• Journal of the Institute of Electronics Engineers of Korea SP
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• v.49 no.1
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• pp.19-30
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• 2012

For digital data compression, the quantization is the main part of the lossy source coding. In order to improve the performance of quantization, the vector quantizer(VQ) can be employed. The encoding complexity, however, exponentially increases as the vector dimension or bit rate gets large. Much research has been conducted to alleviate such problems of VQ. Especially for high bit rates, a constrained VQ, which is called the sample-adaptive product quantizer(SAPQ), has been proposed for reducing the hugh encoding complexity of regular VQs. SAPQ has very similar structure as to the product VQ(PQ). However, the quantizer performance can be better than the PQ case. Further, the encoding complexity and the memory requirement for the codebooks are lower than the regular full-search VQ case. Among SAPQs, 1-SAPQ has a simple quantizer structure, where each product codebook is symmetric with respect to the diagonal line in the underlying vector space. It is known that 1-SAPQ shows a good performance for i.i.d. sources. In this paper, a study on designing 1-SAPQ for the first-order Markov process. For an efficient design of 1-SAPQ, an algorithm for the initial codebook is proposed, and through the numerical analysis it is shown that 1-SAPQ shows better quantizer distortion than the VQ case, of which encoding complexity is similar to that of 1-SAPQ, and shows distortions, which are close to that of the DPCM(differential pulse coded modulation) scheme with the Lloyd-Max quantizer.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.11a
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• pp.186-187
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• 2012

본 논문에서는 기존의 표준 동영상 부호기의 산술적 연산 복잡도 및 대역폭을 낮추기 위하여 양자화된 두 영상에서 움직임을 예측하는 고속 영상 부호화 알고리즘을 제안한다. 기존에 제안된 이진 변환 기반 움직임 예측 알고리즘은 표적 영상과 참조 영상의 각 매크로 블록 단위로 가우시안 양자화를 적용한 뒤, 움직임 예측을 수행하기 때문에 블록 단위의 아티팩트로 인한 탐색 성능 저하를 피할 수 없다. 따라서, 우리는 참조 영상의 탐색 영역에 대해 하나의 양자화기를 적용함으로써 보다 정확한 움직임을 예측한다. 또한, 기존 알고리즘이 하나의 가우시안 양자화기를 적용하는 것과 달리, 제안 알고리즘은 데이터 특성 파악에 따른 다양한 확률 모델을 가정한 뒤 각 모델에 적합한 최적의 양자화기를 적용함으로써 블록 매칭 오류를 낮춘다. 실험 결과를 통해 제안 알고리즘이 기존의 이진 변환 기반 움직임 예측 알고리즘에 비해 보다 정확한 움직임 벡터를 예측함을 보인다.

• Journal of KIISE:Software and Applications
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• v.28 no.4
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• pp.369-379
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• 2001

본 논문은 부영역 분할과 코드워드 인텍스의 캐시 개념을 이용하여 벡터 양자화를 위한 고속코드북 생성 및 부호화 방법을 제안한다. 제안한 방법은 인접한 입력 벡터는 대개 코드북내 특정 코드워드에 의해 나타내어지는 국부성에 바탕을 두고 있다. 초기에 모든 학습 벡터가 거리에 기반한 근접성을 이용하여 정해진 수의 부영역으로 분할된다. 각 부영역에 하나의 코드워드 인덱스 캐시가 할당되는데 이 캐시는 학습 초기에는 전체 코드북 크기에 대응하는 코드워드 인덱스를 갖는다. 학습이 진행되면서 입력 벡터가 갖는 국부성 때문에 각 부영역내 캐시중 사용되지 않는 코드워드 인덱스가 점차 발생하게 되므로 이들은 LRU(Least Recently Used) 삭제 알고리즘에 의해 제거된다. 학습이 진행됨에 따라 부영역 캐시에는 주어진 입력 벡터에 의해 참조되는 코드워드 인덱스만이 남게 되므로 한 학습 주기 동한 필요한 학습 시간이 점차 짧아지게 되어 전체적으로 코드북 생성 시간을 크게 줄일 수 있게 된다. 제안한 방법은 매 학습주기마다, 코드워드 인덱스 삭제 후보 중 주어진 부영역 중심으로부터 거리에 의해 멀리 떨어진 것부터 반만을 제거함에 따라. 복원된 영상의 화질 열화가 거의 없다. 시뮬레이션 결과 제안한 방법은 기존의 LBG 방법에 비해 화질 열화는 거의 없지만 코드북 생성 (또는 부호화) 속도를 2.6-5.4배 (또는3.7-18.8배) 향상시킨다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3C
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• pp.315-326
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• 2003

Abstract In this paper, an improved index assignment procedure is proposed to reduce the channel error effect in a communication system employing classified vector quantization(CVQ). The proposed algorithm consists of two parts: inner index assignment (IIA) and cross index assignment (CIA). The II A reduces the distortion resulting from the error in order bits, presenting the identity of each code vector in a subcodebook. The CIA modifies the indexes assigned by the IIA in such a way that the effect of the channel error occurring in class bits, indicating the class information of the code vector, can be minimized. Simulation results show that the proposed algorithms enable a reliable communication over noisy channels even without employing the channel encoding. Index Terms Classified vector quantization, index assignment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.4
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• pp.772-780
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• 1994

Vector quantization with two-channel conjugate codebook has been researched as an efficient coding technique that can reduce the computational complexity and codebook storage. This paper proposes FSVQ using two-channel conjugate codebook in order to reduce the number of state codebooks. Input vector in the two-channel conjugate FSVQ is coded with state codebook of a seperated state according to each codebook. In addition, LOT is adopted to obtain to obtain a high coding gain and to reduce blocking effect which appears in the block coding. As a result, although FSVQ can achieve higher data compression ratio than general vector quantization, it has a disadvantage of having a very large number of state codebooks. However FSVQ with two-channel conjugate codebooks can employ a significantly reduced number of state codebooks, even though it has a small loss in the PSNR compared with the conventional FSVQ using one codebook. Moreover FSVQ in the LOT domain can reduce blocking effect and high coding gain compared with FSVQ in the spatial domain.

