Search

Immersive media such as virtual reality, augmented reality, and 360° video have seen tremendous technological developments in recent years. Furthermore, the advances in head-mounted displays (HMDs) offer the users increased immersive experiences compared to conventional displays. To develop novel immersive media systems and services that satisfy the expectations of the users, it is essential to conduct subjective tests revealing users’ perceived quality of immersive media. However, due to the new viewing dimensions provided by HMDs and the potential of interacting with the content, a wide range of subjective tests are required to understand the many aspects of user behavior in and quality perception of immersive media. The ground truth obtained by such subjective tests enable the development of optimized immersive media systems that fulfill the expectations of the users. This article focuses on the consistency of 360° video quality assessment to reveal whether users’ subjective quality assessment of such immersive visual stimuli changes fundamentally over time or is kept consistent for each user. A pilot study was conducted under pandemic conditions with participants given the task of rating the quality of 360° video stimuli on an HMD in standing and seated viewing. The choice of conducting a pilot study is motivated by the fact that immersive media impose high cognitive load on the participants and the need to keep the number of participants under pandemic conditions as low as possible. To gain insight into the consistency of the participants’ 360° video assessment over time, three sessions were held for each participant and each viewing condition with long and short breaks between sessions. In particular, the opinion scores and head movements were recorded for each participant and each session in standing and seated viewing. The statistical analysis of this data leads to the conjecture that the quality rating stays consistent throughout these sessions with each pa

Non-terrestrial networks based on unmanned aerial vehicles (UAVs) are considered for integration with 6G mobile networks to provide ubiquitous communication through heterogeneous networks. UAVs offer benefits such as flexible deployment, mobility control, and strong line-of-sight links. In this paper, orthogonal multiple access (OMA) and nonorthogonal multiple access (NOMA) are combined to form a hybrid OMA-NOMA cognitive radio (CR) assisted cooperative UAV system. The selection of either the OMA or NOMA mode is carried out such that the best link quality is offered to the user equipments (UEs) compared to the individual modes. In this system, the base station uses the NOMA mode for the transmission to the UAVs which act as decode-and-forward relays each serving a cluster of UEs. The CR paradigm is used for the NOMA mode of the hybrid system to reduce the interference caused by the UAVs to adjacent clusters of UEs. Analytical expressions of the outage probability and sum rate of the OMA, NOMA, and hybrid OMA-NOMA systems are derived. Numerical results are provided to reveal the performance advantages of the proposed hybrid OMA-NOMA CR-assisted cooperative UAV system over Nakagami-m fading. Further, design options and tradeoffs between the OMA, NOMA, and hybrid OMA-NOMA systems are illustrated. © 2024 IEEE.

Future 6G mobile networks are expected to provide ubiquitous communication to a wide range of mobile devices through heterogeneous networks including non-terrestrial networks (NTNs). As an important complement to terrestrial networks, unmanned aerial vehicles (UAVs) based NTNs offer benefits such as flexible deployment, mobility control, and strong line-of-sight links. In this paper, a cognitive radio (CR) assisted cooperative non-orthogonal multiple access (NOMA) UAV system is proposed and its performance is analysed. In this system, the base station uses power-domain NOMA regarding the UAVs. The UAVs act as decode-and-forward relays serving clusters of user equipments (UEs). The CR concept is applied to reduce the interference caused by the UAVs to adjacent clusters of UEs. Analytical expressions of the outage probability and sum rate of this system are derived for the case of Nakagami-m fading. Numerical results are provided to reveal the impact of system parameters on the outage probability and sum rate. Further, design options and trade-offs between orthogonal multiple access and CR assisted cooperative NOMA UAV systems are illustrated. © 2024 IEEE.

In this paper, a mobile virtual reality (VR) video streaming system is considered and assessed. The system comprises of a VR server, a VR center offering mobile edge computing along with a buffer, and a mobile head-mounted display (HMD). Markov-modulated processes are used to model the arrival and departure traffic at the VR center and the time-varying link quality of the wireless channel to the mobile HMD. As the Markovian arrival process at the VR center is independent of the link quality variations of the wireless channel, the VR center controls the delivery of VR video packets to the mobile HMD subject to the link quality of the wireless channel. The Markov models are used to derive expressions of queueing theoretical performance measures, i.e., throughput, queueing delay, and packet loss probability. Numerical results are provided to investigate performance trade-offs for real data traces. © 2024 IEEE.

