• Journal of the Korea Society of Computer and Information
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• v.8 no.4
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• pp.47-56
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• 2003

According to rapidly developed mobile terminals and network in the play environment for multimedia presentation, different end-to-end QoS situations appear. Then the generation of transcoding path algorithm was reviewed to transcode a source'data satisfying the needed QoS from a destination and play it considering given transcoders and network. This method used only workload as a parameter although two parameters, workload and throughput, were needed to process multimedia stream in a transcoder, Therefore generated transcoding path with this method had additional calculation to check playability whether it was safisfed the QoS of a destination or not. To solve the problem this paper suggests T algorithm with evaluation function using isochronous property that is needed for multimedia stream to arrive a destination. That means, most playable path is selected with heuristic search based isochronous property between many transcoding paths. Using the suggested algorithm, a transcoding path can be generated faster to play the multimedia data with different end-to-end QoS in real-time transmission.

• Journal of Korea Multimedia Society
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• v.10 no.5
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• pp.642-651
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• 2007

Recently, digital convergence, whose core demand is OSMU (One Sourse Multi Use),has been the main topic in e-learning domain and industry. However, the existing web learning content and the new resource developed toprovide contents to different learning environment must be processed to adapt the new learning settings, which causes the cost and time problem, So in this paper we design and implement a Java based SCORM content transcoding system which can transcode the SCORM-based learning content into MHP-based DiTV content in order to adapt t-learning environment using DiTV, which is closer to our real life. Using this system which has ability of inter-operation, reuse, highly-use, the problem mentioned above can be solved well. Moreover, it is possible for a learner who is not familiar with computer to study using DiTV instead of PC.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.2
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• pp.95-105
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• 2005

This paper proposes a new dynamic video adaptation scheme that could generate an adapted video stream customized to the requesting mobile device and current network status without repeated decode-encode cycles. In the proposed adaptation scheme, the characteristics of the video codec such as MPEG-1/-2/-4 are analyzed in advance focused on the relationships between the size and Quality of the encoded video stream, and they are stored in the proxy as a codec-dependent characteristic table. When a mobile device requests a video stream, it is dynamically decoded-encoded in the proxy with the highest quality to extract the contents-dependent attributes of the requested video stream. By comparing these attributes with codec-dependent characteristic table, the size and Quality of the requested video stream when being adapted to the target mobile device could be predicted. With this prediction, a version of adapted video stream, that meets the size constraints of mobile device while keeping the quality of encoded video stream as high as possible, could be selected without repeated decode-encode cycles. Experimental results show that the errors in our proposed scheme are less than 5% and produce an appropriate adapted video stream very quickly. It could be used t(1 build a proxy server for mobile devices that could quickly transcode the video streams widely spread in Internet which are encoded with various video codecs.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.2
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• pp.138-148
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• 2001

Digital Video (DV) coding standards for digital video cassette recorder are based mainly on DCT and variable length coding. DV has low hardware complexity but high compressed bit rate of about 26 Mb/s. Thus, it is necessary to encode video with low complex video coding at the studios and then transcode compressed video into MPEG-2 for video-on-demand system. Because these coding methods exploit DCT, transcoding in the DCT domain can reduce computational complexity by excluding duplicated procedures. In transcoding DV into MPEC-2 intra coding, multiplying matrix by transformed data is used for 4:1:1-to-4:2:2 chroma format conversion and the conversion from 2-4-8 to 8-8 DCT mode, and therefore enables parallel processing. Variance of sub block for MPEG-2 rate control is computed completely in the DCT domain. These are verified through experiments. We estimate motion hierarchically using DCT coefficients for transcoding into MPEG-2 inter coding. First, we estimate motion of a macro block (MB) only with 4 DC values of 4 sub blocks and then estimate motion with 16-point MB using IDCT of 2$\times$2 low frequencies in each sub block, and finish estimation at a sub pixel as the fifth step. ME with overlapped search range shows better PSNR performance than ME without overlapping.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.648-653
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• 2008

With development of mobile communications terminal and expansion of mobile Internet, a large number of users can use mobile web contents at anytime and anywhere and will demand service of greater contents. Due to such demand, many studies are being carried out on transcoding contents so that wired web contents can be used in mobile web. However, transcoding and creation of mobile web contents involve difficulties because specifications available from telecommunications companies and mobile terminals have not been standardized. Especially, in order for serving dynamic object of wired web page contents to dynamically change according to time or user, it is required not only to program scripts to suit each terminal, but also to transcode the resources used in advance. For solution to this problem, this study uses the hierarchy structure of DOM (document object model) to display structural characteristics of wired web page. In other words, this study proposes the following technique Wired web pages are analyzed and the results are established as data structure. Then, dynamic object is extracted and the domain is indexed so that, when serving mobile web page, information can be extracted at the indexed position to create mobile web contents for service on real-time basis.

