A.M. Kondoz

Loughborough University, Loughborough, England, United Kingdom

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Publications (279)178.28 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Demand on multimedia content by consumers' handheld devices over wireless channels is on the increase. In view of the accelerated trend towards consumption of high quality video, power utilization by mobile devices is expected to excessively increase. Hence, it becomes equally important to advance more efficient power minimization techniques, in light of the short battery life in portable devices. However, power minimization algorithms that adopt consumers' perceptual quality of video have not received adequate research. This paper proposes a joint optimization of energy and quality requirements in a multiuser orthogonal frequencydivision multiplexing environment. A multi-objective optimization problem is formulated with the aim to identify bitrate allocations among users such that total power is minimized, and average quality is maximized. For this, a content-aware and energy-efficient resource allocation scheme (CaERAS) is proposed based on genetic and greedy algorithms. Simulation results show that CaERAS, as a lowcomplexity scheme, outperforms comparable methods in terms of efficiency and selectivity of suboptimal solutions. It is shown to acquire a suboptimal solution in as low as 0.0025 of the search space in previous methods. Also, a significant average saving of 85.66% in required energy is observed in broadcast transmission as opposed to unicast transmission.
    IEEE ICCE; 08/2014
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    ABSTRACT: An inherent problem of Depth Image Based Rendering (DIBR) is the visual presence of disocclusions in the rendered views. This poses a significant challenge when the subjective assessment of these views is utilised for evaluating the quality of the depth maps used in the rendering process. Although various techniques are available to address this challenge, they result in concealing distortions, which are directly caused by the depth map imperfections. For the purposes of depth map quality evaluation, there is a need for an approach that deals with the presence of disocclusions without having further impact on other distortions. The aim of this approach is to enable the subjective assessments of rendered views to provide results, which are more representative of the quality of the depth map used in the rendering process.
    2014 3DTV-Conference: The True Vision - Capture, Transmission and Display of 3D Video (3DTV-CON 2014); 07/2014
  • Haiyue Yuan · Janko Calic · Ahmet Kondoz
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    ABSTRACT: In spite of a large body of research focused on 3D video technology, very little attention has been dedicated to the design practices of stereoscopic 3D video interaction devices. Interaction tasks such as pointing and selection are critical to the consumer's experience of the 3D video technology. This paper presents implementation and investigation of pointing modalities in the context of stereoscopic 3D display devices. The conducted investigation implements three pointing modalities: standard mouse-based interaction, virtual laser pointer implemented using Wiimote, and hand movement modality using Kinect. The study explores it's utilisation in interactive tasks such as two-handed interaction and zoom functionalities. Finally, we investigate the definition of interaction space for hand movement modality to facilitate effective and comfortable pointing.
    2014 3DTV-Conference: The True Vision - Capture, Transmission and Display of 3D Video (3DTV-CON 2014); 07/2014
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    ABSTRACT: Owing to its wide-interoperability, stereoscopic 3D video format in High Definition (HD) is a popular choice for 3D entertainment media distribution. However, the delivery over bandwidth constrained networks exhibits challenges in terms of intermittent congestions in the network traffic, which enforce the delivery system to perform perception-aware coding to save bandwidth. In the scope of stereoscopic 3D video, asymmetric quality adaptation has proved to be an effective method in terms of maintaining the perceived quality while reducing the required transmission bandwidth. On the other hand, Region-Of-Interest (ROI) based coding in accordance with the visual attention cues, which offers non-uniform quality assignment to regions of different saliency levels has not been widely studied in combination with asymmetric coding of stereoscopic 3D video. In this work, the effectiveness of using visual attention aided non-uniform asymmetric 3D video coding is explored. The importance of incorporating compression artefacts in the formulation of visual attention model is also revealed. The discussions in this paper are based on a comprehensive subjective test with 8 stereoscopic video sequences of different spatial and temporal characteristics at different conditions.
    IEEE Journal of Selected Topics in Signal Processing 06/2014; 8(3):402-414. DOI:10.1109/JSTSP.2014.2313717 · 3.63 Impact Factor
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    ABSTRACT: This article proposes a converged broadcast and broadband platform in order to deliver 3D media to both mobile and fixed users with guaranteed minimum quality of experience (QoE). The work presented offers an ideal business model for operators having both digital video broadcast and Internet Protocol (IP)-based media services. To that end, the DVB and peer-to-peer Internet technologies will be combined to provide sufficient resources for supporting high-bandwidth high-quality 3D multiview video. The motivations behind combining these technologies are outlined with an emphasis on their complementary characteristics. In addition, the overall design of the proposed architecture is presented focusing on the protocols that are exploited to achieve the interworking of the underlying technologies. Moreover, innovative key techniques for supporting both fixed and mobile users in an efficient manner are introduced.
