Prof. Christos Grecos Profile

Prof. Christos Grecos

Professor at SENIOR TECHNICAL CONSULTANT

SPIE Involvement:

Conference Program Committee | Author

Area of Expertise:

image/video processing , image/video analysis , image/video compression , image/video transmission , image/video compression standards , computer vision

Publications (51)

Proceedings Article | 7 June 2024 Presentation + Paper

Presentation + Paper

Multi-reward optimization using genetic algorithms for edge AI

Blake Richey, Christos Grecos, Mukul Shirvaikar

Proceedings Volume 13034, 1303402 (2024) https://doi.org/10.1117/12.3013331

KEYWORDS: Genetic algorithms, Neural networks, Education and training, Mathematical optimization, Computer architecture, Network architectures, Artificial intelligence, Gallium, Portability, Performance modeling

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Proceedings Article | 13 June 2023 Presentation + Paper

Presentation + Paper

Evolution of hardware-aware neural architecture search (NAS) on the edge

Blake Richey, Mitchell Clay, Christos Grecos, Mukul Shirvaikar

Proceedings Volume 12528, 125280A (2023) https://doi.org/10.1117/12.2664894

KEYWORDS: Performance modeling, Education and training, Genetic algorithms, Data modeling, Power consumption, Instrument modeling, Design and modelling, Network architectures, Neural networks, Computer hardware

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Proceedings Article | 27 May 2022 Presentation + Paper

Presentation + Paper

Benchmarking the MAX78000 artificial intelligence microcontroller for deep learning applications

Mitchell Clay, Christos Grecos, Mukul Shirvaikar, Blake Richey

Proceedings Volume 12102, 1210207 (2022) https://doi.org/10.1117/12.2622390

KEYWORDS: Performance modeling, Image processing, Microcontrollers, Data modeling, Quantization, Artificial intelligence, Process modeling, Network architectures, System on a chip, Data processing

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Proceedings Article | 12 April 2021 Presentation + Paper

Presentation + Paper

Heuristic approaches for porting deep neural networks onto mobile devices

Christos Grecos, Mukul Shirvaikar, Nasser Kehtarnavaz

Proceedings Volume 11736, 1173602 (2021) https://doi.org/10.1117/12.2580047

KEYWORDS: Neural networks, Mobile devices, Performance modeling, Image processing, Convolutional neural networks, Very large scale integration, Systems modeling, Pattern recognition, Optical character recognition

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Proceedings Article | 22 April 2020 Presentation + Paper

Presentation + Paper

No-reference image quality assessment based on residual neural networks (ResNets)

Ravi Ravela, Mukul Shirvaikar, Christos Grecos

Proceedings Volume 11401, 114010C (2020) https://doi.org/10.1117/12.2556347

KEYWORDS: Image quality, Neural networks, Data modeling, JPEG2000, Image fusion, Databases, RGB color model, Performance modeling, Image compression, Convolutional neural networks

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Image Quality assessment (IQA) is a tricky field to master, as it attempts to measure the quality of an image with reference to the complex human visual system. In IQA, there are three dominant strands of research, namely: fullreference, reduced-reference and no-reference image quality assessment. No-reference image quality assessment is the hardest one to achieve, as the reference images required for determining the quality of the given images are not available. In one of our previous papers, we quantified no-reference IQA, using state-of-the-art multitasking neural networks, particularly the VGG-16 and shallow neural networks. We achieved good accuracy for the classification of most distortions. However, one of the drawbacks of the networks used was that the classification accuracy was not good for JPEG2000 compressed images. These images were classified incorrectly as blurry or noisy images. In this paper, we try to classify compressed images more accurately using residual neural networks (ResNets). These deep learning models were built based upon micro-architecture modules and are specific task-focused entities, each one determining the distortion type and distortion level of an artifact present in the image. The test images were obtained from the LIVE II, CSIQ, and TID2013 databases for comparison with previous work. In contrast to our previous approach, where the training was limited to one specific distortion at a time, we train the collection of ResNets with all the possible distortion types present in the test databases. Preprocessing of the images is done using local contrast normalization and global contrast normalization methods. All the hyper-parameters in the ResNets collection, such as activation functions, dropout regularizations, optimizers are tuned to produce optimal classification accuracy. The results are evaluated with different methods such as PLCC, SROCC and MSE and high linear correlation is achieved using the ResNets collection and compared to previous results.

Proceedings Article | 14 May 2019 Presentation + Paper

Presentation + Paper

No-reference image quality assessment based on deep convolutional neural networks

Ravi Ravela, Mukul Shirvaikar, Christos Grecos

Proceedings Volume 10996, 1099604 (2019) https://doi.org/10.1117/12.2518438

KEYWORDS: Distortion, Image quality, Databases, Data modeling, Performance modeling, Image compression, Image processing, Neural networks, Convolutional neural networks, Image fusion

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Proceedings Article | 14 May 2018 Presentation + Paper

Presentation + Paper

Blind image sharpness metric based on edge and texture features

Priti Maheshwary, Mukul Shirvaikar, Christos Grecos

Proceedings Volume 10670, 1067004 (2018) https://doi.org/10.1117/12.2304701

KEYWORDS: Image fusion, Image quality, Cameras, Edge detection, Image processing, Video, Distortion, Wavelets, Feature extraction, Wavelet transforms

