Multimedia Quality Assessment PDF
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Multimedia Quality Assessment Pengpeng Ni Context Simula Research Laboratory AS 2010-04-29 Content ✴ What is multimedia “quality”? ✴ How to measure multimedia “quality”? ✴ What are the difficulties and challenges? Quality of Service requirements in distributed multimedia systems Network Quality Link Quality Capacity Bitrate Coverage Frame/Bit/Packet loss Handoff Delay User Perceived Quality Speech fidelity Audio fidelity Image fidelity Video fidelity Quality of service (QoS) is defined in [ITU-T E.800] as the collective effect of performance which determines the degree of satisfaction of a user of the service. Quality of Experience (QoE) : The overall acceptability of an application or service, as perceived subjectively by the end-user. ✴ QoE includes the complete end-to-end system effects. ✴ Context Over acceptability may be influenced by user expectations and context. Quality of Service vs Quality of Experience ✴ QoS: Value of the average userʼs experience richness estimated by a service/product/content provider - Service provider-centric concept ✴ QoE: Value (estimated or actually measured ) of a specific userʼs experience richness. - User centric concept ✴ QoE is the dual and extended view of QoS problem Human centered multimedia services need measure/ predict QoE accurately. How is the quality of multimedia experience measured today? ✴ Subjective evaluation - Mean Opinion Score (MOS) rating test ✴ Objective quality metrics, estimating subjective MOS. - MOS predictors based on fidelity measures, examples include PSNR, SSIM, etc. Subjective evaluation tests ✴ International recommendation for subjective test methodologies: -Recommendation ITU-R BT. 500-11 “Methodology for the subjective assessment of the quality of television pictures” (1974-2002). -Recommendation ITU-T P. 910 “Subjective video quality assessment methods for multimedia applications” (1999). -Recommendation ITU-R BT. 1788 “Methodology for the subjective assessment of video quality in multimedia applications” (2007). ✴ Viewing condition, Test material, Test procedure, Measurement scales and basic statistics for data analysis. Subjective Test Methodology I Double Stimulus (DS) method Explicit reference 5 Impercep)ble 4 Percep)ble but not annoying 3 Slightly annoying 2 Annoying 1 Very annoying Hidden reference A B Excellent A B Bad Categorical or Numerical Scale Subjective Test Methodology II Single Stimulus (SS) methods Categorical scale 5 Excellent 5 Impercep)ble 4 Good 4 Percep)ble but not annoying 3 Fair 3 Slightly annoying 2 Poor 2 Annoying 1 Bad 1 Very annoying A 11-grade numerical categorical scale shows best results in SS method
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