The recent advances in immersive technologies have been essential in the development of a wide range of novel standalone and networked immersive media applications. The concepts of virtual reality, augmented reality, and mixed reality relate to different compositions of real and computer-generated virtual objects. In this context, 360° video streaming has become increasingly popular offering improved immersive experiences when viewed on a head-mounted display (HMD). An important component in the development of novel immersive media systems are subjective tests in which participants assess the quality of experience of representative test stimuli. In this paper, the annotated ACR360 dataset is presented which is publicly available on GitHub. The ACR360 dataset contains a wide range of psychophysical and psychophysiological data that was collected in Subjective tests on 360° video quality. The test stimuli were shown on an HMD and rated according to the absolute category rating (ACR) and modified ACR (MACR) methods. To support an easy exploration and utilization of the ACR360 dataset by the research community, its structure on GitHub is described and a comprehensive illustration of analysis options are provided for each data category. The ACR360 dataset may be used for conducting meta-analysis in combination with other datasets to improve precision and to pursue research questions that cannot be answered by an individual study. © 2023 IEEE.

Directed Air Data Link

During the last decade, we have witnessed a rapiddevelopment of extended reality (XR) technologies such asaugmented reality (AR) and virtual reality (VR). Further, therehave been tremendous advancements in artificial intelligence(AI) and machine learning (ML). These two trends will havea significant impact on future digital societies. The vision ofan immersive, ubiquitous, and intelligent virtual space opensup new opportunities for creating an enhanced digital world inwhich the users are at the center of the development process,so-calledintelligent realities(IRs).The “Human-Centered Intelligent Realities” (HINTS) profileproject will develop concepts, principles, methods, algorithms,and tools for human-centered IRs, thus leading the wayfor future immersive, user-aware, and intelligent interactivedigital environments. The HINTS project is centered aroundan ecosystem combining XR and communication paradigms toform novel intelligent digital systems.HINTS will provide users with new ways to understand,collaborate with, and control digital systems. These novelways will be based on visual and data-driven platforms whichenable tangible, immersive cognitive interactions within realand virtual realities. Thus, exploiting digital systems in a moreefficient, effective, engaging, and resource-aware condition.Moreover, the systems will be equipped with cognitive featuresbased on AI and ML, which allow users to engage with digitalrealities and data in novel forms. This paper describes theHINTS profile project and its initial results. ©2023, Copyright held by the authors

In this paper, we consider a downlink scenario in which a base station (BS) communicates with user equipment (UE) that move with high speed. Orthogonal time frequency space (OTFS) modulation is used to overcome the effects of high Doppler shifts inherent with high-mobility scenarios. To increase spectral efficiency, power-domain non-orthogonal multiple access (NOMA) is combined with OTFS to form an OTFS-NOMA system. The K-means clustering algorithm is deployed which partitions the coverage area of the BS into clusters such that the UEs within a cluster have a shorter distance to the respective cluster center than to the centers of the other clusters. The cluster centers act as simultaneous multiple users on which basis power-domain NOMA selects the power allocation coefficients to reduce the mutual interference among UEs. OTFS can control the resolution of the delay-Doppler domain to more accurately compensate for propagation delays and Doppler shifts. The performance of this OTFS-NOMA system with K-means clustering of the UEs is assessed in terms of sum rate. The numerical results illustrate that the successive interference cancellation of power-domain NOMA significantly improves sum rate. Additional improvements are obtained by choosing a sufficiently large size of the delay-Doppler grid of OTFS which effectively copes with the high Doppler shifts of the considered high-mobility scenario. © 2023 IEEE.

