Making a difference

 作者:苍质份     |      日期:2019-03-08 03:18:04
By Barry Fox Digital TV stations try to cram as many subscription channels as possible into their allotted frequencies. But if they use too much data compression, the picture can judder and lose sharpness, causing viewers to complain. Tektronix of Beaverton, Oregon, has patented a method of avoiding this (EP 869 685). Before the compressed signal is transmitted, it is fed to a comparator along with the original, perfect signal. The compressed signal is subtracted from the original to produce a difference signal,