Measurement and control of the end-to-end quality of service (QoS) for advanced television technologies, from image acquisition to rendering, in contribution, primary distribution and secondary distribution networks

(Continuation of Question 2/9 - Measurement and control of the end-to-end quality of service (QoS) for advanced television technologies, from image acquisition to rendering, in contribution, primary distribution and secondary distribution networks)

Motivation
ITU‑T has adopted several Recommendations for the transmission of digital television signals for contribution, primary distribution and secondary distribution applications. However, a number of issues related to the measurement, monitoring and control of digital and mixed analogue-digital television transmission chains still remain to be solved.

This Question focuses on perceptual impacts of audiovisual quality of the entire video stream, also taking into account perceptual quality impacts of the camera and display. The effect of the source and display is particularly important and necessary for the case of 3DTV and high-dynamic range (HDR) displays, as both these technologies are not mature and still introduce quality problems. Display technologies are evolving from 2D to 3D, high-definition to ultra-high definition, low dynamic range to wide-gamut and high-dynamic range displays. In particular, HDR images are currently typically displayed on low-dynamic range (LDR) displays because of the limited availability of HDR displays. In order to visualize HDR images on LDR displays, tone mapping is necessary and this creates information loss that can deteriorate the quality and details of the HDR image. Recently, HDR displays have appeared on the market but they use internal processing that can affect the video quality. 3DTVs exhibit crosstalk to various degrees and can impact negatively the viewing experience. For these new technologies, the quality impact of the display and transmission (or camera, production and transmission) cannot always be separated. Although bandwidths available in cable transmission are well suited for ultra-high definition television (UHDTV), maintaining adequate video quality still represents a challenge.

• ITU‑R has recommended methods for the subjective assessment of picture quality (e.g. BT.500-13, BT.1788, BT.2021). There is a need to confirm that those subjective assessment methods and set-up requirements (including selection of the display, settings/calibration of the display, viewing distance, angle, luminance levels etc.) are equally applicable to the case of next-generation visual media, such as television transmission on digital or mixed analogue-digital chains, 3D, HDR and UHDTV images. In particular, current 3DTVs exhibit crosstalk to various degrees and can affect more or less the viewing experience even though the intrinsic 3D signal quality is very high. Subjective testing requires (objective) measurement or characterization means to adequately select display equipment to conduct such subjective testing in a reliable and repeatable manner.
• In the digital domain, ITU‑R Study Group 6 and ITU‑T Study Groups 9 and 12 have been also studying together, in a video quality experts group (VQEG), the identification of appropriate parameters and algorithms that are representative of digital picture quality, as well as the correlation of the objective measurement of those parameters to the subjective picture quality. This work has resulted in Recommendations J.143, J.144, J.242, J.244, J.246, J.247, J.249, J.340, J.341, J.342, and J.343-series.
• Concerning the measurement of the overall quality of experience (QoE), it includes not only a single impairment of each mono-media but also inter-media relation and response time of user operation. There is a need to identify the group of parameters that can provide objective measurement of the overall QoE and continuous in-service monitoring and control of it along the transmission chain.
• For some objective video quality models to operate effectively, the source and processed video sequences need to be aligned in the spatial and temporal dimensions. (In some cases such video registration can be treated separately from objective perceptual video quality assessment). Furthermore, in order to test processed video sequences to see if they meet validation test requirements (e.g. maximum spatial and temporal shifts), reliable methods to measure video registration are required. Therefore, it would be helpful and necessary to develop methods for video registration.
• Sometimes there is also a need for calibration methods in order to identify any modifications introduced into the video signals (e.g. gain and offset).

Question
Study items to be considered include, but are not limited to:

• What are the quality requirements for transmission of UHDTV?
• Are the current methods recommended for subjective assessment of digital picture quality also applicable to scenarios where the display is not transparent, such as in 3DTV or HDR images? Are the current quality assessment methods applicable to ultra-high definition television?
• If they are not, should any different or additional methods for picture quality assessment be recommended by Study Group 12?
• How should the impairment introduced by the display be taken into account in evaluation of the viewing experience?
• How should the impairments introduced by the transmission chain be taken into account, such as those introduced by digital or mixed analogue-digital television transmission chains?
• How should the impairment introduced by the (stereo-) camera be taken into account in evaluation of the viewing experience?
• What objective methodology can be used to jointly analyse the perceptual quality of the entire stream, including the quality of both the camera and the display?
• Which parameters and algorithms are representative of digital picture quality and how does the objective measurement of them correlate to subjective picture quality? (This work is to be carried out in cooperation with the VQEG.)
• How should the objective measurement of impairments introduced by digital or mixed analogue-digital transmission networks be carried out?
• Which network parameters should be used to provide objective measurement of the overall QoE and should be the basis for continuous in-service monitoring along the transmission chain both for digital and for mixed analogue-digital television transmission?
• Which network parameters can be dynamically adjusted for the supervision and control of the overall QoE in digital television transmission networks and how can such supervision and control be implemented in operation?
• What methods can be used for video registration of source and processed sequences for use in objective video quality assessment?
• What methods can be used for video calibration?
• What are the necessary test materials and test signals required for video registration and calibration?
• What trade-offs are inherent in different registration and calibration methods with respect to such factors as speed, accuracy and complexity and what are the effects on accuracy when limited information is available for video registration and calibration?
• What perceptual image/video quality assessment methods can be used to determine which tone-mapping operator maintains best the visual information of an HDR image or produces the highest-quality LDR image? What perceptual image/video quality assessment methods can be used to assess the quality of HDR content?
• What methods can be used to measure the visual fatigue in 3D video from the video capture, rendering and display?
• What enhancements to existing Recommendations are required to provide energy savings directly or indirectly in information and communication technologies (ICTs) or in other industries? What enhancements to developing or new Recommendations are required to provide such energy savings?

Tasks
Tasks include, but are not limited to:

• Maintenance and enhancement of J-series and P.900-series Recommendations.
• It is anticipated that new Recommendations will address:
  • methods to characterize and select appropriately 3D displays for subjective evaluation of 3D picture quality;
  • methods for HDR and UHDTV quality evaluation;
  • methods to assess/characterize the impact of non-transparent displays on viewing experience.

An up-to-date status of work under this Question is contained in the SG12 work programme
http://www.itu.int/ITU-T/workprog/wp_search.aspx?q=18/12 

Relationships

Recommendations

• ITU-T J- and P-series, ITU‑R BT-series

Questions

• 19/12

Study groups

• ITU‑T SG9, SG16
• ITU‑R SG6
• ITU IRG-AVQA

Standardization bodies

• ISO/IEC, IEEE P3333

Other groups

• VQEG​​