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Video is fast becoming the most common medium for media content in the present era. It is especially helpful in security situations for the detection of criminal or threat-related activity. Police routinely use videos as evidence in the analysis of criminal cases. It is important in such applications to get a high-quality still image from such videos. However, there are situations where the images are blurred and have artifacts as they are extracted from moving video repositories. A practical solution to this problem is to sharpen these images using advanced processing techniques to obtain higher display quality. Due to vast amount of data, it is extremely important that any such enhancement technique satisfy real-time processing constraints, in order for it to be usable by the end user. In this paper, a blind image sharpness metric is proposed using a combination of edge and textural features. Edges can be detected using different methods like Canny, Sobel, Prewitt and Roberts that are commonly accepted in the image processing literature. The Canny edge detection method typically provides better results due to extra processing steps and can be effectively used as a model feature extractor for the image. Wavelet processing based on the db2, sym4, and haar is also utilized to extract texture features. The normalized luminance coefficients of natural images are known to obey the generalized Gaussian probability distribution. Consequently, this characteristic is utilized to extract statistical features in the regions of interest (ROI) and regions of non-interest respectively. The extracted features are then merged together to obtain the sharpened image. The principle behind image formation is to merge the wavelet decompositions of the two original images using fusion methods applied to the approximation and details coefficients. The two images must be of the same size and are supposed to be associated with indexed images on a common color map. It is worth noting that the image fusion results are more consistent with human subjective visual perception of image quality, ground truth data for which is obtained from publicly available databases. Popular standard images such as Cameraman and Lena are used for the experiments. Results also show that the proposed method provides better objective quality than competing methods.

Proceedings Article | 3 May 2018 Presentation + Paper

Presentation + Paper

Adopting cyber security practices in Internet of Things: a review

Priti Maheshwary, Timothy Malche, Christos Grecos, Mukul Shirvaikar

Proceedings Volume 10643, 1064305 (2018) https://doi.org/10.1117/12.2304704

KEYWORDS: Computer security, Network security, Clouds, Sensors, Internet, Control systems, Data processing, Telecommunications, Information security, Environmental monitoring

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Proceedings Article | 1 May 2017 Presentation + Paper

Presentation + Paper

Beyond the High Efficiency Video Coding standard: an overview

Christos Grecos

Proceedings Volume 10223, 102230F (2017) https://doi.org/10.1117/12.2261109

KEYWORDS: Transform theory, Digital filtering, Video compression, Video coding, Optical filters, Linear filtering, Video, Image resolution, Affine motion model, Motion models, Copper, Computer programming, Chromium, Motion estimation, Binary data, Signal processing

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Proceedings Article | 1 May 2017 Paper

Paper

Pre-processing techniques to improve HEVC subjective quality

D. G. Fernández, A. Del Barrio, Guillermo Botella, Uwe Meyer-Baese, Anke Meyer-Baese, Christos Grecos

Proceedings Volume 10223, 102230E (2017) https://doi.org/10.1117/12.2260433

KEYWORDS: Image filtering, Video compression, Copper, Digital filtering, Computer programming, Video coding, Video, Detection and tracking algorithms, Image classification, Image processing, Video processing, Internet technology, Internet

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Proceedings Article | 1 May 2017 Paper

Paper

Information fusion based techniques for HEVC

D. G. Fernández, A. Del Barrio, Guillermo Botella, Uwe Meyer-Baese, Anke Meyer-Baese, Christos Grecos

Proceedings Volume 10223, 102230M (2017) https://doi.org/10.1117/12.2262604

KEYWORDS: Video, Video compression, Video coding, Quantization, Copper, Visualization, Video processing, Detection and tracking algorithms, Information fusion, Computer programming, Data modeling, Data fusion

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Proceedings Article | 29 April 2016 Paper

Paper

Architecture of web services in the enhancement of real-time 3D video virtualization in cloud environment

Adedayo Bada, Qi Wang, Jose Alcaraz-Calero, Christos Grecos

Proceedings Volume 9897, 98970G (2016) https://doi.org/10.1117/12.2227609

KEYWORDS: Video acceleration, Video, 3D video streaming, Clouds, Web services, Computer architecture, Video processing, Mobile devices, 3D applications, Virtual reality, Computer architecture, Visualization, Neodymium, Graphics processing units, Operating systems

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Proceedings Article | 29 April 2016 Paper

Paper

In-network adaptation of SHVC video in software-defined networks

Olatunde Awobuluyi, James Nightingale, Qi Wang, Jose Maria Alcaraz Calero, Christos Grecos

Proceedings Volume 9897, 98970C (2016) https://doi.org/10.1117/12.2227550

KEYWORDS: Video, Network architectures, Internet, Video coding, Scalable video coding, Switches, Multimedia, Video compression, Standards development, Switching

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Software Defined Networks (SDN), when combined with Network Function Virtualization (NFV) represents a paradigm shift in how future networks will behave and be managed. SDN’s are expected to provide the underpinning technologies for future innovations such as 5G mobile networks and the Internet of Everything. The SDN architecture offers features that facilitate an abstracted and centralized global network view in which packet forwarding or dropping decisions are based on application flows. Software Defined Networks facilitate a wide range of network management tasks, including the adaptation of real-time video streams as they traverse the network. SHVC, the scalable extension to the recent H.265 standard is a new video encoding standard that supports ultra-high definition video streams with spatial resolutions of up to 7680×4320 and frame rates of 60fps or more. The massive increase in bandwidth required to deliver these U-HD video streams dwarfs the bandwidth requirements of current high definition (HD) video. Such large bandwidth increases pose very significant challenges for network operators. In this paper we go substantially beyond the limited number of existing implementations and proposals for video streaming in SDN’s all of which have primarily focused on traffic engineering solutions such as load balancing. By implementing and empirically evaluating an SDN enabled Media Adaptation Network Entity (MANE) we provide a valuable empirical insight into the benefits and limitations of SDN enabled video adaptation for real time video applications. The SDN-MANE is the video adaptation component of our Video Quality Assurance Manager (VQAM) SDN control plane application, which also includes an SDN monitoring component to acquire network metrics and a decision making engine using algorithms to determine the optimum adaptation strategy for any real time video application flow given the current network conditions. Our proposed VQAM application has been implemented and evaluated on an SDN allowing us to provide important benchmarks for video streaming over SDN and for SDN control plane latency.

