Video quality

About: Video quality is a research topic. Over the lifetime, 13143 publications have been published within this topic receiving 178307 citations.

Q-STAR: A Perceptual Video Quality Model Considering Impact of Spatial, Temporal, and Amplitude Resolutions

Abstract: In this paper, we investigate the impact of spatial, temporal, and amplitude resolution on the perceptual quality of a compressed video. Subjective quality tests were carried out on a mobile device and a total of 189 processed video sequences with 10 source sequences included in the test. Subjective data reveal that the impact of spatial resolution (SR), temporal resolution (TR), and quantization stepsize (QS) can each be captured by a function with a single content-dependent parameter, which indicates the decay rate of the quality with each resolution factor. The joint impact of SR, TR, and QS can be accurately modeled by the product of these three functions with only three parameters. The impact of SR and QS on the quality are independent of that of TR, but there are significant interactions between SR and QS. Furthermore, the model parameters can be predicted accurately from a few content features derived from the original video. The proposed model correlates well with the subjective ratings with a Pearson correlation coefficient of 0.985 when the model parameters are predicted from content features. The quality model is further validated on six other subjective rating data sets with very high accuracy and outperforms several well-known quality models.

Spherical Structural Similarity Index for Objective Omnidirectional Video Quality Assessment

Abstract: Objective quality assessment plays a crucial role in the evaluation and optimization processes of Virtual Reality (VR) technologies, for which state-of-the-art objective quality evaluation metrics for omnidirectional video, i.e., 360 degree video, are typically derived from traditional MSE (or PSNR). Here we propose an objective omnidirectional video quality assessment method based on structural similarity (SSIM) in the spherical domain. Adopting the relationship of the structural similarity between the 2-D plane and sphere, the interference brought by the projection between the two domains can be well handled in the assessment process. The performance of the proposed spherical structural similarity (S-SSIM) index is evaluated with a subjective omnidirectional video quality assessment database. As demonstrated in the experimental results, the proposed S-SSIM outperforms state-of-the-art objective quality assessment metrics in omnidirectional video quality assessment.

Coping With Heterogeneous Video Contributors and Viewers in Crowdsourced Live Streaming: A Cloud-Based Approach

Abstract: With the advances in personal computing devices and the prevalence of broadband network and wireless mobile network accesses, end-users are no longer pure content consumers, but contributors, too. In today's crowdsourced streaming systems, numerous broadcasters lively stream their video content, e.g., live events or online game scenes, to fellow viewers. Compared to professional video producers and broadcasters, these new generation broadcasters are geo-distributed globally and highly heterogeneous in terms of the generated video quality and the network/system configurations. The scalability and heterogeneity challenges therefore lie on both broadcasters and the viewers, which call for massive transcoding, and two critical issues: 1) choosing video representation set that maximizes viewer satisfaction and 2) allocating computational resources that minimize operational costs, must be systematically optimized in the global scale. In this paper, we present a generic framework utilizing the powerful and elastic cloud computing services for crowdsourced live streaming with heterogeneous broadcasters and viewers. We jointly consider the viewer satisfaction and the service availability/pricing of geo-distributed cloud resources for transcoding. We develop an optimal scheduler for allocating cloud instances with no regional constraints. We then extend the solution to accommodate regional constraints, and discuss a series of practical enhancements, including popularity forecasting, initialization latency, and viewer feedbacks. Our solutions have been evaluated under diverse networks and cloud system configurations as well as parameter settings. The trace-driven simulation confirms the superiority of our design, while our Planetlab-based experiment offers further practical hints toward real-world migration.

Reduced-Reference Video Quality Assessment Using Discriminative Local Harmonic Strength With Motion Consideration

Abstract: This paper presents a reduced-reference objective picture quality measurement tool of compressed video. We have used a discriminative analysis of harmonic strength computed from edge-detected pictures to create harmonics gain and loss information that could be associated with the picture. The harmonics gain/loss are derived through the harmonic analysis of the compressed and source pictures to be incorporated in the reduced-reference video quality meter. This information corresponds with the two most prominent compression distortions, namely blockiness and blurriness. We have also studied the impact of motion in a video sequence on these compression distortions and the way they should be weighted and combined to give the best objective quality metric model. The model has been calibrated using several video sequences with dominant blockiness and blurriness. Validation of the model is performed by applying the model to the 50 Hz video sequences of VQEG Test Phase-I. Our results show that the proposed model achieves good correlations with the subjective evaluations of the VQEG datasets and its performance is comparable to those of the full-reference models in the literature.

Dynamic GOP system and method for digital video encoding

Abstract: This invention discloses an intra-frame complexity based dynamic GOP system and method for the encoding of MPEG-2 video streams. The present invention may be used as a rate control tool to improve video quality. The selective insertion of low complexity I frames in scene changes such as fades is disclosed. It is disclosed that the selective use of I frames in certain scene change situations can improve encoder performance, particularly when encoding at a low bit rate.