| 1. |
- Barkowsky, Marcus, et al.
(författare)
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Crosstalk Measurements of Shutter Glasses 3D Displays
- 2011
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Ingår i: 49th Annual SID Symposium, Seminar, and Exhibition 2011, Display Week 2011. - : Wiley-Blackwell. - 9781618390967 ; , s. 812-815
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Konferensbidrag (refereegranskat)abstract
- Crosstalk is probably one of the main perceptual factors contributing to perceived image quality and visual comfort. The Video Quality Experts Group (VQEG) within their 3D video quality project is specifying a practical measurement procedure that will produce consistent results across laboratories. This paper is part of that effort. Two different method of measuring cross talk on shutter glasses stereo displays have been studied. One is based on time average luminance measurements and the other on temporal measurements. The results show that crosstalk is roughly 0.5% but that there are differences in the crosstalk between the two eyes in the shutter glasses.
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| 2. |
- Barkowsky, Marcus, et al.
(författare)
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Hybrid video quality prediction : Re-viewing video quality measurement for widening application scope
- 2015
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Ingår i: Multimedia tools and applications. - : Springer Science and Business Media LLC. - 1380-7501 .- 1573-7721. ; 74:2, s. 323-343
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Tidskriftsartikel (refereegranskat)abstract
- A tremendous number of objective video quality measurement algorithms have been developed during the last two decades. Most of them either measure a very limited aspect of the perceived video quality or they measure broad ranges of quality with limited prediction accuracy. This paper lists several perceptual artifacts that may be computationally measured in an isolated algorithm and some of the modeling approaches that have been proposed to predict the resulting quality from those algorithms. These algorithms usually have a very limited application scope but have been verified carefully. The paper continues with a review of some standardized and well-known video quality measurement algorithms that are meant for a wide range of applications, thus have a larger scope. Their individual artifacts prediction accuracy is usually lower but some of them were validated to perform sufficiently well for standardization. Several difficulties and shortcomings in developing a general purpose model with high prediction performance are identified such as a common objective quality scale or the behavior of individual indicators when confronted with stimuli that are out of their prediction scope. The paper concludes with a systematic framework approach to tackle the development of a hybrid video quality measurement in a joint research collaboration.
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| 3. |
- Barkowsky, Marcus, et al.
(författare)
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Objective Video Quality Assessment - Towards large scale video database enhanced model development
- 2015
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Ingår i: IEICE transactions on communications. - 0916-8516 .- 1745-1345. ; E98.B:1, s. 2-11
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Tidskriftsartikel (refereegranskat)abstract
- The current development of video quality assessment algorithms suffers from the lack of available video sequences for training, verification and validation to determine and enhance the algorithm’s application scope. The Joint Effort Group of the Video Quality Experts Group (VQEG-JEG) is currently driving efforts towards the creation of large scale, reproducible, and easy to use databases. These databases will contain bitstreams of recent video encoders (H.264, H.265), packet loss impairment patterns and impaired bitstreams, pre-parsed bitstream information into files in XML syntax, and well-known objective video quality measurement outputs. The database is continuously updated and enlarged using reproducible processing chains. Currently, more than 70,000 sequences are available for statistical analysis of video quality measurement algorithms. New research questions are posed as the database is designed to verify and validate models on a very large scale, testing and validating various scopes of applications, while subjective assessment has to be limited to a comparably small subset of the database. Special focus is given on the principles guiding the database development, and some results are given to illustrate the practical usefulness of such a database with respect to the detailed new research questions.
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| 4. |
- Barkowsky, Marcus, et al.
(författare)
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Subjective and objective visual quality assessment in the context of stereoscopic 3D-TV
- 2013
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Ingår i: 3D-TV System with Depth-Image-Based Rendering: Architectures, Techniques and Challenges. - New York, NY : Springer New York. - 9781441999641 - 1441999639 - 9781441999634 ; , s. 413-437
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Subjective and objective visual quality assessment in the context of stereoscopic three-dimensional TV (3D-TV) is still in the nascent stage and needs to consider the effect of the added depth dimension. As a matter of fact, quality assessment of 3D-TV cannot be considered as a trivial extension of two-dimensional (2D) cases. Furthermore, it may also introduce negative effects not experienced in 2D, e.g., discomfort or nausea. Based on efforts initiated within the cost action ICT 1003 QUALINET, this chapter discusses current challenges in relation to subjective and objective visual quality assessment for stereo-based 3D-TV. Two case studies are presented to illustrate the current state of the art and some of the remaining challenges.
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| 5. |
- Barkowsky, Marcus, et al.
