• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.38 no.4
• /
• pp.38-38
• /
• 2001

본 논문에서는 웨이브릿 영역에서의 영역 분류와 대역간 예측 및 선택적 벡터 양자화를 이용한 다분광 화상테이타 압축 기법을 제안하였다. 이 방법에서는 각 대역을 웨이브릿 변환 후, 각 대역의 기저밴드의 대역별 특성을 이용하여 영역 분류를 행하였다. 그리고, 다른 대역과 해상도가 동일하고 공간적 분산이 작으며 분광적 상관성이 큰 기준대역 (reference channel)을 결정한 뒤, 이를 영역별 스칼라 및 분류별 가변 벡터 양자화를 행하여 부호화 하였다. 또한 기준대역과의 대역간 상관성이 큰 대역들에 대해서는 영역별 대역간 예측을 행한 후, 활동도가 높은 블록에 대해서만 선택적 벡터 양자화로 부호화를 행하였다. 이때, 활동도가 높은 블록들의 위치정보는 기준대역으로부터 얻어지는 임계치 지도 (threshold map; THMAP)를 이용하였다. 즉, 제안한 방법에서는 각 대역에 대해 웨이브릿 영역에서의 영역 분류 후 영역별 대역간 예측을 행함으로써 다분광 화상데이타에 존재하는 대역간 중복성을 제거하고 선택적 벡터 양자화를 행함으로써 대역내 중복성을 효과적으로 제거하여 압축효율을 향상시킨다. 실제 원격 센싱된 인공위성 화상데이타에 대한 실험을 통하여 제안한 기법의 부호화 효율이 기존의 기법에 비하여 우수함을 확인하였다.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.49 no.2
• /
• pp.18-27
• /
• 2012

Optimal quantizers in conducting the entropy-constrained quantization for high bit rates have the lattice structure. The quantization process is simple due to the regular structure and various quantization algorithms are proposed depending on the lattice. In this paper, such a lattice vector quantization is implemented by using the sample-adaptive product quantizer (SAPQ). It is shown that several important lattices can be implemented by SAPQ and the lattice vector quantization can be performed by using a simple integer-transform function of scalar values within SAPQ. The performance of the proposed lattice SAPQ is compared to the entropy-constrained scalar quantizer and the entropy-constrained SAPQ (ECSAPQ) at a similar encoding complexity. Even though ECSAPQ shows a good performance at low bit-rates, lattice SAPQ shows better performance than the ECSAPQ case for a wide range of bit rates.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.3C
• /
• pp.234-240
• /
• 2007

In this paper, low complexity block constrained trellis coded quantization (BC-TCQ) structures are introduced, and a predictive BC TCQ encoding method is developed for quantization of line spectrum frequencies (LSF) parameters for narrowband speech coding applications. Trellis-coded quantization(TCQ) is a form of VQ that builds the VQ codebook from interleaved constituent scalar quantization codebooks. The performance is compared to the other VQ, demonstrating reduction in spectral distortion and significant reduction in encoding complexity. The predictive BC-TCQ is about 0.47107 dB superior to the IS-641 split-VQ, 26bits/frame, in spectral distortion sense. The BC-TCQ is 64.54%, 76.93%, 2.35% of the IS-641 split-VQ, respectively, in the complexity of the additions, multiplies, comparisons.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.49 no.1
• /
• pp.11-18
• /
• 2012

In this paper, an entropy constrained vector quantizer for high bit-rates is proposed. The sample-adaptive product quantizer (SAPQ), which is based on the product codebooks, is employed, and a design algorithm for the entropy constrained sample adaptive product quantizer (ECSAPQ) is proposed. The performance of the proposed ECSAPQ is better than the case of the entropy constrained vector quantizer by 0.5dB. It is also shown that the ECSAPQ distortion curve, which is based on the scalar quantizer, is lower than the high-rate theoretical curve of the entropy constrained scalar quantizer, where the theoretical curve have 1.53dB difference from Shannon's lower bound.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2019.06a
• /
• pp.114-115
• /
• 2019

This paper introduces an adaptive scalar quantization scheme for video coding technology. The method utilizes the property of the coefficient groups (CG) inside each transform block so that the dead-zone interval of the scalar quantizer is adaptively set up for different CGs. Its experimental results show that our proposed quantization scheme can achieve BDBR reduction of 4.75%, 5.93, and 5.16% for Y, Cb, and Cr channel respectively when encoding with HEVC.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.24 no.12B
• /
• pp.2391-2400
• /
• 1999

Vector quantizer (VQ) is an efficient data compression technique for low bit rate applications. However, the major disadvantage of VQ is its encoding complexity which increases dramatically as the vector dimension and bit rate increase. Even though one can use a modified VQ to reduce the encoding complexity, it is nearly impossible to implement such a VQ at a high bit rate or for a large vector dimension because of the enormously large memory requirement for the codebook and the very large training sequence (TS) size. To overcome this difficulty, in this paper we propose a novel structurally constrained VQ for the high bit rate and the large vector dimension cases in order to obtain VQ-level performance. Furthermore, this VQ can be extended to the low bit rate applications. The proposed quantization scheme has a form of feed-forward adaptive quantizer with a short adaptation period. Hence, we call this quantization scheme sample-adaptive product quantizer (SAPQ). SAPQ can provide a 2 ~3dB improvement over the Lloyd-Max scalar quantizers.

