• Journal of Broadcast Engineering
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• v.6 no.2
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• pp.121-130
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• 2001

We propose an efficient DCT-domain video transcoding algorithm for flexible for bit-rate video communications. Video transcoding provides communication fiexibility by adaptively changing the bit-rate of compressed bit stream. During the transcoding process, adrift error is unavoidable because of the difference between reference images in the series of encoding and decoding. For solving the drift error problem, cascade pixel-domain transcoder (CPDT) has been proposed. CPDT, however, requires highly complex hardware and heavy computational overhead. In this paper we propose a DCT-domain transcoding technique, which enables efficient transcoding without any drift error. The proposed cascade DCT-domain transcoder (CDDT) is realized by new motion compensation and down-sampling methods in the DCT-domain.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.6
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• pp.2785-2792
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• 2011

Such problems as delay, congestion, and crosstalk in the proxy system degrade not only QoS (Quality of Service) but responsiveness and reliability of the streaming media service. To solve this problem this paper proposed a FRTP (Fuzzy Relevance-based Transcoding Proxy) mechanism. The proposed FRTP mechanism analyzes fuzzy similarity for partitioned segment versions of media objects to create a FRTG (Fuzzy Relevance-based Transcoding Graph). Created FRTG determines the transcoding for partitioned media object segment versions. Determined transcoding improves DSR (Delay Saving Ratios), CHPR (Cache Hit Precision Ratio), and CHRR (Cache Hit Recall Ratio). The proposed mechanism is simulated to evaluate such performance parameters as DSR, CHPR, and CHRR. Simulation results shows that the proposed mechanism outperforms in DSR, CHPR and CHRR compared with the other existing mechanisms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.7C
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• pp.548-553
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• 2008

To reduce the bit-rate requirements imposed by a network or satisfy processing limitations imposed by a terminal, Conversion the temporal resolution of a video bit stream is a technique that may be used. This paper discusses the problem of reduced resolution transcoding of compressed video bit streams, and discussed the technique for temporal transcoding. To speed up this operation, a video transcoder usually reuses the coded motion vectors from the input video bit stream. In this paper we propose an enhanced motion re-estimation technique to maintain higher quality of coded frames. The performance of experimental results can be improved while maintaining low computational complexity for a reduced frame rate video transcoder.

• Journal of Advanced Navigation Technology
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• v.15 no.3
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• pp.355-363
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• 2011

Transcoding in the wireless mobile network is an important mechanism that reduces the delay time and improves the stream processing capacity. Wireless mobile streaming media services, however, have such problems as congestion, interference and delay due to narrow network bandwidth and limited resources. These problems degrade not only Quality of Service (QoS) but also responsiveness of the streaming media service. To solve this problem, this paper proposes a object version transcoding method. The proposed method analyzes the object versions to construct the transcoding graph. This paper utilizes a reference rate-based control function for an efficient streaming, and measures MVDS(Multiple Version Delay Saving) for an efficient delay savings. The simulation results show that the proposed mechanism achieves improved performance in delay rate and cache hit rate compared with those of other existing methods.

• Journal of Korea Multimedia Society
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• v.8 no.2
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• pp.137-153
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• 2005

This paper presents a transcoding method that dynamically adapts Web pages to various devices. The proposed method is based on a CC/PP profile that is a standard description of a device's context information. Additionally, to support a sophisticated transcoding, we define an annotation schema for representing additional information about original contents. Since a mobile device has a screen of limited size, A Web page is splitted into many small ones. Our method constructs a navigation-map that represents the hierarchical relations among the splitted pages. Experimental results with various Web contents show that the proposed method is superior in terms of user's convenience of navigation and the transcoding Quality.