(författare)
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Towards standardized 3DTV QoE assessment : Cross-lab study on display technology and viewing environment parameters
- 2013
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 9780819494214
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Konferensbidrag (refereegranskat)abstract
- Subjective assessment of Quality of Experience in stereoscopic 3D requires new guidelines for the environmental setup as existing standards such as ITU-R BT.500 may no longer be appropriate. A first step is to perform cross-lab experiments in different viewing conditions on the same video sequences. Three international labs performed Absolute Category Rating studies on a freely available video database containing degradations that are mainly related to video quality degradations. Different conditions have been used in the labs: Passive polarized displays, active shutter displays, differences in viewing distance, the number of parallel viewers, and the voting device. Implicit variations were introduced due to the three different languages in Sweden, South Korea, and France. Although the obtained Mean Opinion Scores are comparable, slight differences occur in function of the video degradations and the viewing distance. An analysis on the statistical differences obtained between the MOS of the video sequences revealed that obtaining an equivalent number of differences may require more observers in some viewing conditions. It was also seen that the alignment of the meaning of the attributes used in Absolute Category Rating in different languages may be beneficial. Statistical analysis was performed showing influence of the viewing distance on votes and MOS results.
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| 6. |
- Brunnstrom, Kjell, 1960-, et al.
(författare)
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Statistical quality of experience analysis: on planning the sample size and statistical significance testing
- 2018
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Ingår i: Journal of Electronic Imaging (JEI). - SPIE/IS&T : IS&T - the Society for Imaging Science and Technology. - 1017-9909 .- 1560-229X. ; 27:5, s. 053013-1-053013-11
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Tidskriftsartikel (refereegranskat)abstract
- This paper analyzes how an experimenter can balance errors in subjective video quality tests betweenthe 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 ofcomparisons that are performed in statistical tests. We will show that when controlling for this and at thesame time keeping the power of the experiment at a reasonably high level, it is unlikely that the number oftest 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 likelyto be sufficient. Examples will also be given for the influence of Type I error on the statistical significance ofcomparing objective metrics by correlation. We also present a comparison between parametric and nonparametricstatistics. The comparison targets the question whether we would reach different conclusions on the statisticaldifference between the video quality ratings of different video clips in a subjective test, based on thecomparison between the student T-test and the Mann–Whitney U-test. We found that there was hardly a differencewhen few comparisons are compensated for, i.e., then almost the same conclusions are reached. Whenthe number of comparisons is increased, then larger and larger differences between the two methods arerevealed. In these cases, the parametric T-test gives clearly more significant cases, than the nonparametrictest, which makes it more important to investigate whether the assumptions are met for performing a certaintest.
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| 7. |
- Brunnström, Kjell, et al.
(författare)
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Balancing type I errors and statistical power in video quality assessment
- 2017
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Ingår i: IS and T International Symposium on Electronic Imaging Science and Technology. - : Society for Imaging Science and Technology. ; , s. 91-96
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Konferensbidrag (refereegranskat)abstract
- 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 it 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 will require more test subjects than are normally used and recommended by international standardization bodies like the ITU. Examples will also be given for the influence of Type I error on the statistical significance of comparing objective metrics by correlation.
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| 8. |
- Brunnström, Kjell, 1960-, et al.
(författare)
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Comparison between different rating scales for 3D TV
- 2013
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Ingår i: Digest of Technical Papers - SID International Symposium. - : Blackwell Publishing Ltd. - 0097-966X. ; 44:1, s. 509-512
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Tidskriftsartikel (refereegranskat)abstract
- Stereoscopic 3D viewing experience has been studied quite intensively recently, but still the subjective test methods have not yet been settled. It has become clear that the 3D viewing experience cannot easily be described by just one scale. This paper describes a study where three different rating scales (Quality, Discomfort and Presence) are compared in a subjective test, combined with two viewing distances. The results shows that in a stereoscopic 3D video quality test targeting mainly coding distortions one scale such as video quality could be sufficient.
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| 9. |
- Engelke, Ulrich, et al.
(författare)
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Modelling Saliency Awareness for Objective Video Quality Assessment
- 2010
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Konferensbidrag (refereegranskat)abstract
- Existing video quality metrics do usually not take into consideration that spatial regions in video frames are of varying saliency and thus, differently attract the viewer's attention. This paper proposes a model of saliency awareness to complement existing video quality metrics, with the aim to improve the agreement of objectively predicted quality with subjectively rated quality. For this purpose, we conducted a subjective experiment in which human observers rated the annoyance of videos with transmission distortions appearing either in a salient region or in a non-salient region. The mean opinion scores confirm that distortions in salient regions are perceived much more annoying. It is shown that application of the saliency awareness model to two video quality metrics considerably improves their quality prediction performance.
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| 10. |
- Shahid, Muhammad, et al.
(författare)
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Predicting full-reference video quality measures using HEVC bitstream-based no-reference features
- 2015
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Ingår i: International Workshop on Quality of Multimedia Experience. - : IEEE Communications Society. - 9781479989584
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Konferensbidrag (refereegranskat)abstract
- 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. © 2015 IEEE.
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