Line doubler
Encyclopedia
A line doubler is a device used to deinterlace video signals
Video
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...

 prior to display.

The main function of a line doubler is to take an interlaced video source which consists of a two-field frame and create a progressive scan
Progressive scan
Progressive scanning is a way of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence...

 (single non-interlaced frame) output. This can produce a brighter, smoother, higher-resolution picture. The additional lines provide greater light output and makes for an image that is smoother and more film like. CRT
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...

-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. Most other types of display, including LCD
Liquid crystal display
A liquid crystal display is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals . LCs do not emit light directly....

, plasma
Plasma display
A plasma display panel is a type of flat panel display common to large TV displays or larger. They are called "plasma" displays because the technology utilizes small cells containing electrically charged ionized gases, or what are in essence chambers more commonly known as fluorescent...

 and DLP, generally cannot accept an interlaced signal directly, and therefore some kind of line doubler must be used. This is usually built in and transparent to the user. Progressive scan DVD players also feature a line doubler.

The most basic and literal way to double lines is to repeat each scanline, though the results of this are generally very crude. Most line doublers use digital interpolation to recreate the missing lines in an interlaced signal, and the resulting quality depends on the technique used. Generally a line doubler will only interpolate within a single field, rather than merging information from adjacent fields, to preserve the smoothness of motion, resulting in a frame rate equal to the field rate (i.e. a 60i signal would be converted to 60p.) Some line doublers are capable of using the former technique in moving areas and the latter in static areas, which improves overall sharpness.

Line doublers have been replaced recently by video scaler
Video scaler
A video scaler is a device for converting video signals from one size or resolution to another: usually "upscaling" or "upconverting" a video signal from a low resolution to one of higher resolution A video scaler is a device for converting video signals from one size or resolution to another:...

s which incorporate 3:2 pulldown removal and the ability to scale the image to the various screen resolutions used on LCD
TFT LCD
Thin film transistor liquid crystal display is a variant of liquid crystal display which uses thin-film transistor technology to improve image quality . TFT LCD is one type of Active matrix LCD, though all LCD-screens are based on TFT active matrix addressing...

, plasma display
Plasma display
A plasma display panel is a type of flat panel display common to large TV displays or larger. They are called "plasma" displays because the technology utilizes small cells containing electrically charged ionized gases, or what are in essence chambers more commonly known as fluorescent...

 and DLP projectors and displays.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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