• Title/Summary/Keyword: Variable block sizes

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Variable Block Size for Performance Improvement of Compressed Sensing (압축 센싱의 성능 향상을 위한 가변 블록 크기 기술)

  • Ham, Woo-Gyu;Ku, Jaseong;Ahn, Chang-Beom;Park, Hochong
    • Journal of the Institute of Electronics and Information Engineers
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    • v.50 no.4
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    • pp.155-162
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    • 2013
  • The conventional block-based compressed sensing uses a fixed block size for signal reconstruction, and the reconstructed signal is degraded because the block size suitable to the signal characteristics is not used. To solve this problem, in this paper, a variable block size method for compressed sensing is proposed that estimates the signal characteristics and selects a proper block size for each frame, thereby improving the quality of the reconstructed signal. The proposed method reconstructs the signal with different block sizes, analyzes the signal characteristics using correlation coefficients for each frame, and select the block size for the frame. It is confirmed that, with the same acquired data, the proposed method reconstructs the signal of higher quality than the conventional fixed block size method.

A Study on the Use of Hierarchical Elements (계층 요소 사용에 대한 연구)

  • Kim, J.W.
    • Journal of Power System Engineering
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    • v.4 no.1
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    • pp.68-73
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    • 2000
  • A mixed degree finite element solutions using hierarchical elements are investigated for convergences on a 2-D simple cases. Elements are generated block by block and each block is assigned an arbitrary solution degree. The numerical study showed that a well constructed blocks can increase the convergence and accuracy of finite element solutions. Also, it has been found that for higher order elements, the convergence trends can be deteriorated for smaller mesh sizes. A procedure for a variable fixed boundary condition has been included.

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Fast motion estimation and mode decision for variable block sizes motion compensation in H.264 (H.264의 가변 블록 움직임 보상을 위한 고속 움직임 벡터 탐색 및 모드 결정법)

  • 이제윤;최웅일;전병우;석민수
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.40 no.4
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    • pp.275-285
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    • 2003
  • The now video coding standard H.264 employs variable block size motion compensation, multiple references, and quarter-pel motion vector accuracy. These techniques are key features to accomplish higher coding gain, however, at the same time main factors that increase overall computational complexity. Therefore, in order to apply H.264 to many applications, key techniques are requested to improve their speed. For this reason, we propose a fast motion estimation which is suited for variable block size motion communication. In addition, we propose a fast mode decision method to choose the best mode at early stage. Experimental results show the reduction of the number of SAT SATD calculations by a factor of 4.5 and 2.6 times respectively, when we compare the proposed fast motion estimation and the conventional MVFAS $T^{[8-10]}$. Besides, the number of RDcost computations is reduced by about 45%. Therefore, the proposed methods reduces significantly its computational complexity without noticeable coding loss.

Fast Multiple Reference Frame Selection Method for Motion Estimation and Compensation in Video Coding (동영상 부호화의 움직임 추정 및 보상을 위한 고속 다중 참조 프레임 선택 기법)

  • Kim, Jae-Hoon;Kim, Myoung-Jin;Hong, Min-Cheol
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.11C
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    • pp.1066-1072
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    • 2007
  • In this paper, we propose a fast multiple reference frame selection method for motion estimation and compensation in video coding. Reference frames selected as an optimal reference frame by variable block sizes motion estimation have the statistical characteristic that was based on block size. Using the statistical characteristic, reference frames for smaller block size motion estimation can be selected from reference frame which was decided as an optimal one for the upper layer block size. Simulation results show that the proposal method decreased the computations about 60%. Nevertheless, PSNR and bit rate were almost same as the performances of original H.264 multiple reference motion estimation.

Coding Efficiency Improvement By Applying Rate-Distortion Optimization To 3D-DCT Based Integral Image Compression Method (3D-DCT 기반 집적영상 압축 방법의 율-왜곡 최적화를 통한 부호화 효율 향상 방법)

  • Jeon, Ju-Il;Kang, Hyun-Soo
    • The Journal of the Korea Contents Association
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    • v.12 no.9
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    • pp.1-8
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    • 2012
  • In this paper, we propose a rate-distortion optimization method to improve the coding efficiency of the conventional 3D-DCT based compression method using adaptive block mode selection for integral images. In the conventional 3D-DCT based compression method, 3D-DCT blocks of variable block sizes are adaptively selected depending on the characteristics of integral images, and then 3D-DCT is performed. The proposed method applies a rate-distortion optimization to determine the optimal block mode. In addition, we suggest the optimal Lagrangian parameter for integral images. Experimental results show that the proposed method gives bit-rate reduction of about 5%.

Fast Mode Decision using Block Size Activity for H.264/AVC (블록 크기 활동도를 이용한 H.264/AVC 부호화 고속 모드 결정)

  • Jung, Bong-Soo;Jeon, Byeung-Woo;Choi, Kwang-Pyo;Oh, Yun-Je
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.44 no.2 s.314
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    • pp.1-11
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    • 2007
  • H.264/AVC uses variable block sizes to achieve significant coding gain. It has 7 different coding modes having different motion compensation block sizes in Inter slice, and 2 different intra prediction modes in Intra slice. This fine-tuned new coding feature has achieved far more significant coding gain compared with previous video coding standards. However, extremely high computational complexity is required when rate-distortion optimization (RDO) algorithm is used. This computational complexity is a major problem in implementing real-time H.264/AVC encoder on computationally constrained devices. Therefore, there is a clear need for complexity reduction algorithm of H.264/AVC such as fast mode decision. In this paper, we propose a fast mode decision with early $P8\times8$ mode rejection based on block size activity using large block history map (LBHM). Simulation results show that without any meaningful degradation, the proposed method reduces whole encoding time on average by 53%. Also the hybrid usage of the proposed method and the early SKIP mode decision in H.264/AVC reference model reduces whole encoding time by 63% on average.

