Interlaced Video - Deinterlacing

Deinterlacing

Although CRTs and ALiS plasma panels can display interlaced video directly, modern computer video displays and TV sets are mostly based on LCD technology, which utilizes progressive scanning.

To allow displaying interlaced video on a progressive scan display, a process called deinterlacing is required; however it is not perfect, and it generally results in a lower resolution and various artifacts, particularly in areas with objects in motion. In order to provide the best possible picture quality for interlaced video signals, very expensive and complex devices and algorithms should be used.

For television displays, deinterlacing systems are integrated into progressive scan TV sets which accept interlaced signal, such as broadcast SDTV signal.

Most modern computer monitors do not support interlaced video besides some legacy text-only display modes; playing back interlaced video on a computer display requires some form of deinterlacing in the software player, which often uses very simple methods for interlacing so interlaced video will have visible artifacts when it is displayed on computer systems. Computer systems are frequently used to edit video, and the disparity between computer video display systems and television signal formats means that the video content being edited cannot be viewed properly unless separate video display hardware is used.

Current manufacture TV sets employ a system of intelligently extrapolating the extra information that would be present in a progressive signal entirely from an interlaced original. In theory: this should simply be a problem of applying the appropriate algorithms to the interlaced signal as all the information needed should be present in that signal. In practice: the results are, at present, somewhat variable and are dependent on the quality of the input signal and the amount of processing power applied to the conversion. The biggest impediment, at present, is the artifacts present in the lower quality interlaced signals (generally broadcast video), as these are not consistent from field to field. On the other hand, high bit rate interlaced signals such as from HD camcorders operating in their highest bit rate mode work surprisingly well.