Standards for diagnosing the quality of transmitted speech and their improvements

This contribution deals with the diagnosis of the quality of transmitted speech. The two current work items approaching this topic of Study Group 12 of the International Telecommunication Union (ITU) are introduced. The first, called P.AMD, is proposed to estimate perceptual quality dimension scores and is in its final steps to become a standard. The second, called P.TCA, identifies technical causes of the transmission channel and recommends a standardized expert annotation methodology which still needs to be validated and improved. For this improvement, this paper presents a systematic approach to process and validate a set of listening material that is suitable for the P.TCA methodology. Motivation for the approach presented here is that former studies showed that the current draft explanations of degradations, which expert listeners are supposed to use for annotation, need improvement. In fact, it was found that it would be best to provide exemplarily listening material together with the P.TCA instructions. For that purpose, this paper describes the processing steps to generate the required example material and presents the results of a validation experiment in which experts annotated the processed speech material according to the P.TCA instructions. The analysis of those annotations reveals that 71% of the example material was labelled correctly. Furthermore, the results suggest to investigate if disagreement of experts can be reduced by modifying the P.TCA annotation procedure as such, or by providing further appropriate example material.