• Journal of Korea Multimedia Society
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• v.9 no.1
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• pp.59-72
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• 2006

The rapid growth of technology for network and terminal devices is able to service multimedia contents in mobile environments. But as the environment of networks and the performance of devices is varied, the same quality service is very difficult to be provided for user in internet and mobile environment. Therefore, multimedia streaming system must provide an adaptive service in considering network and device environment. Video transcoding techniques are the good solution that can provide video streaming service in various network environments adaptively. This paper proposes a dynamic frame-skipping transcoding scheme to provide adaptive streaming service in various network environments. This scheme uses the prediction period for transcoding. A proposed transcoding scheme can reduce time complexity through combination of prediction period and skipping period to control frame-skipping rate in encoder. In simulation results, the performance of proposed scheme is similar to the performance of a traditional dynamic frame-skipping scheme in PSNR value. But the performance of proposed scheme outperforms the performance of traditional scheme in time complexity.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.05a
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• pp.909-912
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• 2008

무선 네트워크의 발달로 인해 이동 사용자가 급증함에 따라 무선 네트워크 환경에서도 질 높은 미디어 스트리밍 서비스를 받기 위한 수요가 증가하고 있다. 그러나 무선 네트워크는 유선 네트워크보다 상대적으로 좁은 네트워크 대역폭을 가진다. 또한 유선 네트워크 환경의 단말기에 비해 제한된 시스템 자원을 가지므로 유선 네트워크 환경의 사용자를 위한 고화질 미디어 데이터를 그대로 스트리밍 서비스 받기에 적합하지 않다. 최근 이러한 문제를 해결하기 위한 방법으로 미디어 트랜스코딩 서비스가 활발하게 연구되고 있다. 다수의 트랜스코딩 서버로 구성된 분산 트랜스코딩 시스템에서 특정 서버로 트랜스코딩 작업이 집중될 경우 사용자에게 질 높은 수준의 미디어 스트리밍 서비스를 제공하기 어렵다. 때문에 각 트랜스코딩 서버간의 균형적인 부하 분산이 중요한 문제가 되며, 처리되는 미디어 데이터의 특성을 부하 분산에 반영할 필요가 있다. 본 논문에서는 MPEG-2 미디어 데이터의 트랜스코딩 과정을 분석함으로써 비트율 변경에 따른 트랜스코딩 작업 시간 예측 기법을 제안한다. 제안된 기법은 트랜스코딩 서버 정보와 영화 정보, 목적 트랜스코딩 비트율을 이용하여 예상 트랜스코딩 시간을 예측한다.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.39 no.2
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• pp.54-63
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• 2002

Recently, many web-enabled personal devices are becoming available for connecting to the internet, and there are many use]-s who access the internet from hand-held devices such as PDAs, cell phones. Most pages on the world wide web are designed for displaying on desktop computers with color monitor having at least 640$\times$480 resolution. But these devices do not have the same rendering capabilities as desktop computer, so the same web content needs to be rendered differently on hand-held devices. Therefore, there have been a variety of web transcoding techniques proposed to solve the problem between the web contents and hand-held devices. In this paper, we propose a web transcoding system(WebPrism) for real-time information providing using the semi-automatic transcoding method. The semi-automatic web transcoding method is a good solution when if mobile users access the limited number of web pages which layout is not changed frequently, also WebPrism is implemented as a desktop PC and experimental result shows that the proposed system generates the best looking document for a given display size of PDA.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.105-108
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• 2003

In the framework of universal multimedia access, one challenge for video transmission (communication) is to deliver video content through heterogeneous network channels matching the diversity of client devices. As one of the many adaptation methods, media transcoding is commonly considered. Particularly, FD (Frame Dropping)/CD Coefficient Dropping) transcoding is used due to the low computational complexity and simple implementation. In this scheme, CD is simply implemented by truncating the high frequency AC DCT coefficient bits. But, the CD error tends to be propagated within single GOV. In this paper, we derive the distortion relationships between CD error and propagation error, and investigate the error characteristics by computer simulations. The CD error characteristics can be effectively used in the FD/CD transcoding scheme.

• Journal of KIISE:Computing Practices and Letters
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• v.13 no.5
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• pp.260-270
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• 2007

Owing to the improved wireless communication technologies, it is possible to provide streaming service of multimedia with PDAs and mobile phones in addition to desktop PCs. Since mobile client devices have low computing power and low network bandwidth due to wireless network, the transcoding technology to adapt media for mobile client devices considering their characteristics is necessary. However, since mobile clients use wireless network and the wireless network have less stable bandwidth according to distance from AP and environments, it is hard to support stable QoS to mobile clients. In this paper, we propose a dynamic bit rate control method for transcoding in order to supprot stable QoS of streaming media service to mobile clients via wireless network. The proposed method is shown to serve seamless streaming media service with adaptive bit rate control according to state of wireless network in real time and to reduce transmission failure from experiment.