Fifth generation (5G), beyond 5G (B5G), and future sixth generation (6G) mobile networks are foreseen to increasingly account for heterogeneous networks toward ubiquitous communications with non-terrestrial networks (NTNs). Furthermore, in 5G mobile networks, massive machine type communications has been introduced for Internet of Things (IoT) applications aiming at low energy consumption, low to medium data rates, burst transmissions, and massive connectivity. It is expected that IoT communications will take an even larger portion in B5G and 6G mobile networks. Robust communications in such high-mobility NTN deployments including unmanned aerial vehicles (UAVs), airborne platforms, and satellite systems, need novel modulation waveforms that can deal with the induced severe Doppler effects. Orthogonal time frequency space (OTFS) modulation has gained tremendous interest in recent years as an effective technology for coping with high Doppler channels. OTFS essentially transforms a time-varying fading channel into a quasi-static channel in the delay-Doppler domain. In this paper, for the first time, an overview on OTFS modulation for NTNs is provided including basic concepts and applications in UAVs, airborne networks, and satellite systems. A case study related to an application in high Doppler airborne communication networks is also provided to illustrate the potential of OTFS modulation in providing robust transmission links in high-mobility scenarios. This survey will be helpful for researchers and practitioners to keep abreast about the potential of OTFS modulation in NTNs. © 2023 IEEE., Riktad luftdatalänk

Sixth-generation (6G) networks are considered as key enablers in the development of the intelligent information society offering ultra-reliable low-latency communications in the context of massive machine-type communications and the emergence of the Internet-of-everything. In this paper, we consider a short-packet cooperative nonorthogonal multiple access (C-NOMA) communication system that uses the K-means algorithm for user clustering. The short-packet component of the system facilitates low-latency communications. In addition, C-NOMA using decode-and-forward relays allows extended coverage in terms of user equipment (UE) clusters and spectral efficiency in terms of sum rate. Given the trend toward irregular deployment of heterogeneous infrastructure elements in 6G networks and massive amounts of UEs, the K-means algorithm is used to generate clusters of UEs around the locations of the relays that assist the communication between the base station and the UEs. Analytical expressions of the block error rate (BLER) and sum rate are derived allowing a performance assessment of the short-packet C-NOMA communication system. Numerical results are provided revealing the impact of the number of channel uses and the number of UEs on the BLER and sum rate of the considered system. © 2023 IEEE.

Fifth-generation (5G) and future sixth-generation (6G) mobile networks aim at offering ultra-reliable, low-latency, and massive machine-type communications. In this context, this paper studies full-duplex (FD) cooperative non-orthogonal multiple access (C-NOMA) short-packet communications (SPC) with K-means clustering of user equipment regarding block error rate (BLER) and sum rate. Analytical expressions are derived for the BLER and sum rate allowing to assess the performance of the considered system. The numerical results reveal the benefits of the FD C-NOMA SPC system, illustrate trade-offs between BLER and sum rate, and show the impact of the transmit signal-to-noise ratio and number of channel uses on the performance. © 2023 IEEE.

The performance of remotely rendered Virtual Reality (VR) is sensitive to temporal disturbances in communication channels. An earlier Quality of Experience (QoE) study of temporal impacts in the form of frame stalls has revealed difficulties with subjective disturbance ratings while performing a task in an interactive 6-degrees-of-freedom (DOF) VR environment. This study follows up on above observation by comparing QoE ratings in the presence and absence of a task. The exploratory findings show that the task-free subjective tests yield lower ratings compared to the subjective tests with task. This indicates that the participants became more sensitive to temporal impairments in the absence of a task. Also, the positive impact of reprojection on the QoE ratings decreased in the task-free environment. The simulator sickness results for individual symptoms were on similar low levels in both settings. The total score (TS) of sickness severity was higher after than before the subjective tests with task while the difference between the TS before and after the task-free subjective tests was insignificant, © 2023 IEEE.

