In the parallelization for high-throughput applications, the number of independent memory access usually dominates the coding throughput. Moreover, a class of large-girth low-density parity check (LDPC) codes usually has difficulties to realize the parallelization in the decoder. To cope with these obstacles, we propose an efficient code construction to take the number of required parallel decoding unit and the large-girth constraint into considerations at once. First, the parity check matrix would be split into the block-wise structure to fit the parallelization in the decoder. Second, the conversion of the cycle-checking inequalities can transform the girth issue into a linear system. Finally, based on the decomposition of the polyhedral set, the Smith normal form can efficiently solve inequalities of the proposed system. Simulation results show that the proposed code construction can satisfy the requirements of parallelization and high-performance coding with girth g = 12.

With the development of the high‐speed communication channel or high‐capacity storage device, the intersymbol interference (ISI) occurs more frequently in the condensed data. The traditional Bahl – Cocke – Jelineu – Raviv (BCJR) method is capable of solving the two‐dimensional (2D) symbol influence problem with extremely high cost. By analysing the complexity in terms of branch, state and path in the 2D trellis‐based ISI detection, the authors verify that the system complexity is mainly dominated by the window size. To reduce the detection complexity, the conventional simplifications are applied in the 2D strip‐wise ISI detection. In addition, a two‐phase strip‐wise detection is proposed to achieve a lower complexity than that of the conventional simplifications. In this system, the first detector can be realised by a low‐complexity method (like the hard detection or Viterbi algorithm) to provide the mask shrinking with predicted data. After reducing the mask size, the second detector can detect the main portion of ISI by the trellis‐based detection (like BCJR algorithm) with a small mask. Under the similar detection performance, the proposed scheme can achieve more than 91.76% saving in the metric computation compared with the 5 × 3‐window IRCSDFA (iterative row–column soft‐decision feedback algorithm) simplified by the M ‐algorithm with M = 8.

This paper proposes an error concealment technique for video transmission, focusing on motion vector (MV) recovery for both inter- and intra-coded frames, to improve video quality at decoder when video bit stream data incur transmission errors. The proposed algorithm considers slice (i.e., a row of macroblocks (MBs)) errors and uses DP (Dynamic Programming) optimization technique to estimate the lost MVs in a global manner, differing from the traditional Boundary Matching Algorithm (BMA) and others that recover MVs independently for individual MBs in an erroneous slice. We also propose an iterative DP process based on 8 × 8 pixels blocks to resolve finer motions (for 8 × 8, 8 × 16, and 16 × 8 pixels blocks) that will aid in the enhancement of reconstruction quality. Experiment results show that our algorithm outperforms the well-known BMA by up to 7.28 dB and the DMVE and another prior work by Qian by up to 1.0 dB at a packet loss rate of 15%. Subjective evaluation shows that our algorithm is especially promising in preserving line/curve features and motion details.

Among the emerging video coding schemes, the effectual solution for the separate-encoding and joint-decoding architecture is the distributed source coding (DSC). In the DSC-based video system, the side information is available in the Wyner-Ziv (WZ) decoder and video reconstruction. Theoretically, the quality of side information (SI), usually referring to the difference between SI and source, dominates the coding efficiency. In order to improve the coding efficiency of DVC with temporal group of blocks, we proposed three SI generations after analyzing the correlation between the SI and original information. In contrast to the traditional improvement in the DVC decoder, the complexity of SI generator was dramatically reduced in our schemes. Experimental results show that the best method can reduce 0.7% bit-rate with less computation and no codec delay compared to the bi-linear interpolation (BLI) method.

In this paper, a new block-based pixel domain distributed video coding scheme featured with variable block modes is proposed. In addition to intra mode and Wyner-Ziv mode employed in conventional block-based distributed video coding scheme, two supplementary block modes “SKIP mode” and “zero motion mode” are introduced in the proposed scheme to improve the overall coding efficiency, as well as to reduce the decoding complexity. Moreover, the channel coding is performed on macroblcok level to reduce the coding loss due to inserted information in the parity bits. The simulation results show that the proposed scheme outperforms both the conventional frame-based transform-domain and the block-based pixel-domain distributed coding schemes.

