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ROFC-LF: Recursive Online Fountain Code With Limited Feedback for Underwater Acoustic Networks

IEEE TRANSACTIONS ON COMMUNICATIONS 2022年第7期70卷 4327-4342页

作者： Liu, Xiuxiu Du, Xiujuan Zhang, Jiliang Han, Duoliang Jin, Long Qinghai Normal Univ Coll Comp Xining 810008 Peoples R China Acad Plateau Sci & Sustainabil Xining 810008 Peoples R China Qinghai Normal Univ Coll Comp Qinghai Prov Key Lab IoT Xining 810008 Peoples R China Acad Plateau Sci & Sustainabil State Key Lab Tibetan Intelligent Informat Proc & Xining 810008 Peoples R China Univ Sheffield Dept Elect & Elect Engn Sheffield S1 4DT S Yorkshire England Lanzhou Univ Sch Informat Sci & Engn Lanzhou 730000 Peoples R China

Online fountain codes (OFCs) have many advantages, such as low overhead, online feedback and optimal encoding, due to the feedback of the instantaneous decoding state. This paper analyzes the characteristics of underwater acoustic networks (UANs) as well as the issues of existing OFCs applied in UANs. Aiming at these issues, two optimization objectives of OFCs are put forward for UANs. In addition, a recursive OFC with limited feedback (ROFC-LF) is presented for UANs. The ROFC-LF reduces the consumption of bandwidth and energy caused by the transmission of useless coding packets. Through limited feedback, the problem of low channel utilization in UANs with half-duplex communication is solved. Furthermore, a data transmission mechanism based on the ROFC-LF for UANs is presented. The theoretical analysis and simulation results show that the proposed transmission mechanism based on the ROFC-LF scheme outperforms the existing OFC schemes in terms of overhead, computational complexity, coding efficiency and energy consumption. Consequently, the ROFC-LF is suitable for UANs with constrained resources.

关键词： Codes Encoding Decoding Bandwidth Receivers Optimization Half-duplex system ROFC-LF UANs overhead feedback coding efficiency computational complexity energy consumption

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Evaluation of JPE'G XT for high dynamic range cameras

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SIGNAL PROCESSING-IMAGE COMMUNICATION 2017年 50卷 9-20页

作者： Hanhart, Philippe Ebrahimi, Touradj Ecole Polytech Fed Lausanne Multimedia Signal Proc Grp Lausanne Switzerland

Modern cameras can be used to capture high dynamic range (HDR) images by taking multiple low dynamic range (LDR) pictures at different exposure settings. However, DSLR cameras often store the multiple exposure pictures, which increases storage requirements proportionally to the number of exposures, while smartphones and tablets only store a tone-mapped representation of the HDR image instead of the original HDR data. In this paper, we investigate the bit rate reduction that could be achieved by storing HDR images compressed with JPEG XT, a JPEG backward-compatible HDR image compression standard, over multiple exposures JPEG. We also investigate the quality increase that could be achieved by fusing images with linear values and native sensor bit depth over pictures with sRGB gamma encoded values and 8 bits per sample. To investigate the impact of the different parameters on the performance, we perform a set of experiments with 14 contents, 4 resolutions (ranging from 2.5 megapixels (MP) to 16MP), 4 exposures configurations (2, 3, 5, and 7 exposures), 5 tone mapping operators (TMOs) used to generate the JPEG XT base layer, and 5 quality levels representative of values commonly used in smartphones and DSLR cameras. Results show that the performance is dependent on the TMO and number of exposures, with maximum average bit rate savings ranging from 10% for two exposures up to 70% for seven exposures. Additionally, quality improvements of 1.7 dB to 5.1 dB can be achieved when using the native image sensor data format.

关键词： High dynamic range Digital photography Image storage Image coding JPEG XT coding efficiency

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Fast Mode Decision Technique for HEVC Intra Prediction Based on Reliability Metric for Motion Vectors

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IEICE TRANSACTIONS ON INFORMATION AND SYSTEMS 2016年第4期E99D卷 1193-1201页

作者： Tsutake, Chihiro Nakano, Yutaka Yoshida, Toshiyuki Univ Fukui Grad Sch Engn Dept Informat Sci Fukui 9108507 Japan

This paper proposes a fast mode decision technique for intra prediction of High efficiency Video coding (HEVC) based on a reliability metric for motion vectors (RMMV). Since such a decision problem can be regarded as a kind of pattern classification, an efficient classifier is required for the reduction of computation complexity. This paper employs the RMMV as a classifier because the RMMV can efficiently categorize image blocks into flat(uniform), active, and edge blocks, and can estimate the direction of an edge block as well. A local search for angular modes is introduced to further speed up the decision process. An experiment shows the advantage of our technique over other techniques.

