M.U. Demircin

Georgia Institute of Technology, Atlanta, GA, United States

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Publications (9)3.51 Total impact

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    ABSTRACT: In this paper, we consider a hybrid P2P video on-demand architecture that utilizes both the server and the peer resources for efficient transmission of popular videos. In our system architecture, each peer dedicates some cache space to store a particular segment of a video file as well as some of its upload bandwidth to serve the cached segment to other peers. Peers join the system and issue a streaming request to a control server. Control server directs the peers to streaming servers or to other peers who have the desired video segments. Control server also decides which peer should cache which video segment. Our main contribution in this paper is to determine the proper caching strategies at peers such that we minimize the average load on the streaming servers. To minimize the server load, we pose the caching problem as a supply-demand-based utility optimization problem. By exploiting the inherent structure of a typical on-demand streaming application as well as the availability of a global view on the current supply-demand at the control server, we demonstrate how the system performance can be significantly improved over the brute-force caching decisions. In our analysis, we mainly consider three caching mechanisms. In the first mechanism (cache prefetching), a segment is prefetched to a given peer for caching purposes upon peer's arrival to the system regardless of whether that segment is currently demanded by that peer or not. In the second mechanism (opportunistic cache update), a peer has the option of replacing the segment that is currently in its cache with the last segment that it finished streaming. In the third mechanism, we combine both mechanisms as a hybrid caching strategy. In particular, we find that a dynamic-programming (DP)-based utility maximization solution using only the cache update method performs significantly better in reducing the server load. Furthermore, our findings suggest that even less sophisticated cache update solutions can perfo- - rm almost as good as prefetching strategies in interesting regions of operation.
    IEEE Transactions on Multimedia 05/2009; · 1.75 Impact Factor
  • M.U. Demircin, P. van Beek, Y. Altunbasak
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    ABSTRACT: In this study, we propose bit-rate adaptation techniques for compressed high-definition video transmission over wireless home networks. Application-layer methods are developed to minimize quality impairments caused by wireless channel degradations. A transrater located at a home video server adjusts the transmission rate of the video stream based on bandwidth measurements. We consider delay constraints of multiple video frames across various time scales, and dynamically select an appropriate time scale for bit-rate adjustments. This novel feature prevents playout buffer underflows and avoids unnecessary rate reductions. Furthermore, distortion due to transrating is minimized by coding type-dependent rate allocation among the frames to be transmitted in the projected time scale. Using a realistic simulation setup, we demonstrated that the proposed technique significantly reduces video glitches. Up to 3.12 dB average PSNR improvement is achieved, compared to a non-delay constrained rate adaptation method, which also utilizes bandwidth measurements. Our approach maintains compliance with existing wireless local area (WLAN) devices and standards, as well as consumer video standards and applications.
    IEEE Transactions on Multimedia 11/2008; · 1.75 Impact Factor
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    M. Umut Demircin, P. van Beek
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    ABSTRACT: In this paper, we propose a transrating based video rate adaptation technique for compressed high-definition video transmission over wireless local area networks. Our application layer technique targets to prevent the quality impairments caused by inconsistent wireless bandwidth. The transrater at the server adjusts the transmission rate for each video frame, based on bandwidth measurements, to sustain the playout buffer fullness. Client periodically sends feedbacks after probing the available bandwidth using the video packet dispersions. The superiority of the proposed technique over the existing ones comes from its ability to select various time scales for rate adjustments. This feature avoids unnecessary rate reductions. Furthermore, transrating distortion is minimized by encoding type dependent rate allocation among the frames that will be transmitted in the projected time scale. Experimental results show that the proposed technique significantly reduces video glitches. Up to 2.43 dB average PSNR improvement is achieved compared to a delay-constraint unaware rate adaptation method, which also utilizes bandwidth measurements
    Image Processing, 2006 IEEE International Conference on; 11/2006
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    P. van Beek, M.U. Demircin
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    ABSTRACT: In this paper, we consider rate adaptation for robust transmission of high-quality video over home networks, in particular IEEE 802.11 wireless LANs. Our approach includes on-line estimation of the time-varying bandwidth available at the application-/transport-layer. We propose a delay-constrained rate adaptation algorithm to select an optimal bit rate, subsequently enforced by a video transcoder. We examine the effectiveness of our novel delay-constrained rate adaptation algorithm, utilizing a simulation environment based on NS-2. Our simulation results show that transmission of MPEG-2 video over an IEEE 802.11b channel results in significantly better quality with rate adaptation compared to transmission without rate adaptation, and that delay-constrained rate adaptation performs significantly better than rate adaptation without a delay constraint.
    Image Processing, 2005. ICIP 2005. IEEE International Conference on; 10/2005
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    M.U. Demircin, P. van Beek
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    ABSTRACT: Streaming high quality audio/video (AV) from home media sources to TV sets over a wireless local area network (WLAN) is a challenging problem because of the fluctuating bandwidth caused by interference. Our approach is to adjust the video bit-rate dynamically in order to improve the experienced audiovisual quality. The effectiveness of rate adaptation depends on the accurate and timely estimation of the available bandwidth. In this paper we specifically focus on robust video streaming with IEEE 802.11e medium access control (MAC) enhancements for quality-of-service (QoS). These enhancements to 802.11e increase the WLAN throughput and decrease packet latencies. However, bandwidth estimation methods used in prior work, based on packet dispersion measurements, cannot be used in this context. To address this problem, we propose a new on-line application-layer bandwidth measurement method that runs at the sender application and uses the differences of packet send times and feedback receive times. The bandwidth estimation technique is implemented in a video streaming simulation environment that also includes a delay-constrained rate adaptation algorithm at the sender. Experimental results show that streaming with bandwidth estimation and rate adaptation achieves a PSNR gain up to 3.3 dB compared to streaming without rate adaptation.