Proceedings Article | 29 April 2016 Paper

Paper

Optimized adaptation algorithm for HEVC/H.265 dynamic adaptive streaming over HTTP using variable segment duration

Iheanyi Irondi, Qi Wang, Christos Grecos

Proceedings Volume 9897, 98970O (2016) https://doi.org/10.1117/12.2227733

KEYWORDS: Video, Switching, Internet, Video processing, Multimedia, Hardware testing, Analytical research, Video compression, Switches, Probability theory

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Adaptive video streaming using HTTP has become popular in recent years for commercial video delivery. The recent MPEG-DASH standard allows interoperability and adaptability between servers and clients from different vendors. The delivery of the MPD (Media Presentation Description) files in DASH and the DASH client behaviours are beyond the scope of the DASH standard. However, the different adaptation algorithms employed by the clients do affect the overall performance of the system and users’ QoE (Quality of Experience), hence the need for research in this field. Moreover, standard DASH delivery is based on fixed segments of the video. However, there is no standard segment duration for DASH where various fixed segment durations have been employed by different commercial solutions and researchers with their own individual merits. Most recently, the use of variable segment duration in DASH has emerged but only a few preliminary studies without practical implementation exist. In addition, such a technique requires a DASH client to be aware of segment duration variations, and this requirement and the corresponding implications on the DASH system design have not been investigated. This paper proposes a segment-duration-aware bandwidth estimation and next-segment selection adaptation strategy for DASH. Firstly, an MPD file extension scheme to support variable segment duration is proposed and implemented in a realistic hardware testbed. The scheme is tested on a DASH client, and the tests and analysis have led to an insight on the time to download next segment and the buffer behaviour when fetching and switching between segments of different playback durations. Issues like sustained buffering when switching between segments of different durations and slow response to changing network conditions are highlighted and investigated. An enhanced adaptation algorithm is then proposed to accurately estimate the bandwidth and precisely determine the time to download the next optimal segment considering the variable segment duration. Furthermore, objective metrics are employed to highlight the merits of the achieved compression efficiency using longer segment sizes for higher bitrate representations.

Proceedings Article | 29 April 2016 Paper

Paper

The QoE implications of ultra-high definition video adaptation strategies

James Nightingale, Olatunde Awobuluyi, Qi Wang, Jose Alcaraz-Calero, Christos Grecos

Proceedings Volume 9897, 98970D (2016) https://doi.org/10.1117/12.2227951

KEYWORDS: Video, Video coding, Internet, Mobile devices, Spatial resolution, Temporal resolution, Video surveillance, Video compression, Molybdenum, Computer programming

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As the capabilities of high-end consumer devices increase, streaming and playback of Ultra-High Definition (UHD) is set to become commonplace. The move to these new, higher resolution, video services is one of the main factors contributing to the predicted continuation of growth in video related traffic in the Internet. This massive increases in bandwidth requirement, even when mitigated by the use of new video compression standards such as H.265, will place an ever-increasing burden on network service providers. This will be especially true in mobile environments where users have come to expect ubiquitous access to content. Consequently, delivering UHD and Full UHD (FUHD) video content is one of the key drivers for future Fifth Generation (5G) mobile networks. One often voiced, but as yet unanswered question, is whether users of mobile devices with modest screen sizes (e.g. smartphones or smaller tablet) will actually benefit from consuming the much higher bandwidth required to watch online UHD video, in terms of an improved user experience. In this paper, we use scalable H.265 encoded video streams to conduct a subjective evaluation of the impact on a user’s perception of video quality across a comprehensive range of adaptation strategies, covering each of the three adaptation domains, for UHD and FUHD video. The results of our subjective study provide insightful and useful indications of which methods of adapting UHD and FUHD streams have the least impact on user’s perceived QoE. In particular, it was observed that, in over 70% of cases, users were unable to distinguish between full HD (1080p) and UHD (4K) videos when they were unaware of which version was being shown to them. Our results from this evaluation can be used to provide adaptation rule sets that will facilitate fast, QoE aware in-network adaptation of video streams in support of realtime adaptation objectives. Undoubtedly they will also promote discussion around how network service providers manage their relationships with end users and how service level agreements might be shaped to account for what may be viewed as ‘unproductive’ use of bandwidth to deliver very marginal or imperceptible improvements in viewing experience.

Proceedings Article | 27 February 2015 Paper

Paper

Subjective evaluation of H.265/HEVC based dynamic adaptive video streaming over HTTP (HEVC-DASH)

Iheanyi Irondi, Qi Wang, Christos Grecos

Proceedings Volume 9400, 94000B (2015) https://doi.org/10.1117/12.2080365

KEYWORDS: Video, Molybdenum, Internet, Video coding, Switching, Switches, Video compression, Hardware testing, Scalable video coding, Parallel processing

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Proceedings Article | 27 February 2015 Paper

Paper

Task-oriented quality assessment and adaptation in real-time mission critical video streaming applications

James Nightingale, Qi Wang, Christos Grecos

Proceedings Volume 9400, 94000M (2015) https://doi.org/10.1117/12.2078741

KEYWORDS: Video, Video surveillance, Scalable video coding, Safety, Target recognition, Defense and security, Spatial resolution, Image quality, Databases, Network security

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In recent years video traffic has become the dominant application on the Internet with global year-on-year increases in video-oriented consumer services. Driven by improved bandwidth in both mobile and fixed networks, steadily reducing hardware costs and the development of new technologies, many existing and new classes of commercial and industrial video applications are now being upgraded or emerging. Some of the use cases for these applications include areas such as public and private security monitoring for loss prevention or intruder detection, industrial process monitoring and critical infrastructure monitoring. The use of video is becoming commonplace in defence, security, commercial, industrial, educational and health contexts. Towards optimal performances, the design or optimisation in each of these applications should be context aware and task oriented with the characteristics of the video stream (frame rate, spatial resolution, bandwidth etc.) chosen to match the use case requirements. For example, in the security domain, a task-oriented consideration may be that higher resolution video would be required to identify an intruder than to simply detect his presence. Whilst in the same case, contextual factors such as the requirement to transmit over a resource-limited wireless link, may impose constraints on the selection of optimum task-oriented parameters. This paper presents a novel, conceptually simple and easily implemented method of assessing video quality relative to its suitability for a particular task and dynamically adapting videos streams during transmission to ensure that the task can be successfully completed. Firstly we defined two principle classes of tasks: recognition tasks and event detection tasks. These task classes are further subdivided into a set of task-related profiles, each of which is associated with a set of taskoriented attributes (minimum spatial resolution, minimum frame rate etc.). For example, in the detection class, profiles for intruder detection will require different temporal characteristics (frame rate) from those used for detection of high motion objects such as vehicles or aircrafts. We also define a set of contextual attributes that are associated with each instance of a running application that include resource constraints imposed by the transmission system employed and the hardware platforms used as source and destination of the video stream. Empirical results are presented and analysed to demonstrate the advantages of the proposed schemes.

