• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.07a
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• pp.176-177
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• 2012

사람의 음성을 압축하는 방법으로 Code Excited Linear Prediction (CELP) 코더가 주로 사용되어 왔다. CELP 코더의 수신단에서는 양자화 된 여기신호를 LPC 필터로 합성하여 신호를 복원한다. LPC 합성필터의 영향으로 양자화 된 여기신호의 보로노이 셀 모양이 변형되는 문제점이 있기 때문에 이런 문제점을 해결하기 위해서 Karhunen-Loeve-Transform based Classify vector Quantization (KLT-CVQ) 코더가 제안되었다. 기존 KLT-CVQ 코더는 KLT 변환과 class 선택을 위해서 Eigen Value Decomposition (EVD)을 이용해서 eigen vector와 eigen value를 계산한다. 본 논문에서는 EVD 대신에 UTV Decomposition (UTVD)을 이용하여 KLT-CVQ의 계산량 문제점을 개선하는 방법을 제안한다.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10c
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• pp.611-613
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• 1999

본고에서는 실시간 비트율 변환을 위한 트랜스코딩에서 프레임 제거를 통한 비트율 제어 방법을 설계한다. 트랜스코더에서 비트율을 제어하는 방법에는 재양자화에 의한 비트율 변환과 프레임 제거에 의한 비트율 변환이 있을 수 있다. 전자에 대해서는 많은 연구가 수행되었기 때문에 본고에서는 후자에 대한 방법을 제시하여 제어량에 따라 효율적인 방법을 선택할 수 있는 새로운 형태의 트랜스코더를 설계하는 기반을 마련하였다. 즉, 기존의 공간적 측면에서의 비트율 변화뿐만 아니라 시간적 측면에서 비트율 변환을 고려할 수 있도록 함으로써 PSNR과 변환 속도간의 타협점을 찾도록 하였다. 제안한 방식은 이종 망에서 실시간 비디오 서비스를 위하여 유용하게 사용될 것으로 예상된다.

• Journal of Broadcast Engineering
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• v.10 no.3
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• pp.270-285
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• 2005

A joint design scheme is proposed to optimize the up/down scaler and the motion vector estimation module in the transcoder system. The proposed scheme first optimizes the resolution scaler for a fixed motion vector, and then a new motion vector is estimated for the fixed scaler. These two steps are iteratively repeated until they reach a local optimum solution. In the optimization of the scaler, we derive an adaptive version of a cubic convolution interpolator to enlarge or reduce digital images by arbitrary scaling factors. The adaptation is performed at each macroblock of an image. In order to estimate the optimal motion vector, a temporary motion vector is composed from the given motion vectors. Then the motion vector is refined over a narrow search range. It is well-known that this refinement scheme provides the comparable performance compared to the full search method. Simulation results show that a jointly optimized system based on the proposed algorithms outperforms the conventional systems. We can also see that the algorithms exhibit significant improvement in the minimization of information loss compared with other techniques.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2003.11a
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• pp.143-146
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• 2003

최근 디지털 당송과 이동통신 단말기의 대중화가 이루어짐에 따라 고화질 고해상도의 멀티미디어 컨텐츠의 이동통신 단말기에서의 재생 서비스에 대한 수요가 증가하고 있다 이동통신 단말기에서 멀티미디어 컨텐츠 재생 서비스를 제공하기 위해서는 디지털 방송 컨텐츠를 단말기에 적합한 컨텐츠로 변환할 필요가 있다. 본 논문은 디지털 방송 규격인 MPEG-2 컨텐츠를 이동통신 단말기에서 지원하는 MPEG-4 SP(Simple Profile) 컨텐츠로 실시간으로 변환하는 트랜스 코더에 대한 설계와 구현 기술을 제안한다. 구현된 트래스코더는 화질 유지와 계산량 감소를 위한 적응적 움직임벡터 재구성, 매크로블록 모드 선택, 그리고 움직임벡터 scaling 등의 알고리즘을 포함하고, 인텔사에서 제공하는 SIMD(Single Instruction Multiple Data) 명령어를 이용하여 최적화되었다. 트랜스코더는 30fps, 8Mbps, $720\times480$ 해상도의 멀티미디어 컨텐츠를 다양한 비트율의 30fps, $352\times240$ 해상도의 MPEG-4 컨텐츠로 실시간 변환할 수 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.3C
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• pp.269-277
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• 2007

In this paper, we present a efficient transcoding method from MPEG-2 to H.264. The proposed transcoder is the transcoding method for spatial domain which consists of MPEG-2 decoder part and H.264 encoding part. In transcoder, we can get useful information to estimate less probable modes from MPEG-2 decoder. Using this information, H.264 encoder chooses the macroblock mode of I-frame and P-frame adaptively to reduce the whole complexity of the transcoder. Our experimental result shows that the proposed algorithm can archive about $30\sim60%$ computational saving without significant degradation of visual quality and increasing of bit rate.

