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Interlaced Terminology | Dictionary | Explanation As in a nuke reason: A movie release is interlaced when the video doesn't refresh properly. There are black lines on movement as the field order is incorrect. To understand this, read the explanation about interlaced and non-interlaced by Adobe Systems: Analog or digital video can be classified as interlaced or non-interlaced (progressive scan). Video programs using the NTSC, PAL, and SECAM standards are interlaced, where each frame consists of two fields displayed in two passes. Most personal computers display using progressive scan, in which all lines in a frame are displayed in one pass from top to bottom before the next frame appears. 
In interlaced video, a frame is divided into two fields. Each field contains every other horizontal line in the frame. A TV displays the first field of alternating lines over the entire screen, and then displays the second field to fill in the alternating gaps left by the first field. One NTSC video frame, displayed approximately every 1/30th of a second, contains two interlaced fields, displayed approximately every 1/60th of a second each. PAL and SECAM video frames display at 1/25 of a second and contain two interlaced fields displayed 1/50th of a second each. The field that contains the topmost scan line in the frame is called the upper field, and the other field is called the lower field. When playing back or exporting to interlaced video, make sure the field order you specify matches the receiving system, otherwise motion may appear stuttered and edges of objects in the frame may break up with a comb-like appearance. 
Interlaced video describes a frame with two passes of alternating scan lines. Progressive-scan video describes a frame with one pass of sequential scan lines Television signals are interlaced because of problems with early television sets. The screen phosphors displaying the image faded too quickly, so that when a early television displayed a picture using progressive scan, the picture was already dark at the top of the screen before the last scan line was displayed. By addressing this problem, interlaced video became one of the world’s television standards. Even with current technology, interlaced video is still useful because it can increase the perceived resolution of motion using less bandwidth than progressive scan. By the time computers began using video monitors, the problems with phosphor fading and display rates had been solved, making progressive scan practical for computer monitors. Motion-picture film, while not technically video, is similar to progressive scan because it displays an entire frame at once. Interlacing is a characteristic of capturing and displaying clips, not a structural component of file formats or media. For example, it is possible to play back a digitized NTSC movie (interlaced) on a Mac OS or Windows monitor (progressive scan), or display a scanned 35mm film frame (progressive scan) on an NTSC video monitor (interlaced). However, progressive-scan video provides better final picture quality when editing with filters and effects that affect motion, including rotating a frame or compositing live-action video with special effects. In addition, thin lines and small text are more likely to flicker on an interlaced display. When you diagnose problems related to interlaced fields, view the clips on an interlaced television display, because diagnosing field problems on a progressive-scan monitor is unreliable. If you plan to slow down or hold a frame in a clip, you may want to prevent flickering or visual stuttering by deinterlacing its frames, which converts the interlaced fields into complete frames. In the opposite case, if you’re using progressive-scan source clips (such as motion-picture film or computer animation) in a program intended for an interlaced medium such as television, you can separate frames into fields using a process known as field rendering so that motion and effects are properly interlaced. For information about deinterlacing, see Freezing a video frame. |
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