Proceedings Article | 27 February 2015 Paper

Paper

A simulator tool set for evaluating HEVC/SHVC streaming

Tawfik Al Hadhrami, James Nightingale, Qi Wang, Christos Grecos, Nasser Kehtarnavaz

Proceedings Volume 9400, 94000N (2015) https://doi.org/10.1117/12.2078770

KEYWORDS: Video, Computer programming, Video coding, Scalable video coding, Standards development, Spatial resolution, Computer simulations, Multimedia, Video surveillance, Signal to noise ratio

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Video streaming and other multimedia applications account for an ever increasing proportion of all network traffic. The recent adoption of High Efficiency Video Coding (HEVC) as the H.265 standard provides many opportunities for new and improved services multimedia services and applications in the consumer domain. Since the delivery of version one of H.265, the Joint Collaborative Team on Video Coding have been working towards standardisation of a scalable extension (SHVC) to the H.265 standard and a series of range extensions and new profiles. As these enhancements are added to the standard the range of potential applications and research opportunities will expend. For example the use of video is also growing rapidly in other sectors such as safety, security, defence and health with real-time high quality video transmission playing an important role in areas like critical infrastructure monitoring and disaster management. Each of which may benefit from the application of enhanced HEVC/H.265 and SHVC capabilities. The majority of existing research into HEVC/H.265 transmission has focussed on the consumer domain addressing issues such as broadcast transmission and delivery to mobile devices with the lack of freely available tools widely cited as an obstacle to conducting this type of research. In this paper we present a toolset which facilitates the transmission and evaluation of HEVC/H.265 and SHVC encoded video on the popular open source NCTUns simulator. Our toolset provides researchers with a modular, easy to use platform for evaluating video transmission and adaptation proposals on large scale wired, wireless and hybrid architectures. The toolset consists of pre-processing, transmission, SHVC adaptation and post-processing tools to gather and analyse statistics. It has been implemented using HM15 and SHM5, the latest versions of the HEVC and SHVC reference software implementations to ensure that currently adopted proposals for scalable and range extensions to the standard can be investigated. We demonstrate the effectiveness and usability of our toolset by evaluating SHVC streaming and adaptation to meet terminal constraints and network conditions in a range of wired, wireless, and large scale wireless mesh network scenarios, each of which is designed to simulate a realistic environment. Our results are compared to those for H264/SVC, the scalable extension to the existing H.264/AVC advanced video coding standard.

Proceedings Article | 27 February 2015 Paper

Paper

Dynamic resource allocation engine for cloud-based real-time video transcoding in mobile cloud computing environments

Bada Adedayo, Qi Wang, Jose Alcaraz Calero, Christos Grecos

Proceedings Volume 9400, 94000O (2015) https://doi.org/10.1117/12.2079017

KEYWORDS: Video, Clouds, Mobile devices, Video compression, Video processing, Video coding, Computer programming, Video surveillance, Internet, Temporal resolution

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Proceedings Article | 27 February 2015 Paper

Paper

Impact of different cloud deployments on real-time video applications for mobile video cloud users

Kashif Khan, Qi Wang, Chunbo Luo, Xinheng Wang, Christos Grecos

Proceedings Volume 9400, 94000P (2015) https://doi.org/10.1117/12.2080436

KEYWORDS: Clouds, Video, Internet, Network architectures, Network security, Video surveillance, Analytical research, Image segmentation, Mobile communications, Web services

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The latest trend to access mobile cloud services through wireless network connectivity has amplified globally among both entrepreneurs and home end users. Although existing public cloud service vendors such as Google, Microsoft Azure etc. are providing on-demand cloud services with affordable cost for mobile users, there are still a number of challenges to achieve high-quality mobile cloud based video applications, especially due to the bandwidth-constrained and errorprone mobile network connectivity, which is the communication bottleneck for end-to-end video delivery. In addition, existing accessible clouds networking architectures are different in term of their implementation, services, resources, storage, pricing, support and so on, and these differences have varied impact on the performance of cloud-based real-time video applications. Nevertheless, these challenges and impacts have not been thoroughly investigated in the literature. In our previous work, we have implemented a mobile cloud network model that integrates localized and decentralized cloudlets (mini-clouds) and wireless mesh networks. In this paper, we deploy a real-time framework consisting of various existing Internet cloud networking architectures (Google Cloud, Microsoft Azure and Eucalyptus Cloud) and a cloudlet based on Ubuntu Enterprise Cloud over wireless mesh networking technology for mobile cloud end users. It is noted that the increasing trend to access real-time video streaming over HTTP/HTTPS is gaining popularity among both research and industrial communities to leverage the existing web services and HTTP infrastructure in the Internet. To study the performance under different deployments using different public and private cloud service providers, we employ real-time video streaming over the HTTP/HTTPS standard, and conduct experimental evaluation and in-depth comparative analysis of the impact of different deployments on the quality of service for mobile video cloud users. Empirical results are presented and discussed to quantify and explain the different impacts resulted from various cloud deployments, video application and wireless/mobile network setting, and user mobility. Additionally, this paper analyses the advantages, disadvantages, limitations and optimization techniques in various cloud networking deployments, in particular the cloudlet approach compared with the Internet cloud approach, with recommendations of optimized deployments highlighted. Finally, federated clouds and inter-cloud collaboration challenges and opportunities are discussed in the context of supporting real-time video applications for mobile users.

