Search

In general, an inevitable side effect of the block-based transform coding includes grid noise in the monotone area, staircase noise along the edges, ringing around the strong edges, corner outliers, and edge corruption near the block boundaries. We propose a comprehensive postprocessing method for removing all the blocking-related artifacts in block-based discrete cosine transfer compressed image in the framework of overcomplete wavelet expansion (OWE) proposed by Mallat and Zhong [IEEE Trans. Pattern Anal. Mach. Intell 14(7), 710–732 (1992)], which is translationally invariant and can efficiently characterize signal singularities. We propose to use the wavelet transform modulus maxima extension (WTMME) to represent the image. The WTMME is extracted from the wavelet coefficients of three-level OWE of the blocky image. The artifacts related to blockiness are modeled and detected through multiscale edge analysis of the image using the information of both modulus and angle. Both the WTMME and the angle image are reconstructed accordingly using inter-/intraband correlation to suppress the influence of the distortions. Finally, the inverse OWE transform is performed for the processed image. Because the algorithm takes no assumption that the blockiness occurs at block boundaries, it is also applicable to video, where due to motion estimation and compensation, the grid noise may propagate into blocks. Extensive simulation and comparative study with 21 exiting relevant algorithms have demonstrated the effectiveness of the proposed algorithm in terms of subjective and objective quality of the resultant images. [ABSTRACT FROM AUTHOR]

Transmit diversity can be applied to OFDM systems by adopting space time code. Since the received signal is the overlapped signals transmitted from different transmit antennas, channel estimation is a rather challenging task for space time coded OFDM (ST-OFDM) systems. Pilot structure can help the receiver to effectively separate the overlapped signals and perform accurate channel estimation. In this paper, we propose three different channel estimation algorithms based on specially designed comb type pilots inserted in frequency domain. One of our proposed algorithms is performed in frequency domain and the other two are performed in time domain. Such comb type pilot based algorithms can provide higher bandwidth efficiency than common significant-tap-catching algorithm using training block pilots. Numerical analyzes and computational simulation show that our proposed estimation schemes have the same good performance while the time domain methods have relatively simple structure. [ABSTRACT FROM AUTHOR]

Fade and dissolve transitions are two of the most frequently used special effects in video non-linear editing (NLE). In this paper, we propose an adaptive motion vector re-sampling (AMVR) algorithm to achieve fast fade and dissolve transitions on MPEG video sequences. Experimental results show that our algorithm greatly reduces the computational complexity while keeping the quality of the reconstructed edited video in comparison with conventional motion vector re-sampling (MVR) algorithms. [ABSTRACT FROM AUTHOR]

A channel estimation method based on frequency-domain pilots and time-domain processing (FPTP) is proposed for OFDM systems in time-varying channels. Through Discrete Fourier Transform (DFT), the channel impulse response (CIR) is estimated by using the frequency-domain pilots, which is equivalent to the CIR estimated by cyclic correlation using time-domain pilot sequence. Hence, the channel estimation error, caused by the spectral leakage of the DFT, can be reduced by canceling the non-idea auto-correlation property of the pilot sequence in time-domain. At the same time, the complicated cyclic correlation computation in time-domain is evitable. The theoretical analysis and simulation results show that the proposed method outperforms the traditional DFT-based method and Wiener filter algorithm in time-varying multi-path fading channels. Moreover, the uncoded bit error rate (BER) performance of proposed algorithm is very close to that with perfect channel knowledge, especially in fast fading channels. [ABSTRACT FROM AUTHOR]

Presents a temporal compensated motion estimation algorithm using simple block based prediction. Use of three candidate vectors per block by the simple block-based prediction due to spatial temporal correlation; Reduction of computational complexity; Acceleration of the algorithm convergence for the global motion field; Performance superiority of the temporal compensated simple block-based prediction algorithm.

Irreversible electroporation (IRE), a relatively new energy-based tumor ablation technology, has shown itself in the last decade to be able to safely ablate tumors with favorable clinical outcomes, yet little work has been done on optimizing the IRE protocol to variously sized tumors. Incomplete tumor ablation has been shown to be the main reason leading to the local recurrence and thus treatment failure. The goal of this study was to develop a general optimization approach to optimize the IRE protocol for cervical tumors in different sizes, while minimizing the damage to normal tissues. This kind of approach can lay a foundation for future personalized treatment of IRE. First, a statistical IRE cervical tumor death model was built using previous data in our group. Then, a multi-objective optimization problem model was built, in which the decision variables are five IRE-setting parameters, namely, the pulse strength (U), the length of active tip (H), the number of pulses delivered in one round between a pair of electrodes (A), the distance between electrodes (D), and the number of electrodes (N). The domains of the decision variables were determined based on the clinical experience. Finally, the problem model was solved by using nondominated sorting genetic algorithms II (NSGA-II) algorithm to give respective optimal protocol for three sizes of cervical tumors. Every protocol was assessed by the evaluation criterion established in the study to show the efficacy in a more straightforward way. The results of the study demonstrate this approach can theoretically provide the optimal IRE protocol for different sizes of tumors and may be generalizable to other types, sizes, and locations of tumors. [ABSTRACT FROM AUTHOR]

Almost all existing color demosaicking algorithms for digital cameras are designed on the assumption of high correlation between red, green, blue (or some other primary color) bands. They exploit spectral correlations between the primary color bands to interpolate the missing color samples, but in areas of no or weak spectral correlations, these algorithms are prone to large interpolation errors. Such demosaicking errors are visually objectionable because they tend to correlate with object boundaries and edges. This paper proposes a remedy to the above problem that has long been overlooked in the literature. The main contribution of this work is a hybrid demosaicking approach that supplements an existing color demosaicking algorithm by combining its results with those of adaptive intraband interpolation. This is formulated as an optimal data fusion problem, and two solutions are proposed: one is based on linear minimum mean-square estimation and the other based on support vector regression. Experimental results demonstrate that the new hybrid approach is more robust and eliminates the worst type of color artifacts of existing color demosaicking methods. [ABSTRACT FROM AUTHOR]

In this paper we present a Base-matrix based decoder architecture for multi-rate QC-LDPC codes proposed in broadband broadcasting system. We use the Modified Min-Sum Algorithm (MMSA) as the decoding algorithm in this architecture, which lowers the complexity of the LDPC decoder while keeping almost the same performance or even better. Based on this algorithm, we designed a novel check node processing unit to reduce the complexity of the decoder and facilitate the multiplex of the processing units. The decoder designed with hardware constraints is not only scalable in throughput, but also easily configurable to support different QC-LDPC codes flexible in code rate and code length. [ABSTRACT FROM AUTHOR]

Images are often coded using block-based discrete cosine transform (DCT), where blocking and ringing artifacts are the most common visual distortion. In this letter, a fast algorithm is proposed to alleviate the said artifacts in the DCT domain. The new concept is to decompose a row or column image vector to a gradually changed signal and a fast variational signal, which correspond to low-frequency (LF) and high-frequency (HF) DCT subbands, respectively. Blocking artifacts between adjacent LF blocks are suppressed by smoothing LF components and discarding invalid HF ones, and ringing artifacts inside HF vectors are reduced by a simplified bilateral filter. With such a process, edges are preserved while blockiness and ringing are alleviated. Analytic and experimental results confirm the robustness and computational efficiency of the proposed method. [ABSTRACT FROM AUTHOR]