Objective and subjective quality assessments of 3D videos
Creators: name: Choy, Siu Ming
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400607
subject: Signal processing
classificationCode: 460399
subject: Computer vision and multimedia computation not elsewhere classified

description: Three-dimensional (3D) image viewing is rapidly increasing the popularity of applications such as 3D videos, movies, computer games, and Virtual Reality (VR) environments. Several techniques related to 3D video have been developed, including stereoscopic video, multi-view video, autostereoscopic video and holography. This study focuses on stereoscopic 3D (S3D) video, which is used most widely in the movie industry and in 3D television (3DTV) broadcasting. This broadcasting services have been introduced in several countries in recent years, and video service providers have also offered S3D video services over the Internet. To cope with the market's increasing need for high-quality 3D images, quality assessment of S3D video has been identified as an important area for research and development.

This research proposes novel methods for both objective and subjective quality assessments of S3D video, with a view to extending these methods to the development of S3D quality metrics and multi-view 3D video technologies. The novel methods were verified with software simulations in objective quality assessments and experimental test validations in subjective quality assessments. Firstly, this study conducted objective and subjective assessments to investigate differences in the viewers' Quality of Experience (QoE) between two-dimensional (2D) and S3D videos. Visually Induced Motion Sickness (VIMS) and visual attention were evaluated and verified against previous findings. Secondly, the study was extended to the assessment of the quality of experience of viewers who watched S3D videos in three viewing environments: a flat 3D screen, a panoramic screen and a VR headset. This experiment was performed to identify the effects of VIMS and to analyse 3D fatigue in the three viewing environments. Thirdly, eye-tracking experiments were conducted to obtain eye-gaze data and to develop human saliency maps for the investigation of human visual attention. Existing human saliency maps and saliency prediction models are compared for benchmarking and validation. These results were evaluated to determine whether visual attention obtained from eye-tracking methods contribute to QoE assessments of S3D videos. Finally, the application of the objective quality metrics and subjective evaluation approaches is proposed as a practical use-case in video coding evaluation.

Comparing the objective and subjective quality assessments between 2D and S3D videos, the findings show that S3D videos create more fatigue for the participants than the 2D video sequences. Also, there is more eye blinking movement when viewing 2D videos compared to S3D videos. When viewers watch S3D videos in three viewing environments, the findings show that the viewers who used a VR device to view the stereoscopic video sequences resulted in higher Simulator Sickness Questionnaire (SSQ) scores. For the panoramic screen, the participants reported the lowest SSQ scores and the highest enjoyment ratings. The difference in results experienced when viewing the same S3D video sequence on different screens reveal that the projection screen is an essential factor that influences the level of visual fatigue, QoE and VIMS. The content of the video sequence and the projection screen used are also key factors that affect the enjoyment rating of the S3D videos. In addition, it is found that eye-tracking is a key method to obtain the visual attention of viewers. Existing saliency prediction models are not accurate enough to predict an actual visual attention model, especially for S3D video sequences. The application of the objective quality metrics and the subjective evaluation in a proposed video coding use-case of S3D video sequences show that a perceptual quality similar to that of uncompressed videos can be provided when the 3D effects are moderate and scenes are stable.

The key contribution of this thesis is in providing more reliable and accurate objective and subjective quality assessments for S3D video, including the QoE, visual fatigue and visual attention from the S3D video in different viewing environments. Finally, this thesis is concluded discussing the recommended future research work in extending into multi-view S3D video technology.