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Suche nach „[Barkowsky] [Marcus]“ hat 114 Publikationen gefunden
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    DigitalAngewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    Katharina Heydn, Marc-Philipp Dietrich, Marcus Barkowsky, Götz Winterfeldt, S. Mammen, A. Nüchter

    The Golden Bullet: A Comparative Study for Target Acquisition, Pointing and Shooting

    Proceedings of the 2019 11th International Conference on Virtual Worlds and Games for Serious Applications (VS-Games) [4-6 Sept. 2019; Vienna, Austria]

    2019

    DOI: 10.1109/VS-Games.2019.8864589

    Abstract anzeigen

    In this study, we evaluate an interaction sequence performed by six modalities consisting of desktop-based (DB) and virtual reality (VR) environments using different input devices. For the given study, we implemented a vertical prototype of a first person shooter (FPS) game scenario, focusing on the genre-defining point-and-shoot mechanic. We introduce measures to evaluate the success of the according interaction sequence (times for target acquisition, pointing, shooting, overall net time, and number of shots) and conduct experiments to record and compare the users' performances. We show that interacting using head-tracking for landscape-rotation is performing similarly to the input of a screen-centered mouse and also yielded shortest times in target acquisition and pointing. Although using head-tracking for target acquisition and pointing was most efficient, subjects rated the modality using head-tracking for target acquisition and a 3DOF Controller for pointing best. Eye-tracking (ET) yields promising results, but calibration issues need to be resolved to enhance reliability and overall user experience.

    DigitalAngewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    L. Tiotsop, E. Masala, A. Aldahdooh, G. Wallendael, Marcus Barkowsky

    Computing Quality-of-Experience Ranges for Video Quality Estimation

    Proceedings of the 2019 Eleventh International Conference on Quality of Multimedia Experience (QoMEX) [5-7 June 2019; Berlin]

    2019

    DOI: 10.1109/QoMEX.2019.8743303

    Abstract anzeigen

    Typically, the measurement of the Quality of Experience for video sequences aims at a single value, in most cases the Mean Opinion Score (MOS). Predicting this value using various algorithms has been widely studied. However, deviation from the MOS is often handled as an unpredictable error. The approach in this contribution estimates intervals of video quality instead of the single valued MOS. Well-known video quality estimators are fused together to output a lower and upper border for the expected video quality, on the basis of a model derived from a well-known subjectively annotated dataset. Results on different datasets provide insight on the suitability of the well-known estimators for this particular approach.

    DigitalAngewandte Informatik

    Zeitschriftenartikel

    A. Aldahdooh, E. Masala, G. Wallendael, P. Lambert, Marcus Barkowsky

    Improving relevant subjective testing for validation: Comparing machine learning algorithms for finding similarities in VQA datasets using objective measures

    Signal Processing: Image Communication, vol. 74, no. May, pp. 32-41

    2019

    DOI: 10.1016/j.image.2019.01.004

    Abstract anzeigen

    Subjective quality assessment is a necessary activity to validate objective measures or to assess the performance of innovative video processing technologies. However, designing and performing comprehensive tests requires expertise and a large effort especially for the execution part. In this work we propose a methodology that, given a set of processed video sequences prepared by video quality experts, attempts to reduce the number of subjective tests by selecting a subset with minimum size which is expected to yield the same conclusions of the larger set. To this aim, we combine information coming from different types of objective quality metrics with clustering and machine learning algorithms that perform the actual selection, therefore reducing the required subjective assessment effort while trying to preserve the variety of content and conditions needed to ensure the validity of the conclusions. Experiments are conducted on one of the largest publicly available subjectively annotated video sequence dataset. As performance criterion, we chose the validation criteria for video quality measurement algorithms established by the International Telecommunication Union.

