BBC R&D

Abstract

This report describes objective measurements of signal-to-noise ratios and of waveform distortions using a 'pulse-and-bar' test waveform. The results of these measurements are compared with subjective assessments. The agreement is fairly good in view of the fact that the objective measurements did not include noise or waveform distortion occurring at the picture source, although the subjective assessments would have been influenced by any such noise or distortion.

The results show that if the peak-to-peak noise is less than 8% of the double-amplitude-peak video signal, as measured with a waveform monitor, the most probable subjective assessment of overall picture quality would be "good". If the noise-to-signal ratio is between 8% and 20%, an assessment of "fairly-good" is indicated.

As regards waveform distortion, the results show that a distortion rating of 3% would indicate a 90% probability of a subjective assessment of overall quality in the grade 1 or 2, "excellent or good". A rating of 7.5% indicates a 50% probability of such an assessment.