• Proceedings of the IEEK Conference
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• 2003.07e
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• pp.2232-2235
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• 2003

In speech communication systems where two different speech codecs are interoperated, transcoding algorithm is a good approach because of its low complexity and improved synthesized speech quality. This paper proposes an efficient method to further improve the performance of transcoding algorithms as well as to reduce the complexity. In the conventional transcoding algorithms. a post-filter and a perceptual weighting filter should be operated sequentially because both decoding and encoding processes are needed. This results in the redundancy of the processing in terms of complexity and perceptual quality. Using the fact that their filter structures are similar, we replaced the two filters with one. The proposed algorithm requires 72.8% lower complexity than the conventional transcoding algorithm when we compare only the complexity of the filtering processes. The results of both objective and subjective tests verify that the proposed algorithm has slightly better quality than the conventional one.

• The KIPS Transactions:PartD
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• v.14D no.7
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• pp.783-790
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• 2007

One of the particulars to be considered for providing wireless web service with PC web page is the hardware environment between PC and mobile device. It is because time cost is required in producing mobile contents to suit environment of the connected terminal. Therefore, server side should take account of response time and disk capacity of server. Response time is delayed by content conversion and disk capacity need to store various versions about one content. This paper suggests a pre-service and post-transcoding method to provide faster response time for a mobile terminal. The pre-service is to minimize response time by placing the top priority in servicing contents saved in cache as much as possible even if the quality of contents serviced to mobile terminal may be low. After pre-service is provided, the mobile content is transcoded for the terminal later. Performance level of method proposed was compared through experiment and the result of analysis was described.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11A
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• pp.1957-1962
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• 2001

Image and video compression requires quantization error model of DCT coefficients for post processing, restoration or transcoding. Once DCT coefficients are quantized, it is impossible to recover the original distribution. We assume that the original probability density function (pdf) is the Laplacian function. We calculate the variance of the quantized variable, and estimate the variance of the DCT coefficients. We can confirm that the proposed method enhances the accuracy of the quantization error estimation.