Objective Assessment of Single and Concatenated Compression Codecs

Abstract

With the inception of broadcast equipment incorporating bit-rate reduction techniques, concern is being voiced by some broadcasters on the cumulative effects of cascading compression codecs of different types. Compression can now be found in all parts of the broadcast chain, from acquisition, contribution, processing, recording, and distribution. Subjective viewing can give an overall assessment of perceived picture quality but may not indicate the quantitative levels of distortion that could later affect post-production, or the susceptibility to gross errors if the signal is subsequently passed through further compression. This paper discusses conventional and new subjective and objective assessment methods with the aim of providing background information for seminar discussion. Some tentative proposals are put forward for objective evaluation together with initial observations when concatenating codecs of similar and different types.