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Service quality assessment – management
[Principal research results]
- Research result 1:
A comprehensive quality assessment model for videophone services (ITU-T recommendation G.1070) - Research result 2:
An objective quality assessment model for video delivery services (ITU-T recommendation J.247)
Research result 1
A parametric quality planning model for videophone services (ITU-T recommendation G.1070)
To deliver high-quality communication services, it is essential to clarify the quality requirements based on the quality of experience (QoE), which is what user's perceive, and to design terminals and networks to satisfy these requirements before the service is launched. To efficiently perform such quality planning, it is necessary to develop a parametric quality planning model for estimating QoE using the quality-planning parameters.
At NTT Network Technology Laboratories, we have researched and developed a quality-planning model for video phone services such as the E-model described in ITU-T recommendation G.107 (the algorithm that calculates the R-value), which is widely used as a quality assessment model for IP telephony services, and we have successfully developed a quality assessment model that takes into account the interaction of audio and video quality and the effects of synchronization errors between audio and video. This model has been adopted as International Telecommunication Union - Telecommunication Sector (ITU-T) Recommendation G.1070, which is an international standards organization.
As shown in the figure below, the quality assessment model is an estimation model that models characteristics between quality planning parameters associated with applications, networks and terminals, and QoE. It estimates audio and video quality from the quality planning parameters, and then estimates the multimedia quality by taking into account the interaction of these qualities and the synchronization (lip sync) of the audio and video.
Fig. 1: Assessment model of ITU-T recommendation G.1070
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Research result 2
An objective quality assessment model for video delivery services (ITU-T recommendation J.247)
To provide video delivery services of acceptable quality, we need a quality assessment model that can accurately ascertain the service quality (QoE). At NTT Network Technology Laboratories, we have researched and developed an objective quality assessment model called full-reference assessment that quantifies quality by comparing the pixel information of degraded video with a reference video (Fig. 2).
This model made it through a large-scale international technology competition in the ITU's Video Quality Expert Group (VQEG), and was selected as recommendation J.247. This model can evaluate video in which degradation has occurred due to the use of diverse coding schemes and bit rate conditions by video delivery services operating on IP networks, and due to packet loss (a characteristic of IP networks). This model makes it possible to automate the pre-delivery monitoring of quality in coded video content (a task which has hitherto relied on human eyes), thereby allowing video delivery services of suitable quality to be provided efficiently.
Fig. 2: The full-reference objective quality assessment model of ITU-T recommendation J.247
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