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Conference on Image and Video Communications and Processing

作者： Chen, QY Subbalakshmi, KP Stevens Inst Technol Dept Elect & Comp Engn Multimedia Syst Networking & Commun Lab Hoboken NJ 07030 USA

ISBN: (纸本)0819448222

Most video coding standards, including MPEG-4, use variable length codes to encode the discrete cosine transform (DCT) coefficients of intra. frames and inter frames, and the motion vector information. Although variable length codes can achieve good compression, they are very sensitive to channel errors, especially in Wireless channels, which are characterized by bursty errors. joint source-channel decoding (JSCD) is emerging as a potential alternative to traditional error resilience methods. for dealing with this sensitivity to channel errors. This paper describes one such JSCD for the reliable transmission of MPEG-4 video over wireless channels. We apply the maximum a posteriori probability based JSCD developed for first order Markov sources' to both inter and intra coded macroblocks. Experiments indicate that the proposed decoder gives significant improvements (9 dB in some cases) for MPEG-4 video with error resilience at various channel error rates.

关键词： multimedia over wireless networks MPEG-4 video over wireless channels joint source-channel coding error-resilient multimedia communication

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Optimised constructions for variable-length error correcting codes

Optimised constructions for variable-length error correcting...

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IEEE Information Theory Workshop

作者： Lamy, C Paccaut, J THALES Commun France Gennevilliers France

ISBN: (纸本)0780377990

An optimised construction of variable-length error-correcting codes (VLEC) is proposed in this paper. Compared to the state-of-the-art, the three main improvements consist first in improving the codewords search algorithm complexity/efficiency trade-off, second in loosening the codewords deletion rule, and third in taking advantage of eventual previous searches. It is shown that the optimised algorithm can find good VLEC codes for alphabets up to 200 symbols, and outperforms existing algorithms.

关键词： variable-length error-correcting codes joint source-channel coding variable-length codes error correction coding code construction

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An end-to-end embedded approach for digital video multicast/broadcast over CDMA cellular networks

An end-to-end embedded approach for digital video multicast/...

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Conference on Visual Communications and Image Processing 2003

作者： Chan, YS Modestino, JW Rensselaer Polytech Inst Ctr Image Proc Res Troy NY 12180 USA

ISBN: (纸本)0819450235

We investigate multicast/broadcast of digital video over spread-spectrum CDMA cellular networks, a platform targeted at various kinds of multimedia services. In particular, we propose an end-to-end embedded transmission scheme which combines a scalable video source coder, adaptive power allocation, adaptive channel coding and an embedded multiresolution modulation strategy to simultaneously deliver a basic quality-of-service (QoS) to less capable receivers and an enhanced QoS for more capable receivers. We demonstrate the efficacy of this approach using the ITU-T H.263+ video source coder, although the approach is generally applicable to other scalable source coding schemes as well.

关键词： wireless video CDMA multicast/broadcast adaptive modulation and coding joint source coding-power control turbo codes embedded transmission cross-layer joint source-channel coding H.263+

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joint source channel rate-distortion analysis for adaptive mode selection and rate control in wireless video coding

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 2002年第6期12卷 511-523页

作者： He, ZH Cai, JF Chen, CW Sarnoff Corp Interact Media Grp Princeton NJ 08543 USA Univ Missouri Dept Elect Engn Columbia MO 65201 USA

In this paper, we first develop a rate-distortion (R-D) model for DCT-based video coding incorporating the macroblock (MB) intra refreshing rate. For any given bit rate and intra refreshing rate, this model is capable of estimating the corresponding coding distortion even before a video frame is coded. We then present a theoretical analysis of the picture distortion caused by channel errors and the subsequent inter-frame propagation. Based on this analysis, we develop a statistical model to estimate such channel errors induced distortion for different channel conditions and encoder settings. The proposed analytic model mathematically describes the complex behavior of channel errors,in a video coding and transmission system. Unlike other experimental approaches for distortion estimation reported in the literature, this analytic model has very low computational complexity and implementation cost, which are highly desirable in wireless video applications. Simulation results show that this model is able to accurately estimate the channel errors induced distortion with a minimum delay in processing. Based on the proposed source coding R-D model and the analytic channel-distortion estimation, we derive an analytic solution for adaptive intra mode selection and joint source-channel rate control under time-varying wireless channel conditions. Extensive experimental results demonstrate that this scheme significantly improves the end-to-end video quality in wireless video coding and transmission.