Effective MCTF based on Correlation Improvement of Motion Vector Field (움직임 벡터 필드의 상관도 향상을 통한 효과적인 MCTF 방법)

  • Kim, Jongho
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.18 no.5
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    • pp.1187-1193
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    • 2014
  • This paper presents an effective motion estimation to improve the performance of the motion compensated temporal filtering (MCTF) which is a core part of the wavelet-based scalable video coding. The proposed scheme makes the motion vector field uniform by the modified median operation and the search strategies using adjacent motion vectors, in order to enhance the pixel connectivity which is significantly relevant to the performance of the MCTF. Moreover, the motion estimation with variable block sizes that reflects the features of frames is introduced for further correlation improvement of the motion vector field. Experimental results illustrate that the proposed method reduces the decomposed energy on the temporal high frequency subband frame up to 30.33% in terms of variance compared to the case of the full search with fixed block sizes.

Low-Complexity H.264/AVC Deblocking Filter based on Variable Block Sizes (가변블록 기반 저복잡도 H.264/AVC 디블록킹 필터)

  • Shin, Seung-Ho;Doh, Nam-Keum;Kim, Tae-Yong
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.45 no.4
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    • pp.41-49
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    • 2008
  • H.264/AVC supports variable block motion compensation, multiple reference images, 1/4-pixel motion vector accuracy, and in-loop deblocking filter, compared with the existing compression technologies. While these coding technologies are major functions of compression rate improvement, they lead to high complexity at the same time. For the H.264 video coding technology to be actually applied on low-end / low-bit rates terminals more extensively, it is essential to improve tile coding speed. Currently the deblocking filter that can improve the moving picture's subjective image quality to a certain degree is used on low-end terminals to a limited extent due to computational complexity. In this paper, a performance improvement method of the deblocking filter that efficiently reduces the blocking artifacts occurred during the compression of low-bit rates digital motion pictures is suggested. In the method proposed in this paper, the image's spatial correlational characteristics are extracted by using the variable block information of motion compensation; the filtering is divided into 4 modes according to the characteristics, and adaptive filtering is executed in the divided regions. The proposed deblocking method reduces the blocking artifacts, prevents excessive blurring effects, and improves the performance about $30{\sim}40%$ compared with the existing method.

A High Speed Block Turbo Code Decoding Algorithm and Hardware Architecture Design (고속 블록 터보 코드 복호 알고리즘 및 하드웨어 구조 설계)

  • 유경철;신형식;정윤호;김근회;김재석
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.41 no.7
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    • pp.97-103
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    • 2004
  • In this paper, we propose a high speed block turbo code decoding algorithm and an efficient hardware architecture. The multimedia wireless data communication systems need channel codes which have the high-performance error correcting capabilities. Block turbo codes support variable code rates and packet sizes, and show a high performance due to a soft decision iteration decoding of turbo codes. However, block turbo codes have a long decoding time because of the iteration decoding and a complicated extrinsic information operation. The proposed algorithm using the threshold that represents a channel information reduces the long decoding time. After the threshold is decided by a simulation result, the proposed algorithm eliminates the calculation for the bits which have a good channel information and assigns a high reliability value to the bits. The threshold is decided by the absolute mean and the standard deviation of a LLR(Log Likelihood Ratio) in consideration that the LLR distribution is a gaussian one. Also, the proposed algorithm assigns '1', the highest reliable value, to those bits. The hardware design result using verilog HDL reduces a decoding time about 30% in comparison with conventional algorithm, and includes about 20K logic gate and 32Kbit memory sizes.

Efficient Coding of Motion Vector Predictor using Phased-in Code (Phased-in 코드를 이용한 움직임 벡터 예측기의 효율적인 부호화 방법)

  • Moon, Ji-Hee;Choi, Jung-Ah;Ho, Yo-Sung
    • Journal of Broadcast Engineering
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    • v.15 no.3
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    • pp.426-433
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    • 2010
  • The H.264/AVC video coding standard performs inter prediction using variable block sizes to improve coding efficiency. Since we predict not only the motion of homogeneous regions but also the motion of non-homogeneous regions accurately using variable block sizes, we can reduce residual information effectively. However, each motion vector should be transmitted to the decoder. In low bit rate environments, motion vector information takes approximately 40% of the total bitstream. Thus, motion vector competition was proposed to reduce the amount of motion vector information. Since the size of the motion vector difference is reduced by motion vector competition, it requires only a small number of bits for motion vector information. However, we need to send the corresponding index of the best motion vector predictor for decoding. In this paper, we propose a new codeword table based on the phased-in code to encode the index of motion vector predictor efficiently. Experimental results show that the proposed algorithm reduces the average bit rate by 7.24% for similar PSNR values, and it improves the average image quality by 0.36dB at similar bit rates.