• 융합신호처리학회 학술대회논문집
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• 한국신호처리시스템학회 2000년도 추계종합학술대회논문집
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• pp.161-164
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• 2000

Recently efficient image coding using zerotree have been proposed. In these methods, the locations of nonzero wavelet coefficient are encoded with a tree structure, called zerotree, which can exploit the self-similarity of the wavelet pyramid decomposition across different scales. These are very especially in low bit rate image coding. In this paper, two zerotree image coding algorithm, EZW and SPHIT are briefly introduced, and a new zerotree searching scheme is proposed to emphasize the significance of a wavelet coefficient by its orientation as well as its scale.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.851-854
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• 1998

Recently efficient image coding algorithms using zerotree have been proposed. In these methods, the locations of nonzero wavelet coefficients are encoded with a tree structure, called zerotree, which can exploit the self-similarity of the wavelet pyramid decomposition across different scales. These are very effective, especially in low bit rate image coding. In this paper, two zerotree image coding algorithms, EZW and SPIHT, are briefly introduced, and a new zerotree searching scheme is proposed to emphasize the significance of a wavelet coefficient by its orientations as well as its scale.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2002년도 춘계종합학술대회
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• pp.211-214
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• 2002

Recently efficient image coding using zerotree have been proposed. In these methods, the locations of nonzero wavelet coefficient are enrolled with a tree structure, called zerotree, which ran exploit the self-similarity of the wavelet pyramid decomposition across different scales. These are very especially in low bit rate image coding. In this paper, two zerotree image rolling algorithm, EZW and SPHIT are briefly introduced, and a new zerotree searching scheme is proposed to emphasize the significance of a wavelet coefficient by its orientation as well as its scale.

• 한국산업정보학회논문지
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• 제6권1호
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• pp.39-47
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• 2001

A blocked zerotree coding algorithm for compression of subband image is proposed. Significance of blocks with respect to a certain threshold are coded with a set of transition rules for the significance of blocks. Significant blocks are quantized by vector quantization. The basic idea for this coding approach are: 1) Subband images are coded by blocks, 2) Important blocks based on the significance of blocks are coded and quantized, 3) Multiband codebook which is composed of sub-codebooks dedicated for each threshold and subband level is adapted to produce good reproduction vectors for vector quantization. The compression results are similar to Shapiro's zerotree coding even though ours are obtained without entropy coding of bit streams from blocked zerotree encoder. If an entropy coding is applied to the bitstream, PSNR will be improved.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 제14회 신호처리 합동 학술대회 논문집
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• pp.743-746
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• 2001

An improved zerotree-structure based wavelet coding algorithm is proposed. When the descendants of a significant coefficient are all zerotree, its four-childs are coded respectively in conventional EZW. But in the proposed algorithm, a new symbol is assigned for the significant coefficient. Entropy for both methods are analyzed and new coding scheme is proposed. The experimental results show that the Proposed algorithm has a better performance than the original EZW algorithm.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(4)
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• pp.19-22
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• 2000

In this paper, we present a new multiple description embedded zerotree wavelet coding method using the two splitted thresholds. We first model a half EZW coder and then we present multiple description coder which has two coding channels using wide threshold EZW(WTEZW) coders. To evaluate the performance of the proposed coder, we provide an image coding applications with two descriptions and compare MDC image coding results reported to date.

• 전자공학회논문지S
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• 제34S권10호
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• pp.112-119
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• 1997

Zerotreeimage coding is known as a simple and effective image comprssion algorithm. It has the property that the compression is generated in order of improtance. Conventionally, a fixed threshold is applied to the entire wavelet coefficients regardless of frequency and local features of an image. In this paper, we propose a new zerotree coding scheme with adaptive threshold. The adaptive threshold is determined by human visual characteristics. It is shown that the image quality of the proposed method is better than that of the conventional method.

• 한국통신학회논문지
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• 제29권6C호
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• pp.785-792
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• 2004

본 논문에서는 Sharipo에 의해 소개된 EZW(embedded zerotree wavelet) 알고리즘을 개선하여 실시간 처리가 가능하며 효율이 더 좋은 방법을 제안하였다. 기존의 EZW는 각각의 심벌(symbol)마다 2비트를 할당하는데 이는 각 대역(band)에서 나타날 수 있는 심벌의 수를 고려하지 않고 부호화를 수행하는 것이므로 압축 효율이 떨어지는 단점이 있으며 부호화 과정에서 제로트리 코딩(zerotree coding)을 함으로써 많은 시간이 소요된다. 본 논문에서는 각 역별로 심별마다 가변 비트를 할당하여 압축 효율을 높였다. 그리고 Backscan방식을 사용하여 부호화 시간을 상당히 단축하였고 웨이블릿(wavelet) 변환을 리프팅 구조로 나타내어 전체적인 부호화 시간을 줄였다. 실험 결과 본 논문에서 제안한 방법이 기존의 EZW보다 PSNR은 약 0.3∼l.5［㏈］, 부호화 시간은 2∼10배 이상 향상됨을 확인하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -2
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• pp.908-911
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• 2002

Over the past 30 years, many efficient 2D video coding techniques have been presented and developed from many research centers for commercialization. However, direct application of these monocular compression schemes is not optimal for stereo video coding. In this paper, we present a new technique for coding stereo video sequences based on Discrete Wavelet Transform (DWT). The proposed technique exploits Zerotree Entropy Coding (ZTE) that makes use of the wavelet block concept to achieve low bit rate stereo video coding. The one of two image streams, called main stream, is independently coded by modified MPEG-4 encoder and the other stream, called auxiliary stream, is coded by predicting from its corresponding image, its previous image or its follow image.

• 한국통신학회논문지
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• 제27권8A호
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• pp.814-821
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• 2002

SPIHT(set partitioning in hierarchical tree)는 제로트리 알고리즘 중 효율적이며 잘 알려져 있다. 그러나 높은 메모리 요구로 인해 하드웨어 구현에 큰 어려움을 가지고 있다. 본 논문에서는 저 메모리 사용과 빠른 제로트리 부호화 알고리즘을 제안한다. 메모리를 줄이고 빠른 코딩을 위한 방법으로 다음 3가지를 제안한다. 첫 번째, 리프팅(lifting)을 이용한 웨이블릿(wavelet) 변환은 기존의 필터뱅크 방식의 변환보다 저 메모리와 계산량의 감소를 가진다. 두 번째 방법은 웨이블릿 계수들을 블록으로 나누어 각각 부호화 한다. 여기서 블록은 제로트리 구조가 유지되는 STB(spatial tree-based block)이다. 마지막으로 Wheeler와 Pearlmandl 제안한 NLS(no list SPIHT)를 이용한 부호화이다. NLS의 효율성은 SPIHT와 거의 같으며 작고 고정된 메모리와 빠른 부호화 속도를 보여준다.