The emerging 5G mobile networks are essential enablers for mobile virtual reality (VR) video streaming applications assuring high quality of experience (QoE) at the end-user. In addition, mobile edge computing brings computational resources closer to the user equipment (UE), which allows offloading computationally intensive processing. In this paper, we consider a network architecture for mobile VR video streaming applications consisting of a server that holds the VR video content, a mobile edge virtualization with prefetching (MVP) unit that handles the VR video packets, and a head-mounted display along with a buffer, which together serve as the UE. Several modulation and coding schemes with different rates are provided by the MVP unit to adaptively cope with the varying wireless link conditions to the UE and the state of the UE buffer. The UE buffer caches VR video packets as needed to compensate for the adaptive rates. A performance analysis is conducted in terms of blocking probability, throughput, queueing delay, and average packet error rate. To capture the effect of fading severity, the analytical expressions for these performance metrics are derived for Nakagami-m fading on the wireless link from the MVP unit to the UE. Numerical results show that the proposed system meets the network requirements needed to assure the QoE levels of different mobile VR video streaming applications. © 2022 by the authors. Licensee MDPI, Basel, Switzerland., open access

Data hiding or information hiding is a prominent class of information security that aims at reliably conveying secret data embedded in a cover object over a covert channel. Digital media such as audio, image, video, and three-dimensional (3D) media can act as cover objects to carry such secret data. Digital media security has acquired tremendous significance in recent years and will be even more important with the development and delivery of new digital media over digital communication networks. In particular, least significant bit (LSB) data hiding is easy to implement and to combine with other hiding techniques, offers high embedding capacity for data, can resist steganalysis and several types of attacks, and is well suited for real-time applications. This article provides a comprehensive survey on LSB data hiding in digital media. The fundamental concepts and terminologies used in data hiding are reviewed along with a general data hiding model. The five attributes of data hiding, i.e., capacity, imperceptibility, robustness, detectability, and security, and the related performance metrics used in this survey to compare the characteristics of the different LSB data hiding methods are discussed. Given the classification of data hiding methods with respect to audio, image, video, and 3D media, a comprehensive survey of LSB data hiding for each of these four digital media is provided. In particular, landmark studies, state-of-the-art approaches, and applications of LSB data hiding are described for each of the four digital media. Their performance is compared with respect to the data hiding attributes which illustrates benefits and drawbacks of the reviewed LSB data hiding methods. The article concludes with summarizing main findings and suggesting directions for future research. This survey will be helpful for researchers and practitioners to keep abreast about the potential of LSB data hiding in digital media and to develop novel applications based on suitable perf

Wireless virtual reality (VR) offers a seamless user experience but has to cope with higher sensitivity to temporal impairments induced on the wireless link. Apart from bandwidth dynamics and latency, video freezes and their lengths are important temporal performance indicators that impact on the quality of experience (QoE) of networked VR applications and services. This paper reports an experimental study that focuses on the VR video frame freeze length characteristics of a wireless VR solution. A comprehensive measurement campaign using a commercial TPCAST wireless VR solution with an HTC Vive head-mounted display was conducted to obtain real VR video traces. The number of detected freezes and freeze intensities are reported both accumulated over four room quadrants as well as for each of the four quadrants subject to six transmitter-receiver distances. The statistical analysis of the VR video traces of the different experiments includes histograms of the freeze lengths and cumulative complementary histograms of the freeze length. The results of this analysis offer insights into the density of the underlying distributions of the measured data, illustrate the impact of the room topology on the freeze characteristics, and suggest the statistical modeling of the freeze characteristics as exponential and geometric distributions. The statistical models of the freeze characteristics may be included in wireless VR simulators supporting the development of physical layer, medium access layer, and higher layer functionalities. They also may serve as network-disturbance models for VR QoE studies, e.g., generating realistic freeze events in wireless VR stimuli. © 2022 by the authors. Licensee MDPI, Basel, Switzerland., open access

In this paper, we consider airborne communication networks with directed air data links between high-mobility airborne platforms. Orthogonal time frequency space (OTFS) modulation is used to overcome the effects of the high Doppler shifts induced by the high relative speeds among airborne platforms which can be in excess of 1200 m/s. The performance of the considered system is assessed using the Rician channel to model the directed air data links accounting for the ratio of the signal power in the line-of-sight path to the signal power in the scattered paths. The numerical results reveal significant bit error rate (BER) improvements with increased Rician K-factor, illustrate the trade-offs between BER and bits per symbol offered by different modulation schemes, and show the independence of the BER from the relative speeds among airborne platforms. Further, it is shown that the BER of a single path directed air data link approaches that of a two-ray channel for a sufficiently large Rician K-factor. © 2022 IEEE., Riktad luftdatalänk

