Three-two pull down

In the United States and other countries where television uses the 59.94 Hz vertical scanning frequency, video is broadcast at 29.97 frame/s.

The term "pulldown" comes from the mechanical process of "pulling" (physically moving) the film downward within the film portion of the transport mechanism to advance it from one frame to the next at a repetitive rate (nominally 24 frames/s).

The second step of is distributing cinema frames into video fields.

For instance, a cycle that starts with film frame B yields a 3:2 pattern: B1-B2, B2-C1, C2-D1, D1-D2, A1-A2 or 3-2-3-2 or simply 3-2.

In fact, the "3-2" notation is misleading because according to SMPTE standards for every four-frame film sequence the first frame is scanned twice, not three times.

While this method has a slight bit more judder, it allows for easier upconversion (the dirty frame can be dropped without losing information) and a better overall compression when encoding.

Note that just fields are displayed—no frames hence no dirty frames—in interlaced displays such as on a CRT.

A pull down will slow the audio speed down by 0.1%, necessary for transferring film to video.