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A practical postprocessing technique for real-time block-based coding system

IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 1998年第1期8卷 4-8页

作者： Chan, YH Hong, SW Siu, WC Hong Kong Polytech Univ Dept Elect Engn Kowloon Hong Kong

In this paper, a noniterative postprocessing method is proposed to restore the images encoded with block-based compression standards such as Joint Photographic Experts Group (JPEG). This method classifies small local boundary regions according to their intensity distribution and then selects appropriate linear predictors to estimate the corresponding boundary pixels in the regions. This approach is easy to implement and we found in our simulations that its restoration performance was very respectable compared with the reported postprocessing methods.

关键词： block-based coding codec deblocking image restoration JPEG postprocessing technique vector quantization

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Efficient block-based coding of noisy images by combining pre-filtering and DCT

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ELECTRONICS LETTERS 1999年第20期35卷 1717-1719页

作者： Kim, SD Jang, SK Kim, MJ Ra, JB Korea Adv Inst Sci & Technol Dept Elect Engn Yusong Gu Taejon 305701 South Korea

An efficient block-based coding scheme for noisy images is proposed. Unlike a conventional encoder where pre-filtering, discrete cosine transforms (DCT), quantisation, and variable length coding (VLC) are cascaded, the proposed image coder has only a modified DCT and a VLC, and performs pre-filtering and quantisation simultaneously in the modified DCT operation.

关键词： block-based coding VLC discrete cosine transforms pre-filtering Integral transforms in numerical analysis Image and video coding DCT noisy images image coding Codes quantisation (signal) variable length coding quantisation Signal processing theory variable length codes Computer vision and image processing techniques Image recognition block codes

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Measuring Acceptance of block-based coding Environments

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TECHNOLOGY KNOWLEDGE AND LEARNING 2023年第1期28卷 241-251页

作者： Toma, Radu Bogdan Univ Burgos Fac Educ Dept Specif Didact C Villadiego S-N Burgos 09001 Spain

The development of computational thinking skills is attracting attention worldwide. The use of visual or block-based coding in primary schools has gained momentum. Yet, students' acceptance of such coding environments has been neglected in the literature. This study presents a measurement instrument that will allow pursuing such an endeavor. The Technology Acceptance Model was used as a guiding framework. A panel of eight experts and a purposive sample of 315 elementary school students (Mage = 10.18 years, SD = 1.13) were recruited. Inter-rater agreement between experts (75-100%) confirmed the content validity of the items. Exploratory factor analysis resulted in a three-factor solution of 12 items measuring perceived usefulness, perceived ease of use, and attitudes towards visual coding. Inspection of the correlation matrix provided evidence of convergent and discriminant validity. Cronbach's alpha (.75-.82), McDonald's omega (.68-.83), and Spearman-Brown's split-half coefficients (.67-.80) provided evidence of reliability. Overall, findings support the validity and reliability of the proposed instrument. Its use can shed light on students' acceptance of different block-based coding environments.

关键词： block-based coding Visual coding Computational thinking Instrument Acceptance Validity and reliability

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Preparing preservice teachers to use block-based coding in scientific modeling lessons

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INSTRUCTIONAL SCIENCE 2020年第6期48卷 765-797页

作者： Vasconcelos, Lucas Kim, ChanMin Univ South Carolina Dept Educ Studies Wardlaw Coll Educ 820 Main St Columbia SC 29208 USA Penn State Univ Coll Educ Learning Design & Technol 314D Keller Bldg University Pk PA 16802 USA

Scientific modeling and coding are critical skills to be integrated into K-12 instruction. Research has shown that preservice teachers are often ill-prepared for teaching scientific modeling, and lack opportunities to learn coding within teacher education programs. The present study reports the implementation of an instructional module and online system, called coding in Scientific Modeling Lessons (CS-ModeL), which was designed to scaffold preservice science teachers' learning to code simulations and design scientific modeling lessons that feature simulation coding. In this study, we examined preservice teachers' epistemic discourse during simulation coding, perceptions of coding for future teaching, and coding-enhanced scientific modeling lessons. This was a qualitative single case study that involved six participants enrolled in a science teacher education course. Participants worked in pairs during scientific modeling activities, and each pair was considered an embedded unit within the single case. Data sources included transcripts of screen recordings captured during simulation coding, transcripts of individual semi-structured interviews, and lessons in which participants used simulation coding as part of scientific modeling activities. Qualitative thematic analysis was conducted. Findings revealed that participants' epistemic discourse led to correction of science misconceptions. However, lack of debugging and conflict argumentation skills detracted from their epistemic discourse quality. Participants perceived coding as a beneficial skill for K-12 students though they voiced concerns about teaching with coding unassisted. Participants failed to design truly interdisciplinary and authentic scientific modeling activities including simulation coding. Study limitations and future research directions are discussed.