• The KIPS Transactions:PartB
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• v.12B no.6 s.102
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• pp.637-646
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• 2005

Most of the multimedia contents for DBM services art provided as MPEG-2 bit streams. However, they have to be transcoded to H.264 bit streams for practical services because the standard video codec for DMB is H.264. The existing transcoder architecture is Cascaded Pixel-Domain Transcoding Architecture, which consists of the MPEG-2 dacoding phase and the H.264 encoding phase. This architecture can be easily implemented using MPEG-2 decoder and H.264 encoder without source modifying. However. It has disadvantages in transcoding time and DCT-mismatch problem. In this paper, we propose two kinds of transcoder architecture, DCT-OPEN and DCT-CLOSED, to complement the CPDT architecture. Although DCT-OPEN has lower PSNR than CPDT due to drift problem, it is efficient for real-time transcoding. On the contrary, the DCT-CLOSED architecture has the advantage of PSNR over CPDT at the cost of transcoding time.

• Journal of Digital Convergence
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• v.13 no.9
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• pp.287-295
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• 2015

The IPTV service has to be converted into an unified media format that fits for a variety of terminal equipments in terms of the bulk high-capacity media contents, and is spending a lot of time in the conversion time of contents including the process of collecting the media contents and extracting the information for conversion. In order to solve the problem, this paper designed the database in accordance with the automatic collection of time, and proposed a system that could increase the productivity of the contents through the automation process of the entire process using the media server and the transcoder. The media server collected contents and extracted information automatically with respect to the contents servers placed in specific locations and the media files of the storage whereas the transcoder conducted the automatic upload of the converted results to a specific server through the process of automatic conversion. As a result, the various convergence through compared to existing conversion method could minimized unnecessary waste of time.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.4 no.1
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• pp.9-16
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• 2011

In this paper, we propose an efficience transcoder architecture to support a simutaneous multibitrate output. First, we discuss about some architectures to realize this feature. Next, we explain the proposed architecture, it shares not only VLD-IQ but alse Q-VlD which have the same quantization step sizes each other. We anlyze the numbers of Q-VLC times per on Macroblock to the investigate an effect of sharing, and evaluate its computation complexity. The result of simulation, that complexity has an upper limit and it cn support any numbers of bitstream by about 3~6 times complexity than single output.

• Journal of Broadcast Engineering
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• v.8 no.3
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• pp.288-296
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• 2003

ATSC (Advanced Television System Committee) has specified 18 video formats for DTV (Digital Television), e.g., scan format, size format, and frame rate format conversion. Effective MPEG-2 video transcoders should support any conversion between the above-mentioned formats. Scan format conversion Is hard to Implement because it may often induce frame rate and size format conversion together. Especially. because of picture type conversion caused by scan format conversion, the computational burden of motion estimation (ME) in transcoding becomes serious. This paper proposes a fast ME algorithm for MPEG-2 video transcoding supporting scan format conversion. Firstly, we extract and compose a set of candidate motion vectors (MVs) from the input bit-stream to comply with the re-encoding format. Secondly, the best MV is chosen among several candidate MVs by using a weighted median selector. Simulation results show that the proposed ME algorithm provides outstanding PSNR performance close to full search ME, while reducing the transcoding complexity significantly.

• The KIPS Transactions:PartB
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• v.17B no.1
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• pp.31-36
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• 2010

After the launch of MPEG-2, it is widely used in multimedia applications like a Digital-TV or a DVD. Then, After the launch of H.264 at 2004, it has been expected to replace MPEG-2 and services IPTV and DMB. As we have been used to MPEG-2 devices by this time, we can not access H.264 Broadcast with MPEG-2 device. So We propose a new approach to transcode H.264 video into MPEG-2 form which can facilitate to display H.264 video with MPEG-2 device. To reduce the quality loss by transcoding, we use CPDT(Cascaded Pixel Domain Transcoder) structure. And to minimize processing time, SKIP block, INTRA block and motion vectors obtain from decoding process is employed for transcoding. we use BMA(Boundary Matching Algorithm) to select only one from candidate motion vectors. Experimental results show a considerable improved PSNR with reduction in processing time compared with existing methods.