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Conference on Visual Communications and Image Processing 2001

作者： van der Schaar, M Radha, H Philips Labs USA Briarcliff Manor NY 10510 USA

ISBN: (纸本)0819439886

Several embedded video coding schemes have been recently developed for multimedia streaming over IP. In particular, Fine-Granular -Scalability, (FGS) video coding has been recently adopted by the MPEG-4 standard as the core video-compression method for streaming applications. From its inception, the FGS scalability, structure was designed to be packet-loss resilient especially under Unequal Packet-loss Protection (UPP). In this paper we introduce the notion of Fine Grained Loss Protection (FGLP), which provides UPP within the FGS enhancement-layer, and we develop an analytical framework for evaluating FGLP bounds. Based on these bounds, we show the impact of applying fine-grained protection to the FGS enhancement-layer for different types of video sequences and over a wide range of bit-rates and packet-loss ratios. Subsequently the FGLP framework has been implemented using forward error correction codes and its performance for Internet video streaming has been evaluated. As illustrated by our extensive simulation results, fine-grained loss protection for the FGS enhancement-layer can provide significant resilience under moderate-to-high packet-loss ratios (e.g. 5-10%).

关键词： Internet video streaming joint source-channel coding unequal error protection Fine Granular Scalability

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Adaptive unequal error protection for subband image coding

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IEEE TRANSACTIONS ON BROADCASTING 2000年第3期46卷 197-205页

作者： Alavi, A Link, R Kallel, S Univ British Columbia Dept Elect & Comp Engn Vancouver BC V6T 1Z4 Canada

An adaptive subband image coding system is proposed to investigate the performance offered by implementing unequal error protection among the subbands and within the subbands, The proposed system uses DPCM and PCM codecs for source encoding the individual subbands, and a family of variable rate channel codes for forward error correction. A low resolution family of trellis coded modulation codes and a high resolution family of punctured convolutional codes are considered. Under the constraints of a fixed information rate, and a fixed transmission bandwidth, for any given image, the proposed system adaptively selects the best combination of channel source coding rates according to the current channel condition. Simulations are performed on the AWGN channel, and comparisons are made with corresponding systems where the source coder is optimized for a noiseless transmission (classical optimization) and a single channel code is selected. Our proposed joint source-channel systems greatly outperform any of the nonadaptive conventional nonjoint systems that use only a single channel code at ail channel SNR's, extending the useful channel SNR range by an amount that depends on the code family. A nonjoint adaptive equal error protection system is considered which uses the classically optimized source codec, but chooses the best single channel code for the whole transmission according to the channel SNR, Our systems outperform the corresponding adaptive equal error protection system by at most 2 dB in PSNR;and more importantly, show a greater robustness to channel mismatch. It is found that most of the performance gain of the proposed systems is obtained from implementation of unequal error protection among the subbands, with at most 0.7 dB in PSNR additional gain achieved by also applying unequal error protection within the subbands, We use and improve a known modeling technique which enables the system to configure itself optimally for the transmission of an arbitrary image,

关键词： subband coding unequal error protection joint source-channel coding trellis coded modulation punctured convolutional codes

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Optimal overcomplete subband expansions for multiple description coding

Optimal overcomplete subband expansions for multiple descrip...

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Conference on Wavelet Applications in Signal and Image Processing VIII

作者： Mehrotra, S Microsoft Corp Redmond WA 98052 USA

ISBN: (纸本)0819437646

We study the use of overcomplete (also known as oversampled) subband expansions for multiple description coding. The system proposed uses an overcomplete subband expansion (a subband expansion in which the number of subbands is larger than the downsampling factor of each subband) followed by independent coding (quantization and coding) of each of the subbands. The entire coding of each of the subbands is entirely contained within a single description. Using analysis in the polyphase domain, we study finding frequency responses of optimal filterbanks and the rate allocation across the subbands to minimize the end-to-end reconstruction error subject to a transmission rate constraint when a distribution over channel states is known. A general analysis of the problem is given and results are shown for a 3 x 2 expansion of a first-order autoregressive process.

