Dot crawl reduction in NTSC/PAL graphic encoder

Details Dot crawl reduction in NTSC/PAL graphic encoder Dot crawl reduction in NTSC/PAL graphic encoder

1997-09-29

2000-12-19

Hsia, Sherrie

Television

Image signal processing circuitry specific to television

Noise or undesired signal reduction

348612, 348649, 348645, H04N 521, H04N 964

Patent

active

061633461

ABSTRACT:
By reducing the saturation (amplitude) at changes in the hue (phase) of the chrominance subcarrier of a video signal, the phenomenon of "dot crawl" can be substantially reduced for graphic data. It has been found that large hue (phase) changes associated with graphic data can cause large frequency shifts of the chrominance subcarrier resulting in a substantial portion of the chrominance subcarrier being unsuppressed by the chrominance subcarrier rejection filter of the luminance decoder. By reducing the saturation during the hue transition, the intensity of the spurious luminance information of the non-suppressed chrominance subcarrier is reduced.

REFERENCES:
patent: 3688021 (1972-08-01), Ekstrand
patent: 4679072 (1987-07-01), Takayama
patent: 4714954 (1987-12-01), Yoshinaka et al.
patent: 4788586 (1988-11-01), Eckenbrecht
patent: 4939572 (1990-07-01), Kosaka et al.
patent: 5355225 (1994-10-01), Bachmann
patent: 5867169 (1999-02-01), Prater
"Video Demystified," Second Edition; Keith Jack; HighText Publications, San Diego, California; 19 .

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