HD

1036 Part XIII Appendixes
About Progressive Scanning
Progressive scanning is much simpler than interlaced scanning: each line is scanned
consecutively until a complete frame is drawn. Computer monitors and many recent
high definition televisions use progressive scanning.
Here are some significant facts about interlaced and progressive scanning methods:
 Interlacing provides twice the perceived frame rate with only half the recording or
transmission requirements.
 Progressive scanning is preferred when interlacing artifacts (such as thin flickering
horizontal lines) would be unacceptable. Progressive images are often considered
more film-like because there are no flickering interlacing artifacts.
 Computer displays are almost always scanned progressively.
 NTSC and PAL televisions always use interlaced scanning.
 Many high definition video cameras can record progressive frames.
 Video destined for computer-only use, such as web video, should always be
made progressive.
About Field Dominance
Field dominance is an issue when recording and playing back interlaced video material.
With progressive video, there is only one way to play back a video frame: Start at line 1
and scan until you reach the last line. With interlaced video, the video player must
choose whether to scan the odd lines first, or the even lines. In other words, each time
a frame is displayed, which field should be played first, field 1 or 2? This is totally
dependent on which field was recorded first.
Each field is a snapshot in time, so if field 1 is recorded earlier in time than field 2, field
1 must be played back before field 2. If the wrong field order is chosen, each frame’s
fields plays backward in time, even though each frame as a whole still moves forward.
The effect is a very noticeable stutter happening 60 (NTSC) or 50 (PAL) times a second.
Each piece of video equipment and each video format has a preferred field dominance.
This prevents you from editing two field 2s back to back, and makes sure that each
field is played back in the right order.
Setting Field Dominance in Final Cut Express HD
In Final Cut Express HD, the field dominance of clips must match the sequence field
dominance. Otherwise, the fields stutter during playback because each pair of fields
plays back in the wrong order. For example, DV NTSC and DV PAL always have a field
dominance of Lower (Even). If you’re working in a sequence and you see that imported
clips are flickering, check to make sure the field dominance of those additional clips
matches the field dominance of your edited sequence.
Important: You need to change the Field Dominance setting of your projects and
sequences only if you change your video hardware setup.