Proceedings Article | 15 May 2014 Paper

Paper

Comparative analysis of video processing and 3D rendering for cloud video games using different virtualization technologies

Adedayo Bada, Jose Alcaraz-Calero, Qi Wang, Christos Grecos

Proceedings Volume 9139, 913906 (2014) https://doi.org/10.1117/12.2051991

KEYWORDS: Video, Visualization, Video acceleration, Clouds, Video processing, OpenGL, 3D video streaming, Video coding, 3D displays, Computer programming

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Proceedings Article | 15 May 2014 Paper

Paper

Network-aware scalable video monitoring system for emergency situations with operator-managed fidelity control

Tawfik Al Hadhrami, James Nightingale, Qi Wang, Christos Grecos

Proceedings Volume 9139, 91390M (2014) https://doi.org/10.1117/12.2052175

KEYWORDS: Video, Scalable video coding, Wireless communications, Receivers, Telecommunications, Control systems, Signal to noise ratio, Computer simulations, Visual communications, Natural disasters

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In emergency situations, the ability to remotely monitor unfolding events using high-quality video feeds will significantly improve the incident commander’s understanding of the situation and thereby aids effective decision making. This paper presents a novel, adaptive video monitoring system for emergency situations where the normal communications network infrastructure has been severely impaired or is no longer operational. The proposed scheme, operating over a rapidly deployable wireless mesh network, supports real-time video feeds between first responders, forward operating bases and primary command and control centers. Video feeds captured on portable devices carried by first responders and by static visual sensors are encoded in H.264/SVC, the scalable extension to H.264/AVC, allowing efficient, standard-based temporal, spatial, and quality scalability of the video. A three-tier video delivery system is proposed, which balances the need to avoid overuse of mesh nodes with the operational requirements of the emergency management team. In the first tier, the video feeds are delivered at a low spatial and temporal resolution employing only the base layer of the H.264/SVC video stream. Routing in this mode is designed to employ all nodes across the entire mesh network. In the second tier, whenever operational considerations require that commanders or operators focus on a particular video feed, a ‘fidelity control’ mechanism at the monitoring station sends control messages to the routing and scheduling agents in the mesh network, which increase the quality of the received picture using SNR scalability while conserving bandwidth by maintaining a low frame rate. In this mode, routing decisions are based on reliable packet delivery with the most reliable routes being used to deliver the base and lower enhancement layers; as fidelity is increased and more scalable layers are transmitted they will be assigned to routes in descending order of reliability. The third tier of video delivery transmits a high-quality video stream including all available scalable layers using the most reliable routes through the mesh network ensuring the highest possible video quality. The proposed scheme is implemented in a proven simulator, and the performance of the proposed system is numerically evaluated through extensive simulations. We further present an in-depth analysis of the proposed solutions and potential approaches towards supporting high-quality visual communications in such a demanding context.

Proceedings Article | 15 May 2014 Paper

Paper

Empirical evaluation of H.265/HEVC-based dynamic adaptive video streaming over HTTP (HEVC-DASH)

Iheanyi Irondi, Qi Wang, Christos Grecos

Proceedings Volume 9139, 91390L (2014) https://doi.org/10.1117/12.2052196

KEYWORDS: Video, Internet, Video coding, Standards development, Switching, Switches, Video processing, Parallel processing, Operating systems, Multimedia

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Proceedings Article | 15 May 2014 Paper

Paper

Comparative study of internet cloud and cloudlet over wireless mesh networks for real-time applications

Kashif Khan, Qi Wang, Chunbo Luo, Xinheng Wang, Christos Grecos

Proceedings Volume 9139, 91390K (2014) https://doi.org/10.1117/12.2052474

KEYWORDS: Clouds, Internet, Video, Network architectures, Image processing, Data centers, Local area networks, Computer simulations, Switches, Web services

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Proceedings Article | 15 May 2014 Paper

Paper

Deriving video content type from HEVC bitstream semantics

James Nightingale, Qi Wang, Christos Grecos, Sergio Goma

Proceedings Volume 9139, 913902 (2014) https://doi.org/10.1117/12.2051757

KEYWORDS: Video, Copper, Computer programming, Video compression, Plutonium, Video coding, Semantic video, Feature extraction, Visual process modeling, Internet

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As network service providers seek to improve customer satisfaction and retention levels, they are increasingly moving from traditional quality of service (QoS) driven delivery models to customer-centred quality of experience (QoE) delivery models. QoS models only consider metrics derived from the network however, QoE models also consider metrics derived from within the video sequence itself. Various spatial and temporal characteristics of a video sequence have been proposed, both individually and in combination, to derive methods of classifying video content either on a continuous scale or as a set of discrete classes. QoE models can be divided into three broad categories, full reference, reduced reference and no-reference models. Due to the need to have the original video available at the client for comparison, full reference metrics are of limited practical value in adaptive real-time video applications. Reduced reference metrics often require metadata to be transmitted with the bitstream, while no-reference metrics typically operate in the decompressed domain at the client side and require significant processing to extract spatial and temporal features. This paper proposes a heuristic, no-reference approach to video content classification which is specific to HEVC encoded bitstreams. The HEVC encoder already makes use of spatial characteristics to determine partitioning of coding units and temporal characteristics to determine the splitting of prediction units. We derive a function which approximates the spatio-temporal characteristics of the video sequence by using the weighted averages of the depth at which the coding unit quadtree is split and the prediction mode decision made by the encoder to estimate spatial and temporal characteristics respectively. Since the video content type of a sequence is determined by using high level information parsed from the video stream, spatio-temporal characteristics are identified without the need for full decoding and can be used in a timely manner to aid decision making in QoE oriented adaptive real time streaming.