    IEEE Wireless Communications 06/2014; 21(3):62-69. DOI:10.1109/MWC.2014.6845050 · 6.52 Impact Factor
  • G.C.V. Perera · V. De Silva · A.M. Kondoz · S. Dogan
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    ABSTRACT: With the exponential growth of stereoscopic imaging in various applications, it has become very demanding to have a reliable quality assessment technique to measure the human perception of stereoscopic images. Quality assessment of stereoscopic visual content in the presence of artefacts caused by compression and transmission is a key component of end-to-end 3D media delivery systems. Despite a few recent attempts to develop stereoscopic image/video quality metrics, there is still a lack of a robust stereoscopic image quality metric. Towards addressing this issue, this paper proposes a full reference stereoscopic image quality metric, which mimics the human perception while viewing stereoscopic images. A signal processing model that is consistent with physiological literature is developed in the paper to simulate the behaviour of simple and complex cells of the primary visual cortex in the Human Visual System (HVS). The model is trained with two publicly available stereoscopic image databases to match the perceptual judgement of impaired stereoscopic images. The experimental results demonstrate a significant improvement in prediction performance as compared with several state-of-the-art stereoscopic image quality metrics.
    ICASSP 2014 - 2014 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP); 05/2014
  • Ikhwana Elfitri · Xiyu Shi · Ahmet Kondoz
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    ABSTRACT: This study presents a novel spatial audio coding (SAC) technique, called analysis by synthesis SAC (AbS-SAC), with a capability of minimising signal distortion introduced during the encoding processes. The reverse one-to-two (R-OTT), a module applied in the MPEG Surround to down-mix two channels as a single channel, is first configured as a closed-loop system. This closed-loop module offers a capability to reduce the quantisation errors of the spatial parameters, leading to an improved quality of the synthesised audio signals. Moreover, a sub-optimal AbS optimisation, based on the closed-loop R-OTT module, is proposed. This algorithm addresses a problem of practicality in implementing an optimal AbS optimisation while it is still capable of improving further the quality of the reconstructed audio signals. In terms of algorithm complexity, the proposed sub-optimal algorithm provides scalability. The results of objective and subjective tests are presented. It is shown that significant improvement of the objective performance, when compared to the conventional open-loop approach, is achieved. On the other hand, subjective test show that the proposed technique achieves higher subjective difference grade scores than the tested advanced audio coding multichannel.
    IET Signal Processing 02/2014; 8(1):30-38. DOI:10.1049/iet-spr.2013.0015 · 0.69 Impact Factor
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    ABSTRACT: This paper suggests a power and bandwidth efficient resource allocation approach for mobile networks based on consumer's perception of 3D video. We simulate a mobile 3D video transmission through which we identify the correlation between receiver's signal-to-noise ratio and perceived quality. Our QoE-based approach is shown to save up to 33.13% in power and grant up to 50% more data bits for transmission, compared to QoS-based techniques.
    2014 IEEE International Conference on Consumer Electronics (ICCE); 01/2014
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    ABSTRACT: A neural network based technique is proposed to estimate subjective quality of stereoscopic videos. Moreover, to utilize this model for applications where availability of reference signal is not possible to receiver, it applies objective quality of video with minimum dependency on reference signal. This paper presents fast, accurate and consistent subjective quality estimation. Feasibility and accuracy of the proposed technique is thoroughly analyzed with extensive subjective experiments and simulations. Results illustrate that performance measure of 92.3% in subjective quality estimation can be achieved with the proposed technique.
    2014 IEEE International Conference on Consumer Electronics (ICCE); 01/2014
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    ABSTRACT: We present a method to estimate the probability of decoding a network coded packet generation transmitted across an erasure network. Simulation results closely correlate to estimated results. The proposed method is used to multicast delay sensitive data at the a.) required delivery probability b.) optimal throughput.
    2014 IEEE International Conference on Consumer Electronics (ICCE); 01/2014
  • Chungeun Kim · Ahmet Kondoz · Xiyu Shi
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    ABSTRACT: This study investigates the metrics for spatial audio quality of experience (QoE) prediction, particularly considering the existence of video whose viewpoint may not match that of the auditory scene. Subjective tests were conducted for 5.1-channel audio quality evaluation following a previously developed testing and prediction methodology, with the addition of accompanying video cues and with the spatial correlation between audio and video as a new variable for the QoE prediction. The first experiment with a synthesized visual cue showed that the spatial mismatch between audio and video affects the perceived audio QoE. A prediction model of the QoE score was suggested through statistical analysis, using the audio-video angular mismatch as well as other known measurable low-level parameters. The model was validated through another set of subjective test using a captured real-life audiovisual content.
