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International SoC Design Conference, ISOCC

作者： Sehyun Song Changwoo Seo Kichul Kim School of Electrical & Computer Engineering University of Seoul Seoul South Korea

ISBN: (纸本)9781424425983

This paper presents a unified transform unit that can efficiently perform forward integer transform, quantization, dequantization, inverse integer transform, and Hadamard transform in H.264/AVC. To reduce hardware cost, the proposed architecture uses shifters, adder/subtractors instead of multipliers for quantization and de-quantization, and reuses 1-D transform unit for all supporting transforms. Hardware utilization is maximized to achieve required performance with low cost. It takes about 250 cycles to perform forward integer transform, quantization, de-quantization, and inverse integer transform for a macroblock, and additional 35 cycles for forward and inverse Hadamard transforms. The architecture can process about 6,000 frames of QCIF at 150 MHz. The unified transform unit can be widely used in mobile devices.

关键词： Quantization Costs Hardware Automatic voltage control Motion estimation entropy coding Computer architecture Video codecs Arithmetic Frequency domain analysis

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Parallel CABAC for low power video coding

Parallel CABAC for low power video coding

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IEEE International Conference on Image Processing

作者： Vivienne Sze Anantha P. Chandrakasan Madhukar Budagavi Minhua Zhou Massachusetts Institute of Technology Cambridge MA USA Texas Instruments Inc. Dallas TX USA

With the growing presence of high definition video content on battery-operated handheld devices such as camera phones, digital still cameras, digital camcorders, and personal media players, it is becoming ever more important that video compression be power efficient. A popular form of entropy coding called context-based adaptive binary arithmetic coding (CABAC) provides high coding efficiency but has limited throughput. This can lead to high operating frequencies resulting in high power dissipation. This paper presents a novel parallel CABAC scheme which enables a throughput increase of N-fold (depending on the degree parallelism), reducing the frequency requirement and expected power consumption of the coding engine. Experiments show that this new scheme (with N=2) can deliver ~2x throughput improvement at a cost of 0.76% average increase in bit-rate or equivalently a decrease in average PSNR of 0.025 dB on five 720 p resolution video clips when compared with H.264/AVC.

关键词： Video coding Throughput Digital cameras Frequency High definition video Handheld computers Video equipment Video compression entropy coding Arithmetic

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Efficient Intra-4X4 Mode Decision Based on Bit-rate Estimation in H.264/AVC

Efficient Intra-4X4 Mode Decision Based on Bit-rate Estimati...

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2008 IEEE International Symposium on Circuits and Systems (ISCAS 2008), vol.2

作者： Jiaying Liu Zongming Guo Institute of Computer Science and Technology Peking University Beijing China

Rate-distortion optimization (RDO) technique is widely employed by H.264/AVC for the purpose of determining the best mode. However, such technique results in dramatic increase in the computation complexity of the underlying encoder. In this paper, we address this problem by presenting an efficient intra-4X4 mode decision algorithm. The algorithm works by approximating the bit-rate so as to reduce the computational cost of RDO and the main idea is the following: First we have found a quick way to estimate the bit-rate via the number of DCT coefficients to be quantized to 0 and that to be quantized to +-1. The parameters of the estimated function are adaptively obtained by using the Least Squares Fitting method of the above and the left block in the current frame and the co-location one in the previous encoded frame as the feedback. This close loop bit-rate estimation would skip the processes of quantization, inverse transform, entropy coding and reconstruction;we then use the estimated bit-rate and Sum of Absolute Differences (SAD) to simplify the optimization process of R-D cost function. Experimental results show that our scheme decreases the time for intra coding by 50percent with negligible loss of PSNR, and that comparing with those fast mode-decision algorithms based-on local edge direction, the optimal prediction mode obtained via our scheme is closer to that obtained via the original RDO in statistic.