    2012 IEEE International Conference on Multimedia and Expo. 01/2005;
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    A.C. Begen, M.U. Demircin, Y. Altunbasak
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    ABSTRACT: This paper presents a client-driven rate-distortion optimized packet scheduling algorithm for streaming multiple description (MD) encoded video, where the descriptions are distributed among different video-on-demand servers. Previously, multiple description coding (MDC) has been proposed to provide reliable video communication within a content delivery network, where the main goal was to imitate path diversity by using multiple servers concurrently. Although this approach can alleviate the severe effects of bursty packet losses, transmitting video packets in a time-sensitive and network-adaptive manner is fundamental to the success of MD streaming. Hence, in this paper we propose a packet scheduling algorithm that maximizes the quality of the video rendered at the client under the given rate constraints. This algorithm jointly considers the timeliness requirements of the streaming application, dependency structure of the streamed video, network conditions as well as the error-resiliency features of MDC.
    Communications, 2004 IEEE International Conference on; 07/2004
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    M.U. Demircin, Y. Altunbasak
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    ABSTRACT: In this work, we propose an error-control technique for efficient streaming of packetized multimedia over time-varying wireless channels. Our objective is to obtain maximum media presentation quality for a given channel capacity. In the proposed technique, forward error correction (FEC) redundancy rate of media packets are optimized based on a distortion model. Such multimedia-source and channel characteristics as the packet importance, dependencies, decoding deadlines and channel state information are utilized in the optimization process. In addition, we also consider the effect of residual channel resources for future transmissions on the overall quality. Real-time streaming simulations with H.263+ video sequences show that the proposed technique achieves up to 1.8 dB quality improvement over nonoptimized error control methods.
    Wireless Communications and Networking Conference, 2004. WCNC. 2004 IEEE; 04/2004
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    Mehmet Umut Demircin
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    ABSTRACT: Multimedia services and applications became the driving force in the development and widespread deployment of wireless broadband access technologies and high speed local area networks. Mobile phone service providers are offering wide range of multimedia applications over high speed wireless data networks. People can watch live TV, stream on-demand video clips and place videotelephony calls using multimedia capable mobile devices. Mobile devices will soon support capturing and displaying high definition video. Similar evolution is also occurring in the local area domain. The video receiver or storage devices were conventionally connected to display devices using cables. By using wireless local area networking (WLAN) technologies, convenient and cable-free connectivity can be achieved. Media over wireless home networks prevents the cable mess and provides mobility to portable TVs. However, there still exit challenges for improving the quality-of-service (QoS) of multimedia applications. Conventional service architectures, network structures and protocols lack to provide a robust distribution medium since most of them are not designed considering the high data rate and real-time transmission requirements of digital video. In this thesis the challenges of wireless video streaming are addressed in two main categories. Streaming protocol level issues constitute the first category. We will refer to the collection of network protocols that enable transmitting digital compressed video from a source to a receiver as the streaming protocol. The objective of streaming protocol solutions is the high quality video transfer between two networked devices. Novel application-layer video bit-rate adaptation methods are designed for handling short- and long-term bandwidth variations of the wireless local area network (WLAN) links. Both transrating and scalable video coding techniques are used to generate video bit-rate flexibility. Another contribution of this thesis study is an error control method that dynamically adjusts the forward error correction (FEC) rate based on channel bit-error rate (BER) estimation and video coding structure. The second category is the streaming service level issues, which generally surface in large scale systems. Service system solutions target to achieve system scalability and provide low cost / high quality service to consumers. Peer-to-peer assisted video streaming technologies are developed to reduce the load of video servers. Novel video file segment caching strategies are proposed for more efficient peer-to-peer collaboration. Ph.D. Committee Chair: Yucel Altunbasak; Committee Member: Chuanyi Ji; Committee Member: Ghassan AlRegib; Committee Member: Ozlem Ergun; Committee Member: Russell M. Mersereau
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we propose a transrating based video rate adaptation technique for compressed high-definition video transmission over wireless local area networks. Our application layer technique targets to prevent the quality impairments caused by inconsistent wireless bandwidth. The transrater at the server adjusts the transmission rate for each video frame, based on bandwidth measurements, to sustain the playout buffer fullness. Client periodically sends feedbacks after probing the available bandwidth using the video packet dispersions. The superiority of the proposed technique over the existing ones comes from its ability to select various time scales for rate adjustments. This feature avoids unnecessary rate reductions. Furthermore, transrating distortion is minimized by encoding type dependent rate allocation among the frames that will be transmitted in the projected time scale. Experimental results show that the proposed technique significantly reduces video glitches. Up to 2.43 dB average PSNR improvement is achieved compared to a delay-constraint unaware rate adaptation method, which also utilizes bandwidth measurements.