    DigitalAngewandte Informatik

    Zeitschriftenartikel

    T. Mizdos, Marcus Barkowsky, M. Uhrina, P. Pocta

    Linking Bitstream Information to QoE: A Study on Still Images Using HEVC Intra Coding

    Advances in Electrical and Electronic Engineering, vol. 17, no. 4, pp. 436-445

    2019

    DOI: 10.15598/aeee.v17i4.3625

    Abstract anzeigen

    The coding tools used in image and video encoders aim at high perceptual quality for low bitrates. Analyzing the results of the encoders in terms of quantization parameter, image partitioning, prediction modes or residuals may provide important insight into the link between those tools and the human perception. As a first step, this contribution analyzes the possibility to transcode reference images of three well-known image databases, i.e. IRCCyN/IVC, LIVE and TID2013, from their original, older formats to HEVC; thus creating a homogeneous database of 327 HEVC encoded images accompanied with bitstream parameters and values obtained from objective and subjective assessments. Secondly, it analyzes some of the HEVC intra coding parameters regarding their influence on the image quality by using machine learning, namely Support Vector Machine - Regression.

    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.

    DigitalAngewandte Informatik

    Zeitschriftenartikel

    A. Aldahdooh, E. Masala, G. Wallendael, Marcus Barkowsky

    Framework for reproducible objective video quality research with case study on PSNR implementations

    Digital Signal Processing, vol. 77, no. June, pp. 195-206

    2018

    DOI: 10.1016/j.dsp.2017.09.013

    Abstract anzeigen

    Reproducibility is an important and recurrent issue in objective video quality research because the presented algorithms are complex, depend on specific implementations in software packages or their parameters need to be trained on a particular, sometimes unpublished, dataset. Textual descriptions often lack the required detail and even for the simple Peak Signal to Noise Ratio (PSNR) several mutations exist for images and videos, in particular considering the choice of the peak value and the temporal pooling. This work presents results achieved through the analysis of objective video quality measures evaluated on a reproducible large scale database containing about 60,000 HEVC coded video sequences. We focus on PSNR, one of the most widespread measures, considering its two most common definitions. The sometimes largely different results achieved by applying the two definitions highlight the importance of the strict reproducibility of the research in video quality evaluation in particular. Reproducibility is also often a question of computational power and PSNR is a computationally inexpensive algorithm running faster than realtime. Complex algorithms cannot be reasonably developed and evaluated on the abovementioned 160 hours of video sequences. Therefore, techniques to select subsets of coding parameters are then introduced. Results show that an accurate selection can preserve the variety of the results seen on the large database but with much lower complexity. Finally, note that our SoftwareX accompanying paper presents the software framework which allows the full reproducibility of all the research results presented here, as well as how the same framework can be used to produce derived work for other measures or indexes proposed by other researchers which we strongly encourage for integration in our open framework.

    DigitalAngewandte Informatik

    Zeitschriftenartikel

    A. Aldahdooh, Marcus Barkowsky, P. Le Callet

    Proof-of-concept: role of generic content characteristics in optimizing video encoders

    Multimedia Tools and Applications, vol. 77, pp. 16069-16097

    2018

    DOI: 10.1007/s11042-017-5180-1

    Abstract anzeigen

    The influence of content characteristics on the efficiency of redundancy and irrelevance reduction in video coding is well known. Each new standard in video coding includes additional coding tools that potentially increase the complexity of the encoding process in order to gain further rate-distortion efficiency. In order to be versatile, encoder implementations often neglect the content dependency or they optimize the encoding complexity on a local scale, i.e. on a single frame or on the coding unit level without being aware of the global content type. In this contribution, an analysis is presented which coding tool settings of the recent High Efficiency Video Coding (HEVC) standard are most efficient for a given content type when balancing rate-distortion against computational complexity measured in encoding time. The content type is algorithmically determined, leading to a framework for rate-distortion-complexity based encoder parameter decision for any given video sequence. The implementability is demonstrated using a set of 35 Ultra-HD (UHD) sequences. The performance results and evaluations show that the encoding parameters may be predicted to optimize the video coding. For instance, predicting motion search range achieves complexity reduction of 36% on average when HEVC reference HM is used at a cost of bitrate (2%). When another HEVC coding standard software, x265, is used to predict the coding unit (CU) size, there is a reduction of 20% in bitrate and of 8% in distortion but there is a reduction of 6% in execution time.

