A line doubler is a device or algorithm used to

deinterlace Deinterlacing is the process of converting interlaced video into a non-interlaced or progressive form. Interlaced video signals are commonly found in analog television, digital television (HDTV) when in the 1080i format, some DVD titles, and a ...

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 used ...

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

NTSC The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...

analogue video Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) syste ...

signal or 50 fields of a PAL 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. Liquid crystals do not emit light directly but in ...

displays,

plasma displays A plasma display panel (PDP) is a type of flat panel display that uses small cells containing plasma: ionized gas that responds to electric fields. Plasma televisions were the first large (over 32 inches diagonal) flat panel displays to be releas ...

, DLP projectors, and OLED displays, 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. 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 A scan line (also scanline) is one line, or row, in a raster scanning pattern, such as a line of video on a cathode ray tube (CRT) display of a television set or computer monitor. On CRT screens the horizontal scan lines are visually discernible, ...

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. It is worth noting that even if a line doubler employs the merging method it cannot be considered an inverse

telecine Telecine ( or ) 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 the post-production process. Telecine enables a motion picture, captured originally on f ...

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 which 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 High ...

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 A video game console is an electronic device that outputs a video signal or image to display a video game that can be played with a game controller. These may be home consoles, which are generally placed in a permanent location connected to a t ...

and have found popularity among

retro gaming Retrogaming, also known as classic gaming and old school gaming, is the current playing and collection of obsolete personal computers, consoles, and video games. Usually, retrogaming is based upon systems that are outmoded or discontinued, alt ...

enthusiasts due to their minimal contribution to

input lag Input lag or input latency is the amount of time that passes between sending an electrical signal and the occurrence of a corresponding action. In video games the term is often used to describe any latency between an input and either the game or ...

References

Film and video technology {{film-tech-stub

See also

References