interlacer

An interlacer is a device or process used in video technology to increase the perceived frame rate or resolution of a display. It achieves this by splitting a full frame into two fields, one containing the odd-numbered scan lines and the other containing the even-numbered scan lines. These fields are then displayed sequentially, creating the illusion of a smoother or more detailed image than would be possible with a single progressive scan.

Historically, interlacing was developed to overcome limitations in broadcast television bandwidth and display technology. By sending only half the lines at a time, a higher frame rate could be achieved with the same amount of data. This resulted in less flicker and smoother motion for viewers. Common examples of interlaced video standards include NTSC and PAL.

Modern displays, particularly high-definition televisions and computer monitors, predominantly use progressive scanning. In progressive scanning, all scan lines of a frame are displayed at once. This eliminates the artifacts associated with interlacing, such as "combing" or "jagged" lines, which can become noticeable during fast motion. However, interlaced content is still common, and many displays include deinterlacing circuits to convert interlaced signals into a progressive format for display. Deinterlacing algorithms attempt to reconstruct the missing lines from each field to create a full progressive frame, though the effectiveness of these algorithms can vary.