• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.2063-2066
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• 2002

In this paper, we propose a structure far lossless audio coding method. Prediction model is used in the wavelet transform domain. After DWT, wavelet coefficients is quantized and decorrelated by prediction modeling. The DWT can be constructed to critical bands. We can get a lower data rate representation of audio signal which has a good quality like the result of perceptual coding. Then the prediction errors are efficiently coded by the Golomb-coding method. The prediction coefficients are fixed for reducing the computational burden when we find prediction coefficients.

• ETRI Journal
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• 제33권2호
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• pp.145-154
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• 2011

We present a novel video codec for supporting entertainment-quality video. It has new coding tools such as an intra prediction with offset, integer sine transform, and enhanced block-based adaptive loop filter. These tools are used adaptively in the processing of intra prediction, transform, and loop filtering. In our experiments, the proposed codec achieved an average reduction of 13.35% in BD-rate relative to H.264/AVC for 720p sequences.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권4호
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• pp.1457-1470
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• 2015

In wireless multimedia sensor networks (WMSN), the latency of transmission is an increasingly problem. With the improvement of resolution, the time cost in image and video compression is more and more, which seriously affects the real-time of WMSN. In JPEG system, the core of the system is DCT, but DCT-JPEG is not the best choice. Block-based DCT transform coding has serious blocking artifacts when the image is highly compressed at low bit rates. APBT is used in this paper to solve that problem, but APBT does not have a fast algorithm. In this paper, we analyze the structure in JPEG and propose a parallel framework to speed up the algorithm of JPEG on GPU. And we use all phase biorthogonal transform (APBT) to replace the discrete cosine transform (DCT) for the better performance of reconstructed image. Therefore, parallel APBT-JPEG is proposed to solve the real-time of WMSN and the blocking artifacts in DCT-JPEG in this paper. We use the CUDA toolkit based on GPU which is released by NVIDIA to design the parallel algorithm of APBT-JPEG. Experimental results show that the maximum speedup ratio of parallel algorithm of APBT-JPEG can reach more than 100 times with a very low version GPU, compared with conventional serial APBT-JPEG. And the reconstructed image using the proposed algorithm has better performance than the DCT-JPEG in terms of objective quality and subjective effect. The proposed parallel algorithm based on GPU of APBT also can be used in image compression, video compression, the edge detection and some other fields of image processing.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1995년도 추계학술대회
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• pp.113-116
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• 1995

Medical image compression using the wavelet transform has been tried. Due to the flexibility in representing nonstationary image signal in both time and frequency domains and its ability to adapt human visual characteristics, wavelet transform has unique advantage in images compression. In the proposed wavelet compression original image is decomposed into multi-scale bands. Different scale factors are employed in the quantization of wavelet decomposed images in different bands. For the lowest band, a predictor is designed and error signal is entropy coded. For high scale bands, runlength coding for toro run is used with Huffman coding. From simulation with magnetic resonance images($256\times256$ size, 256 graylevels) the proposed algorithm is superior to the JPEG by more than 2.5 dB in near lossless compression (CR = 8 - 10).

• Journal of the Optical Society of Korea
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• 제15권4호
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• pp.335-339
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• 2011

Recently, we reported a single input channel joint transform correlator for the color pattern recognition which decomposes the input color image into three R, G, and B gray components and adds those components into a single gray image in the input plane. This technique has the merit of a single input channel instead of three input channels. However, we found this technique has some problems with discrimination impossibility in the case of a simple primary color pattern which results in the same gray level through the addition process. Thus, we propose a modified coding technique which selectively recombines the decomposed three R, G, and B gray components instead of the simple adding process. Simulated results show that the modified coding technique can accurately discriminate a variety of kinds of color images.

• 한국통신학회논문지
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• 제21권5호
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• pp.1089-1095
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• 1996

가변블록 변환부호화는 변환부호화에 적용되는 블럭의 크기를 다르게 하여 코딩의 효율을 좋게 한다. 변환블록의 크기는 블럭의 활성도에 따라 적응된다. 즉, 블럭의 활성도가 크면 블럭의 크기는 작아지고, 반대로 활성도가 작으면 블럭의 크기가 커진다. 본 논문에서는 블럭의 활성도로서 분산값 대신에 변환계수의 고주파 에너지를 이용하였다. 컴퓨터 시뮬레이션 결과, 제안한 방법이 분산값을 이용한 방법보다는 약 1~5dB, MAD를 이용한 방법보다는 약 0.5~3dB정도의 성능개선을 보여주었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -1
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• pp.437-440
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• 2000

This paper proposes a method to improve video quality on images that have blocking artifacts at block boundary. Block image transform coding suffers from blocking artifact that is a main cause of degrading video quality because of the quantization error of transform coefficients in quantization process. filtering and DPCM for DC components have been widely used to reduce blocking artifact. Recently, lots of works focus on the technique that minimizes block effects using discontinuity of block boundaries. In this paper, image blurring in decoding stage is improved by adding compensation factor to each transformed blocks so that discontinuity of block boundaries can be decreased. The compensation factor is applied on each block without much loss of edge components.

• 한국통신학회논문지
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• 제10권3호
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• pp.130-134
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• 1985

영상신호의 이차원 코사인 변환부호화에 있어서 변환계수의 분포계수화는 매우 중요하다. 그 이유는 블록양자화 시 분포함수를 잘못 가정하면 양자화잡음이 매우 커지기 때문이다. 본 논문에서는 일반화된 가우시안 분포함수를 이용하여 test를 행한 결과 AC변환계수들은 shape parameter가 0.6인 일반화된 가우시안 분포로 잘 근사화된다는 결과를 얻었다. 이차원코사인 변환부호화의 컴퓨터 시뮤레이션을 통해 Laplacian이나 Gaussian분포로의 근사화와 비교한 결과 shape parameter가 0.6인 일반화된 가우시안 분포로 근사화하는 경우 실험치와 이론치가 거의 일치하며 추력신호 잡음비도 가장 크게 나타났다.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송∙미디어공학회 2018년도 하계학술대회
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• pp.141-144
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• 2018

비디오 압축에서, 변환은 데이터를 공간 영역에서 주파수 영역으로 변환 함으로써 에너지 압축에서 중요한 역할을 수행한다. HEVC(High Efficiency Video Coding)에서는 DCT-II(Discrete Cosine Transform type-II)를 사용하여 잔차신호 변환을 수행한다. DCT-II는 픽셀간 상관도가 높은 신호일수록 높은 에너지 집중도를 보이지만, 픽셀간 상관도가 비교적 낮은 블록일수록 낮은 에너지 집중도를 보인다. 본 논문에서는 DST-VII(Discrete Sine Transform type-VII) 및 잔차신호 플리핑을 사용하여 다양한 변환 방법으로 영상을 부호화 및 복호화 하는 알고리즘에 대해 제안한다. 다양한 변환 방법은 부호화기에서 블록단위로 1 가지를 선택하여 비트스트림으로 선택된 방법에 대한 정보를 전송한다. 제안된 방법은 HEVC 대비 약 2.47%의 BD-rate 감소를 보인다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.1383-1386
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• 1997

Discrete cosine transform(DCT) is the most popular block transform coding in lossy mode. DCT is close to statistically optimal transform-the Karhunen Loeve transform. In this paper, a module for DCT encoder is made with TMS320C80 based on JPEG and MPEG, which are intermational standards for image compression. the DCT encoder consists of three parts-a transformer, a vector quantizer and an entropy encoder.