Noise (video)
From Wikipedia, the free encyclopedia
Noise in analog video and television is perceived as a random dot pattern which is superimposed on the picture as a result of electronic noise and radiated electromagnetic noise picked up by the receiver's antenna – it is the "snow" which is seen with poor analog television reception or on VHS tapes.
When there is no transmission, which is to say no signal, the noise or "snow" is due mostly to thermal noise from the device itself, stray electromagnetic fields from other household electric devices, and remnants of the microwave cosmic background radiation from the Big Bang[1], all of which is interpreted as luminance signal. Approximately one-third to one-quarter of such static is residual background radiation from the birth of the cosmos.[2]
Due to the algorithmic functioning of a digital television set's electronic circuitry and the inherent quantization of its screen, the "snow" seen on digital TV is less random, and being almost entirely a product of its own electronics, no cosmic background radiation is displayed.[3]
UK viewers see "snow" on black after sign-off, instead of "bugs" on white, a purely technical artifact due to British receivers using positive rather than the negative video modulation used in Canada and the U.S.
Since one impression of the "snow" is of fast-flickering black bugs on a cool white background, in Sweden the phenomenon is often called Myrornas Krig, "War of the Ants".[citation needed]
