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Fifth IEE Conference on Telecommunications 1995

作者： S.D. Zhang G.B. Lockhart University of Leeds UK

Embedded speech coding offers a graceful and acceptable degradation of speech quality when a network or channel becomes congested and transmitted information is lost. Unlike PCM which is inherently an embedded code, the more efficient differential codes such as DPCM and delta modulation (DM) do not possess embedded coding properties without modification. Embedded versions of both DPCM and DM have therefore been proposed (Goodman (1980), Wassell et al. (1988), Jayant (1983), Zhang and Lockhart (1991)). The present authors demonstrate a novel embedded adaptive DPCM (EADPCM) speech coder. The coder uses the explicit noise coding technique (Jayant) to generate a supplemental bit stream which may be wholly or partly discarded during transmission. A new low-complexity algorithm is employed to match the supplemental adaptive PCM (APCM) coder to the ADPCM reconstruction error. The step size for the APCM coder is determined in two stages. First, a basic step size is estimated from the ADPCM step based on instantaneous or syllabic adaptation or their combination. This is followed by further instantaneous step size adjustment based on the APCM output. Simulation shows that a graceful reduction of reconstructed speech quality with progressive bit deletion is achieved over the range from 48 (or 40) kb/s to 16 kb/s in 8 kb/s steps.< >

关键词： differential pulse code modulation Speech coding

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DPCM ENCODING OF REGENERATIVE COMPOSITE PROCESSES

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IEEE TRANSACTIONS ON INFORMATION THEORY 1994年第1期40卷 153-159页

作者： NARAGHIPOUR, M HEGDE, M ARORA, N Department of Electrical and Computer Engineering Louisiana State University Baton Rouge LA USA

Fixed (nonadaptive) and forward adaptive differential pulse code modulation of regenerative composite sources is investigated. In the fixed code, an approximate formula is given for the optimal value of the prediction coefficient. This is then used as an initial guess to optimize the code (predictor and quantizer) through a numerical method. In the forward adaptive scheme, the state of the switch in the composite source is estimated using a MAP sequence estimation algorithm, and the code is then matched to the mode process corresponding to the estimated switch state. The performance of the two systems is evaluated with quantizers of 4, 8, and 16 levels. The results show that the forward adaptive scheme significantly outperforms optimized fixed DPCM in the sense of mean-squared error. Stochastic stability of the code is also established for the fixed DPCM scheme as well as for an adaptive scheme which receives the switch state as side information.

关键词： SOURCE CODING differential pulse code modulation COMPOSITE SOURCES STOCHASTIC STABILITY

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Displaying radiologic images on personal computers. Image storage and compression. Part 2

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Journal of Digital Imaging 1994年第1期7卷 1-1页

作者： Gillespy, Thurman III Rowberg, Alan H. Department of Radiology SB-05 University of Washington Seattle

This is part 2 of our article on image storage and compression, the third article of our series for radiologists and imaging scientists on displaying, manipulating, and analyzing radiologic images on personal computers. Image compression is classified as lossless (nondestructive) or lossy (destructive). Common lossless compression algorithms include variable-length bit codes (Huffman codes and variants), dictionary-based compression (Lempel-Ziv variants), and arithmetic coding. Huffman codes and the Lempel-Ziv-Welch (LZW) algorithm are commonly used for image compression. All of these compression methods are enhanced if the image has been transformed into a differential image based on a differential pulse-code modulation (DPCM) algorithm. The LZW compression after the DPCM image transformation performed the best on our example images, and performed almost as well as the best of the three commercial compression programs tested. Lossy compression techniques are capable of much higher data compression, but reduced image quality and compression artifacts may be noticeable. Lossy compression is comprised of three steps: transformation, quantization, and coding. Two commonly used transformation methods are the discrete cosine transformation and discrete wavelet transformation. In both methods, most of the image information is contained in a relatively few of the transformation coefficients. The quantization step reduces many of the lower order coefficients to 0, which greatly improves the efficiency of the coding (compression) step. In fractal-based image compression, image patterns are stored as equations that can be reconstructed at different levels of resolution.

关键词： differential pulse code modulation discrete cosine transformation discrete wavelet transformation fractal compression Huffman codes image compression Lempel-Ziv-Welch compression personal computer tagged interchange file format

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Interplay Betweeen Recursive System Identification and Adaptive Filtering in Communication Systems

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IFAC Proceedings Volumes 1994年第8期27卷 13-24页

作者： C. Richard Johnson School of Electrical Engineering Cornell University Ithaca NY 14853 USA

Three successful applications of adaptive filtering in communications systems (network echo cancellation, differential pulse code modulation, and linear channel equalization) emerged concurrently just over 25 years ago. This paper surveys these topics with an emphasis on links with the work of recursive system identification experts.

