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Suche nach „[P.] [Callet]“ hat 6 Publikationen gefunden
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    DigitalAngewandte Informatik

    Zeitschriftenartikel

    J. Li, Wang, J., Marcus Barkowsky, P. Callet

    Exploring the effects of subjective methodology on assessing visual discomfort in immersive multimedia

    Electronic Imaging, Human Vision and Electronic Imaging

    2018

    DOI: 10.2352/ISSN.2470-1173.2018.14.HVEI-527

    Abstract anzeigen

    Visual discomfort is an important factor that influences viewing experience in immersive multimedia, for example, 3DTV and VR. With the added value of depth, the novel perceptual experience, visual discomfort is not an easy task for observers to evaluate. In this study, we investigate how the subjective methodology affects the test results in 3DTV condition. Two subjective visual discomfort experiments were conducted. One used the Pair Comparison (PC) method and the other used the Absolute-Category Rating (ACR) method. The results demonstrated that PC method had more powerful discriminability. For a difficult perceptualrelated tasks, such as visual discomfort in our study, PC was more easy to understand and conduct for the observers which led to reliable results. It also showed some very important but usually ignored conclusions on the subjective experiment, i.e., for measuring the perceived visual discomfort, the observer\textquoterights judgment behavior might be affected by the test methodology.

    DigitalElektrotechnik und Medientechnik

    Zeitschriftenartikel

    A. Aldahdooh, E. Masala, O. Janssens, G. Wallendael, Marcus Barkowsky, P. Callet, G. van Wallendael, P. Lambert

    Improved Performance Measures for Video Quality Assessment Algorithms Using Training and Validation Sets

    IEEE Transactions on Multimedia, vol. 74, pp. 32-41

    2018

    Abstract anzeigen

    Due to the three-dimensional spatiotemporal regularities of natural videos and small-scale video quality databases, effective objective video quality assessment (VQA) metrics are difficult to obtain but highly desirable. In this paper, we propose a general-purpose no-reference VQA framework that is based on weakly supervised learning with convolutional neural network (CNN) and resampling strategy. First, an eight-layer CNN is trained by weakly supervised learning to construct the relationship between the deformations of the three dimensional discrete cosine transform of video blocks and corresponding weak labels judged by a full-reference (FR) VQA metric. Thus, the CNN obtains the quality assessment capacity converted from the FR-VQA metric, and the effective features of the distorted videos can be extracted through the trained network. Then, we map the frequency histogram calculated from the quality score vectors predicted by the trained network onto the perceptual quality. Specially, to improve the performance of the mapping function, we transfer the frequency histogram of the distorted images and videos to resample the training set. The experiments are carried out on several widely used video quality assessment databases. The experimental results demonstrate that the proposed method is on a par with some state-of-the-art VQA metrics and has promising robustness.

    DigitalAngewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    Y. Rai, A. Aldahdooh, S. Ling, Marcus Barkowsky, P. Callet

    Effect of content features on short-term video quality in the visual periphery

    2016 IEEE 18th International Workshop on Multimedia Signal Processing (MMSP)

    2016

    Abstract anzeigen

    The area outside our central field of vision, also referred to as the visual periphery, captures most information in a visual scene, although much less sensitive than the central Fovea. Vision studies in the past have stated that there is reduced sensitivity of texture, color, motion and flicker (temporal harmonic) perception in this area, that bears an interesting application in the domain of quality perception. In this work, we particularly analyze the perceived subjective quality of videos containing H.264/AVC transmission impairments, incident at various degrees of retinal eccentricities of observers. We relate the perceived drop in quality, to five basic types of features that are important from a perceptive standpoint: texture, color, flicker, motion trajectory distortions and also the semantic importance of the underlying regions. We are able to observe that the perceived drop in quality across the visual periphery, is closely related to the Cortical Magnification fall-off characteristics of the V1 cortical region. Additionally, we see that while object importance and low frequency spatial distortions are important indicators of quality in the central foveal region, temporal flicker and color distortions are the most important determinants of quality in the periphery. We therefore conclude that, although users are more forgiving of distortions they viewed peripherally, they are nevertheless not totally blind towards it: the effects of flicker and color distortions being particularly important.

    DigitalAngewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    A. Aldahdooh, Marcus Barkowsky, P. Callet

    Spatio-temporal error concealment technique for high order multiple description coding schemes including subjective assessment

    2016 Eighth International Conference on Quality of Multimedia Experience (QoMEX)

    2016

    Abstract anzeigen

    Error resilience (ER) is an important tool in video coding to maximize the quality of Experience (QoE). The prediction process in video coding became complex which yields an unsatisfying video quality when NALunit packets are lost in error-prone channels. There are different ER techniques and multiple description coding (MDC) is one of the promising technique for this problem. MDC is categorized into different types and, in this paper, we focus on temporal MDC techniques. In this paper, a new temporal MDC scheme is proposed. In the encoding process, the encoded descriptions contain primary frames and secondary frames (redundant representations). The secondary frames represent the MVs that are predicted from previous primary frames such that the residual signal is set to zero and is not part of the rate distortion optimization. In the decoding process of the lost frames, a weighted average error concealment (EC) strategy is proposed to conceal these frames. The proposed scheme is subjectively evaluated along with other schemes and the results show that the proposed scheme is significantly different from most of other temporal MDC schemes.

    DigitalAngewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    K. Zhu, Marcus Barkowsky, M. Shen, P. Callet, D. Saupe

    Optimizing feature pooling and prediction models of VQA algorithms

    2014 IEEE International Conference on Image Processing (ICIP)

    2014

    Abstract anzeigen

    In this paper, we propose a strategy to optimize feature pooling and prediction models of video quality assessment (VQA) algorithms with a much smaller number of parameters than methods based on machine learning, such as neural networks. Based on optimization, the proposed mapping strategy is composed of a global linear model for pooling extracted features, a simple linear model for local alignment in which local factors depend on source videos, and a non-linear model for quality calibration. Also, a reduced-reference VQA algorithm is proposed to predict the local factors from the source video. In the IRCCyN/IVC video database of content influence and the LIVE mobile video database, the performance of VQA algorithms is improved significantly by local alignment. The proposed mapping strategy with prediction of local factors outperforms one no-reference VQA metric and is comparable to one full-reference VQA metric. Thus predicting the local factors in local alignment based on video content will be a promising new approach for VQA.

    DigitalAngewandte Informatik

    Zeitschriftenartikel

    J. Li, Marcus Barkowsky, P. Callet

    Visual discomfort of stereoscopic 3D videos: Influence of 3D motion

    Displays, vol. 35, no. 1, pp. 49-57

    2014

    DOI: 10.1016/j.displa.2014.01.002

    Abstract anzeigen

    Visual discomfort is one of the most frequent complaints of the viewers while watching 3D images and videos. Large disparity and large amount of motion are two main causes of visual discomfort. To quantify this influence, three objectives are set in this paper. The first one is the comparative analysis on the influence of different types of motion, i.e., static stereoscopic image, planar motion and in-depth motion, on visual discomfort. The second one is the investigation on the influence factors for each motion type, for example, the disparity offset, the disparity amplitude and velocity. The third one is to propose an objective model for visual discomfort. Thirty-six synthetic stereoscopic video stimuli with different types of motion are used in this study. In the subjective test, an efficient paired comparison method called Adaptive Square Design (ASD) was used to reduce the number of comparisons for each observer and keep the results reliable. The experimental results showed that motion does not always induce more visual discomfort than static conditions. The in-depth motion generally induces more visual discomfort than the planar motion. The relative disparity between the foreground and the background, and the motion velocity are identified as main factors for visual discomfort. According to the subjective results, an objective model for comparing visual discomfort induced by different types of motion is proposed which shows high correlation with the subjective perception.