In this paper, we propose and assess the performance of a downlink non-orthogonal multiple access (NOMA)based full-duplex (FD) unmanned aerial vehicle (UAV) network for disaster scenarios. The K-means algorithm is used to partition the user equipments (UEs) residing in the disaster region into a number of clusters. The UAVs are located at the cluster centers and act as decode-and-forward relays to secure coverage from an operational base station (BS) into the disaster region. The power-domain NOMA used at the BS and the UAVs operating in FD mode improve the system performance in terms of outage probability and sum rate compared to orthogonal multiple access and half-duplex mode. In particular, analytical expressions for the outage probability and sum rate are derived. Numerical results are provided to reveal the impact of system parameters on the performance of the NOMA-based FD UAV network over Nakagami-m fading which in turn illustrate design options for applications in disaster scenarios. © 2022 IEEE.

Remotely rendered Virtual Reality (VR) typically has to rely upon less capable and less reliable communication channels as compared to locally rendered VR. Such communication channels pose the risk of impairing the VR experience with temporary disturbances in form of frame stalls that would not be present in local VR. However, it is not obvious to which extent the durations of temporary stalls affect the Quality of Experience (QoE) in interactive 6-degrees-of-freedom (DOF) VR, and neither to which extent present reprojection/warping techniques mitigate any adverse effects of such stalls on user perception. In this paper, subjective experiments were conducted with N =29 users to quantify the relationship between QoE and single, isolated stall durations in interactive 6-DOF remote VR when stalls either freeze the frame in place, or when frames are reprojected by the VR driver. Results indicate that given a 90 fps headset and a simple task that requires moderate head-movement; (1) short, isolated stalls of up to 4 frames go unnoticed on average, no matter whether reprojection is used or not, (2) the number of perceived stalls when using reprojection is the same or lower than the reference (no stall) in the range 1-4 frame stalls, (3) reprojection entails significantly higher user ratings for stalls ranging from 8 frames and beyond, (4) the improvement of using reprojection over freezes in terms of making more stalling events imperceptible is highest in the range 8-16 frames. © 2022 IEEE.

To support ultra-reliable low latency communication (URLLC) services in fifth-generation mobile networks, short-packet transmission is essential. However, due to the limited packet size, errors cannot be reduced to arbitrarily low levels for a given coding rate as for conventional communication systems covered by the Shannon theory. In this paper, we consider URLLC in dual-hop decode-and-forward relaying networks where the channel in each hop varies fast. A simple but efficient optimization of the block lengths is performed to minimize the block error rate (BLER) of the proposed system. In particular, we deploy machine learning models using the linear regression and normalized method to determine the optimal fraction of channel uses for the transmission over each hop. Numerical results show that the BLER of the consider relaying system with optimal block lengths for each hop based on the machine learning model outperforms conventional relaying systems with equal block lengths. © 2022 IEEE.

In this paper, a stochastic geometry approach is used to model and analyse a downlink small cell network (SCN). Carrier sense multiple access with collision avoidance (CSMA/CA) is used as medium access control (MAC) protocol at the base stations (BSs). To boost spectral efficiency, each active BS deploys both orthogonal multiple access (OMA) and nonorthogonal multiple access (NOMA) to transmit signals to the user equipments (UEs) in its coverage area. The choice between OMA and NOMA mode is based on the density of UEs and aims to improve the sum rate of the BS. If there exist two UEs that sufficiently differ in their channel power gains to the BS, the BS will use NOMA superimposing the signals of the UEs in the power-domain. Otherwise, the BS will operate in OMA mode to transmit the signal of a single UE in its coverage area. Stochastic geometry is used to include the spatial densities of the UEs and BSs in the performance assessment of the SCN. On this basis, analytical expressions for the coverage probability, data rates of the UEs, and sum rate of the BSs of the considered system are derived. Numerical results are provided to illustrate the impact of system parameters on the performance of this SCN with NOMA subject to the spatial densities of the BSs and UEs., open access

