# No-Reference Quality Assessment of Transmitted Stereoscopic Videos Based on Human Visual System
## 1 Introduction  
Quality Assessment is an imperative aspect of video services aimed at human observers in applications such as television, Blu-ray, DVD, mobile TV, web TV, gaming, and video streaming. An objective 3D video QA is a statistical mathematical model that approximates the results for video perception that would be obtained from typical human viewers [1]. No-reference (NR) models can objectively estimate a video's quality based on the received frames that have been subjected to distortions from coding and transmission losses [2]. Since it does not require any information from the source video, it generates less precise scores when evaluating the quality of a video compared to full- and reduced-reference approaches, but can be applied in many real-time applications for which source information is unavailable. NR models are widely used for continuous quality monitoring at the receiver end in video playback and streaming systems [1], with a basic system shown in Figure 1. The figure shows a conventional quality measure system for video transmission where stereoscopic videos are differently encoded, transmitted, and then decoded in the receiving system. For any kind of transmission losses or distortion, the end devices perform some checking of the videos, perform real-time error concealment, and then show it to the viewer. 3D video transmission has received significant research attention driven by commercial applications in recent years [1,3,4]. More attention has been paid to analyzing and mitigating the effects by applying various techniques in the 3D video transmission chain and display to ensure better Quality of Experience (QoE) [5]. However, the impacts of artifacts introduced into a 3D video by its transmission system have not received as much interest as those in a 2D video [6] although they influence the overall image quality similarly. Because stereoscopic 3D video has two separate channels, each of which may experience unrelated attenuation, transmission errors over unreliable wireless communication channels are higher than in 2D video. For example, lag in a view can lead to a time-lapse out-of-sync process, reducing the comfort of 3D [7] viewing. In addition, the methods used to reduce these spurious structures (e.g., error masking) do not work as well for 3D videos as they do for 2D [8] videos. To create a good 3D depth perception [9,10] and avoid the competition of two binoculars [11,12], ideally the two 3D channels should be maintained and synchronized. Numerous factors, including spatial or temporal frequencies, binocular depth cues, and transmission media, can significantly affect the video quality experienced by users during 3D viewing. Previous studies of binocular vision and its sensitivity showed that the behaviors of viewers during 2D and 3D viewing are different and the observations are tightly linked to the way in which 3D videos are perceived [13, 14, 15]. Existing 2D image or video quality models are not adequate for measuring 3D visual experiences since they do not incorporate various 3D perceptual characteristics, including at least the most positive (binocular depth) and negative (cross-talk and visual discomfort) factors of S3D [7,12]. As shown in Figure 2, the brain employs binocular disparity to extract depth information from two-dimensional (2D) retinal pictures. The difference in the coordinates of similar features in two stereo views is referred to as \"binocular disparity\". The horopter is a curving line that connects all sites that have a zero retinal disparity (same relative coordinate), with the points positioned at it having the same perceived distances from a human subject's fixation point. Panum's fusional area is located around the horopter and is a zone within which views with non-zero retinal disparities can be merged binocularly; however, things located outside of this area result in double pictures. Panum's area size varies across the retina and is regulated by the spatial and temporal characteristics of the fixation object [16].