A line doubler is a device or algorithm used to deinterlace video signals prior to display on a

progressive scan Progressive scanning (alternatively referred to as noninterlaced scanning) is a format of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence. This is in contrast to interlaced video us ...

display.

Function

The main function of a deinterlacer is to take an interlaced video frame which consists of 60 two-field interlaced fields of an

NTSC NTSC (from National Television System Committee) is the first American standard for analog television, published and adopted in 1941. In 1961, it was assigned the designation System M. It is also known as EIA standard 170. In 1953, a second ...

analogue video signal or 50 fields of a

PAL Phase Alternating Line (PAL) is a color encoding system for analog television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields (25 ...

signal, and create a progressive scan output. Cathode ray tube (CRT) based displays (both direct-view and projection) are capable of directly displaying both interlaced and progressive video, and therefore the line-doubling process is an optional step to enhance picture quality. Other types of displays are fixed pixel displays, including

LCD A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers to display information. Liquid crystals do not em ...

displays,

plasma displays A plasma display panel is a type of flat-panel display that uses small cells containing Plasma (physics), plasma: Ionization, ionized gas that responds to electric fields. Plasma televisions were the first large (over diagonal) flat-panel displ ...

, DLP projectors, and

OLED An organic light-emitting diode (OLED), also known as organic electroluminescent (organic EL) diode, is a type of light-emitting diode (LED) in which the emissive electroluminescent layer is an organic compound film that emits light in respon ...

displays, which are not scanned from top left to bottom right corners and generally cannot accept an interlaced signal ''directly'', and so require some kind of

deinterlacing Deinterlacing is the process of converting interlaced video into a non-interlaced or Progressive scan, progressive form. Interlaced video signals are commonly found in analog television, VHS, Laserdisc, digital television (HDTV) when in the 1080 ...

. Often, this is built in to the display and transparent to the user. Progressive scan DVD players also feature a deinterlacer. Line doubling is a literal way to deinterlace an interlaced signal, although the method used may differ. Typically the use of the term "line doubler" refers to a simple repeat of a scanline so that the lines in a field match the lines of a frame. However, this produces a "bobbing" effect and has led to this method of deinterlacing being referred to as "bob deinterlacing". An iteration on bob deinterlacing is to average adjacent scanlines of two frames which can produce a smoother, although blurrier, image. This technique is referred to as "blend deinterlacing". Some line doublers are capable of using the former technique in moving areas and the latter in static areas (to avoid the "bob" effect), which improves overall sharpness. Even if a line doubler employs the merging method it cannot be considered an inverse

telecine Telecine ( or ), or TK, is the process of transferring film into video and is performed in a color suite. The term is also used to refer to the equipment used in this post-production process. Telecine enables a motion picture, captured origi ...

device if a frame rate of 60p other than the original 24p is obtained. From this aspect of view some hyped progressive scan technologies (including Pioneer's PureCinema Progressive Scan) bearing an inverse telecine insignia are thus overstated. Line doublers have been replaced recently by

video scaler A video scaler is a system that converts video signals from one display resolution to another; typically, scalers are used to convert a signal from a lower resolution (such as 480p standard definition) to a higher resolution (such as 1080i hig ...

s which incorporate 3:2 pulldown removal and the ability to scale the image to the various screen resolutions used on modern projectors and displays. However, line doublers such as the Open Source Scan Converter have been developed to convert signals from older video game consoles and have found popularity among

retro gaming Retro gaming, also known as classic gaming and old school gaming, is the playing and collection of computer game, personal computers, video game console, consoles, and video games from earlier decades. Usually, retro gaming is based upon syste ...

enthusiasts due to their minimal contribution to input lag.

References

Film and video technology {{film-tech-stub

Function

See also

References