Proceedings Article | 18 February 2014 Paper

Paper

Evaluation of in-network adaptation of scalable high efficiency video coding (SHVC) in mobile environments

James Nightingale, Qi Wang, Christos Grecos, Sergio Goma

Proceedings Volume 9030, 90300B (2014) https://doi.org/10.1117/12.2036721

KEYWORDS: Video, Video coding, Video compression, Scalable video coding, Computer programming, Spatial resolution, Standards development, Mobile devices, Error analysis, Signal to noise ratio

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Proceedings Article | 19 February 2013 Paper

Paper

Priority-based methods for reducing the impact of packet loss on HEVC encoded video streams

James Nightingale, Qi Wang, Christos Grecos

Proceedings Volume 8656, 86560E (2013) https://doi.org/10.1117/12.2002451

KEYWORDS: Video, Computer programming, Video coding, Distortion, Standards development, Copper, Error analysis, Video processing, Receivers, Surface plasmons

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The rapid growth in the use of video streaming over IP networks has outstripped the rate at which new network infrastructure has been deployed. These bandwidth-hungry applications now comprise a significant part of all Internet traffic and present major challenges for network service providers. The situation is more acute in mobile networks where the available bandwidth is often limited. Work towards the standardisation of High Efficiency Video Coding (HEVC), the next generation video coding scheme, is currently on track for completion in 2013. HEVC offers the prospect of a 50% improvement in compression over the current H.264 Advanced Video Coding standard (H.264/AVC) for the same quality. However, there has been very little published research on HEVC streaming or the challenges of delivering HEVC streams in resource-constrained network environments. In this paper we consider the problem of adapting an HEVC encoded video stream to meet the bandwidth limitation in a mobile networks environment. Video sequences were encoded using the Test Model under Consideration (TMuC HM6) for HEVC. Network abstraction layers (NAL) units were packetized, on a one NAL unit per RTP packet basis, and transmitted over a realistic hybrid wired/wireless testbed configured with dynamically changing network path conditions and multiple independent network paths from the streamer to the client. Two different schemes for the prioritisation of RTP packets, based on the NAL units they contain, have been implemented and empirically compared using a range of video sequences, encoder configurations, bandwidths and network topologies. In the first prioritisation method the importance of an RTP packet was determined by the type of picture and the temporal switching point information carried in the NAL unit header. Packets containing parameter set NAL units and video coding layer (VCL) NAL units of the instantaneous decoder refresh (IDR) and the clean random access (CRA) pictures were given the highest priority followed by NAL units containing pictures used as reference pictures from which others can be predicted. The second method assigned a priority to each NAL unit based on the rate-distortion cost of the VCL coding units contained in the NAL unit. The sum of the rate-distortion costs of each coding unit contained in a NAL unit was used as the priority weighting. The preliminary results of extensive experiments have shown that all three schemes offered an improvement in PSNR, when comparing original and decoded received streams, over uncontrolled packet loss. Using the first method consistently delivered a significant average improvement of 0.97dB over the uncontrolled scenario while the second method provided a measurable, but less consistent, improvement across the range of testing conditions and encoder configurations.

Proceedings Article | 2 May 2012 Paper

Paper

Real-time visual communication to aid disaster recovery in a multi-segment hybrid wireless networking system

Tawfik Al Hadhrami, Qi Wang, Christos Grecos

Proceedings Volume 8437, 84370R (2012) https://doi.org/10.1117/12.924257

KEYWORDS: Video, Sensor networks, Visualization, Telecommunications, Visual communications, Satellites, Wireless communications, Networks, Image segmentation, Computer simulations

Read Abstract +

Proceedings Article | 2 May 2012 Paper

Paper

Real-time video streaming in mobile cloud over heterogeneous wireless networks

Saleh Abdallah-Saleh, Qi Wang, Christos Grecos

Proceedings Volume 8437, 84370S (2012) https://doi.org/10.1117/12.924258

KEYWORDS: Clouds, Video, Video coding, Human-machine interfaces, Internet, Standards development, Network security, Mobile devices, Visualization, Computer simulations

Read Abstract +

Recently, the concept of Mobile Cloud Computing (MCC) has been proposed to offload the resource requirements in computational capabilities, storage and security from mobile devices into the cloud. Internet video applications such as real-time streaming are expected to be ubiquitously deployed and supported over the cloud for mobile users, who typically encounter a range of wireless networks of diverse radio access technologies during their roaming. However, real-time video streaming for mobile cloud users across heterogeneous wireless networks presents multiple challenges. The network-layer quality of service (QoS) provision to support high-quality mobile video delivery in this demanding scenario remains an open research question, and this in turn affects the application-level visual quality and impedes mobile users' perceived quality of experience (QoE). In this paper, we devise a framework to support real-time video streaming in this new mobile video networking paradigm and evaluate the performance of the proposed framework empirically through a lab-based yet realistic testing platform. One particular issue we focus on is the effect of users' mobility on the QoS of video streaming over the cloud. We design and implement a hybrid platform comprising of a test-bed and an emulator, on which our concept of mobile cloud computing, video streaming and heterogeneous wireless networks are implemented and integrated to allow the testing of our framework. As representative heterogeneous wireless networks, the popular WLAN (Wi-Fi) and MAN (WiMAX) networks are incorporated in order to evaluate effects of handovers between these different radio access technologies. The H.264/AVC (Advanced Video Coding) standard is employed for real-time video streaming from a server to mobile users (client nodes) in the networks. Mobility support is introduced to enable continuous streaming experience for a mobile user across the heterogeneous wireless network. Real-time video stream packets are captured for analytical purposes on the mobile user node. Experimental results are obtained and analysed. Future work is identified towards further improvement of the current design and implementation. With this new mobile video networking concept and paradigm implemented and evaluated, results and observations obtained from this study would form the basis of a more in-depth, comprehensive understanding of various challenges and opportunities in supporting high-quality real-time video streaming in mobile cloud over heterogeneous wireless networks.