关键词： Preservice teachers Professional learning Scientific modeling block-based coding Simulations Epistemic discourse

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Automated Structural Evaluation of block-based coding Assignments 2023

Automated Structural Evaluation of Block-based Coding Assign...

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54th Annual ACM SIGCSE Technical Symposium on Computer Science Education (SIGCSE TS)

作者： Damle, Param Bull, Glen Watts, Jo Nguyen, N. Rich Univ Virginia Charlottesville VA 22904 USA

ISBN: (纸本)9781450394338

As computer science is integrated into a wider variety of fields, block-based programming languages like Snap!, which assemble code with visual blocks rather than text syntax, are increasingly used to teach computational thinking (CT) to students from diverse backgrounds. Although automated evaluators (autograders) for programming assignments usually focus on runtime efficiency and output accuracy, effective evaluation of a student's CT skills requires assessing coding best practices, such as decomposition, abstraction, and algorithm design. While autograders are commonplace for text languages like Python, we present a machine learning approach to assess how effectively block-based code demonstrates understanding of CT fundamentals. Our dataset consists of Snap! programs written by students new to coding and evaluated by instructors using a CT rubric. We explore how to best transform these programs into low-dimensional features to allow encapsulation and repetition patterns to emerge. Experimentation involves comparing the effectiveness of a suite of clustering models and similarity metrics by analyzing how directly automated feedback correlates to the course staff's manual evaluation. Lastly, we demonstrate the practical application of the autograder in a classroom setting and discuss scalability and feasibility in other domains of CS education.

关键词： clustering visual programming block-based coding student assessment computational thinking machine learning

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A deblocking filter with two separate modes in block-based video coding

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 1999年第1期9卷 156-160页

作者： Kim, SD Yi, J Kim, HM Ra, JB Korea Adv Inst Sci & Technol Dept Elect Engn Taejon 305701 South Korea LG Semicon Co Ltd Seoul South Korea

This paper presents a method to remove blocking artifacts in low bit-rate block-based video coding. The proposed algorithm has two separate filtering modes, which are selected by pixel behavior around the block boundary, In each mode, proper one-dimensional filtering operations are performed across the block boundary along the horizontal and vertical directions, respectively. In the first mode, corresponding to Bat regions, a strong filter is applied inside the block as well as on the block boundary because the Bat regions are more sensitive to the human visual system (HVS) and the artifacts propagated from the previous frame due to motion compensation are distributed inside the block. In the second mode, corresponding to other regions, a sophisticated smoothing filter, which is based on the frequency information around block boundaries, is used to reduce blocking artifacts adaptively without introducing undesired blur. Even though the proposed deblocking filter is quite simple, it improves both subjective and objective image quality for various image features.

关键词： block-based coding blocking artifacts deblocking postprocessing technique

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block-based Learned Image coding with Convolutional Autoencoder and Intra-Prediction Aided Entropy coding 35

Block-based Learned Image Coding with Convolutional Autoenco...

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Picture coding Symposium (PCS)

作者： Yuan, Zhongzheng Liu, Haojie Mukherjee, Debargha Adsumilli, Balu Wang, Yao NYU Tandon Sch Engn Dept Elect & Comp Engn Brooklyn NY 11201 USA Nanjing Univ Sch Elect Sci & Engn Nanjing Jiangsu Peoples R China Google Res Mountain View CA USA

ISBN: (纸本)9781665425452

Recent works on learned image coding using autoencoder models have achieved promising results in rate-distortion performance. Typically, an autoencoder is used to transform an image into a latent tensor, which is then quantized and entropy coded. based on a work by Ball ' e et al., we adapted the autoencoder with a hyperprior model to code images in a block-based approach. When the autoencoder model is directly applied to code small image blocks, spatial redundancy in the larger image cannot be fully utilized, resulting in a decrease in rate-distortion performance. We propose a method to utilize border information in the entropy coding of latent and hyper-latent tensors, which has achieved promising results. We show that using intra-prediction to help entropy coding is more effective than applying a convolutional autoencoder with hyper priors to intra-prediction residual blocks.