关键词： H.265/HEVC intra prediction mode decision reliability metric coding efficiency computational complexity

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CMOS RF class-D power amplifier with bandpass sigma-delta modulation

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MICROELECTRONICS JOURNAL 2007年第3期38卷 439-446页

作者： Johnson, Thomas Sobot, Robert Stapleton, Shawn PulseWave RF Austin TX 78746 USA Univ Western Ontario Dept Elect & Comp Engn London ON N6A 5B9 Canada Simon Fraser Univ Sch Engn Sci Burnaby BC V5A 1S6 Canada

A 0.5 mu m CMOS radio frequency class-D amplifier is analysed and simulated with a bandpass Sigma Delta modulated drive signal. The design includes a five stage driver and operates from 3.3 V. The simulated power efficiency at 181 MHz is 40.1% for a two tone source, and 16.6% for a 8.7 dB peak-to-average wideband code-division multiple access source signal. Equations are derived which demonstrate the relationship between amplifier load power, power efficiency, and modulator parameters called coding efficiency and average transition frequency. (C) 2007 Elsevier Ltd. All rights reserved.

关键词： bandpass sigma-delta modulation class-D amplifier class-S amplifier radio frequency power amplifier coding efficiency

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Image Insertion Using Depth- and Topology- Constrained Minimum Spanning Tree for Compressed Image Sets

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IEEE ACCESS 2024年 12卷 29083-29092页

作者： Sha, Lina Wu, Wei Huang, Wanlin Yangling Vocat & Tech Coll Sch Informat Engn Yangling 712100 Shaanxi Peoples R China Xidian Univ State Key Lab Integrated Serv Networks Xidian 710071 Shaanxi Peoples R China

As an important paradigm of image set management, image insertion refers to adding new photos to an existing compressed image set. Recently, several algorithms have made significant progress in image insertion. However, due to complexity image relationships, coding performance still remains to rise. To address the issue, in this paper a high-coding-efficiency image insertion algorithm is proposed for compressed image sets. In order to maximize coding performance, it is necessary for each new picture to thoroughly exploit the correlations between it and all the other images. To be specific, in our proposed approach images are first divided into two kinds: to-be-inserted images and compressed images, where the former includes new photographs and the latter composes that compressed image set. Second, a depth- and topology-constrained minimum spanning tree (DTCMST) heuristics is also proposed, to fully investigate the relationships not only between to-be-inserted images and compressed images but among different to-be-inserted images. With the generated DTCMST, the depth requirement and the topology structure of the existing compressed image set can be satisfied and kept unchanged, respectively. Finally, after the encoding of every to-be-inserted image by using its assigned parent vertex from the DTCMST as its prediction reference, a new compressed image is eventually established. Compared with state-of-the-art methods, experimental results show that average bit rate saving and Bjontegaard delta peak signal-to-noise ratio enhancement are achieved up to 5.1 % and 0.41 dB by using our proposed algorithm, respectively, with the similar computational complexity.

关键词： Image insertion compressed image set minimum spanning tree coding efficiency image set management

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A Broadband Almost-Digital RF Transmitter With an Efficient Power Amplifier

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IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 2016年第5期64卷 1526-1534页

作者： Jang, Wonhoon Cordeiro, Rui Oliveira, Arnaldo Carvalho, Nuno Borges Inst Telecomunicacoes P-3810193 Aveiro Portugal

A new architecture of an almost-digital RF transmitter is proposed. It consists of easy-to-have functional modules. Among the modules, a broadband Doherty amplifier is focused through a modified design approach. A proof-of-concept transmitter is built and measured. It demonstrates quite comparable performances: more than 40% of power-amplifier efficiency, adjacent channel leakage ratios between -26 and -37 dB, and average 2.6% of error vector magnitude over a frequency band from 0.7 to 1.1 GHz, which corresponds to a fractional bandwidth of 44%, when it is driven by a signal with 5.6 dB of peak-to-average power ratio.

关键词： All-digital transmitter coding efficiency power amplifier (PA) power efficiency software-defined radio

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Segmentation-Based Video Compression Using Texture and Motion Models

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IEEE JOURNAL OF SELECTED TOPICS IN SIGNAL PROCESSING 2011年第7期5卷 1366-1377页

作者： Bosch, Marc Zhu, Fengqing Delp, Edward J. Purdue Univ Sch Elect & Comp Engn W Lafayette IN 47907 USA

In recent years, there has been a growing interest in developing novel techniques for increasing the coding efficiency of video compression methods. One approach is to use texture and motion models of the content in a scene. Based on these models parts of the video frame are not coded or "skipped" by a classical motion compensated coder. The models are then used at the decoder to reconstruct the missing or skipped regions. In this paper, we describe several spatial-texture models for video coding. We investigate several texture features in combination with two segmentation strategies in order to detect texture regions in a video sequence. These detected areas are not encoded using motion compensated coding. The model parameters are sent to the decoder as side information. After the decoding process, frame reconstruction is done by inserting the skipped texture areas into the decoded frames. Using similar approach, we consider motion models based on human visual motion perception. We describe a motion classification model to separate foreground objects containing noticeable motion from the background. This motion model is then used in the encoder to again allow regions to be skipped and not coded using a motion compensated encoder. Our results indicate significant increase in terms of coding efficiency in comparison to the spatial texture-based methods. Finally, we discuss the effects and tradeoffs of these techniques based on perceptual experiments and show that in many cases the coding efficiency can be increased by up to 25% given a fixed perceptual quality.