关键词： multiple description coding overcomplete subband expansions oversampled subband expansions overcomplete linear expansions frame expansions joint source-channel coding erasure channel coding

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Analysis of video transmission over lossy channels

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2000年第6期18卷 1012-1032页

作者： Stuhlmüller, K Färber, N Link, M Girod, B Univ Erlangen Nurnberg Telecommun Lab D-91058 Erlangen Germany Lucent Technol Nurnberg Germany Stanford Univ Informat Syst Lab Stanford CA 94305 USA

A theoretical analysis of the overall mean squared error (MSE) in hybrid video coding is presented for the case of error prone transmission. Our model covers the complete transmission system including the rate-distortion performance of the video encoder, forward error correction, interleaving, and the effect of error concealment and interframe error propagation at the video decoder. The channel model used is a 2-state Markov model describing burst errors on the symbol level. Reed-Solomon codes are used for forward error correction. Extensive simulation results using an H.263 video codec are provided for verification. Using the model, the optimal tradeoff between INTRA and INTER coding as well as the optimal channel code rate can be determined for given channel parameters by minimizing the expected MSE at the decoder. The main focus of this paper is to show the accuracy of the derived analytical model and its applicability to the analysis and optimization of an entire video transmission system.

关键词： error resilience intra-update joint source-channel coding robust video transmission tradeoff source-channel coding video transmission system model

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Design of channel-optimized vector quantizers in the presence of channel mismatch

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IEEE TRANSACTIONS ON COMMUNICATIONS 2000年第1期48卷 118-124页

作者： Jafarkhani, H Farvardin, N Univ Maryland Dept Elect Engn College Pk MD 20742 USA Univ Maryland Syst Res Inst College Pk MD 20742 USA

We study the design of channel-optimized vector quantizers in the presence of channel mismatch, We show that when the statistics of the channel bit-error rate (BER) are not known, a minimax solution is the one obtained by designing for the worst possible channel. Then, we consider the case when the probability density function of channel BER is known and propose an algorithm that provides a minimum average distortion. Also, by using an estimate of the channel BER at the decoder, we develop a decoder-adaptive scheme that further improves the performance. In all cases, me have limited ourselves to table-lookup decoders, which amount to very small computational complexities. Finally, the utilization of lookup tables at the encoder and the effects of imperfect estimation of channel BER's are considered.

关键词： channel mismatch decoder-adaptive joint source-channel coding lookup tables vector quantization

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Robust vector quantizer design using self-organizing neural networks

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SIGNAL PROCESSING 2000年第7期80卷 1289-1298页

作者： Azami, SBZ Feng, G Ecole Natl Super Telecommun F-75634 Paris 13 France

In this paper we propose a new method to design vector quantizers for noisy channels. Self-organizing neural networks are known for their efficiency in voice and image data compression;we use self-organizing algorithm to create a topological similarity between the input space and the index space. This similarity reduces the effect of channel noise because any single bit error in a transmitted index will be translated to a close codevector in the input space which yields relatively small distortion. For an 8-bit vector quantizer, the proposed system resulted in 4.59 dB spectral distortion in a highly noisy channel while a simple LEG, LEG with splitting and 2-D self-organizing map (SOM) resulted in 5.96, 5.46 and 5.02 dB of distortion, respectively. (C) 2000 Published by Elsevier Science B.V. All rights reserved.

关键词： robust vector quantization self-organizing neural networks competitive learning index assignment hamming distance vocoder joint source-channel coding

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Image processing for multimedia terminals and related architectures

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SIGNAL PROCESSING 2000年第7期80卷 1167-1183页

作者： Macq, B Labeau, F Desset, C Vandendorpe, L Catholic Univ Louvain Commun & Remote Sensing Lab B-1348 Louvain Belgium

The multimedia terminals of tomorrow are seen today as toolboxes containing flexible solutions not only able to compress audio-visual flows, but also to interact with the contents, provide tools for copyright protection, adapt the signal representations to the communication channels, etc. The aim of this paper is to overview a flexible architecture suited for dynamically downloadable environments, discuss briefly new functionalities demanded for image communications and present more deeply a system globally optimized for noisy channels. The description of these three items illustrates the needs for image processing research to integrate in a global approach the communication software design, the new functionalities, among which security and copyright protection are of major importance, and to globally optimize the different codings, e.g. source and channel codings. (C) 2000 Elsevier Science B.V. All rights reserved.

