Comparison of HD and UHD video quality with and without the influence of the labeling effect

Abstract

The past decades have shown a steady rise in the pixel resolution of digital visualization technologies. New TVs and computer displays available on the consumer market are commonly UHD/4K, and 8K recently started appearing in the commercial world. The added value of such higher resolution is not only indicated by the purported level of visual performance, but also by the labels that emphasize the devices' properties, especially the resolution. However, the genuinely perceived difference between two resolutions, such as HD and UHD, may not have the same effect on user experience as the labels attached to the devices or sequences themselves. In this paper we present four subjective studies in which we investigated the influence of the labeling effect in the context of HD and UHD video. Subjects were shown pairs of either HD or UHD video sequences and had to determine whether there was a difference in quality between the sequences. Two of the subjective tests involved labels in these paired comparisons, indicating to the subject which sequence was which, while the other two tests excluded these labels. For both test sets with and without labels, one test used a 3-point comparison scale for the subjective assessment of visual quality, while the other used a more fine-grained 7-point scale. Our findings show that the sole inclusion of quality labels can strongly impact subjective rating behavior and the overall opinion on UHD quality; also, visual differences between HD and UHD video were rarely noticeable by the subjects. Standards and recommendationsAs with most technologies finding widespread use among the consumers, there are standards that govern how a technology is to be developed, evaluated, and integrated with other technologies. Standards or international recommendations are provided for that interoperability. Among the most relevant international standards on the topic of UHD are documents from the International Telecommunication Union's telecommunication and broadcasting sectors (ITU-T and ITU-R).While ITU-R Rec. BT.709 addresses HDTV (i.e., TV up to 1080p resolution), Rec. BT.2020 [3] covers UHD and the corresponding specifications of dynamic range, color gamut and primaries, bit depths, frame rates, and pixel resolutions. Additional recommendations include Rec. BT.1769 which specifies parameter values for large screen digital imagery and how to design a system that gives viewers visual experiences of a high-sensation of reality-which UHD was also developed for.Subjective quality assessment tests are typically carried out in a rigorous fashion: users are placed in a dedicated testing room with specific lighting conditions and a certain viewing distance to the screen. Guidelines in ITU-T Recommendations P.910, P.911, and P.913 as well as ITU-R Rec. BT.500-13 may be applied in those tests. When subjectively evaluating the quality of UHD systems, the aspect of viewing distance plays a crucial role. Typically, for HDTV applications, human testers are seated at a distance of about 3 H to the TV, where H is the ...

Multi-Model Standard for Bitstream-, Pixel-Based and Hybrid Video Quality Assessment of UHD/4K: ITU-T P.1204

“…When aiming for a sensitive assessment of encoding quality for high resolutions such as 4K UHD (3840 × 2160 pixels), laboratory tests with a controlled and 4K-appropriate viewing distance of 1.5 to 1.6 times the height of the screen ("1.5H" or "1.6H") are recommended, see [26,27]. As was shown in a number of studies, even in laboratory tests with highquality screens and controlled viewing conditions that follow recommendations such as those in [27,28], in many cases video quality can hardly be distinguished between HD and 4K UHD resolution, specifically depending on the initial quality of the source content used [29,30,31,32,33]. On the other hand, test contents in video quality tests 1 often are rather artificial and not representative of actual target applications such as VoD or live streaming.…”

Quality assessment of higher resolution images and videos with remote testing

“…Similar to image quality assessment, video quality is usually evaluated in traditionally conducted lab tests, especially in the case of higher resolutions such as UHD-1/4K or even UHD-2/8K. There are various examples of quality evaluation for videos reported in the literature, e.g., [4,11,12,31,46,47,58,86,111,115]. All the mentioned studies have in common that they are conducted in controlled lab environments.…”

Beyond Perceptual Thresholds and Personal Preference: Towards Novel Research Questions and Methodologies of Quality of Experience Studies on Light Field Visualization

“…When the use cases of light field displays are addressed, the framing effect [53] may be relevant as well, which affects perception through the context itself. Additionally, since the vast majority of naïve test participants have never seen any light field system prior to the experiment-or has never even heard of the technology-the initial visual experience may result in the effect of anchoring [54], and introducing light field technology to such individuals may induce the labeling effect, the influence of which has already been studied for Ultra-High Definition (UHD) [55] and High Dynamic Range (HDR) [56] displays.…”