    2013 IEEE Globecom Workshops (GC Wkshps); 12/2013
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    Cagri Ozcinar · Erhan Ekmekcioglu · Ahmet Kondoz
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    ABSTRACT: Increasing throughput rates and technical developments in video streaming over the Internet offer an attractive solution for the distribution of immersive 3D multi-view. Nevertheless, robustness of video streaming is subject to its utilisation of efficient error resiliency and content aware adaptation techniques. Dynamic network characteristics resulting in frequent congestions may prevent video packets from being delivered in a timely manner. Packet delivery failures may become prominent, degrading 3D immersive video experience significantly. In order to overcome this problem, a novel view recovery technique for 3D free-viewpoint video is introduced to maintain 3D video quality in a cost-effective manner. In this concept, the undelivered (discarded) views as a result of adaptation in the network are recovered with high quality at the receiver side, using Side Information (SI) and the delivered frames of neighbouring views. The proposed adaptive 3D multi-view video streaming scheme is tested using Dynamic Adaptive Streaming over HTTP (MPEG-DASH) standard. Tests using the proposed adaptive technique have revealed that the perceptual 3D video quality under adverse network conditions is significantly improved thanks to the utilisation of the extra side information in view recovery.
    Proceedings of the 2013 ACM international workshop on Immersive media experiences; 10/2013
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    ABSTRACT: The quality assessment of impaired stereoscopic video is a key element in designing and deploying advanced immersive media distribution platforms. However, a widely accepted quality metric to measure impairments of stereoscopic video is still to be developed. As a step towards finding a solution to this problem this paper proposes a full reference stereoscopic video quality metric to measure the perceptual quality of compressed stereoscopic video. A comprehensive set of subjective experiments are performed with 14 different stereoscopic video sequences, which are encoded using both the H.264 and High Efficiency Video Coding (HEVC) compliant video codecs, to develop a subjective test results database of 116 test stimuli. The subjective results are analyzed using statistical techniques to uncover different patterns of subjective scoring for symmetrically and asymmetrically encoded stereoscopic video. The subjective results database is subsequently used for training and validating a simple but effective stereoscopic video quality metric considering heuristics of binocular vision. The proposed metric performs significantly better than state-of-the-art stereoscopic image and video quality metrics in predicting the subjective scores. The proposed metric and the subjective results database will be made publicly available and it is expected that the proposed metric and the subjective assessments will have important use cases in advanced 3-Dimensional (3D) media delivery systems.
    IEEE Transactions on Image Processing 06/2013; 22(9). DOI:10.1109/TIP.2013.2268422 · 3.11 Impact Factor
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    ABSTRACT: Stereoscopic 3D video is an important technology for immersive and interactive multimedia. Quality of Experience (QoE) provision is a key objective of the emerging multimedia delivery systems. While subjective assessment of QoE remains the most reliable option, objective metrics are often sought after while engineering practical media distribution solutions. While there have been several efforts in the recent past to develop metrics for stereoscopic video/image quality measurement, an objective metric to measure artefacts caused by transmission packet losses is yet to be realised. Furthermore, most of the existing metrics rely on disparity estimation techniques to provide a quality measure. This paper proposes two metrics for the measurement of compression artefacts and artefacts caused due to packet losses and concealment. The metrics are based on ANSI Video Quality Metric (VQM) metric, and do not rely on disparity estimation. The metrics are trained and validated by conducting two separate sets of subjective experiments, and which illustrate promising results.
    Communications Workshops (ICC), 2013 IEEE International Conference on; 06/2013
  • H. Malekmohamadi · W.A.C. Fernando · A. M. Kondoz
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    ABSTRACT: A new reduced reference objective quality metric for stereoscopic video is proposed that incorporates spatial neighbouring information from grey-level co-occurrence matrices and edge properties. Extracted colour and depth features are combined unequally to maximise the performance of the proposed metric. The performance of this metric is validated through a series of subjective tests and the average correlation 0.82 is achieved when colour to depth importance ratio is near 0.80.
    Electronics Letters 05/2013; 49(11):701-702. DOI:10.1049/el.2013.0559 · 1.07 Impact Factor
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    ABSTRACT: The delivery of 3D immersive media to individual users remains a highly challenging problem due to the large amount of data involved, diverse network characteristics and user terminal requirements, as well as users' context such as their preferences and location. As the number of visual views increases, current systems struggle to meet the demanding requirements in terms of delivery of consistent video quality to fixed and mobile users. The ROMEO (Remote Collaborate Multimedia Experience over the Future Internet) project funded under the 7th Framework Programme of the European Commission focuses on the delivery of live and collaborative 3D immersive media. This facilitates application scenarios such as immersive social TV and high quality immersive and real-time collaboration. In order to support these application scenarios, the project focuses on developing new methods for compressing and delivering 3D multi-view video and spatial audio, as well as optimising the networking and compression jointly across the Future Internet. The proposed solution combines the Digital Video Broadcast-Terrestrial2 (DVB-T2) broadcast technology together with a Quality of Experience (QoE) aware Peer-to-Peer (P2P) distribution system that operates over wired and wireless links. An audio-visual communication overlay is also utilised for bringing the remote collaborators together to jointly enjoy the streamed 3D immersive media, which in turn requires the live streaming 3D content to be received by the collaborating users all at the same time with only an un-noticeable latency. This paper introduces the overall system architecture of the ROMEO project as well as some preliminary results.
