Noise (video)

Noise, in analog video and television, is a random dot pixel pattern of static displayed when no transmission signal is obtained by the antenna receiver of television sets and other display devices. The random pattern superimposed on the picture, visible as a random flicker of "dots" or "snow", is the result of electronic noise and radiated electromagnetic noise accidentally picked up by the antenna. This effect is most commonly seen with analog TV sets or blank VHS tapes.

There are many sources of electromagnetic noise which cause the characteristic display patterns of static. Atmospheric sources of noise are the most ubiquitous, and include electromagnetic signals prompted by cosmic microwave background radiation,^[1] or more localized radio wave noise from nearby electronic devices.^[2]

The display device itself is also a source of noise, due in part to thermal noise produced by the inner electronics. Most of this noise comes from the first transistor the antenna is attached to.^[2]

UK viewers used to see "snow" on black after sign-off, instead of "bugs" on white, a purely technical artifact due to old 405-line British senders using positive rather than the negative video modulation used in Canada, the U.S., and (currently) the UK as well. Since one impression of the "snow" is of fast-flickering black bugs on a white background, in Sweden and Denmark the phenomenon is often called myrornas krig in Swedish, myrekrig in Danish, hangyák háborúja in Hungarian, and semut bertengkar in Indonesian, which translate to "war of the ants" or sometimes hangyafoci in Hungarian which means "ant soccer", and in Romanian, purici, which translates into "fleas".

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. Most modern televisions automatically change to a blue screen or turn to standby after some time if static is present.

References

↑ "Background on the Background Explorer and the Science of John Mather". NASA.
1 2 "Antenna basics". HDTV Primer.

Noise (physics and telecommunications)

General	Acoustic quieting Distortion Noise cancellation Noise control Noise measurement Noise power Noise reduction Noise temperature Phase distortion

Noise in...	Audio Buildings Electronics Environment Government regulation Human health Images Radio Rooms Ships Sound masking Transportation Video

Class of noise	Additive white Gaussian noise (AWGN) Atmospheric noise Background noise Brownian noise Burst noise Cosmic noise Flicker noise Gaussian noise Grey noise Jitter Johnson–Nyquist noise (thermal noise) Pink noise Quantization error (or q. noise) Shot noise White noise Coherent noise Value noise Gradient noise Worley noise

Engineering terms	Channel noise level Circuit noise level Effective input noise temperature Equivalent noise resistance Equivalent pulse code modulation noise Impulse noise (audio) Noise figure Noise floor Noise shaping Noise spectral density Noise, vibration, and harshness (NVH) Phase noise Pseudorandom noise Statistical noise

Ratios	Carrier-to-noise ratio (C/N) Carrier-to-receiver noise density (C/kT) dBrnC E_b/N₀ (energy per bit to noise density) E_s/N₀ (energy per symbol to noise density) Modulation error ratio (MER) Signal, noise and distortion (SINAD) Signal-to-interference ratio (S/I) Signal-to-noise ratio (S/N, SNR) Signal-to-noise ratio (imaging) Signal to noise plus interference (SNIR) Signal-to-quantization-noise ratio (SQNR)

Related topics	List of noise topics Acoustics Colors of noise Interference (communication) Noise generator Radio noise source Spectrum analyzer Thermal radiation

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Noise (video)

See also

References