Methodology for the subjective assessment of the quality of television pictures

The ITU Radiocommunication Assembly, considering a) that a large amount of information has been collected about the methods used in various laboratories for the assessment of picture quality; b) that examination of these methods shows that there exists a considerable measure of agreement between the different laboratories about a number of aspects of the tests; c) that the adoption of standardized methods is of importance in the exchange of information between various laboratories; d) that routine or operational assessments of picture quality and/or impairments using a five-grade quality and impairment scale made during routine or special operations by certain supervisory engineers, can also make some use of certain aspects of the methods recommended for laboratory assessments; e) that the introduction of new kinds of television signal processing such as digital coding and bit-rate reduction, new kinds of television signals using time-multiplexed components and, possibly, new services such as enhanced television and HDTV may require changes in the methods of making subjective assessments; f) that the introduction of such processing, signals and services, will increase the likelihood that the performance of each section of the signal chain will be conditioned by processes carried out in previous parts of the chain, recommends 1 that the general methods of test, the grading scales and the viewing conditions for the assessment of picture quality, described in the following Annexes should be used for laboratory experiments and whenever possible for operational assessments; 2 that, in the near future and notwithstanding the existence of alternative methods and the development of new methods, those described in § 4 and 5 of Annex 1 to this Recommendation should be used when possible; and 3 that, in view of the importance of establishing the basis of subjective assessments, the fullest descriptions possible of test configurations, test materials, observers, and methods should be provided in all test reports; 4 that, in order to facilitate the exchange of information between different laboratories, the collected data should be processed in accordance with the statistical techniques detailed in Annex 2 to this Recommendation.