关键词： block-based coding deep learning intraprediction learned image compression

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Learned Image Compression With Efficient Cross-Platform Entropy coding

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IEEE JOURNAL ON EMERGING AND SELECTED TOPICS IN CIRCUITS AND SYSTEMS 2025年第1期15卷 72-82页

作者： Yang, Runyu Liu, Dong Wu, Feng Gao, Wen Univ Sci & Technol China Key Lab Brain Inspired Intelligent Percept & Cogni MOE Hefei 230027 Peoples R China Peking Univ Sch Comp Sci Beijing 100871 Peoples R China Peng Cheng Lab Shenzhen 518055 Peoples R China

Learned image compression has shown remarkable compression efficiency gain over the traditional image compression solutions, which is partially attributed to the learned entropy models and the adopted entropy coding engine. However, the inference of the entropy models and the sequential nature of the entropy coding both incur high time complexity. Meanwhile, the neural network-based entropy models usually involve floating-point computations, which incur inconsistent probability estimation and decoding failure in different platforms. We address these limitations by introducing an efficient and cross-platform entropy coding method, chain coding-based latent compression (CC-LC), into learned image compression. First, we leverage the classic chain coding and carefully design a block-based entropy coding procedure, significantly reducing the number of coding symbols and thus the coding time. Second, since CC-LC is not based on neural networks, we propose a rate estimation network as a surrogate of CC-LC during the end-to-end training. Third, we alternately train the analysis/synthesis networks and the rate estimation network for the rate-distortion optimization, making the learned latent fit CC-LC. Experimental results show that our method achieves much lower time complexity than the other learned image compression methods, ensures cross-platform consistency, and has comparable compression efficiency with BPG. Our code and models are publicly available at https://***/Yang-Runyu/CC-LC.

关键词： Image coding Estimation Entropy coding Entropy Computational modeling Training Symbols Transforms Circuits and systems Time complexity block-based coding chain coding cross-platform consistency entropy coding learned image compression

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Adaptive image compression using local pattern information

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PATTERN RECOGNITION LETTERS 2002年第14期23卷 1837-1845页

作者： Pan, F Nanyang Technol Univ Ctr Signal Proc Sch EEE Singapore 639798 Singapore

This paper describes a new adaptive coding technique to the coding of transform coefficients used in block based image compression schemes. The presence and orientation of the edge information in a sub-block are used to select different quantization tables and zigzag scan paths to cater for the local image pattern. Measures of the edge presence and edge orientation in a sub-block are calculated out of their DCT coefficients, and each sub-block can be classified into four different edge patterns. Experimental results show that compared to JPEG and the improved HVS-based coding, the new scheme has significantly increased the compression ratio without sacrificing the reconstructed image quality. (C) 2002 Elsevier Science B.V. All rights reserved.

关键词： image compression JPEG block-based coding adaptive quantization

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Reduction of blocking artifacts for HDTV using offset-and-shift technique

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IEEE TRANSACTIONS ON CONSUMER ELECTRONICS 2007年第4期53卷 1736-1743页

作者： Kim, Jongho Choi, Minseok Jeong, Jechang Hanyang Univ Dept Elect & Comp Engn Seoul 133791 South Korea

This paper addresses an effective post-processing technique to remove blocking artifacts, which severely degrade visual quality in block-based image coding. The proposed algorithm classifies blocks into four types based on directional activity and removes the blocking artifacts while preserving edges and texture information by applying different types and strength of filter for each block type. Moreover, the proposed scheme includes a two-dimensional filtering method in order to remove staircase noises and corner outliers around diagonal and curved edges. Experimental results show that the proposed algorithm outperforms a number of deblocking methods in the literature in terms of PSNR and subjective visual quality. Furthermore, the execution time of the proposed algorithm takes less than that of the other methods, and thus it can be incorporated into real-time applications for moving pictures as well as still images.

关键词： deblocking post-processing offset-and-shift technique blocking artifact block-based coding

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