About 3:2 and 24pA pulldown

When you transfer 24-fps film to 29.97-fps video, you use a process called 3:2 pulldown, in which the film frames are distributed across video fields in a repeating 3:2 pattern. The first frame of film is copied to fields 1 and 2 of the first frame of video, and also to field 1 of the second video frame. The second frame of film is then spread across the next two fields of video—field 2 of the second video frame and field 1 of the third frame of video. This 3:2 pattern is repeated until four frames of film are spread over five frames of video, and then the pattern is repeated.

The 3:2 pulldown process results in whole frames (represented by a W) and split-field frames (represented by an S). The three whole video frames contain two fields from the same film frame. The remaining two split-field frames contain a video frame from two different film frames. The two split-field frames are always adjacent to each other.

The phase of 3:2 pulldown refers to the point at which the two split-field frames fall within the first five frames of the footage. Phase occurs as a result of two conversions that happen during 3:2 pulldown: 24-fps film is redistributed through 30-fps video, so each of four frames of 24-fps film is spread out over five frames of 30 (29.97)-fps video. First, the film is slowed down 0.1% to match the speed difference between 29.97 fps and 30 fps. Next, each film frame is repeated in a special pattern and mated to fields of video.

When you apply 3:2 pulldown to footage, one frame of the film (A) is separated into two or three interlaced video fields (B) which are grouped into video frames containing two fields each.

It’s important to remove 3:2 pulldown from video footage that was originally film, so that effects you add synchronize perfectly with the original frame rate of film. Removing 3:2 pulldown reduces the frame rate by 1/5: from 30 to 24 fps or from 29.97 to 23.976 fps. Reducing the frame rate also reduces the number of frames you have to change.

Adobe Premiere Pro also supports Panasonic DVX100 24p DV camera pulldown, called 24p Advance (24pA). This format is used by some cameras to capture 23.976 progressive-scan imagery using standard DV tapes.

For more information about 24p pulldown schemes, see the video tutorial, Digital Video Principals: Converting 24 fps video, on the lynda.com website.