Proceedings Article | 2 May 2012 Paper

Paper

Benchmarking real-time HEVC streaming

James Nightingale, Qi Wang, Christos Grecos

Proceedings Volume 8437, 84370D (2012) https://doi.org/10.1117/12.921406

KEYWORDS: Video, Computer programming, Copper, Video coding, Standards development, Video compression, Transform theory, Video processing, Distortion, Digital filtering

Read Abstract +

Work towards the standardisation of High Efficiency Video Coding (HEVC), the next generation video coding scheme, is currently gaining pace. HEVC offers the prospect of a 50% improvement in compression over the current H.264 Advanced Video Coding standard (H.264/AVC). Thus far, work on HEVC has concentrated on improvements to the coding efficiency and has not yet addressed transmission in networks other than to mandate byte stream compliance with Annex B of H.264/AVC. For practical networked HEVC applications a number of essential building blocks have yet to be defined. In this work, we design and prototype a real-time HEVC streaming system and empirically evaluate its performance, in particular we consider the robustness of the current Test Model under Consideration (TMuC HM4.0) for HEVC to packet loss caused by a reduction in available bandwidth both in terms of decoder resilience and degradation in perceptual video quality. A NAL unit packetisation and streaming framework for HEVC encoded video streams is designed, implemented and empirically tested in a number of streaming environments including wired, wireless, single path and multiple path network scenarios. As a first step the HEVC decoder's error resilience is tested under a comprehensive set of packet loss conditions and a simple error concealment method for HEVC is implemented. Similarly to H.264 encoded streams, the size and distribution of NAL units within an HEVC stream and the nature of the NAL unit dependencies influences the packetisation and streaming strategies which may be employed for such streams. The relationships between HEVC encoding mode and the quality of the received video are shown under a wide range of bandwidth constraints. HEVC streaming is evaluated in both single and multipath network configuration scenarios. Through the use of extensive experimentation, we establish a comprehensive set of benchmarks for HEVC streaming in loss prone network environments. We show the visual quality reduction in terms of PSNR which results from a reduction in available bandwidth. To the best of our knowledge, this is the first time that such a fully functional streaming system for HEVC, together with the benchmark evaluation results, has been reported. This study will open up more timely research opportunities in this cutting edge area.

Proceedings Article | 2 February 2011 Paper

Paper

Fast multilayered prediction algorithm for group of pictures in H.264/SVC

Abdelrahman Abdelazim, Stephen James Mein, Martin Roy Varley, Christos Grecos, Djamel Ait-Boudaoud

Proceedings Volume 7871, 78710P (2011) https://doi.org/10.1117/12.873079

KEYWORDS: Scalable video coding, Computer programming, Signal to noise ratio, Algorithm development, Motion estimation, Video coding, Video, Temporal resolution, Distortion, Multilayers

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Proceedings Article | 2 February 2011 Paper

Paper

Real-time video streaming using H.264 scalable video coding (SVC) in multihomed mobile networks: a testbed approach

James Nightingale, Qi Wang, Christos Grecos

Proceedings Volume 7871, 78710B (2011) https://doi.org/10.1117/12.872111

KEYWORDS: Scalable video coding, Switching, Video, Video coding, Computer programming, Multimedia, Internet, Switches, Standards development, Video processing

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Proceedings Article | 2 February 2011 Paper

Paper

Towards real-time image quality assessment

Bobby Geary, Christos Grecos

Proceedings Volume 7871, 787102 (2011) https://doi.org/10.1117/12.872369

KEYWORDS: Image quality, Distortion, Image processing, Molybdenum, Databases, Data modeling, Software, Cognitive modeling, Image analysis, Systems modeling

Read Abstract +

Proceedings Article | 2 February 2011 Paper

Paper

Phase correlation based adaptive mode decision for the H.264/AVC

Abdelrahman Abdelazim, Stephen James Mein, Martin Roy Varley, Christos Grecos, Djamel Ait-Boudaoud

Proceedings Volume 7871, 78710O (2011) https://doi.org/10.1117/12.873077

KEYWORDS: Motion estimation, Computer programming, Video, Distortion, Image quality standards, Image processing, Video coding, Image compression, Algorithm development, Image quality

Read Abstract +

Proceedings Article | 28 April 2009 Paper

Paper

Automation of the CCTV-mediated detection of individuals illegally carrying firearms: combining psychological and technological approaches

Iain Darker, Paul Kuo, Ming Yuan Yang, Anastassia Blechko, Christos Grecos, Dimitrios Makris, Jean-Christophe Nebel, Alastair Gale

Proceedings Volume 7341, 73410P (2009) https://doi.org/10.1117/12.819998

KEYWORDS: Firearms, Detection and tracking algorithms, Surveillance, Cameras, Target detection, Image segmentation, Video surveillance, Algorithm development, Visualization, Video

Read Abstract +

SPIE Journal Paper | 1 March 2009 Open Access

Open Access

Fast subpixel motion estimation based on the interpolation effect on different block sizes for H264/AVC

Abdelrahman Abdelazim, Mingyuan Yang, Christos Grecos

OE, Vol. 48, Issue 03, 030504, (March 2009) https://doi.org/10.1117/12.10.1117/1.3095795

KEYWORDS: Motion estimation, Motion measurement, Video coding, Video, Computer programming, Optical engineering, Video processing, Physical sciences, Physical research, Video compression

Read Abstract +

Proceedings Article | 5 February 2009 Paper

Paper

Selective application of sub-pixel motion estimation and Hadamard transform in H.264/AVC

Abdelrahman Abdelazim, Mingyuan Yang, Christos Grecos, Djamel Ait-Boudaoud

Proceedings Volume 7244, 72440C (2009) https://doi.org/10.1117/12.810148

KEYWORDS: Motion estimation, Video coding, Video, Motion measurement, Distortion, Computer programming, Physical sciences, Video compression, Pixel resolution, Image compression

Read Abstract +

Proceedings Article | 27 February 2008 Paper

Paper

A resource constrained MPEG-7 driven rate control scheme for the H264/AVC

Jesús Cánovas Serrano, Mingyuan Yang, Christos Grecos

Proceedings Volume 6811, 68110B (2008) https://doi.org/10.1117/12.765688

KEYWORDS: Video, Standards development, Video coding, Quantization, Nickel, Visualization, Multimedia, Distance measurement, Computer programming, Signal processing