In this paper, antenna grouping together with maximum ratio transmission (MRT), maximum ratio combining (MRC), and interference cancellation is used to improve the performance of MIMO systems. In particular, the transmit and receive antennas are divided into two antenna groups to reduce correlation between antennas and to improve spatial separation between data streams. Analytical expressions for the outage probability, symbol error rate, channel capacity, and total channel capacity of the MIMO MRT-MRC system with antenna grouping and interference cancellation are derived. The effect of the power allocation to the two antenna groupings on system performance is also studied. The numerical results show that an optimal value of the power allocation coefficient exists that achieves a maximum total channel capacity. Further, for a given power allocation coefficient, there exists an antenna configuration that maximizes the total channel capacity of the considered MIMO MRT-MRC system. These findings allow to select both the optimal power allocation coefficient for a given antenna grouping and the preferable antenna grouping for a given power allocation coefficient that maximize the total channel capacity of the system., 8th IEEE International Conference on Communications and Electronics (IEEE ICCE), VIETNAM, JAN 13-15, 2021

This white paper discusses various topics, advances, and projections regarding machine learning (ML) in wireless communications. Sixth generation (6G) wireless communications networks will be the backbone of the digital transformation of societies by providing ubiquitous, reliable, and near-instant wireless connectivity for humans and machines. Recent advances in ML research have enabled a wide range of novel technologies such as self-driving vehicles and voice assistants. Such innovation is made possible by the availability of advanced ML models, large datasets, and high computational power. In addition, the ever-increasing demand for connectivity will require even more extensive innovation in 6G wireless networks. Consequently, ML tools will play a major role in solving the new problems in the wireless domain. In this paper, we offer a vision of how ML will impact wireless communications systems. We first provide an overview of the ML methods that have the highest potential to be used in wireless networks. We then discuss the problems that can be solved by using ML in various layers of the network such as the physical, medium-access, and application layers. Zero-touch optimization of wireless networks using ML is another interesting aspect discussed in this paper. Finally, at the end of each section, a set of important future research questions is presented.

Virtual reality (VR) has seen tremendous advances in head-mounted displays (HMDs), optics, media quality, and other improvements that facilitate immersive experiences. With the occurrence of new technologies like Cloud VR and networked VR video services, applications such as 360° video streaming are becoming more popular within the broader consumer markets. As a result, VR content is accessible to customers with rather different levels of experiences with immersive media, i.e., never, sometimes, or often use of VR. The question, therefore, arises to which degree simulator sickness is induced to viewers depending on their experiences with VR on HMDs. In this paper, simulator sickness is evaluated for 360° videos that were shown on an HTC Vive Pro HMD to participants having different levels of experience with VR on HMDs. The modified absolute category rating with hidden reference (M-ACR-HR) method was used in a subjective experiment for video quality assessment within two subsequent sessions along with a simulator sickness questionnaire (SSQ). A statistical analysis of the SSQ scores is performed to reveal the relationship between simulator sickness and participants' experiences with VR regarding: (1) Individual symptoms, (2) Pairwise comparison of symptoms, and (3) Symptom clusters of nausea, oculomotor, disorientation, and total score. It is shown that the simulator sickness symptoms, in general, are slightly or rarely perceived across the different experience levels for the selected 360° videos. The results indicate that the reported simulator sickness increases in the second session for participants that never used VR on HMDs. Sufficiently long breaks between sessions should therefore be accounted for in the M-ACR-HR method to avoid that simulator sickness influences quality rating. © 2020 IEEE.

