• Journal of KIISE:Computer Systems and Theory
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• v.26 no.8
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• pp.975-983
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• 1999

최근 네트워크의 속도가 빨라지고 멀티미디어 데이터를 다루기 위한 기술들이 개발됨에 따라 많은 멀티미디어 응용 프로그램들이 인터넷에 등장하고 있다. 그러나 이들 응용프로그램들은 수신자에게 전송되는 영상.음성의 품질이 낮기 때문에 기대만큼 빠르게 확산되지 못하고 있다. 영상.음성의 품질이 낮은 이유는 현재 인터넷이 실시간 응용프로그램이 요구하는 만큼 빠르고 신뢰성 있게 데이터를 전송할 수 없기 때문이다. 현재 인터넷의 내부구조를 바꾸지 않고 품질을 높이기 위해 많은 연구들이 진행되고 있는데 그 중 하나는 동적으로 변화하는 인터넷의 상태에 맞게 멀티캐스트 트래픽의 전송율을 조절하는 종단간의 흐름제어이다. 본 논문은 기존의 흐름제어 기법인 IVS와 RLM의 성능을 개선시키기 위한 두 가지 흐름제어 기법을 소개한다. IVS는 송신자가 주기적으로 측정된 네트워크 상태에 따라 전송율을 일정하게 조절한다. 송신자가 하나의 데이타 스트림을 생성하는 IVS와는 달리 RLM에서는 송신자가 계층적 코딩에 의하여 생성된 여러개의 데이타 스트림을 전송하고 각 수신자는 자신의 네트워크 상태에 맞게 데이타 스트림을 선택하는 기법이다. 그러나 IVS는 송신자가 전송율을 일정하게 증가시키고, RLM은 각자의 네트워크 상태를 고려하지 않고 임의의 시간에 하나 이상의 데이타 스트림을 받기 때문에 성능을 저하시킬 수 있다. 본 논문에서는 TCP-like IVS와 Adaptive RLM이라는 두 가지 새로운 기법을 소개한다. TCP-like IVS는 송신자가 전송율을 동적으로 결정하고, Adaptive RLM은 하나 이상의 데이타 스트림을 받기 위해 적당한 시간을 선택할 수 있다. 본 논문에서는 시뮬레이션을 통해 여러 가지 네트워크 구조에서 두 가지 방식이 기존의 방식에 비하여 더욱 높은 대역폭 이용율과 10~20% 정도 적은 패킷손실율을 이룬다는 것을 보여준다.Abstract Nowadays, many multimedia applications for the Internet are introduced as the network gets faster and many techniques manipulating multimedia data are developed. These multimedia applications, however, do not spread widely and are not fast as expected at their introduction time due to the poor quality of image and voice delivered at receivers. The poor quality is mainly attributed to that the current Internet can not carry data as fast and reliably as the real-time applications require. To improve the quality without modifying the internal structure of the current Internet, many researches are conducted. One of them is an end-to-end flow control of multicast traffic adapting the sending rate to the dynamically varying Internet state. This paper proposes two flow-control techniques which can improve the performance of the two conventional techniques; IVS and RLM. IVS statically adjusts the sending rate based on the network state periodically estimated. Differently from IVS in which a sender produces one single data stream, in RLM a sender transmits several data streams generated by the layered coding scheme and each receiver selects some data streams based on its own network state. The more data streams a receiver receives, the better quality of image or voice the receiver can produce. The two techniques, however, can degrade the performance since IVS increases its sending rate statically and RLM accepts one more data stream at arbitrary time regardless of the network state respectively. We introduce two new techniques called TCP-like IVS and Adaptive RLM; TCP-like IVS can determine the sending rate dynamically and Adaptive RLM can select the right time to add one more data stream. Our simulation experiments show that two techniques can achieve better utilization and less packet loss by 10-20% over various network topologies.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7B
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• pp.598-612
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• 2004

Client requests have increased with the improvement of network resources at client side, whereas network resources at server side could not keep pace with the increased client request. Therefore, it is primary factor of the Qos that efficiently utilize network resources at server side. In this paper, we proposed a new model that peer-to-peer transfer scheme for partial multimedia stream based on CIWP which it decrease server network bandwidth by utilizing client disk resources saves additional server network resources. Especially, adapting Threshold_Based Multicast scheme guarantees to do that data transfer within clients never exceed service time of previous peer by restriction of which data size transferring from previous peer less than data size transferring from server. Peer-to-peer transfer within clients is limited in same group classified as ISPs. Our analytical result shows that proposed scheme reduces appling network resources at server side as utilizing additional client disk resource. furthermore, we perform various simulation study demonstrating the performance gain through comparing delay time and proportion of waiting requesters. As a result, when we compared to Threshold_Based Multicast scheme, the proposed scheme reduces server network bandwidth by 35%.

• The Journal of the Korea Contents Association
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• v.8 no.5
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• pp.72-81
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• 2008

High Performance DSP usually supports cache and internal memory. For an optimal implementation of a multimedia stream application on such a high performance DSP, one needs to utilize the cache and internal memory efficiently. In this paper, we investigate performance analysis of cache, and internal memory configuration and placement necessary to achieve an optimal implementation of multimedia stream applications like motion picture encoder on high performance DSP, TMS320C6000 series, and propose strategies to improve performance for cache and internal memory placement. From the results of analysis and experiments, it is verified that 2-way L2 cache configuration with the remaining memory configured as internal memory shows relatively good performance. Also, it is shown that L1P cache hit rate is enhanced when frequently called routines and routines having caller-callee relationships with them are continuously placed in the internal memory and that L1D cache hit rate is enhanced by the simple change of the data size. The results in the paper are expected to contribute to the optimal implementation of multimedia stream applications on high performance DSPs.

