Partial correction of transmission errors in d.p.c.m. without recourse to error correction coding

A method for partially correcting transmission errors in a 1st-order d.p.c.m. system, without recourse to channel coding, is described. A simple detection algorithm based on the statistical properties of a sequence of differences between adjacent samples of a modified decoded sequence is used to identify the erroneous samples. Three different correcting algorithms are described. Substantial improvements in the decoded waveform are achieved, and, for a Markov input process, an error rate of 0.04% in the first and second most significant digits, an improvement in s.n.r. of 7dB is achieved.     

The application of multiwavelet transform to image coding

This work presents a new image coding scheme based on multiwavelet filter banks. First, two dimensional (2-D) multiwavelet decomposition is performed on the original image. Then, several hierarchical trees are constructed in the transform domain, and an extension of set partitioning in hierarchical trees algorithm is proposed to quantize multiwavelet coefficients. Our simulation shows that this scheme is effective and promising.     

Discrete cosine transform in error control coding

The authors define a new class of real-number linear block codes using the discrete cosine transform (DCT). They also show that a subclass with a BCH-like structure can be defined and, therefore, encoding/decoding algorithms for BCH codes can be applied, A (16,10) DCT code is given as an example     

Discrete Hartley transform in error control coding

A new class of real-valued linear code obtained by using the discrete Hartley transform (DHT) is defined. The authors have derived the limitation on the choice of parity frequencies so as to define DHT codes with the cyclic-shift property. Then, by introducing the well-established encoding/decoding algorithm for cyclic codes in error control coding, they have constructed the encoder/decoder for the DHT cyclic codes     

Extended lapped transform in image coding

A modulated lapped transform with extended overlap (ELT) is investigated in image coding with the objective of verifying its potential to replace the discrete cosine transform (DCT) in specific applications. Some of the criteria utilized for the performance comparison are reconstructed image quality (both objective and subjective), reduction of blocking artifacts, robustness against transmission errors, and filtering (for scalability). Also, a fast implementation algorithm for finite-length-signals using symmetric extensions is developed specially for the ELT with overlap factor 2 (ELT-2). This comparison shows that ELT-2 is superior to both DCT and the lapped orthogonal transform (LOT).     

Maximally smooth image recovery in transform coding

The authors consider the reconstruction of images from partial coefficients in block transform coders and its application to packet loss recovery in image transmission over asynchronous transfer mode (ATM) networks. The proposed algorithm uses the smoothness property of common image signals and produces a maximally smooth image among all those with the same coefficients and boundary conditions. It recovers each damaged block by minimizing the intersample variation within the block and across the block boundary. The optimal solution is achievable through two linear transformations, where the transform matrices depend on the loss pattern and can be calculated in advance. The reconstruction of contiguously damaged blocks is accomplished iteratively using the previous solution as the boundary conditions in each new step. This technique is applicable to any unitary block-transform and is effective for recovering the DC and low-frequency coefficients. When applied to still image coders using the discrete cosine transform (DCT), high quality images are reconstructed in the absence of many DC and low-frequency coefficients over spatially adjacent blocks. When the damaged blocks are isolated by block interleaving, satisfactory results have been obtained even when all the coefficients are missing     

High-frequency error concealment in wavelet-based image coding

A new algorithm for high-frequency subband error concealment in wavelet-based picture coding is presented. It is based on a wavelet patch repetition approach: the LBG algorithm, given by Linde et al., is used to generate a codebook of patches and, according to a boundary distance measure, one of these patches is selected to mask the damaged area. Experiments show noteworthy results.     

Predictable sample error detector and a planar prediction corrector for removal of isolated transmission errors in Walsh?Hadamard transformed pictures

An error detection and correction system is described which will correctly detect the amplitude of a sequency error in a transmitted Walsh?Hadamard-transformed picture, provided no more than one error per block occurs. For a head-and-shoulder picture, a planar prediction corrector will then remove any sequency error whose magnitude is ? (10/256) ?, where ? is the quantisation step size.     

Detection and correction of transmission errors in facsimile images

Today, facsimile is recognized as the primary communication tool for both printed and written materials. Most facsimile machines operating on public switched telephone networks use the Group 3 (G3) facsimile compression standards, in which images are entropy-coded. Although the synchronization codeword end of line (EOL) is employed, a transmission error in a codeword may cause the current codeword, the subsequent codewords in the current line, even the codewords in the subsequent lines to be misinterpreted, resulting in a great degradation of the received image. The objective of the proposed error detection and correction approaches is to completely or partially eliminate transmission errors in G3 facsimile images, requiring no extra transmission bit rate and without changing the transmitter and the receiver. The proposed approaches are based on the error checking conditions derived from the relationship between the current line and the previous line as well as the constraints on compressed image data. A corrupted line is detected if any of the error checking conditions is satisfied. When a corrupted line is detected, a sequence of bit inversions and redecoding operations are performed on the current corrupted line and/or its previous lines so that at least one possible (feasible) redecoding solution can be found. Then, the best solution is selected by using some selection criterion. Based on simulation results, the proposed approaches can recover the original or high-quality facsimile images from their corresponding corrupted facsimile images. This shows the feasibility of the proposed approaches     

Forward error correction in DWDM fiber-optic transmission system

In this paper we consider options of antinoise coding application in DWDM fiber-optic transmission systems, and also we represent comparative analysis of predicting correction, defining by G.975.1 recommendation regarding correction possibility and redundancy.     