In contrast with the traditional video compression system, Distributed Video Coding (DVC) architecture dramatically shifts the complexity from the encoder to the decoder. This low-cost encoding concept can be exploited in the emerging applications, e.g. wireless sensor networks. In order to increase the compression efficiency, improvement of side information generation and refinements of Correlation Noise Model (CNM) are main streams to improve DVC. However, most of these schemes are theoretical and expensive for the decoder. In order to retain low-cost and efficient system, a side information refinement with a practical CNM estimation is proposed. While maintaining the video quality, our proposed mechanism totally improves the system compression efficiency about 18% for the bit-rate with a low complexity decoder.

Quasi-cyclic (QC) low-density parity-check (LDPC) codes have advantages over other types of LDPC codes due to their cyclic shifting property. In this paper, a partially parallel QC-LDPC decoder with efficient memory design is proposed. To improve the memory utilization, the structures of efficient chunk and predictor are realized. The efficient chunk can store parts of check-to-variable messages. This design can effectively reduce the memory requirement. Furthermore, the predictor verifies variable-to-check messages and updates efficient chunks instantly. With less check-to-variable messages and variable-to-check messages stored in the memory, this decoding architecture only deposits few messages in several efficient chunks, such that the cost of memory is less. Eventually, the proposed approach dramatically reduces memory requirement about 65% compared to the traditional method while maintaining the same low-cost.

Implementing a belief propagation (BP) based LDPC decoder requires high degrees of parallelism using many component soft-in soft-output (SISO) decoding units to perform message passing from variable nodes to check nodes or vice versa. An obvious complexity-reduction solution is to serialize the decoding process, i.e., dividing a decoding iteration into several serial sub-iterations in which a sub-iteration performs only part of the complete parallel message-passing operation. The group horizontal shuffled BP (GHSBP) and vertical shuffled BP (GVSBP) algorithms respectively partition the check and variable nodes of the code graph into groups to perform group-by-group message-passing decoding. This paper proposes new techniques to improve three key elements of a GHSBP decoding algorithm, namely, the grouping method, the decoding schedule and the log-likelihood updating formulae. The (check nodes) grouping method and decoding schedule optimize certain design criterion. The new normalized min-sum updating formula with a self-adjustable correction (scaling) factor offers better nonlinear approximation. Numerical performance of new GHSBP algorithms that include part or all three new techniques indicate that the combination of the proposed grouping and decoding schedule yields a faster convergence rate and our modified min-sum algorithm gives performance superior to that of the conventional min-sum and normalized min-sum algorithm and is very close to that of the sum-product algorithm.

We present a novel stochastic decoding algorithm for Reed-Solomon codes. We apply an iterative Monte Carlo based approach called the Cross-Entropy method to produce, in every iteration, a set of random error locator vectors, each indicatesn-kpossible erasure positions within a received word. We associate each error locator vector with a candidate codeword by erasures-only decoding the received word, using the error locator vector to locate the erasures. Each iteration results in a new elite set that contains the bestEcandidate codewords. To increase the search radius and enhance the decoder performance we use the randomly drawn samples to generate what we call virtual received words from which extra candidate codewords and thus candidate elite members can be obtained. The proposed algorithms offer both complexity and performance advantages over some existing algebraic decoding algorithms for high rate RS codes.

Most investigations on the effect of channel memory on the performance of block codes use a two-state Gilbert-Elliott (GE) model to describe the channel behavior. As there are circumstances that the channel of concern can not be properly described by the GE model, there are some recent works on coded performance that characterize the channel behavior by a general finite-state Markov chain. This letter presents a new efficient systematic approach to analyze the performance of block codes in such a hidden Markov channel (HMC). An application example is given to predict codeword error probability performance of an RS-coded system in a channel with memory. Numerical results are also provided to validate our analytic results.

