made to film-based material, telecine creates a compatible format for the TV (the process may be reversed when the editing is finished). Lastly, the telecine function is built into DVD players to convert 24 fps source material to the TV format.

Because it is time consuming and costly to do the telecine conversion, videotaped movies that have already undergone the telecine process are sometimes used as the source for DVDs. As a result, DVD content may be comprised of 30 interlaced fps or 24 progressive fps. See cadence correction.

Telecine Cadences: 2:3 and 3:2
Telecine uses "2:3 pulldown" and "3:2 pulldown" techniques, which take four film frames and create 10 interlaced video half frames, known as "fields." With 2:3 pulldown, the first film frame is turned into two fields; the next into three, and so on. With 3:2 pulldown, the first film frame is turned into three fields, then two.

Pulldown Cadences Produce Artifacts

With both pulldown methods, some video frames wind up with content from two film frames (marked "*" in the illustrations). As a result, the telecine process can produce unwanted artifacts when there is a dramatic change of color, brightness or motion from one film frame to another.

Not Perfect
As noted in the illustrations above, the pulldown process cannot create a flawless copy of the original movie because interlaced video frames display odd lines in one field and even lines in the next. If the film frame gets split into odd and even lines in the video frame, artifacts may result. The greater the change between film frames, the more artifacts.

Reverse the Process to Deinterlace
When interlaced video is deinterlaced (converted to progressive scan), the 2:3 and 3:2 cadences found in the source material are reversed back to full film frames before deinterlacing takes place. This happens if the DVD, TV or software in the computer supports film mode detection that can discover the telecine cadences (see cadence correction, DCDi and deinterlace).