What are comb filters? Why do I need one?
The LD video signal is often referred to as a “composite” signal, which means that the black and white alias luminance (Y) and colour alias chrominance (C) information are not sent separately, but in the same signal. It is the responsibility of the receiver of the signal to reseparate these original signals. This task is by no means a simple one if you want to do it well, and so-called comb filters are used to do the separation. If you don’t have a comb filter, or you have a poor one, a picture that should look like the one on picture on the left side may very well look like the one on the right side, or even worse. The following is an article sent by Dave Martindale (davem@cs.ubc.ca), who has done a magnificent job in explaining the basics of comb filters (97-02-13): If you look at a single scanline, you really can’t tell what’s luma and what’s chroma. You could, in theory, build a comb filter that processed only a single line at a time, though it would be difficult to build. I’m not