关键词： image processing joint source-channel coding watermarking dynamic downloadable platform

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Variable-length error-correcting codes

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IEE PROCEEDINGS-COMMUNICATIONS 2000年第4期147卷 211-215页

作者： Buttigieg, V Farrell, PG Univ Malta Dept Commun & Comp Engn Msida Malta Univ Lancaster Fac Sci Appl Commun Res Ctr Lancaster LA1 4YR England

Variable-length error-correcting codes, suitable to perform joint source-channel coding, are presented. A maximum likelihood decoding algorithm for these codes is given. Some performance bounds are derived and it is shown that these codes are similar to convolutional codes. The free distance of these codes is defined and it is shown that it is the most important parameter that determines their performance at high E-b/N-o. It is shown that the performance of these codes can be better than a standard cascade of a Huffman code followed by a BCH code with the same code parameters.

关键词： Viterbi decoding variable length codes maximum likelihood decoding joint source-channel coding performance bounds free distance Codes variable-length error-correcting codes error correction codes combined source-channel coding maximum likelihood decoding algorithm modified Viterbi decoding

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joint source and channel decoding of compressed still images

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SIGNAL PROCESSING-IMAGE COMMUNICATION 1999年第3期15卷 217-229页

作者： Xu, W Hagenauer, J Hollmann, J Tech Univ Munich Lehrstuhl Nachrichtentech D-80290 Munich Germany

A joins source-channel decoding approach is described, which utilizes the residual redundancy in the bit stream of a source-coded image by employing a modified APRI-SOVA (a priori soft-output Viterbi algorithm) at the channel decoder. The source coders used are the nonadaptive discrete cosine transform (]DCT) coding and subband coding with Lloyd-Max quantization. The log-likelihood ratio describing the a priori information is linearized. The reliability of the current bit is computed as a proper linear combination of the soft values characterizing statistical dependency of the zeroth order (probability of 1's or 0's) and the first order (bit correlation among neighboring samples). Substantial subjective and objective performance gains can be obtained by using this method. It is demonstrated that especially in a noisy environment, it may be better to keep the residual redundancy in the data and use it at the receiver side in order to achieve a more reliable decoding, rather than to further remove it by using a variable length coding. The trade-off between the allocation of bits for source and channel coding is also addressed. (C) 1999 Elsevier Science B.V. All rights reserved.

关键词： joint source-channel coding DCT coding subband coding soft-output viterbi algorithm

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A family of efficient and channel error resilient wavelet/subband image coders

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 1999年第1期9卷 95-108页

作者： Man, H Kossentini, F Smith, MJT Georgia Inst Technol Sch Elect & Comp Engn Atlanta GA 30332 USA Univ British Columbia Dept Elect & Comp Engn Vancouver BC V6T 1Z4 Canada

We present a new wavelet/subband framework that allows the efficient and effective quantization/coding of subband coefficients in both noiseless and noisy channel environments, Two different models, one based on a zero-tree structure and another based on a quadtree and context-based modeling structure, are introduced for coding the locations of significant subband coefficients. Then, several multistage residual lattice vector quantizers are proposed for the quantization of such coefficients. The proposed framework features relatively simple modeling and quantization/coding structures that produce a bit stream containing two distinct bit sequences, which can then be protected differently according to their importance and channel noise sensitivity levels. The resulting wavelet/subband image coding algorithms provide good tradeoffs between compression performance and resilience to channel errors. In fact, experimental results indicate that for both noiseless and noisy channels, the resulting coders outperform most of the source-channel coders reported in the literature. More importantly, our coders are substantially more robust than all previously reported source-channel coders with respect to varying channel error conditions, This is a desired feature in low-bandwidth wireless applications.

关键词： error resilience image compression joint source-channel coding lattice VQ quadtrees zero trees

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