Interlacing and field order

Interlacing is a technique developed for transmitting television signals using limited bandwidth. In an interlaced system, only half the number of horizontal lines for each frame of video are transmitted at a time. Because of the speed of transmission, the afterglow of displays, and the persistence of vision, the viewer perceives each frame in full resolution. All of the analog television standards use interlacing. Digital television standards include both interlaced and noninterlaced varieties. Typically, interlaced signals are generated from interlaced scanning, whereas noninterlaced signals are generated from progressive scanning.

Chris Pirazzi provides technical details of fields and interlacing on Lurker's Guide to Video website.

Trish and Chris Meyer provide various materials about interlacing, field order, field dominance, field rendering, and separating fields:

• For information about exporting a PsF (progressive segmented frame) video file from Premiere Pro via Adobe Media Encoder, see this thread on the Premiere Pro user-to-user forum.
  

• More about PsF video.

About field dominance and field reversal

Fields in a clip can become reversed from the state in which they were originally acquired in any of the following ways:

• The video capture card used to capture the footage is set to the field dominance opposite that of the source device,

• The editing or animation software that last rendered the clip had the field dominance set opposite that of the original clip,

• The clip is set to play backward.

Create interlaced or non-interlaced clips

Ordinarily, individual interlaced fields aren’t apparent to a viewer. However, playing a clip in slow-motion, creating a freeze frame, or exporting a field as a still image can make a single field distinguishable. For these purposes, it is sometimes preferable to deinterlace the image—that is, replace pairs of consecutive interlaced fields with single non-interlaced frames. Premiere Pro can generate these new non-interlaced frames from the fields in one or two source frames.

One unwanted interlacing artifact arises from a mismatch between the field order of a clip, and that of a sequence. Field order specifies whether the field of odd-numbered lines (the upper field) or the field of even-numbered lines (the lower field) is drawn first. For example, placing a clip with upper field order in a sequence using lower field order could result in jerky playback. You can correct this problem by reversing the field order of the clip so that it matches that of the project. You use the Reverse Field Dominance option to reverse the field order.

Change the field order of a clip

In the Project panel, you can change the field order of all instances of a clip in all sequences of a project.

Using multiselection for field options

You can apply the field dominance to multiple clips in the timeline (or project panel). The dialog can be used for any valid clip or valid track items that are not nested sequences or have no closed captioning that are in the timeline. Mixed states are also supported for field dominance. If a selection has mixed states for the field dominance field then then the checkbox displays a mixed state UI. If you press OK without changing it, the selected clip states get maintained. However, mixed states are not supported for the field processing radio buttons. If the Field Processing field has mixed states, Premiere Pro displays the state of the first selected item in the Timeline or Project panel. If you press OK without changing anything, the state gets applied to all valid selected clips, overwriting any previous mixed state.