Analysis of low bit rate image transform coding

Calculations based on high-resolution quantizations prove that the distortion rate D(R¯) of an image transform coding is proportional to 2^-2R when R¯ is large enough. In wavelet and block cosine bases, we show that if R¯<1 bit/pixel, then D(R¯) varies like R¯^1-2γ, where γ remains of the order of 1 for most natural images. The improved performance of embedded codings in wavelet bases is analyzed. At low bit rates, we show that the compression performance of an orthonormal basis depends mostly on its ability to approximate images with a few nonzero vectors     

A new approach to reduce the `blocking effect' of transform coding[image coding]

A combined-transform coding (CTC) scheme to reduce the blocking effect of conventional block transform coding and hence to improve the subjective performance is presented. The scheme is described, and its information-theoretic properties are discussed. Computer simulation results for a chest X-ray image are presented. The CTC scheme, the JPEG baseline scheme, and the conventional discrete Walsh-Hadamard transform (DWHT) are compared to demonstrate the performance improvement for the CTC scheme. The advantages of the CTC scheme include no ringing effect as there is no error propagation across the boundary, no additional computation, and distortion always held within a certain level     

小波变换编码及其在军事图像上的应用

提出了一种军事图像压缩的新方法,在嵌入式零树小波(EZW)算法基础上引入提升方案和整数变换以降低算法复杂度,在编码前对系数按重要性进行排序并对低频区域的系数的符号进行改变.实验结果表明,将该算法用于军事图像压缩无论在主观效果还是在峰值信噪比方面都取得了满意的效果.     

Low bit-rate cloud-based image coding in the wavelet transform domain

The rapid growth of image resources on the Internet makes it possible to find some highly correlated images on some Web sites when people plan to transmit an image over the Internet. This study proposes a low bit-rate cloud-based image coding scheme, which utilizes cloud resources to implement image coding. Multiple- discrete wavelet transform was adopted to decompose the input image into a low-frequency sub-band and several high-frequency sub-bands. The low-frequency sub-band image was used to retrieve highly correlated images (HCOIs) in the cloud. The highly correlated regions in the HCOIs were used to reconstruct the high-frequency sub-bands at the decoder to save bits. The final reconstructed image was generated using multiple inverse wavelet transform from a decompressed low-frequency sub-band and reconstructed high-frequency sub-bands. The experimental results showed that the coding scheme performed well, especially at low bit rates. The peak signal-to-noise ratio of the reconstructed image can gain up to 7 and 1.69 dB over JPEG and JPEG2000 under the same compression ratio, respectively. By utilizing the cloud resources, our coding scheme showed an obvious advantage in terms of visual quality. The details in the image can be well reconstructed compared with both JPEG, JPEG2000, and intracoding of HEVC.     

Interleaved coding and sequential transmission scheme for packet‐level forward error correction over burst loss channels

Burst packet loss is a common problem over wired and wireless networks and leads to a significant reduction in the performance of packet‐level forward error correction (FEC) schemes used to recover packet losses during transmission. Traditional FEC interleaving methods adopt the sequential coding‐interleaved transmission (SCIT) process to encode the FEC packets sequentially and reorder the packet transmission sequence. Consequently, the burst loss effect can be mitigated at the expense of an increased end‐to‐end delay. Alternatively, the reversed interleaving scheme, namely, interleaved coding‐sequential transmission (ICST), performs FEC coding in an interleaved manner and transmits the packets sequentially based on their generation order in the application. In this study, the analytical FEC model is constructed to evaluate the performance of the SCIT and ICST schemes. From the analysis results, it can be observed that the interleaving delay of ICST FEC is reduced by transmitting the source packets immediately as they arrive from the application. Accordingly, an Enhanced ICST scheme is further proposed to trade the saved interleaving time for a greater interleaving capacity, and the corresponding packet loss rate can be minimized under a given delay constraint. The simulation results show that the Enhanced ICST scheme achieves a lower packet loss rate and a higher peak signal‐to‐noise‐ratio than the traditional SCIT and ICST schemes for video streaming applications.     

DGT与DCT在图像编码中的性能比较

介绍了二维实值离散Gabor变换（RDGT）的快速算法,并着重探讨了二维实值离散Gabor变换与二维离散余弦变换在图像编码中的性能及差异。     

Improvement in bandwidth efficiency of asynchronous prime-code CDMAnetworks by error correction coding

Error correction codes can be used to significantly improve the bandwidth efficiency of all-optical asynchronous prime-code CDMA networks. It is shown that using asymmetric error correction (AEC) codes not only greatly improves the bit error rate performance of optical CDMA systems, but also can efficiently increase the number of active users without increasing the complexity of tunable optical CDMA encoders/decoders. Therefore, the use of AEC codes can dramatically reduce the network cost     

视觉测量中可纠错编码点的算法研究

在视觉测量中,经常发生椭圆中心点检测错误从而影响图像的匹配问题,甚至导致三维重建任务的失败。针对该问题,设计了1种可纠错的编码点,将信息论中的信道可纠错编码方法用于编码点的设计,基于汉明线性分组码将编码分为信息元和校验元,设计了生成矩阵和校验矩阵,同时在检测出错误时利用伴随矩阵进行纠错,最后进行译码用于三维匹配。实验表明对于只发生1个位置错误的编码可以自动的进行纠错,验证了算法的可行性。     

Context-based entropy coding of block transform coefficients for image compression

It has been well established that state-of-the-art wavelet image coders outperform block transform image coders in the rate-distortion (R-D) sense by a wide margin. Wavelet-based JPEG2000 is emerging as the new high-performance international standard for still image compression. An often asked question is: how much of the coding improvement is due to the transform and how much is due to the encoding strategy? Current block transform coders such as JPEG suffer from poor context modeling and fail to take full advantage of correlation in both space and frequency sense. This paper presents a simple, fast, and efficient adaptive block transform image coding algorithm based on a combination of prefiltering, postfiltering, and high-order space-frequency context modeling of block transform coefficients. Despite the simplicity constraints, coding results show that the proposed coder achieves competitive R-D performance compared to the best wavelet coders in the literature.