Institute for Telecommunication Sciences
the research laboratory of the National Telecommunications and Information Administration

Stephen Wolf

Abstract: This contribution discusses the advantages and disadvantages of two methods for obtaining a composite rating of Hypothetical Reference Circuit (HRC) performance for an ensemble of source material. The term HRC refers to a specific realization of a video transmission system that may include coders, digital transmission circuits, decoders, and even analog processing of the video signal. In the first method, subjects are asked to separately observe and rate each of several HRC-scene combinations, and the separate ratings are then averaged over subjects and scenes to produce a composite rating for each HRC. In the second method, subjects are asked to rate each HRC based on a single observation period in which all the scenes are presented; the individual subject ratings are then averaged to produce a composite rating for each HRC. This contribution evaluates the two methods in light of accepted industry practice and statistical considerations. It is shown that the first method is far more widely used and offers substantial statistical advantages over the second.

Keywords: system; performance; Video; quality; objective; subjective; Testing


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Institute for Telecommunication Sciences
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Margaret H. Pinson
Institute for Telecommunication Sciences
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Disclaimer: Certain commercial equipment, components, and software may be identified in this report to specify adequately the technical aspects of the reported results. In no case does such identification imply recommendation or endorsement by the National Telecommunications and Information Administration, nor does it imply that the equipment or software identified is necessarily the best available for the particular application or uses.

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