关键词： coding efficiency feature extraction motion analysis texture modeling video coding

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Boundary block-merging (BBM) technique for efficient texture coding of arbitrarily shaped object

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 1999年第1期9卷 35-43页

作者： Moon, JH Kweon, JH Kim, HK Hyundai Elect Ind Co Ltd Informat & Telecommun R&D Ctr Seoul South Korea

We present an efficient texture coding method which enhances the coding efficiency of conventional discrete cosine transform (DCT) with padding techniques for arbitrarily shaped objects in object-based video coding where shape information is provided. The BBM (boundary block-merging) technique is applied to the boundary macroblocks of 16 x 16 pixels of a VOP (video object plane) which consist of both background and object pixels. A macroblock consists of four subblocks of 8 x 8 pixels. For boundary subblocks consisting of object and background pixels, padding is performed in the background region. For a pair of padded boundary subblocks in a macroblock of which alignment belongs to a predefined set, one subblock is rotated 180 degrees and merged into another one if object pixels do not overlap, After merging, the boundary macroblock is coded using the conventional DCT coding. The merging process reduces the number of subblocks to be DCT coded, and high correlation between adjacent subblocks makes the number of DCT coding bits small, Experimentation has been done on various test sequences under different test conditions, and verifies significant coding efficiency improvement: reduction of coding bits for luminance boundary blocks by 5.7-11.9 % at the same PSNR values compared with the padding-based DCT without BBM.

关键词： arbitrarily shaped object coding efficiency object-based coding texture coding

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Contrast conservation in human vision

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VISION RESEARCH 2003年第25期43卷 2637-2648页

作者： Fiser, J Bex, PJ Makous, W Univ Rochester Ctr Visual Sci Rochester NY 14627 USA UCL Inst Ophthalmol London EC1V 9EL England

Visual experience. which is defined by brief saccadic sampling of complex scenes at high contrast, has typically been studied with static gratings at threshold contrast. To investigate how suprathreshold visual processing is related to threshold vision, we tested the temporal integration of contrast in the presence of large, sudden changes in the stimuli such occur during saccades under natural conditions. We observed completely different effects under threshold and suprathreshold viewing conditions. The threshold contrast of successively presented gratings that were either perpendicularly oriented or of inverted phase showed probability summation, implying no detectable interaction between independent visual detectors. However, at suprathreshold levels we found complete algebraic summation of contrast for stimuli longer than 53 ms. The same results were obtained during sudden changes between random noise patterns and between natural scenes. These results cannot be explained by traditional contrast gain-control mechanisms or the effect of contrast constancy. Rather, at suprathreshold levels, the visual system seems to conserve the contrast information from recently viewed images, perhaps for the efficient assessment of the contrast of the visual scene while the eye saccades from place to place. (C) 2003 Elsevier Ltd. All rights reserved.

关键词： suprathreshold dynamic contrast discrimination channel model natural scene coding efficiency

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Algorithms for Fast Implementation of 4-Point Integer Sine Type Vii Transformswithout Multiplication and Separable Directional Adaptive Transforms for Intra Prediction in Image/Video coding

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CYBERNETICS AND SYSTEMS ANALYSIS 2020年第1期56卷 159-170页

作者： Hnativ, L. O. Luts, V. K. Natl Acad Sci Ukraine VM Glushkov Inst Cybernet Kiev Ukraine

The separable directional adaptive integer cosine and sine type VII transforms with 4x4 blocks are proposed for intra prediction in image and video coding. Algorithms for fast implementation of 2D 4-point separable directional integer cosine and sine transforms are developed. These algorithms require 7 times fewer multiplication operations and provide higher compression ratio than the well-known algorithms. Two order-4 integer sine type VII transforms are proposed, and algorithms are developed for fast implementation of 4-point integer sine type VII transforms, which require integer operations only. As compared to the known algorithm, these algorithms can significantly reduce the number of multiplication operations or avoid them at all. These integer sine transforms are very close to discrete sine type VII transform and have a higher compression ratio than the well-known sine transform accepted in standard H.265 does.

关键词： discrete cosine transform discrete sine transform integer cosine transform integer sine transform mode-dependent directional transform separate directional adaptive transform factorization fast transform coding efficiency intra prediction video coding H 264 H 265

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