• The Journal of the Acoustical Society of Korea
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• v.19 no.1
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• pp.97-102
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• 2000

Subband coding is to divide the signal frequency band into a set of uncorrelated frequency bands by filtering and then to encode each of these subbands using a bit allocation rationale matched to the signal energy in that subband. The actual coding of the subband signal can be done using waveform encoding techniques such as PCM, DPCM and vector quantizer(VQ) in order to obtain higher data compression. Most researchers have focused on the error in the quantizer, but not on the overall reconstruction error and its dependence on the filter bank. This paper provides a thorough analysis of subband codecs and further development of optimum filter bank design using vector quantizer. We compute the mean squared reconstruction error(MSE) which depends on N the number of entries in each code book, k the length of each code word, and on the filter bank coefficients. We form this MSE measure in terms of the equivalent quantization model and find the optimum FIR filter coefficients for each channel in the M-band structure for a given bit rate, given filter length, and given input signal correlation model. Specific design examples are worked out for 4-tap filter in 2-band paraunitary filter bank structure. These optimum paraunitary filter coefficients are obtained by using Monte Carlo simulation. We expect that the results of this work could be contributed to study on the optimum design of subband codecs using vector quantizer.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.774-776
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• 1998

영상 압축의 표준인 MPEG은 대표적 비대칭 코딩방법으로 인코딩 시간이 디코딩 시간보다 훨씬 많은 시간을 소비한다. MPEG인코딩 과정은 크게 DCT, 양자화, 움직임 벡터 추출, 가변장 부호화로 구성된다. 이중에서 DCT와 움직임 벡터 추출 정도가 많은 계산량을 가지므로 병렬화의 관심이 되고 있다. 본 논문에서는 움직임 벡터의 추출에 관해서 병렬화하는 기법을 제시한다 병렬화의 단위는 fine-grained이며, 통신 오버헤드를 보다 줄일 수 있는 기법을 제시하였다. 최소한의 초기 데이터 할당으로 계산을 시작하여, 계산을 위한 초기화 과정을 줄여 속도를 증대시킨다. 통신비용 즉, 메시지 전달 수 및 메시지 전달 홉(hop) 수를 비교하고, 기존의 기법에 대해 한 프레임에 대한 움직임 벡터 추출 시간을 요소로 할 때 보다나은 결과를 나타냄을 보였다.

• The Journal of the Acoustical Society of Korea
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• v.42 no.6
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• pp.500-510
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• 2023

Passive sonar signals mainly contain both normal and abnormal signals. The abnormal signals mixed with normal signals are primarily detected using an AutoEncoder (AE) that learns only normal signals. However, existing AEs may perform inaccurate detection by reconstructing distorted normal signals from mixed signal. To address these limitations, we propose an abnormal signal detection model based on a Recurrent Neural Network (RNN) and vector quantization. The proposed model generates a codebook representing the learned latent vectors and detects abnormal signals more accurately through the proposed search process of code vectors. In experiments using publicly available underwater acoustic data, the AE and Variational AutoEncoder (VAE) using the proposed method showed at least a 2.4 % improvement in the detection performance and at least a 9.2 % improvement in the extraction performance for abnormal signals than the existing models.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1684-1690
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• 2003

In this paper, we proposed a fuzzy controller for the evaluation of the quantization Parameters in the H.263 coder to optimize the subjective quality of each coded frame, keeping the transmission rate constant. We adopted the Mamdani method for fuzzification and the centroid method for defuzzification. The energy and entropy are correlated to features of the HVS in spatial domain, while motion vectors are used to estimate the temporal characteristics of the signal. And then, the fuzzy inputs adapted the variance and the entropy in spatial domain, and the motion vector in temporal domain. We induced the fuzzy membership function and decided the fuzzy relevance to be compatible in visual characteristics. And then, we designed FAM banks. The fuzzy technology has been applied to a practical video compression. This results is obtained an effective rate control technique, an optimum bit allocation and a high subjective quality using fuzzy quantization.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.3
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• pp.13-20
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• 1990

This paper describes an interframe image coding using motion compensated and classified vector quantizer (MC-CVQ). It is essential to carefully encode blocks with significant pels in motion compensated vector quantizers (MCVQ). In this respect, we propose a new CVQ algorithm which is appropriate to the coding of interframe prediction error after motion compensation. In order to encode an image efficiently at a low bit rate, we partition each block, which is the processing element in MC, into equally sized 4 vectors, and classify vectors into 15 classes according to the position of significant pels. Vectors in each class are then encoded by the vector quantizer with the codebook independently designed for the class. The computer simulation shows that the signal-to-noise ratio and the average bit rate of MC-CVQ are 35-37dB and 0.2-0.25bit/pel, respectively, for the videophone or video conference type image.