• 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.

• Journal of the Institute of Convergence Signal Processing
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• v.7 no.1
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• pp.1-10
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• 2006

To reduce the complexity of video transcoder, transcoding techniques generally use intermediate data such as macroblock types, motion vectors, DCT coefficients, which are extracted from incoming video bitstream. In this Paper, we Propose a new adaptive INTRA update scheme utilizing the importance of each macroblock in a given frame. The importance measure is calculated from the motion vectors which are extracted from the decoding procedure of a incomming video data.'rho ratio of the macroblock to be referred by the next frame is calculated by the motion vectors of the next frame and the macroblocks to be refered higher ratio has more effect on the next frame and the followed frames. The proposed scheme can obtain transcoded bitstreams which has better image quality and more improved resilience against transmission errors.

• 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.

• Broadcasting and Media Magazine
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• v.3 no.3
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• pp.46-51
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• 1998

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.10
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• pp.460-467
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• 2002

This paper proposes new motion vector re-estimation techniques for transcoding of heterogenous video coders. The first case is for transcoder of coding format. The coding algorithm with B-picture like MPEG standards is transcoded into the different algorithm without B-picture like H.261 standards. The second case is for transcoder of spatial resolution reduction. It generates a downscaled video bitstream at the video source. The third case is the integrated method that previous two cases are needed simultaneously. These three transcoding algorithms are compared and verified though reconstructed image quality in PSNR, motion vector errors between optimal motion vectors of cascaded trans- coder and motion vectors estimated by proposed methods and the amount of operation.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.04a
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• pp.151-154
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• 2002

모바일 환경등의 저대역 통신망에서 VOD 서비스를 제공하기 위해서는 영상 데이터의 크기를 줄이는 방법이 요구된다. 데이터를 줄이는 방법 중 가장 효율적인 방법이 영상 크기 축소 트랜스코더 (Resolution Downscale Transcoder)이지만 시스템의 리소스를 많이 소모하게 되므로 이를 줄이는 방법으로 움직임 예측을 최소화하는 움직임 벡터 병합 방법이 연구되었다. 하지만 이러한 방법들은 보다 정확히 움직임 벡터를 생성하지만 실제 영상에는 크게 적용되지 못하고 있다. 따라서 본 논문에서는 움직임벡터를 병합하는 비율을 높여 움직임 예측을 줄이고 인트라 영역에서의 변환 과정을 간소화하여 전체적인 시스템 리소스의 소모를 줄이도록 하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1577-1580
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• 2004

여러 응용 서비스를 유 무선을 포함한 다양한 네트웍을 통해 제공하기 위해서는 네트웍에 적응할 수 있는 서비스 형태가 요구된다. 그 가운데 멀티미디어 서비스의 경우 네트웍이 서로 다른 환경에 적응할 수 있는 해결책으로 트랜스코딩 기술이 제시되었다. 하지만, 트랜스코딩을 위해 필요한 복호 부호의 처리 과정은 실시간으로 제공되는 멀티미디어 스트리밍의 경우에 제약조건으로 작용하고, 이에 따른 처리 과정을 대폭 줄이는 일부 기술들은 사용자 측의 서비스 품질에 문제점을 안고 있다. 본 논문에서는 트랜스코딩을 통한 처리 과정과 사용자 측 서비스 품질의 두 가지 측면을 고려하는 frame dropping 시의 모션 벡터 합성 기법에 대해서 언급한다. 또한, 본 논문에서는 기존의 기법과는 달리 양방향 예측 프레임이 포함된 경우에도 적용할 수 있는 확장성을 제공한다.

• 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.

• Journal of Internet Computing and Services
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• v.6 no.6
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• pp.139-148
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• 2005

The desired level for multimedia services in the mobile web environment, the next generation web environment, is expected to be of PC level quality. And great efforts have been made in the development of hadware technology, communication technology, various kinds of services and standardization to support these services, In the mobile web environment, multimedia contents adaptation services should be available through supporting various kinds of devices, network abilities and users' preferences. It means that due to the variety of both desired devices' hardware specifications, called destinations, and desired QoSes, the QoSes in the destinations are not fixed or defined. If a new user wants to stream multimedia contents in a server through a new kind of terminal device, it should be considered whether the existing transcoders are able to adapt the multimedia contents. However, the existing libraries for multimedia adaptation have heavy transcoder figures which include all adaptive functions in one library, The challenge of universal access is too complex to be solved with these all in one solutions. Therefore, in this paper we propose an application independent multimedia adaptation framework which meets the QoS of new and varied mobile devices. This framework is composed of a group of unit transcoders having only one transcoding function respectively, Instead of heavy transcoders. Also, It includes the transcoder manager supporting the dynamic connections of the unit transcoders in order to satisfy end to end QoS.

• 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.