A comb filter's task is to remove residual chrominance (color) information from the luminance (brightness) signal. Comb filtering enhances fine detail, cleans up image outlines, and eliminates most extraneous colors from analog video signals. A comb filter is very effective for composite video signals, but is not required and not used for S-video or component video since those connections carry the chrominance and luminance information separately. There are 4 different types of comb filters found in today's TVs, listed here in order of ascending quality:
* Glass: may also be referred to as an "analog" comb filter.
* 2-line Digital: compares consecutive scanning lines within one field of video and makes adjustments to reduce cross-color interference.
* 3-line Digital: compares 3 scanning lines within a field of video. By comparing more picture information, a 3-line filter further reduces color bleeding and dot crawl.
* 3D Digital: not only analyzes consecutive scanning lines within a field, but also analyzes the preceding and following fields. Results in improved color purity and a more stable video image, and nearly eliminates dot crawl and color bleeding. Also called 3D Y/C.