• The KIPS Transactions:PartB
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• v.9B no.6
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• pp.745-752
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• 2002

The purpose of the paper is to enable a format transcoding between a heterogeneous compression format in a real time, and to enhance the compression ratio using characteristics of the compressed frame. In this paper, for the heterogeneous format transcoding, we tried to transcode from MPEG2 having a lower compression ratio to H.263 having a higher compression ratio. After analyzing MPEG 2 bit stream and H.263 bit stream of the same original video, we found that the number of intra coded macro blocks in MPEG 2 data is much higher than the number of the intra coded macro blocks in H.263 data. In the process of P frame generation, a intra coded macro block is generated when a motion estimation value representing the similarity between the previous frame and current frame does not meet a threshold. Especially the intra coded macro block has a great impact on the compression ratio. Hence the paper, we tried to minimize the number of intra coded macro blocks in H.263 data stream which is transcoded from MPEG 2 in a compressed domain. For the purpose, we propose a guided search method for transcoding the INTRA coded block into INTER coded block using the information about motion vectors surrounding the intra macro block in order to minimize the complexity of the motion estimation process. The experimental results show that the transcoding of MPEG 2 into H.263 can be done in a real time successfully.

• Journal of KIISE:Software and Applications
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• v.35 no.4
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• pp.207-218
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• 2008

With the growth of the Internet, multimedia streaming becomes an important means to deliver video contents over the Internet and the amount of the streaming multimedia contents is also getting increased. However, it becomes difficult to guarantee the quality of service in real-time over the IP network environment with instantaneously varying bandwidth. In this paper, we propose an optimal adaptation framework for streaming contents over the Internet in the sense that the perceptual quality of the multi-angie content with multiple visual objects is maximized given the constraints such as available bandwidth and transcoding cost. In the multi-angle video service framework, the user can select his/her preferred alternate views among the given multiple video streams captured at different view angles for a same event. This enhanced experience often entails streaming problems in real-time over the network, such as instantaneous bandwidth changes in the Internet. In order to cope with this problem, we assume that multi-angle video contents are encoded at different bitrates and the appropriate video streams are then selected or transcoded for delivery to meet such bandwidth constraints. For the user selective consumption of the various bitstreams in the multi-angle video service, the bitstream in each angle can be encoded in various bitrate, and the user can select a sub-bitrstream in the given bitrstreams or transcode the corresponding content in order to deliver the optimally adapted video contents to the instantaneously changing network condition. Therefore, we define the transcoding cost which means the time taken for transcoding the video stream and formulate a unified optimization framework which maximizes the perceptual quality of the multiple video objects in the given constraints such as the transcoding cost and the network bandwidth. Finally, we present plenty of the experimental results to show the effectiveness of the proposed method.

• The KIPS Transactions:PartD
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• v.14D no.3 s.113
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• pp.355-362
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• 2007

With development of mobile communications terminal and expansion of mobile Internet, a large number of users can use mobile web contents at anytime and anywhere and will demand service of greater contents. Due to such demand, many studies are being carried out on transcoding contents so that wired web contents can be used in mobile web. However, transcoding and creation of mobile web contents involve difficulties because specifications available from telecommunications companies and mobile terminals have not been standardized. Especially, in order for serving dynamic object of wired web page contents to dynamically change according to time or user, it is required not only to program scripts to suit each terminal, but also to transcode the resources used in advance. for solution to this problem, this study uses the hierarchy structure of DOM (document object model) to display structural characteristics of wired web page. In other words, this study proposes the following technique. Wired web pages are analyzed and the results are established as data structure. Then, dynamic object is extracted and the domain is indexed so that, when serving mobile web page, information can be extracted at the indexed position to create mobile web contents for service on real-time basis. Also, this study aims at developing an editing device to edit mobile web contents and mobile web service server to service the edited contents by applying the above technique.

• Journal of Broadcast Engineering
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• v.16 no.1
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• pp.108-122
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• 2011

In this paper, a transcoding method with low computational complexity and high coding efficiency is proposed to transcode distributed video coding (DVC) bitstreams to H.264/AVC ones. For the proposed high-performance transcoding with low complexity, not only Wyner-Ziv frames but also key frames can be transcoded with motion vectors estimated in generation of side information. As a motion vector is estimated from a key frame to a prior key frame for side information generation, the motion vector can be used to encode the intra key frame as a predicted frame. Motion estimation is performed with two predicted motion vectors. One is the motion vector from side information generation and the other is median of motion vectors of neighboring blocks. The proposed method selects the best motion vector between two motion vectors based on rate-distortion optimization. Coding efficiency can be improved with a small size of search range, because a motion vector estimated in side information generation is used as an initial motion vector for transcoding. In the experimental results, complexity of transcoder is reduced about 12% and bitrate performance increases about 28.7%.

• Journal of KIISE:Computing Practices and Letters
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• v.11 no.5
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• pp.401-415
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• 2005

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. Transcoding servers transcode the source media to the target media within corresponding grades and provide QoS in real-time. In particular, an effective load balancing policy for transcoding servers is inevitable to support QoS for large scale mobile users. In this paper, the resource weighted load distribution policy is proposed for a fair load balance and a more scalable performance in cluster-based transcoding servers. Our proposed policy is based on the resource weighted table and number of maximum supported users, which are pre-computed for each pre-defined grade. We implement the proposed policy on cluster-based transcoding servers and evaluate its fair load distribution and scalable performance with the number of transcoding servers.