关键词： Automatic voltage control Least squares approximation Rate-distortion Computational efficiency Discrete cosine transforms Parameter estimation Feedback Quantization entropy coding Cost function

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Lossless compression of chemical fingerprints using integer entropy codes improves storage and retrieval

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JOURNAL OF CHEMICAL INFORMATION AND MODELING 2007年第6期47卷 2098-2109页

作者： Baldi, Pierre Benz, Ryan W. Hirschberg, Daniel S. Swamidass, S. Joshua Univ Calif Irvine Sch Informat & Comp Sci Inst Genom & Bioinformat Irvine CA 92697 USA

Many modem chemoinformatics systems for small molecules rely on large fingerprint vector representations, where the components of the vector record the presence or number of occurrences in the molecular graphs of particular combinatorial features, such as labeled paths or labeled trees. These large fingerprint vectors are often compressed to much shorter fingerprint vectors using a lossy compression scheme based on a simple modulo procedure. Here, we combine statistical models of fingerprints with integer entropy codes, such as Golomb and Elias codes, to encode the indices or the run lengths of the fingerprints. After reordering the fingerprint components by decreasing frequency order, the indices are monotone-increasing and the run lengths are quasi-monotone-increasing, and both exhibit power-law distribution trends. We take advantage of these statistical properties to derive new efficient, lossless, compression algorithms for monotone integer sequences: monotone value (MOV) coding and monotone length (MOL) coding. In contrast to lossy systems that use 1024 or more bits of storage per molecule, we can achieve lossless compression of long chemical fingerprints based on circular substructures in slightly over 300 bits per molecule, close to the Shannon entropy limit, using a MOL Elias Gamma code for run lengths. The improvement in storage comes at a modest computational cost. Furthermore, because the compression is lossless, uncompressed similarity (e.g., Tanimoto) between molecules can be computed exactly from their compressed representations, leading to significant improvements in retrival performance, as shown on six benchmark data sets of druglike molecules.

关键词： Fingerprints Integer Storage storage and retrieval entropy coding lossy compression lossless compression statistical models (nuclear)

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State-of-the-art and trends in scalable video compression with wavelet-based approaches

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 2007年第9期17卷 1238-1255页

作者： Adami, Nicola Signoroni, Alberto Leonardi, Riccardo Univ Brescia Fac Engn Dept Elect & Automat I-25123 Brescia Italy

Scalable Video coding (SVC) differs form traditional single point approaches mainly because it allows to encode in a unique bit stream several working points corresponding to different quality, picture size and frame rate. This work describes the current state-of-the-art in SVC, focusing on wavelet based motion-compensated approaches (WSVC). It reviews individual components that have been designed to address the problem over the years and how such components are typically combined to achieve meaningful WSVC architectures. coding schemes which mainly differ from the space-time order in which the wavelet transforms operate are here compared, discussing strengths and weaknesses of the resulting implementations. An evaluation of the achievable coding performances is provided considering the reference architectures studied and developed by ISO/MPEG in its exploration on WSVC. The paper also attempts to draw a list of major differences between wavelet based solutions and the SVC standard jointly targeted by ITU and ISO/MPEG. A major emphasis is devoted to a promising WSVC solution, named STP-tool, which presents architectural similarities with respect to the SVC standard. The paper ends drawing some evolution trends for WSVC systems and giving insights on video coding applications which could benefit by a wavelet based approach.

关键词： entropy coding motion compensated temporal filtering (MCTF) MPEG Scalable Video coding (SVC) spatio-temporal multiresolution representations video coding architectures video quality assessment wavelets

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Security analysis of multimedia encryption schemes based on multiple Huffman table

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IEEE SIGNAL PROCESSING LETTERS 2007年第3期14卷 201-204页

作者： Zhou, Jiantao Liang, Zhiqin Chen, Yan Au, Oscar C. Hong Kong Univ Sci & Technol Dept Elect & Comp Engn Hong Kong Hong Kong Peoples R China

This letter addresses the security issues of the multimedia encryption schemes using multiple Huffman table (MHT). A known-plaintext attack is presented to show that the MHTs used for encryption should be carefully selected to avoid the weak keys problem. We then propose chosen-plaintext attacks on the basic MHT algorithm as well as the enhanced scheme with random bit insertion. In addition, we suggest two empirical criteria for Huffman table selection, based on which we can simplify the stream cipher integrated scheme, while ensuring a high level of security.

关键词： cryptanalysis entropy coding Huffman coding lightweight encryption multimedia security

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CAVLC encoder design for real-time mobile video applications

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS II-EXPRESS BRIEFS 2007年第10期54卷 873-877页

作者： Rahman, Choudhury A. Badawy, Wael Univ Calgary Dept Elect & Comp Engn Calgary AB T2N 1N4 Canada

This brief presents a new context-based adaptive variable length coding (CAVLC) architecture. The prototype is designed for the H.264/AVC baseline profile entropy coder. The proposed design offers area savings by reducing the size of the statistic buffer. The arithmetic table elimination technique further reduces the area. The split VLC tables simplify the process of bit-stream generation and also help in reducing some area. The proposed architecture is implemented on Xilinx Virtex II field-programmable gate array (20000fg6764). Simulation result shows that the architecture is capable of processing common/quarter-common intermediate format frame sequences in real-time at a core speed of 50 MHz with 6.85-K logic gates.

