http://www.cockam.com/vidcomb.htm
It's interesting to read how much trickery is involved with getting the best picture quality out of the limited composite or RF signal.
The exact methodology described in the article applies only to NTSC, and only where a scanline is exactly one-half more than a whole number of subcarrier cycles, like the standard 227.5 cycles per scanline. The scanlines of an NTSC NES or Super NES are slightly shorter (227.333 cycles), and the scanlines of an Apple II, Atari 2600, Sega Master System, or Sega Genesis are slightly longer (228 cycles), limiting the effectiveness of assuming that phase reverses exactly on each scanline. I imagine that a lot of TVs of the time just disabled the comb filter, going back to a notch, when presented with the nonconforming signal of any second through fourth generation console or 8-bit microcomputer.
It'd have been possible to make the NES output a conforming signal. To make a conforming signal, an NES would have to generate 341.25 dots, probably by extending the last dot of each scanline (x=340) by one master clock cycle. (The CPU would also have to stall by a corresponding amount in order to keep compatibility with existing software.) And because many 3D comb filter designs rely on interlace, the PPU would have to double up the post-render scanline every other field.
It's possible to make a comb filter that works with nonconforming scanline lengths, but it would have to decode rough YUV or YIQ values first rather than operating directly in the composite signal domain.
It doesn't say anything about this in there, but I just thought of a trick.
In a composite signal, certain saturated colors peak past white level and black level, so if there is any time a signal goes beyond black or white, it must be part of the chroma signal. Do any televisions clamp off the luma signal, and use the "trimmings" as chroma information?
Another question. Do any televisions have the signal coming directly out of a comb filter and into a notch filter? You would expect someone would have thought of this before they had all this "adaptive digital 3D comb filter" stuff.
The pictures don't work because they are using backslashes instead of forward slashes to delimit the directory name from the filename.
Pictures don't work because you're using Firefox.
3gengames wrote:
Pictures don't work because you're using Firefox. :P
Actually I am not using Firefox. But I am using the Mozilla-based program