In this paper, we propose a visual attention based least significant bit (LSB) data hiding method for 360° videos. In particular, information about the relative frequency of pixel access is used to control the amount of secret data to be hidden at the different latitudes of 360° videos. In this way, the typical behavior of users paying more attention to the equator region compared to the north and south poles when viewing 360° videos on a head-mounted display is taken into account. An analytical expression for capacity offered by this method to hide secret data in 360° cover videos is derived. A performance assessment of the visual attention based LSB data hiding method is conducted in terms of the peak signal-to-noise ratio (PSNR) and weighted-to-spherically-uniform PSNR (WS-PSNR) which both quantify the fidelity of a 360° stego-video with reference to the related 360° cover video. © 2020 IEEE., open access

Watching 360° videos on head-mounted displays (HMDs) has become more popular in recent years. As such, subjective quality assessment of 360° videos on HMDs is needed to obtain a ground truth on the quality as perceived by users. Due to the lack of standardized methods, the absolute category rating (ACR) with hidden reference (ACR-HR) method for conventional videos has also been used for subjective quality assessment of 360° videos on HMDs. A modified ACR (M-ACR) method tailored for assessing 360° videos on HMDs has recently been proposed. In this paper, we compare the ACR-HR and M-ACR with hidden reference (M-ACR-HR) method regarding subjective quality assessment of 360° videos on HMDs. The comparison is conducted subject to participants' experience with watching immersive media on HMDs. The findings include: 1) Average rating times to cast opinion scores is lower for the ACR-HR method irrespective of participants' experience, 2) Mean opinion scores are similar for both methods irrespective of participants' experience, 3) The M-ACR-HR method is more reliable, especially with experts and participants with no experience, 4) Discomfort is significantly lower for the ACR-HR method, especially, for participants with no experience. © 2020 IEEE., open access

Due to large advances in immersive media systems offering increased resolutions, frame rates, and dynamic ranges, applications such as watching 360° videos on head-mounted displays (HMDs) have become more popular. To assist the development of immersive media applications, subjective tests of 360° videos on HMDs are needed to obtain a ground truth on the quality as perceived by the end-users. The absolute category rating (ACR) method, standardized for subjective quality assessment of conventional videos, has also been used for assessing the subjective quality of 360° videos. Recently, the modified ACR (M-ACR) method has been proposed aiming at subjective quality assessment of 360° videos. Several subjective test campaigns have been conducted to assess the ACR and M-ACR method for evaluating 360° videos covering a wide range of resolutions, bit rates, and quantization parameters. The opinion scores given by the participants in these subjective tests are accumulated to mean option scores (MOSs) and confidence intervals. However, to the best of our knowledge, a detailed statistical analysis and comparison of the rating durations associated with casting opinion scores for 360° test videos in the ACR and M-ACR method has not been reported in the literature. In this paper, we therefore provide a rating duration analysis for subjective quality assessment of 360° videos for the ACR and M-ACR method. The results support experimental designs for 360° video quality assessment and include the following findings: 1) The mean rating duration is shorter for the ACR method, 2) The difference of the standard deviation of rating durations versus MOS between the ACR and M-ACR method is insignificant, 3) For a given mean rating duration, however, the standard deviation is smaller for the M-ACR method indicating that the quality rating task is easier to execute than with ACR. 4) The period to be allocated in subjective tests for rating 360° videos should exceed 5 s but can be kept below

The aim of steganography is to conceal the presence of communication by way of hiding secret data in perceptually irrelevant parts of a cover object. In this paper, we propose a method for hiding secret images in edge regions of high-definition (HD) images because the human visual system is less sensitive to intensity changes in these regions. In particular, least significant bit substitution is used to embed a secret image in the edge regions of a HD cover image. The edge regions are obtained using a Canny edge detector followed by morphological operations which are used to control the hiding capacity. A performance assessment of the proposed method reveals the trade-off between capacity, detectability, and perceptibility of the hidden data. © 2019 IEEE.

In this paper, objective perceptual video quality models are proposed that use spatial and temporal perceptual information differences for predicting video quality as perceived by human observers. Spatial perceptual information characterizes the complexity and temporal perceptual information quantifies the motion contained in a video. As such, differences in the spatial and temporal perceptual information of a reference video (original) and test video (processed) may be used to predict quality of videos that have undergone encoding, transmission, or other processing. In particular, several video quality prediction functions are derived using curve fitting along with training and validation on data from a publicly available annotated database. The obtained functions provide predicted mean opinion scores as a measure of perceptual quality subject to spatial and temporal perceptual information differences. The analysis of the video quality prediction performance of the proposed models shows that differences in spatial and temporal perceptual information can be used for objective video quality prediction. © 2019 IEEE.