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The MPEG-4 Part-10 AVC/H.264 standard employs several powerful coding methods to obtain high compression efficiency. To reduce the temporal and spatial redundancy more effectively, motion compensation uses variable block sizes, and directional intra prediction investigates all available coding modes to decide the best one. When the rate-distortion (R-D) optimization technique is used, an encoder finds the coding mode having minimum R-D cost. Due to the large number of combinations of coding modes, the decision process requires extremely high computation. To reduce the complexity, we propose two methods: early SKIP mode decision and selective intra mode decision. In the simulation results, the proposed methods are verified to significantly reduce the entire encoding time by about 60% with only negligible coding loss. Index Terms--Coding mode selection, early SKIP detection, fast algorithm, mode decision, MPEG-4 Part-10 AVC/H.264, selective intra coding.

In this paper, we propose a reversible visible watermarking algorithm to satisfy a new application scenario where the visible watermark serves as a tag or ownership identifier, but can be completely removed to resume the original image data. It includes two procedures: data hiding and visible watermark embedding. In order to losslessly recover both the watermark-covered and nonwatermark-covered image contents at the receiver end, the payload consists of two reconstruction data packets, one for recovering the watermark-covered region, and the other for the nonwatermark-covered region. The data hiding technique reversibly hides the payload in the image region not covered by the visible watermark. To satisfy the requirements of large capacity and high image quality, our hiding technique is based on data compression and uses a payload-adaptive scheme. It further adopts error diffusion for improving subjective image quality and arithmetic compression using a character-based model for increasing computational efficiency. The visible watermark is securely embedded based on a user-key-controlled embedding mechanism. The data hiding and the visible watermark embedding procedures are integrated into a secure watermarking system by a specially designed user key. Index Terms--Data compression, data hiding, lossless watermark, reversible watermarking, visible watermark.

The problem of a posteriori joint detecting and discriminating pulses in a quasiperiodic pulse train is studied. An efficient computing algorithm for the exact solution to this problem is derived and proved for an exact solution to the problem.

Matching pursuit was demonstrated useful especially in low-bit-rate video coding. However, its massive computation required for finding atoms hinders its use from practical application. This paper is to provide a new method that can drastically reduce the computational load without any degradation in performance of matching pursuit. We compare vector norms based on the Schwarz inequality to preclude substantial number of dictionary functions without actually evaluating their inner products in atom search. Experimental results show that the number of inner product calculation is only about 20%-35% of the conventional separability-based fast method. Index Terms--Fast search, low-bit-rate coding, matching pursuit, video coding.

This paper addresses a classification problem in which class definition through training samples or otherwise is provided a priori only for a particular class of interest. Considerable time and effort may be required to label samples necessary for defining all the classes existent in a given data set by collecting ground truth or by other means. Thus, this problem is very important in practice, because one is often interested in identifying samples belonging to only one or a small number of classes. The problem is considered as an unsupervised clustering problem with initially one known cluster. The definition and statistics of the other classes are automatically developed through a weighted unsupervised clustering procedure that keeps the known cluster from losing its identity as the 'class of interest.' Once all the classes are developed, a conventional supervised classifier such as the maximum likelihood classifier is used in the classification. Experimental results with both simulated and real data verify the effectiveness of the proposed method. Index Terms - One-class classifier, partially supervised classifier, significance testing, single hypothesis testing, unsupervised clustering.

This paper proposes a novel blocking artifacts reduction method based on the notion that the blocking artifacts are caused by heavy accuracy loss of transform coefficients in the quantization process. We define the block boundary discontinuity measure as the sum of the squared differences of pixel values along the block boundary. The proposed method compensates for selected transform coefficients so that the resultant image has a minimum block boundary discontinuity. The proposed method does not require a particular transform domain where the compensation should take place; therefore, an appropriate transform domain can be selected at the user's discretion. In the experiments, the scheme is applied to DCT-based compressed images to show its performance. Index Terms - Block boundary discontinuity, blocking artifacts, postprocessing, transform coding.

This paper proposes a simple and efficient realization of letter-box conversion for displaying 16:9 images on a 4:3 screen. Compared to the true 16:9 letter-box display where 4:3 vertical decimation is used, the new method yields 5:3 display aspect ratio (slightly wider than 16:9 in the vertical direction) by using 5:4 vertical decimation, and enables the decimation filter to be implemented exactly and easily without multipliers. An efficient hardware architecture is also shown for implementing the proposed 5:4 decimation; in case of progressive scan, it requires only two m-bit adders and two m-bit 2:1 multiplexers where m is the number of bits (typically 8) per pixel. Experiment shows little visual difference between the proposed letter-box conversion and the true 16:9 display with the 4:3 decimation.

This correspondence proposes a fast Parzen density estimation algorithm that would be especially useful in the nonparametric discriminant analysis problems. By preclustering the data and applying a simple branch and bound procedure to the clusters, significant numbers of data samples that would contribute little to the density estimate can be excluded without detriment to actual evaluation via the kernel functions. This technique is especially helpful in the multivariant case, and does not require a uniform sampling grid. The proposed algorithm may also be used in conjunction with the data reduction technique of Fukunaga and Hayes to further reduce the computational load. Experimental results are presented to verify the effectiveness of this algorithm.