Read Abstract +

Proceedings Article | 26 February 2007 Paper

Paper

A neighborhood analysis based technique for real-time error concealment in H.264 intra pictures

Steven Beesley, Christos Grecos, Eran Edirisinghe

Proceedings Volume 6507, 650706 (2007) https://doi.org/10.1117/12.704866

KEYWORDS: Error analysis, Convolution, Video, Statistical analysis, Visualization, Binary data, Mobile devices, Video coding, Computer programming, Edge detection

Read Abstract +

Proceedings Article | 15 February 2006 Paper

Paper

A fast eye detector using corners, color, and edges

Li-hui Chen, Christos Grecos

Proceedings Volume 6063, 60630A (2006) https://doi.org/10.1117/12.642759

KEYWORDS: Eye, Sensors, Skin, Databases, Facial recognition systems, Corner detection, Edge detection, RGB color model, Detection and tracking algorithms, Automatic tracking

Read Abstract +

Proceedings Article | 2 February 2006 Paper

Paper

Concealment driven bit rate reduction using the H.264 video coding standard

Steven T. Beesley, Andrew Armstrong, Christos Grecos, David Parish

Proceedings Volume 6074, 607403 (2006) https://doi.org/10.1117/12.643086

KEYWORDS: Video, Computer programming, Video coding, Quantization, Semantic video, Error analysis, Standards development, Visualization, Multimedia, Networks

Read Abstract +

Proceedings Article | 19 January 2006 Paper

Paper

A framework for fast mode decision in the H264 video coding standard

Ming Yuan Yang, Christos Grecos

Proceedings Volume 6077, 60771J (2006) https://doi.org/10.1117/12.641716

KEYWORDS: Video coding, Quantization, Distortion, Computer programming, Einsteinium, Video, Iterated function systems, Standards development, Video compression, Cameras

Read Abstract +

Proceedings Article | 14 March 2005 Paper

Paper

Fast intermode prediction for P slices in the H264 video coding standard

Ming Yuan Yang, Christos Grecos

Proceedings Volume 5685, (2005) https://doi.org/10.1117/12.585342

KEYWORDS: Video coding, Standards development, Quantization, Distortion, Computer programming, Video, Cobalt, Electronics engineering, Video compression, Image compression

Read Abstract +

SPIE Journal Paper | 1 March 2005

Robust multiple-initial-point prediction algorithm for fast motion estimation in the MPEG-2 standard

Christos Grecos, Azilah Saparon

OE, Vol. 44, Issue 03, 037004, (March 2005) https://doi.org/10.1117/12.10.1117/1.1872956

KEYWORDS: Motion estimation, Diamond, Video, Optical engineering, Standards development, Electronics engineering, Error analysis, Motion measurement, Computing systems, Cameras

Read Abstract +

Proceedings Article | 25 February 2005 Paper

Paper

Fast skin color detector for face extraction

Lihui Chen, Christos Grecos

Proceedings Volume 5671, (2005) https://doi.org/10.1117/12.585341

KEYWORDS: Skin, Facial recognition systems, RGB color model, Optical filters, Light sources and illumination, Sensors, Image filtering, Detection and tracking algorithms, Image processing, Binary data

Read Abstract +

Proceedings Article | 7 May 2003 Paper

Paper

Speeding up the optimization of the rate distortion performance in MPEG-2 video coding through quantizer loop parameterization

Christos Grecos, A. Saparon

Proceedings Volume 5022, (2003) https://doi.org/10.1117/12.476434

KEYWORDS: Distortion, Video coding, Quantization, Detection and tracking algorithms, Video, Photonic integrated circuits, Data modeling, Error analysis, Data processing, Computer programming

Read Abstract +

Proceedings Article | 14 April 2003 Paper

Paper

Novel scanning order for fast elimination of candidate predictors in MPEG-2 block-based motion estimation

Christos Grecos, A. Saparon, S. Jones

Proceedings Volume 5012, (2003) https://doi.org/10.1117/12.477489

KEYWORDS: Motion estimation, Raster graphics, Video, Video compression, Algorithm development, Computing systems, Electronics engineering, Diamond, Real time imaging, Electronic imaging

Read Abstract +

SPIE Journal Paper | 1 February 2002

Towards an improvement on prediction accuracy in JPEG-LS

Jianmin Jiang, Christos Grecos

OE, Vol. 41, Issue 02, (February 2002) https://doi.org/10.1117/12.10.1117/1.1428743

KEYWORDS: Edge detection, Error analysis, Image compression, Visualization, Statistical analysis, Image quality standards, Optical engineering, Distance measurement, Image quality, Cameras

Proceedings Article | 4 January 2002 Paper

Paper

Improvements to JPEG-LS via diagonal edge-based prediction

Eran Edirisinghe, Satish Bedi, Christos Grecos

Proceedings Volume 4671, (2002) https://doi.org/10.1117/12.453103

KEYWORDS: Edge detection, Image compression, Image quality standards, Error analysis, Statistical analysis, Quantization, Photography, Computer science, Electronics engineering, Standards development

Read Abstract +

SPIE Journal Paper | 1 July 2001

Adding rate control to JPEG-LS

Jianmin Jiang, Christos Grecos

JEI, Vol. 10, Issue 03, (July 2001) https://doi.org/10.1117/12.10.1117/1.1380387

KEYWORDS: Image compression, Image quality, Detection and tracking algorithms, Visualization, Distortion, Image quality standards, Edge detection, Control systems, Computer programming, Optical inspection

Proceedings Article | 22 March 2001 Paper

Paper

Improved estimation of quantizer moderators in MPEG-2 rate control using a novel robust estimate and a family of exponential modulators

Christos Grecos, Jianmin Jiang

Proceedings Volume 4209, (2001) https://doi.org/10.1117/12.420822

KEYWORDS: Distortion, Quantization, Modulators, Computer programming, Video, Statistical analysis, Video coding, Error analysis, Visualization, Modulation

Read Abstract +

Showing 5 of 51 publications

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