Apparent Increase in Noise Level When Television Pictures are Frame-Repeated

Seemingly attractive schemes for compressing the bandwidth of television signals sometimes render the signal highly sensitive to noise. As a result, the signal-to-noise ratio requirement for the channel becomes extremely large. 1 If this requirement is not met, the errors caused by the noise degrade the picture to an intolerable degree. Thus, noise is a great obstacle to the success of bandwidth-saving schemes, and the authors of any such schcmes should always take care to check the noise-sensitivity of their compressed signals. We report in this paper on some measurements we have made of the noise-vulnerability of picture signals in a frame-repeated television system. In a previous paper concerned with the possibilities of banclwidth-saving by frame-repetition or frame-replenishment, Brainard, Mounts, and Prasada made the observation that with increasing numbers of repeated television frames there appears to be an increase in the picture noise level.2 The noise pattern is "frozen" for the repetition period; this tends to make it more visible to the eye. Any source 527