    Future Network and Mobile Summit (FutureNetworkSummit), IEEE; 01/2013
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    ABSTRACT: A new reduced reference (RR) objective quality metric for 3D video is proposed that incorporates spatial neighboring information. The contrast measures from gray level co-occurrence matrices (GLCM) for both color and depth sections are main parts of spatial information. Side information is extracted from edge properties of reference 3D video and sent through an auxiliary channel. The other important factor in the proposed metric is the unequal weight of color and depth sections, which can maximize the performance of the proposed metric for some specific values. Performance of the proposed metric is validated through series of subjective tests. For validations, compression and transmission artifacts are considered. The average correlation of the proposed metric and subjective quality scores is 0.82 for compressed 3D videos when color to depth importance ratio is near 0.8. This measure for transmitted 3D videos is 0.857 for the same value of color to depth importance ratio.
    Journal of Visual Communication and Image Representation 01/2013; 25(3). DOI:10.1016/j.jvcir.2013.12.009 · 1.36 Impact Factor
  • Zhiru Shi · W.A.C. Fernando · A.M. Kondoz
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    ABSTRACT: The H.264/AVC coding standard has achieved significant coding gain by using flexible block sizes inter prediction. However, the complexity of inter-mode decision is extremely high. In this paper, a fast inter-mode decision algorithm is presented by exploiting residual homogeneity for both macroblock and sub-macroblock levels. In this algorithm, the residual homogeneity indicators calculated in three directions are used to identify the block's homogeneous characteristic. Normalized motion vector activity is also considered to improve the performance. The experimental results illustrate that the proposed algorithm achieves about 49% of computational complexity saving in terms of encoding time, while with negligible quality degradation, compared to H.264/AVC reference software JM.
    Acoustics, Speech and Signal Processing (ICASSP), 2013 IEEE International Conference on; 01/2013
  • U. Ukommi · H.K. Arachchi · S. Dogan · A.M. Kondoz
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    ABSTRACT: Mobile video services are gaining popularity as the preferred means of communication in our daily lives due to its flexibility and portability. Wireless channel facilitates delivery and consumption of media content at “anytime” and “anywhere”. However, the current growth in wireless video services driven by users with insatiable perceived video quality stretches the limited resources beyond nominal limit and deteriorates further on severe congestion. Such scenarios present challenges which include how to efficiently share the constrained-bandwidth among competing media streams to meet the increasing insatiable video quality demand by viewers. This work investigates the effect of content characteristic on received video quality and proposes a scheme for media bitrates adaptation based on the content characteristic. The aim of the study is to devise a strategy for efficient distribution of the limited shared bandwidth resources among competing media streams for improved mobile video services within a fixed limited bandwidth network. Simulations have been carried out in order to evaluate the performance of the proposed scheme. The results obtained, demonstrate the capability and efficiency of the proposed scheme.
    Broadband Multimedia Systems and Broadcasting (BMSB), 2013 IEEE International Symposium on; 01/2013
  • H. Malekmohamadi · WAC Fernando · A. M. Kondoz
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    ABSTRACT: A model exploiting machine learning and content analysis is proposed to predict the subjective quality of stereoscopic videos. This model offers an automated, accurate and consistent subjective quality prediction. The feasibility and accuracy of the proposed technique has been thoroughly analysed with extensive subjective experiments and simulations. Results illustrate that a performance measure of 0.954 in subjective quality prediction can be achieved with the proposed technique.
    Electronics Letters 10/2012; 48(21):1344. DOI:10.1049/el.2012.2365 · 1.07 Impact Factor

Publication Stats

1k Citations
178.28 Total Impact Points

Institutions

  • 2014
    • Loughborough University
      Loughborough, England, United Kingdom
  • 2–2014
    • University of Surrey
      • • I-Lab Multimedia and DSP Research Group
      • • Centre for Communication Systems Research (CCSR)
      • • Department of Electronic Engineering
      Guilford, England, United Kingdom
  • 2011
    • Multimedia Communications Research Laboratory
      Ottawa, Ontario, Canada
  • 2008
    • Deutsche Telekom Laboratories
      Berlín, Berlin, Germany
    • The Kings College
      Brooklyn, New York, United States
  • 2004
    • Eastern Mediterranean University
      Magosa, Ammochostos, Cyprus
  • 2001
    • Kocaeli University
      Cocaeli, Kocaeli, Turkey