gwyn@brl-vld@sri-unix.UUCP (08/30/83)
From: Doug Gwyn (VLD/VMB) <gwyn@brl-vld> The Japanese are developing a "High Definition" television standard that looks pretty good. Of course the bandwidth is greater, thereby crowding the channels more. One improvement is a better aspect ratio, more like a motion picture screen. 30 frames/sec seems to be adequate if the phosphors have typical persistence. P4 requires a higher scan rate to avoid flicker. "Color space" has been thoroughly studied, and there is no simple set of colors that will suffice. Schr"odinger wrote a paper called something like "A Metric for Color Space" that is worth reading. It turns out that RGB can closely approximate a sufficiently wide range of colors for most scenes. Of course fluorescent colors are hopeless. One useful technique for video was developed for the PicturePhone and is called "delta modulation". The idea is to transmit incremental changes to a scene for each frame rather than the entire information content of the frame, since relatively little change occurs between successive frames. True delta modulation involves a _+1 step change of each pixel each frame. See the Bell System Tech. J. about 1976.