• Journal of Korea Multimedia Society
• /
• v.1 no.2
• /
• pp.194-203
• /
• 1998

In this paper, a new DCT-VQ method is proposed which can solve the problems of VQ such as the degradation of edge and enormous calculations. VQ is carried in DCT domain but spatial domain in order to protect the degradation of edge. DCT makes high correlated image data decorrelated and the energy concentrated on a few coefficients. In DCT domain, the DC coefficient is quantized with 8 bits uniform scalar quantizer and the AC coefficients are divided to three regions and coded with vector qiantizer for considering edge components. For the decrease of the calculation and memory, the vectors for three region have small dimension of $1{\times}7$ and use the same codebook. Thus, the proposed method can fully express the edge components by considering AC coefficients in DCT domain and decrease the calculation and memory be reducing the dimension of vectors.

• Journal of the Korea Computer Industry Society
• /
• v.5 no.5
• /
• pp.737-746
• /
• 2004

Two-channel multiwavelet system is investigated for image compression application in this paper. Generally, multiwavelets are known for their superb capability of compressing non-stationary signals like voice. However, multivavelet system have a critical problem in processing and compressing image data due to mesh-grid visual artifacts. In our two-channel multiwavelet system we have investigated incorporation of pre and post filtering to the multiwavelet transform and compression system for alleviating those ingerent visual artifacts due to multiwavelet effect. In addition, to quantify the image data compression performance of proposed multiwavelet system, computer simulations have been performed using various image data. For bit allocation and quantization, the Lagrange multiplier technique considering data rate vs. distortion rate along with a nonlinear companding method are applied equallly to all systems considered, here. The simulation results have yielded 1 ~ 2 dB compression enhancement over the scalar savelet systems. If the more advanced compression methods like SPIHT and run-length channel coding were adopted for the proposed multiwavelet system, a much higher compression gain could be obtained.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.2
• /
• pp.333-339
• /
• 1996

In this paper, an effiicent quatization method of line spectrum pairs(LSP) with cascaded structure of vector quantizer and scalar quantizer is proposed. First, input LSP parameters is vector-quantized using a codebook with a moderate number of entries. In the second stage of quantization, the components of residual vector are individution improve the quantizer by the scalar quantizer. The utilization of ordering property and the inclusion of interframe prediction improve the quantizer performance and remove the stability check routine. The new vector-scalar cascaded quantizer using 27 bits/frame shows a transparent quality that an average specytural distortion is 1 dB and the frame proportion with above 2 dB spectral distion is less than 2%.

• The Transactions of the Korea Information Processing Society
• /
• v.5 no.8
• /
• pp.2190-2202
• /
• 1998

영상은 그래픽, 교육,의료 분야의 멀티미디어 정보에서 중요한 역할을 하고 있다. 특히 지문 영상은 정보화 시대에 매우 중요한 정보로서 보안이나 인증 시스템에 널리 쓰이고 있다. 그러나 기존의 시스템에서는 지문 영상의 데이터 양이 많아 지문의 특징 정보만 일부 추출하여 저장하는 방식을 취하고 있어 지문이나 검색 등의 다양한 응용에 제약을 주고 있다. 정지 영상 압축 표준으로는 JPEG이 있지만, 20:1이상의 고압축에서는 많은 부호화 결점들 때문에 그러한 시스템에서의 실제적인 사용은 매우 어렵다. 따라서 고압축을 수행하면서 선명한 화질을 제공하는 지문 영상 압축 코덱 개발이 매우 필요하게 되었다. 본 논문에서는 이러한 요구에 맞게, 최근 새로운 영상 압축 기법으로 등장한 WSQ를 근간으로 하는 FBI 지문 영상 압축 표준을 EK르는 영상 압축 코덱을 개발하였으며, Windows95 환경하에서 동작하는 소프트웨어를 개발하여 실제로 지문 영상을 압축하는데 사용할 수 있도록 하였다. 또한 원래의 FBI 코덱과의 호환성을 유지하면서 코덱의 성능을 향상시키는 기법을 적용하여 원래의 FBI 코덱 보다 성능이 나아진 코덱을 개발하였다. 개발된 지문 영상 압축 코덱은 전자 주민 카드 및 각종 인증 시스템용 코덱으로 활용 가능하다.