Wyner-Ziv coding has been recognized as the most popular method up to now. For traditional WZC, side information is generated from intra-coded frames for use in the decoding of WZ frames. The unit for intra-coding is a frame and the distance between key-frames is kept constant. In this paper, the unit for intra-coding is a block, and the temporal distance between two consecutive key blocks can varying with time. A block is assigned a mode (WZ or intra-coded), depending on the result of spatio-temporal analysis, and encoded in an alternative manner. This strategy improves the overall coding efficiency, while maintaining a low encoder complexity. The performance gain can achieve up to 6 dB with respect to the traditional pixel-domain WZC.

Robust video coding has attracted increasing attention during the past few years. This paper proposes a joint source channel coding scheme able to resist transmission errors over mixed Internet-wireless channels. It involves motion-compensated oversampled filterbanks (OFBs). The redundancy introduced by the overcomplete representation in signals at the output of OFBs is employed for error correction of the motion compensated frames. The errors may be due to the wireless part of the channel (random noise), but also to the Internet part (packet losses). The performance of the proposed approach is illustrated for compressed streams transmitted through a packet erasure channel with an averaged packet loss of 6.25% followed by a binary symmetric channel with a crossover probability of 10-2

Many source coding standards (JPEG, H263+, H264), rely heavily on entropy coding with variable-length codes (VLC). However, bitstreams made of VLC-encoded data are particularly sensitive to transmission errors. Recent results tend to use knowledge of the VLC structure in order to perform an efficient decoding of the bitstream. These techniques use a trellis describing the structure of the VLC codebook and assume that some a priori information is available at decoder side. Significant improvements, compared with prefix decoding of bitstreams are achieved. However, the complexity of these techniques may become intractable when realistic VLC codebooks are considered. This paper presents an algorithm for compacting VLC tables. The codewords are grouped into a minimum number of classes. Decoding algorithms may then work on a reduced number of classes, instead of working on the whole set of codewords. A proof of optimality is provided for the VLC table-compaction algorithm. The algorithm is applied to the H263+ VLC codebook and merges the 204 codewords into 25 classes. The resulting compact tables are shown to be exactly equivalent to the initial ones when used with hard decoding algorithms. The properties of the associated soft decoding algorithms using these compact tables are also evaluated.

The soft decoding of variable-length encoded texture data generated, e.g., by video coders such as H.263+ and sent over a packetized network (Internet or mixed Internet radio-mobile) is considered here. Existing soft decoding techniques usually make use of either the number of bits in a block or the number of symbols in a block. Thus, this side information has to be transmitted. This paper describes an algorithm making use only of information available in the packetized bitstream, and is thus compatible with existing standards. Simulations illustrating the efficiency of the proposed decoding procedure are provided.

Transmitting video streams on channels impaired with transmission errors is a very demanding task, mainly when images are predicted from previous ones. In this case, errors on motion vectors can be very harmful. In order to overcome this problem, this paper presents a modified H263+ scheme without motion vector transmission. This is obtained by reestimating these motion vectors at the receiver, based on properties of frame expansions. This procedure is obtained at the cost of an increased bit rate, but shows that robust (and efficient) transmission can indeed be obtained in conjunction with image prediction.

With the increasing use of multimedia technologies, video coding requires higher performance as well as new features. To address this need, the latest ITU-T video coding standard, H.264, has been developed. The motion compensation algorithm is the key of the improvements over H.263+. This paper proposes an H.264-based algorithm which does not require the motion vectors to be transmitted. It extends previous results obtained in the H.263+ context. The main purpose of this work is to check whether our procedure of reestimating the motion vectors at the receiver is compatible with the initial H.264 scheme efficiency. It is shown that this property is obtained at some cost in terms of bit rate for comparable PSNR, but that our new H.264-based scheme has about the same performance level as the plain H.263+ coder. This is essentially a preliminary work, which shows that the most sensitive part or the bit stream can be removed, thus allowing new robust coders to be developed.