Linking Distortion Perception and Visual Saliency in H.264/AVC Coded Video Containing Packet Loss

In this paper, distortions caused by packet loss during video transmission are evaluated with respect to their perceived annoyance. In this respect, the impact of visual saliency on the level of annoyance is of particular interest, as regions and objects in a video frame are typically not of equal importance to the viewer. For this purpose, gaze patterns from a task free eye tracking experiment were utilised to identify salient regions in a number of videos. Packet loss was then introduced into the bit stream such as that the corresponding distortions appear either in a salient region or in a non-salient region. A subjective experiment was then conducted in which human observers rated the annoyance of the distortions in the videos. The outcomes show a strong tendency that distortions in a salient region are indeed perceived as much more annoying as compared to distortions in the non-salient region. The saliency of the distorted image content was further found to have a larger impact on the perceived annoyance as compared to the distortion duration. The findings of this work are considered to be of great use to improve prediction performance of video quality metrics in the context of transmission errors

Adaptive Contrast Adjustment for Postprocessing of Tone Mapped High Dynamic Range Images

Abstract—Tone mapping operators (TMOs) employed to visualize high dynamic range (HDR) content on conventional low dynamic range (LDR) devices suffer from two major drawbacks. First, none of them can faithfully reproduce all the contrast present in HDR images. Second, most of them require one or more parameters which are mostly content specific and their optimal values can be set only via subjective testing. To address these issues, this paper proposes that ‘quality driven’ adaptive contrast enhancement is a practical solution. This is achieved by enhancing the contrast adaptively based on the loss of contrast between the HDR and tone mapped image. Experimental results confirm that the proposed adaptive solution always improves upon the contrast achieved from whatever given TMO parameter settings in the tested images. So it helps to achieve the results of a more optimal TMO parameter setting without the human input. I

Exploring the effects of 3D visual discomfort on viewers' emotions

International audienceMuch of the research on stereoscopic 3D (S3D) QoE has dealt with the effects of image features over user's visual discomfort. Nevertheless, the relationships between visual discomfort and other high-level perceptual dimensions such as the viewers' emotional reactions have not been yet explored. Since emotions play a key role on media reception processes, and especially in entertainment contents consumption, this question deserves to be thoroughly addressed to improve the design of image processing techniques. This paper raises and investigates the possible relationship between image distortions and its impact on the emotion context of S3D. We implemented an experimental design in which participants watched a series of 3D contents with different levels of visual distortions supposed to induce visual discomfort, while self-reported and psychophysiological measures of emotions were recorded. Results showed that physiological correlates of emotions were affected by visual discomfort conditions, and that these measures were more sensitive than traditional self-reported measures

An Overview of the SVC4QoE project

The aim of this paper is to give an overview of the SVC4QoE project which purpose is to use Scalable Video Coding (SVC) to optimize video transmission in terms of Quality of Experience over DVB-T2 channels. The originality of this project is to consider the influence of the whole chain of treatments performed on the video data in terms of user-perceived quality. The encoding process, as well as transmission, decoding and display are included in the optimization process. Particularly, the multi-layer structure of SVC is to be exploited to circumvent alterations of the video related to transmission on error-prone networks. Combining SVC with QoE thus provides a way to reduce network operating costs, while increasing the quality from the user's point of view. Several innovations are also to be mentioned, such as the use of a real-time open-source SVC decoder, evaluation of visual quality through subjective quality assessment tests, transmission and synchronization of SVC layers on the receiver's side, and development of a DVB-T2 Gateway which implements the multi-PLP functional-ity in an SVC context