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linedoubler

The classic television standards work with interlaced scanning and two fields, each of which has only 312.5 lines in the PAL television standard. This has a negative effect on large- area displays and projections in that the relative speed of the projected light beam decreases with the size of the projection screen. In addition, the low line structure is disturbing because the dark intermediate lines of the respective other field are visible as black lines.

These limitations can be eliminated by doubling the number of lines. The corresponding devices work with video processors and are called linedoublers or de-interlacers because they cancel the interlacing.

Linedoubler, photo: Philips

Linedoubler, photo: Philips

There are three technical approaches: The line insert, the interpolation and the field insert. With line insert, the line content of a line is repeated; the second line therefore has the same line content as the first. With interpolation, the video processor calculates the intermediate lines from the average value between two lines of a field. The interpolation technique is suitable for moving scenes.

For static video sequences without large motion dynamics, the field insert technique is used. This combines two fields: the odd lines of the first field with the even lines of the following field. With all techniques, the number of lines doubles from 312.5 lines per field to 625 lines.

Informations:
Englisch: linedoubler
Updated at: 26.11.2008
#Words: 214
Links: television (TV), phase alternation line (TV) (PAL), television standard, area, light
Translations: DE
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