    DigitalAngewandte Informatik

    Zeitschriftenartikel

    A. Aldahdooh, E. Masala, G. Wallendael, Marcus Barkowsky

    Reproducible research framework for objective video quality measures using a large-scale database approach

    SoftwareX, vol. 8, no. July-December, pp. 64-68

    2018

    DOI: 10.1016/j.softx.2017.09.004

    Abstract anzeigen

    This work presents a framework to facilitate reproducibility of research in video quality evaluation. Its initial version is built around the JEG-Hybrid database of HEVC coded video sequences. The framework is modular, organized in the form of pipelined activities, which range from the tools needed to generate the whole database from reference signals up to the analysis of the video quality measures already present in the database. Researchers can re-run, modify and extend any module, starting from any point in the pipeline, while always achieving perfect reproducibility of the results. The modularity of the structure allows to work on subsets of the database since for some analysis this might be too computationally intensive. To this purpose, the framework also includes a software module to compute interesting subsets, in terms of coding conditions, of the whole database. An example shows how the framework can be used to investigate how the small differences in the definition of the widespread PSNR metric can yield very different results, discussed in more details in our accompanying research paper Aldahdooh et al. (0000). This further underlines the importance of reproducibility to allow comparing different research work with high confidence. To the best of our knowledge, this framework is the first attempt to bring exact reproducibility end-to-end in the context of video quality evaluation research.

    DigitalAngewandte Informatik

    Zeitschriftenartikel

    K. Brunnström, Marcus Barkowsky

    Statistical quality of experience analysis: on planning the sample size and statistical significance testing

    Journal of Electronic Imaging, vol. 27, no. 5

    2018

    DOI: 10.1117/1.JEI.27.5.053013

    Abstract anzeigen

    This paper analyzes how an experimenter can balance errors in subjective video quality tests between the statistical power of finding an effect if it is there and not claiming that an effect is there if the effect is not there, i.e., balancing Type I and Type II errors. The risk of committing Type I errors increases with the number of comparisons that are performed in statistical tests. We will show that when controlling for this and at the same time keeping the power of the experiment at a reasonably high level, it is unlikely that the number of test subjects that are normally used and recommended by the International Telecommunication Union (ITU), i.e., 15 is sufficient but the number used by the Video Quality Experts Group (VQEG), i.e., 24 is more likely to be sufficient. Examples will also be given for the influence of Type I error on the statistical significance of comparing objective metrics by correlation. We also present a comparison between parametric and nonparametric statistics. The comparison targets the question whether we would reach different conclusions on the statistical difference between the video quality ratings of different video clips in a subjective test, based on the comparison between the student T-test and the Mann‐Whitney U-test. We found that there was hardly a difference when few comparisons are compensated for, i.e., then almost the same conclusions are reached. When the number of comparisons is increased, then larger and larger differences between the two methods are revealed. In these cases, the parametric T-test gives clearly more significant cases, than the nonparametric test, which makes it more important to investigate whether the assumptions are met for performing a certain test.

    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 GesundheitswissenschaftenAngewandte InformatikElektrotechnik und MedientechnikIQW

    Zeitschriftenartikel

    Andreas Gegenfurtner, Armin Eichinger, Richard Latzel, Marc-Philipp Dietrich, Marcus Barkowsky, Alexandra Glufke, Angelika Stadler, Wolfgang Stern

    Mobiles Eye-Tracking in den angewandten Wissenschaften

    Bavarian Journal of Applied Sciences, vol. 4, no. 1, pp. 370-395

    2018

    DOI: 10.25929/bjas.v4i1.54

    Abstract anzeigen

    Mobiles Eye-Tracking ist als Forschungsmethode beliebter denn je und gewinnt in unterschiedlichen Feldern der angewandten Wissenschaften mehr und mehr an Bedeutung. Dieser Beitrag diskutiert, wie die Aufzeichnung und Analyse von Blickbewegungen in der Mobilität, im Usability Engineering, den Sportwissenschaften, der Augmented Reality/Mixed Reality/Virtual Reality und der Medizin bzw. medizinischen Weiterbildung eingesetzt wird. Der Beitrag gliedert sich dabei in drei Teile: in einem ersten Teil werden Grundzüge des Eye-Trackings erläutert; in einem zweiten Teil wird der Einsatz mobilen Eye-Trackings in ausgewählten Feldern der angewandten Wissenschaften veranschaulicht; und in einem abschließenden dritten Teil werden Potentiale und Risiken sowie zukünftige Forschungslinien skizziert, um die Anwendung mobilen Eye-Trackings als digitale Forschungsmethode weiter zu etablieren.

    DigitalAngewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    P. Lebreton, A. Raake, Marcus Barkowsky

    Studying user agreement on aesthetic appeal ratings and its relation with technical knowledge

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

    2016

    DOI: 10.1109/QoMEX.2016.7498934

    Abstract anzeigen

    In this paper, a crowdsourcing experiment was conducted involving different panels of participants. The aim of this study is to evaluate how the preference of one image over another one is related with the knowledge of the participant in photography. In previous work the two discriminant evaluation concepts \textquoteright were found to distinguish group participants with different degrees of knowledge in photography. Each of these groups provided different means of aesthetic appeal ratings when asked to rate on an absolute category scale. The present paper extends previous work by studying preference ratings on a set of image pairs as a function of technical knowledge and more specifically adding a focus on the variance of rating and agreement between participants. The conducted study was composed of two different steps where the participants had to first report their preference of one image over another (paired comparison), and an evaluation of the technical background of the participant using a specific set of images. Based on preference-rating patterns groups of participants were identified. These groups were formed by clustering the participants who saw and shared the same preference rating on images in one group, and the participants with low agreement with other participants in another group. A per-group analysis showed that a high agreement between participants could be observed when participants have technical knowledge. This indicates that higher consistency between participants can be reached when expert users are being recruited, and therefore participants should be carefully selected in image aesthetic appeal evaluation to ensure stable results.

    DigitalAngewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    A. Aldahdooh, E. Masala, G. Wallendael, Marcus Barkowsky

    Comparing temporal behavior of fast objective video quality measures on a large-scale database

    2016 Picture Coding Symposium (PCS)

    2016

    Abstract anzeigen

    In many application scenarios, video quality assessment is required to be fast and reasonably accurate. The characterization of objective algorithms by subjective assessment is well established but limited due to the small number of test samples. Verification using large-scale objectively annotated databases provides a complementary solution. In this contribution, three simple but fast measures are compared regarding their agreement on a large-scale database. In contrast to subjective experiments, not only sequence-wise but also framewise agreement can be analyzed. Insight is gained into the behavior of the measures with respect to 5952 different coding configurations of High Efficiency Video Coding (HEVC). Consistency within a video sequence is analyzed as well as across video sequences. The results show that the occurrence of discrepancies depends mostly on the configured coding structure and the source content. The detailed observations stimulate questions on the combined usage of several video quality measures for encoder optimization.

    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)

    A. Aldahdooh, E. Masala, O. Janssens, G. Wallendael, Marcus Barkowsky

    Comparing simple video quality measures for loss-impaired video sequences on a large-scale database

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

    2016

    Abstract anzeigen

    The performance of objective video quality measures is usually identified by comparing their predictions to subjective assessment results which are regarded as the ground truth. In this work we propose a complementary approach for this performance evaluation by means of a large-scale database of test sequences evaluated with several objective measurement algorithms. Such an approach is expected to detect performance anomalies that could highlight shortcomings in current objective measurement algorithms. Using realistic coding and network transmission conditions, we investigate the consistency of the prediction of different measures as well as how much their behavior can be predicted by content, coding and transmission features, discussing unexpected and peculiar behaviors, and highlighting how a large-scale database can help in identifying anomalies not easily found by means of subjective testing. We expect that this analysis will shed light on directions to pursue in order to overcome some of the limitations of existing reliability assessment methods for objective video quality measures.

    DigitalAngewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    Pierre Lebreton, Alexander Raake, Marcus Barkowsky

    Evaluation of aesthetic appeal with regard of user\textquoterights knowledge

    Proceedings of SPIE Conference Human Vision and Electronic Imaging 2016 (HVEI 2016)

    2016

    DigitalAngewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    Y. Rai, Marcus Barkowsky, P. Le Callet

    Role of spatio-temporal distortions in the visual periphery in disrupting natural attention deployment

    Proceedings of SPIE Conference Human Vision and Electronic Imaging 2016 (HVEI 2016)

    2016

    DOI: 10.2352/ISSN.2470-1173.2016.16.HVEI-117

    Abstract anzeigen

    Human visual system based quality metrics and perceptually optimized video coders often use principles of foveation and saliency to weigh the distortion in certain regions more heavily or hide the artefacts in regions where they are less noticeable. These approaches however fail to consider the impact such a tuning produces on the non-salient surroundings usually incident on the para, peri and extra-peri foveal visual regions. Vision studies on the other hand, have highlighted the enhanced sensitivity of these peripheral visual regions towards spatio-temporal artefacts: more so in the supra-threshold region. Because such analysis has often been performed using controlled synthetic stimuli and forced fixation based experimental approaches, that assume perfect luminance adaptation, tracking and semantic comprehension of underlying content, a thorough understanding of the impact of peripheral disturbances in a natural viewing scenario is missing. The present work therefore uses a Gaze Contingent Display to study the impact of spatiotemporal distortions in the peri foveal and extraperi foveal regions in a free-viewing scenario, using natural scene stimuli. Using four state of the art gaze analysis-techniques to analyze the gaze data collected from 48 observers, spatio-temporally and semantically, confirms and extends our previous understanding of distortion perception in the periphery. Our observations indicate that non-flickering spatial distortions seem to have less of a disruptive effect in the visual periphery as compared to the temporally flickering artefacts and second, the threshold at which disruptions begin to occur is higher in the visual periphery as compared to that of the fovea, both of these effects being strongly scene dependent and prone to natural scene masking. The results highlight the need for sufficient consideration of the supra-threshold effects of peripheral distortions, in order to achieve an optimum perceptual experience.

    DigitalAngewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    M. Shahid, J. Panasiuk, G. van Wallendael, Marcus Barkowsky, B. Lovstrom

    Predicting full-reference video quality measures using HEVC bitstream-based no-reference features

    2015 Seventh International Workshop on Quality of Multimedia Experience (QoMEX)

    2015

    Abstract anzeigen

    This paper presents bitstream-based features for perceptual quality estimation of HEVC coded videos. Various factors including the impact of different sizes of block-partitions, use of reference-frames, the relative amount of various prediction modes, statistics of motion vectors and quantization parameters are taken into consideration for producing 52 features relevant for perceptual quality prediction. The used test stimuli constitutes 560 bitstreams that have been carefully extracted for this analysis from the 59, 520 bistreams of the large-scale database generated by the Joint Effort Group (JEG) of the Video Quality Experts Group (VQEG). The obtained results show the significance of the considered features through reasonably accurate and monotonic prediction of a number of objective quality metrics.

    DigitalAngewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    Y. Rai, Marcus Barkowsky, P. Le Callet

    Does H.265 based peri and para-foveal quality flicker disrupt natural viewing patterns?

    2015 International Conference on Systems, Signals and Image Processing (IWSSIP)

    2015

    Abstract anzeigen

    Region of interest based coders and also those coders that extensively use the Intra coding mode tend to produce flickering artefacts due to the inherent quality fluctuations they produce in the non-salient or homogeneously textured intra coded regions of a scene respectively. These non-salient areas are in turn incident on the para, peri and extra-peri foveal retinal regions that are especially sensitive to temporal artefacts. To study the perceptual effects of such a quality based flicker in the retinal periphery, in this experiment gaze data was collected from 48 observers in a free viewing scenario using a regulated flicker stimulus. The video stimulus in the mentioned peripheral regions were flickered with a predetermined frequency and amplitude by adaptively combining the streams produced using a H.265 video coder, and presenting them in a Gaze Contingent Display(GCD) setup. Utilizing statistical gaze analysis techniques, we observe that, temporal quality flicker in the visual periphery plays a major role in disturbing the natural viewing patterns of an observer. Further, this effect was found to be maximum in the 7.5Hz temporal band thus showing that, encoders that affect temporal quality smoothness must aim to avoid such distraction effects.