Abstract: Processing of digitally-coded pictures to improve perceived quality without increasing transmission channel capacity, featuring dividing the video signal into a low, middle and high frequency signals (16, 26), finely quantizing the low frequency signal (18), adding pseudo-random noise (33) to the middle frequency signal prior to quantizing (28), enhancing (36) and adding pseudo-random noise (48) prior to coarsely quantizing (50) the high frequency signal. The pseudo-random signals are subtracted (37, 52) from the respective signals at the receiver.

Abstract: A laser featuring, in one aspect, a volume of gas having a lasing constituent, a light source arranged to emit light having ionizing photons for ionizing the gas, the effective photon energy spectrum of the ionizing photons lying below the ionization potential of the lasing constituent and below the level of photon absorption bands of the gas, the spectrum being selected to provide an average penetration depth of the ionizing photons into the gas of at least 1 cm. and to photoionize the gas predominantly by a multiple step process involving absorption of successive photons at least the first of which has a photon energy less than the ionization potential of said lasing constituent, and an electric field source for applying to the gas a voltage sufficient to produce an avalanche breakdown in the gas to effectively raise the lasing constituent to its lasing level; and in another aspect a seed gas comprising an amine having the structure ##EQU1## where R.sub.1, R.sub.2, and R.sub.