关键词： end-to-end distortion error propagation joint source-channel coding rate-distortion analysis wireless video

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joint source-channel fractal image coding with unequal error protection

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OPTICAL ENGINEERING 2002年第12期41卷 3168-3176页

作者： Charfi, Y Stankovic, VM Hamzaoui, R Haouari, A Saupe, D Univ Constance Dept Comp & Informat Sci D-78457 Constance Germany Univ Mohammed 5 LEESA Fac Sci Rabat Morocco

We propose a joint source-channel coding system for fractal image compression. We allocate the available total bit rate between the source code and the channel code using a Lagrange multiplier optimization technique. The principle of the proposed unequal error protection strategy is to partition the information bits into sensitivity classes and to assign one code from a range of error-correcting codes to each sensitivity class in a nearly optimal way. Experimental results show that joint source-channel coding with fractal image compression is feasible, leads to efficient protection strategies, and outperforms previous works in this field that covered only channel coding with a fixed source rate. (C) 2002 Society of Photo-Optical Instrumentation Engineers.

关键词： fractal image compression joint source-channel coding unequal error protection

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Robust stack-run coding for low bit-rate image transmission over noisy channels

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IEEE SIGNAL PROCESSING LETTERS 2002年第7期9卷 196-199页

作者： Pépin, C Raffy, P Gray, RM Docomo Commun Labs USA Inc San Jose CA 95110 USA R2 Technol Inc Sunnyvale CA 94087 USA Stanford Univ Dept Elect Engn Informat Syst Lab Stanford CA 94305 USA

We propose a multiresolution algorithm to jointly optimize a source coder and channel coder. The variable-rate source coder combines an optimal bit-allocation strategy and efficient stack-run coding. This compression scheme, concatenated with appropriate rate-compatible punctured convolutional codes, provides a competitive approach to recent state-of-the-art extensions of zerotree methods to noisy channels. Results show that under the assumption of almost zero probability of decoding error, the proposed scheme provides good performance for a lower complexity.

关键词： bit allocation joint source-channel coding rate-compatible punctured convolutional (RCPC) codes stack-run coding

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Adaptive joint H.263-channel coding for memoryless binary channels

Adaptive joint H.263-channel coding for memoryless binary ch...

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13th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications

作者： Navarro, A Tavares, J Univ Aveiro Inst Telecommun P-3810 Aveiro Portugal

ISBN: (纸本)0780375890

The main purpose of this paper is to show that once the video source coding is dependent on the channel characteristics, better performance can be achieved in terms of reconstructed video quality. Our study considers a fixed overall bit rate transmission of 64 kbit/s over error prone memoryless binary channels and the source coder is the ITU-T H.263 video standard. The variable H.263 source coding rate adapts to a particular channel Bit Error Rate (BER) at any instant of time. Firstly, we investigated the error sensitivities of H.263 syntactical elements and grouped them into several classes of different significance. By identifying the most sensitive elements, we developed a data grouping (DG) technique which by itself, exhibits improved error resilience. Secondly, we design an Unequal Error Protection (UEP) scheme and compare its performance with an equivalent (same source coding bit rate) Equal Error Protection (EEP) scheme, using Rate Compatible Punctured Convolutional (RCPC) codes of different rates for forward error protection. Both forward error correction schemes adopted have resulted in PSNR improvements, over 20 dB for BERs higher than of 4x10(-3). Finally, if during the real time encoding process, the encoder is aware of the channel BER and there is an unlimited number of code rates, this paper shows that UEP and EEP strategies provide quite similar performances.