关键词： context-based adaptive variable length coding (CAVLC) entropy coding H264/AVC hardware encoder real-time VLSI architecture

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Least-squares-based switching structure for lossless image coding

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I-REGULAR PAPERS 2007年第7期54卷 1529-1541页

作者： Kau, Lih-Jen Lin, Yuan-Pei Natl Chiao Tung Univ Dept Elect & Control Engn Hsinchu 300 Taiwan Dahan Inst Technol Dept Comp & Commun Engn Hualien 971 Taiwan

Many coding methods are more efficient with some images than others. In particular, run-length coding is very useful for coding areas of little changes. Adaptive predictive coding achieves high coding efficiency for fast changing areas like edges. In this paper, we propose a switching coding scheme that will combine the advantages of both run-length and adaptive linear predictive coding. For pixels in slowly varying areas, run-length coding is used;otherwise least-squares (LS)-adaptive predictive coding is used. Instead of performing LS adaptation in a pixel-by-pixel manner, we adapt the predictor coefficients only when an edge is detected so that the computational complexity can be significantly reduced. For this, we use a simple yet effective edge detector using only causal pixels. This way, the proposed system can look ahead to determine if the coding pixel is around an edge and initiate the LS adaptation in advance to prevent the occurrence of a large prediction error. With the proposed switching structure, very good prediction results can be obtained in both slowly varying areas and pixels around boundaries. Furthermore, only causal pixels are used for estimating the coding pixels in the proposed encoder;no additional side information needs to be transmitted. Extensive experiments as well as comparisons to existing state-of-the-art predictors and coders will be given to demonstrate its usefulness.

关键词： adaptive prediction context modeling edge detection entropy coding least-squares (LS) optimization lossless image coding run-length encodings

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High-speed H.264/AVC CABAC decoding

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 2007年第4期17卷 490-494页

作者： Yi, Yongseok Park, In-Cheol Samsung Elect Co Ltd Seoul 443742 South Korea Korea Adv Inst Sci & Technol Taejon 305701 South Korea

The decoding of context-based adaptive binary arithmetic coding (CABAC) imposes a heavy performance requirement on H.264/AVC decoding systems particularly for large-scale video sequences. As a simple approach of elevating the operating frequency is not sufficient to meet the performance requirement, this paper proposes an efficient approach to accelerate the decoding, which is effective under relatively low operating frequency. Since the CABAC decoding procedure is highly sequential and has strong data dependencies, it is difficult to exploit parallelism and pipeline schemes. The proposed approach resolves the difficulties by modifying the operation chain based on a thorough analysis, eventually enabling both parallel operations and pipelining. More specifically, 1) several context models are simultaneously loaded from memory while context selection is performed in parallel and 2) bin-level pipelining is enabled by employing a small storage to remove structural hazards and data dependencies. Experimental results show that the proposed approach leads to the real-time decoding of HD sequences.

关键词： adaptive binary arithmetic code entropy coding H.264/AVC syntax processing

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Enable efficient compound image compression in H.264/AVC intra coding

Enable efficient compound image compression in H.264/AVC int...

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IEEE International Conference on Image Processing (ICIP 2007)

作者： Ding, Wenpeng Lu, Yan Wu, Feng Univ Sci & Technol China Dept Comp Sci Hefei 230027 Peoples R China Microsoft Res Asia Internet Media Grp Beijing 100080 Peoples R China

ISBN: (纸本)9781424414369

This paper presents an efficient compound image compression approach based on H.264/AVC intra coding. The text blocks are distinguished from the picture blocks and compressed with a new coding mode. In particular, the text blocks are represented by base colors and index map in spatial domain. A color quantization algorithm optimized for compression is designed to generate this representation. As for the entropy coding of text blocks, a structure-aware context-based arithmetic coder is developed. The mode selection algorithm based on rate distortion optimization is used to select the text blocks along with H.264/AVC intra modes, which can adapt to the targeted bit-rate. Experimental results show that the proposed scheme can achieve 2.8dB gain on average for compound images compared with H.264/AVC intra coding.

关键词： compound image compression color quantization entropy coding mode decision

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