关键词： Adaptive filtering recursive identification adaptive control network echo cancellation differential pulse code modulation linear equalization

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Cell voice transport considerations for ATM

Cell voice transport considerations for ATM

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Canadian Conference on Electrical and Computer Engineering (CCECE)

作者： Gedeon Narayanan Vreugdenhil Magellan Networks Bell Northern Research Limited Canada

This paper discusses the cell transport characteristics for a viable ATM voice implementation. A system approach to cell voice, both backbone switching and access, is considered. Bandwidth utilization opportunities, i... 详细信息

关键词： Speech processing Asynchronous transfer mode Speech communication Digital communication differential pulse code modulation Echo suppression

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Progressive image transmission by segmentation coding

Progressive image transmission by segmentation coding

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Canadian Conference on Electrical and Computer Engineering (CCECE)

作者： Caron Rivest Department of Electrical Engineering University of Ottawa Ottawa ONT Canada

A coding algorithm is presented for progressive transmission of gray-tone images. The approach is motivated by the desire to retain edge information at low bit rates. A segmentation is first performed using the watershed algorithm to yield an oversegmented mosaic image that is successively decimated. The region contours are chain encoded and transmitted in reverse order, while the lowpass information is coded using DPCM.< >

关键词： Image communication Image segmentation Image coding Image edge analysis differential pulse code modulation

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NASA PPO microgravity projects support

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1993年

作者： janice f smith

Supplemental catalog subcollection information: NASA Publication Collection; Astrophysics and Technical Documents; Work progress is reported in brief. A summary of this information is provided below. An in-depth study... 详细信息

关键词： data compression differential pulse code modulation information systems

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COMPONENT codeC STANDARDS FOR HIGH-QUALITY DIGITAL TELEVISION

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ELECTRONICS & COMMUNICATION ENGINEERING JOURNAL 1992年第4期4卷 195-202页

作者： WELLS, ND Research Department British Broadcasting Corporation Tadworth UK

Work towards defining standards for digital television transmission codecs has been proceeding for many years. A draft specification for 140 Mbit/s coding using blanking removal and differential pulse code modulation is given in CCIR Recommendation 721. A draft specification for a codec operating at 30-45 Mbit/s and using the discrete cosine transform has been defined by the European Telecommunications Standards Institute. The paper briefly reviews bit-rate-reduction techniques and describes the 140 and 34 Mbit/s codecs.

关键词： Stations and subscriber equipment ETSI DPCM 140 Mbit/s 30 to 45 Mbit/s video equipment DCT blanking removal codes television standards CCIR Recommendation 721 discrete cosine transform codec standards Television and video equipment, systems and applications encoding pulse-code modulation bit-rate-reduction techniques high-quality digital television codecs differential pulse code modulation European Telecommunications Standards Institute

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ADAPTIVE PREDICTIVE IMAGE-CODING USING LOCAL CHARACTERISTICS

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IEE PROCEEDINGS-I COMMUNICATIONS SPEECH AND VISION 1989年第6期136卷 385-390页

作者： HSIEH, CH LU, PC LIOU, WG Department of Electrical Engineering Chung Cheng Institute of Technology Ta-Hsi Republic of China

The paper presents an efficient adaptive predictive coding method using the local characteristics of images. In this method, three coding schemes, namely, mean, subsampling combined with fixed DPCM, and ADPCM/PCM, are used and one of these is chosen adaptively based on the local characteristics of images. The prediction parameters of the 2-d linear predictor in the ADPCM/PCM are extracted on a block by block basis using the 2-d lattice filtering method. The order update 2-d lattice model proposed by Parker and Kayran is extended into order update and time update recursion for more efficient computation. Simulation results show that the proposed method is effective in reducing the slope overload distortion and the granular noise at low bit rates, and thus it can improve the visual quality of reconstructed images. Other advantages of this method are the low computational burden and the suitability for the VLSI implementation.

关键词： PCM adaptive differential pulse code modulation DPCM Pattern recognition VLSI implementation granular noise slope overload distortion codes picture processing filtering and prediction theory adaptive predictive image coding encoding pulse-code modulation local characteristics Optical information, image and video signal processing 2D linear predictor low bit rates prediction parameters visual quality reconstructed images differential pulse code modulation adaptive filters 2D lattice filtering time update recursion order update recursion ADPCM/PCM

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QUANTIZED CONTROL USING differential ENCODING

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OPTIMAL CONTROL APPLICATIONS & METHODS 1984年第1期5卷 69-83页

作者： FISCHER, TR TINNIN, DJ MEAD OFF SYST RICHARDSONTX 75081

A vector generalization of differential pulse code modulation is used to provide quantization of control and measurements in a closed-loop control system. Algorithms are developed for the adaptive quantizer and predictor. Explicit expressions are derived for the quantization and estimation errors resulting from the differential encoding. Simulation results are presented which demonstrate that even for very low bit rates the quantized control performance is very close to the performance of the unquantized optimal control solution.

关键词： Digital control Linear-quadratic regulators differential pulse code modulation Control and measurement quantization

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