• Journal of Korea Multimedia Society
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• v.18 no.8
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• pp.988-995
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• 2015

In 2013, Academy Award for Best Animated Short Film was granted to Walt Disney's short animation, (2012). With various aspects of its excellence, I focus on the very effective use of digital lightings and underscores for storytelling as its success factors. In this respect, this paper aims at analyzing the roles of the visual factors, especially tone, contrast, etc. created by lightings, and audio factors, especially underscores, in the film's story development. I find that can be characterized by the well-built story structure with distinct three acts. The main stream of the story is expressed with the overall mood that is created by the fine adjustments of brightness of the main light, and contrast. And the direction and the intensity of the lighting successfully describe the emotions of the characters in each scene. In addition, I find that properly chosen and positioned underscores make the development of the story more dynamic and more harmonized.

• Journal of Korea Multimedia Society
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• v.15 no.6
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• pp.693-700
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• 2012

The effective extraction of key frames from a video stream is an essential task for summarizing and representing the content of a video. Accordingly, this paper proposes a new and fast method for extracting key frames from a compressed video. In the proposed approach, after the entire video sequence has been segmented into elementary content units, called shots, key frame extraction is performed by first assigning the number of key frames to each shot, and then distributing the key frames over the shot using a probabilistic approach to locate the optimal position of the key frames. The main advantage of the proposed method is that no time-consuming computations are needed for distributing the key frames within the shots and the procedure for key frame extraction is completely automatic. Furthermore, the set of key frames is independent of any subjective thresholds or manually set parameters.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.11
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• pp.2521-2530
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• 1997

In this paepr, we present a video-on-demand (VOD) system design model that address and integrates a number of inter-related issues. Then with analysis and performance evaluation, we investigate various aspects of disk and buffer managements in the given model. Based on the analysis results, we suggest that a distributed buffering scheme with intermediate buffers may te useful to transform bursty disk accesses into a continuous stream for for glitch-free performance of VOD systems. Also, through simulation, we illustrate that massive multimedia information storage design techniques such as prefetching, clustered striping, and real-time disk scheduling integrated with the distributed buffering mechanism may enhance end-to-end real-time performance of VOD systems under wide-area networks.

• Journal of Communications and Networks
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• v.16 no.3
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• pp.322-334
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• 2014

Multimedia content is very sensitive to packet loss and therefore multimedia streams are typically protected against packet loss, either by supporting retransmission requests or by adding redundant forward error correction (FEC) data. However, the redundant FEC information introduces significant additional bandwidth requirements, as compared to the bitrate of the original video stream. Especially on wireless and mobile networks, bandwidth availability is limited and variable. In this article, an adaptive FEC (A-FEC) system is presented whereby the redundancy rate is dynamically adjusted to the packet loss, based on feedback messages from the client. We present a statistical model of our A-FEC system and validate the proposed system under different packet loss conditions and loss probabilities. The experimental results show that 57-95%bandwidth gain can be achieved compared with a static FEC approach.

• Journal of Korea Society of Digital Industry and Information Management
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• v.10 no.3
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• pp.171-179
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• 2014

Among the P2P based multimedia streaming architecture, multiple chain architecture has advantage in adapting to dynamically changing network topology simply and rapidly, so this architecture is used for UCC broadcasting system. In UCC broadcasting system, general peer involved in DSLAM becomes UCC server rather than broadcasting system that transfers data from ISP servers. Therefore UCC data generated from UCC server peers is transmitted to peers through DSLAM, and this transmission uses uplink bandwidth of DSLAM. In this paper, I propose an efficient management method of DSLAM uplink bandwidths through negotiating tracker and UCC server peer or head peers of DSLAM. I propose the method that tracker restricts a bitrate of uplink stream of UCC servers when used uplink bandwidth of DSLAM exceeds a certain point of maximum uplink bandwidths. I will show the improved performance of proposed scheme rather than general method with respect to the uplink bandwidth of DSLAM by numerical analysis and simulation.

• Journal of Korea Multimedia Society
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• v.18 no.7
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• pp.793-805
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• 2015

Nowadays the amount of data obtained from advanced weather radars is growing to provide higher spatio-temporal resolution. Accordingly radar data compression is important to use limited network bandwidth and storage effectively. In this paper, we proposed a hierarchical compression method for weather radar data having high spatio-temporal resolution. The method is applied to radar reflectivity and evaluated in aspects of accuracy of quantitative rainfall intensity. The technique provides three compression levels from only 1 compressed stream for three radar user groups-signal processor, quality controller, weather analyst. Experimental results show that the method has maximum 13% and minimum 33% of compression rates, and outperforms 25% higher than general compression technique such as gzip.

• Journal of Korea Multimedia Society
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• v.20 no.4
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• pp.629-639
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• 2017

Interpolation based information hiding methods are widely used to get information security. Conventional interpolation methods use the neighboring pixel value and simple calculation like average to embed secret bit stream into the image. But these information hiding methods are not appropriate to color images like military images because the characteristics of military images are not considered and these methods are restricted in grayscale images. In this paper, the new information hiding method based on interpolation using RGB pixel values of color image is proposed and the effectiveness is analyzed through experiments.