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What is Interlacing.

What is interlacing

TV video signal is interlaced

A TV video signal is interlaced, meaning each full screen of information is actually made up of two separate fields—the odd field and the even field. First, the odd lines are painted on the screen. Then, before the odd lines fade, the even lines are painted in between the odd lines. This all happens faster than the human eye can perceive.

Computer signal is noninterlaced

In contrast, the computer signal is noninterlaced—the horizontal lines are painted progressively, left to right, top to bottom, in a single pass. So the flickering problem you get in interlaced TV does not exist in computer video.

Line doublers and quadruplers were developed to convert interlaced TV signals to noninterlaced computer signals. However, when compared to line doublers or quadruplers, both video scalers offer several clear advantages:

  • When using a video scaler, a projector or display device is not forced to crop, distort or further process the image in order to display it.
  • The video scalers can provide outputs at multiple refresh rates.
    • For example, a video scaler can display converted PAL video on projectors that don’t support 50-Hz refresh rates. Or converted video can be displayed at 75 Hz, eliminating flicker.
  • The video scalers are not limited to a 4:3 aspect ratio—they can display letterbox-formatted video, too (16:9 aspect ratio).
  • With a video scaler, projectors and displays no longer have to reprocess the output of a doubler or quadrupler to match their