モバイル通信における映像品質の主観評価法の性能比較

摘要

There are many subjective assessment methods, depending on the purpose of the video quality evaluation, provided by ITU-T and ITU-R recommendations. We compared eight subjective assessment methods, Double-Stimulus Continuous Quality-Scale (DSCQS), Double-Stimulus Impairment Scale (DSIS), 5-grade Absolute Category Rating (ACR5), ACR5 with Hidden Reference (ACR5-HR), 11-grade ACR (ACR11), ACR11-HR, Subjective Assessment of Multimedia Video Quality (SAMVIQ), and SAMVIQ-HR, to clarify their applicability to a variety of video quality assessment. To do this, we evaluated the total assessment time and difficult/ease in evaluation for the participants, as well as the characteristics of different rating scales and their statistical reliability. As a result, we clarified that the correlation coefficients and rank correlation coefficients of the mean opinion scores between pairs of the eight methods were high. As for statistical reliability of each rating method, DSIS, ACR5, and SAMVIQ outperformed the other methods. Moreover, participant questionnaire results showed that ACR5 was a suitable method from the viewpoint of total assessment time and ease of evaluation.%映像品質の主観評価法は，評価目的に応じて様々なものがITU-TおよびITU-Rで勧告化されている.本稿では，各種主観品質評価法の性能や適用領域を明らかにすることを目的として品質評価特性を比較した結果を報告する.評価対象は，モバイル通信を想定した各種品質劣化映像とした.比較対象とする主観品質評価法は，DSCQS法，DSIS法，5段階ACR法，5段階ACR-HR法，11段階ACR法，11段階ACR-HR法，SAMVIQ法，SAMVIQ-HR法の8つである.各評価法の性能比較は，相関係数，順位相関係数，および評価値のばらつきを分析するとともに，実験実施の容易性を比較する指標として評価時間および評価のしやすさを測定した.この結果，今回の劣化映像に対する主観品質評価法として評価精度および実験実施の容易性の観点から最適な主観品質評価法は5段階ACR法であることを示した.