关键词： adaptive wireless video communications forward error protection joint source-channel coding

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Hybrid digital-analog (HDA) joint source-channel codes for broadcasting and robust communications

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IEEE TRANSACTIONS ON INFORMATION THEORY 2002年第5期48卷 1082-1102页

作者： Mittal, U Phamdo, N SUNY Stony Brook Dept Elect & Comp Engn Stony Brook NY 11794 USA

We consider the problem of transmitting a band-limited Gaussian source on an additive band-limited Gaussian noise channel. The well-known "threshold effect"dictates that the more powerful a code is, the more sensitive it is to the exact knowledge of the channel noise. A code is said to be robust if it is asymptotically optimal for a wide range of channel noise. Thus, robust codes have a "graceful degradation" characteristic and are free of the threshold effect. It is demonstrated that robust codes exist whenever the source and channel bandwidths are equal. In the unequal-bandwidth case, a collection of nearly robust joint source-channel codes Is constructed using a hybrid digital-analog (HEIA) coding technique. For designing nearly robust codes, a matched tandem code whose channel encoder's output is partially/fully matched to its input is proposed and the existence of an asymptotically optimal matched tandem code is shown. The nearly robust codes achieve the Shannon limit (theoretically optimum distortion) and have a less severe threshold effect. Finally, for the case of two different noise conditions, the distortion regions of these codes are determined.

关键词： Additive white Gaussian noise (AWGN) channel broadcasting joint source-channel coding memoryless Gaussian source robustness

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Design and performance of VQ-based hybrid digital-analog joint source-channel codes

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IEEE TRANSACTIONS ON INFORMATION THEORY 2002年第3期48卷 708-720页

作者： Skoglund, M Phamdo, N Alajaji, F Royal Inst Technol Dept Signals Sensors & Syst SE-10044 Stockholm Sweden SUNY Stony Brook Dept Elect & Comp Engn Stony Brook NY 11794 USA Queens Univ Dept Math & Stat Kingston ON K7L 3N6 Canada Queens Univ Dept Elect & Comp Engn Kingston ON K7L 3N6 Canada

A joint source-channel hybrid digital-analog (HDA) vector quantization (VQ) system is presented. The main advantage of the new VQ-based HDA system is that it achieves excellent rate-distortion-capacity performance at the design signal-to-noise ratio (SNR) while maintaining a "graceful improvement" characteristic at higher SNRs. It is demonstrated that, within the HDA framework, the parameters of the system can be optimized using an iterative procedure similar to that of channel-optimized vector quantizer design. Comparisons are made with three purely digital systems and one purely analog system. It is found that, at high SNRs, the VQ-based HDA system is superior to the other investigated systems. At low SNRs, the performance of the new scheme can be improved using the optimization procedure and using soft decoding in the digital part of the system. These results demonstrate that the introduced scheme provides an attractive method for terrestrial broadcasting applications.

关键词： broadcasting hybrid digital-analog coding joint source-channel coding robust transmission source coding vector quantization (VQ)

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Performances of linear tools and models for error detection and concealment in subband image transmission

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IEEE TRANSACTIONS ON IMAGE PROCESSING 2002年第5期11卷 518-529页

作者： Labeau, F Desset, C Vandendorpe, L Macq, B McGill Univ Dept Elect & Comp Engn Montreal PQ H3A 2A7 Canada Catholic Univ Louvain Commun & Remote Sensing Lab Louvain Belgium

In this paper, we investigate the performances of Gaussian modeling and linear prediction tools for error detection and concealment in the transmission of still images. We consider the transmission of subband encoded images through two types of channels. We model the residual correlation between subband coefficients by considering them as jointly Gaussian variables. The first transmission medium considered is a packet-oriented channel, where some packets are lost during transmission. The problem is to estimate the values of missing coefficients. In this case, particular care must be taken while evaluating correlation matrices from incomplete data. The other system considered is based on a discrete memoryless noisy channel affecting the data being transmitted. The challenge is here first to determine the locations of the errors-which is done through hypotheses tests-and then to replace them by estimates based on their neighbors. The reconstruction via linear prediction is shown to give better results than median filtering based reconstruction. Error detection through this Gaussian model also shows promising results, in particular when channel statistics are taken into account in a joint source-channel decoding framework.

关键词： error detection and concealment joint source-channel coding residual redundancy

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