Hsueh-Ming Hang

A feature-based robust digital image watermarking scheme

A robust digital image watermarking scheme that combines image feature extraction and image normalization is proposed. The goal is to resist both geometric distortion and signal processing attacks. We adopt a feature extraction method called Mexican hat wavelet scale interaction. The extracted feature points can survive a variety of attacks and be used as reference points for both watermark embedding and detection. The normalized image of an image (object) is nearly invariant with respect to rotations. As a result, the watermark detection task can be much simplified when it is applied to the normalized image. However, because image normalization is sensitive to image local variation, we apply image normalization to nonoverlapped image disks separately. The disks are centered at the extracted feature points. Several copies of a 16-bit watermark sequence are embedded in the original image to improve the robustness of watermarks. Simulation results show that our scheme can survive low-quality JPEG compression, color reduction, sharpening, Gaussian filtering, median filtering, row or column removal, shearing, rotation, local warping, cropping, and linear geometric transformations.

Source model for transform video coder and its application. I. Fundamental theory

A source model describing the relationship between bits, distortion, and quantization step sizes of a large class of block-transform video coders is proposed. This model is initially derived from the rate-distortion theory and then modified to match the practical coders and real image data. The realistic constraints such as quantizer dead-zone and threshold coefficient selection are included in our formulation. The most attractive feature of this model is its simplicity in its final form. It enables us to predict the bits needed to encode a picture at a given distortion or to predict the quantization step size at a given bit rate. There are two aspects of our contribution: one, we extend the existing results of rate-distortion theory to the practical video coders, and two, the nonideal factors in real signals and systems are identified, and their mathematical expressions are derived from empirical data. One application of this model, as shown in the second part of this paper, is the buffer/quantizer control on a CCITT P/spl times/64 k coder with the advantage that the picture quality is nearly constant over the entire picture sequence.

An efficient block-matching algorithm for motion-compensated coding

We present an efficient search technique which minimizes the computations necessary for estimating the motion in video-sequences by the block matching method. We also discuss the theoretical basis for conducting such a reduced search by our technique. We then present two algorithms which employ the proposed technique for estimating the motion typical of video-conferencing environment. Next, the results of computer simulations on a real video-sequence are included which demonstrate the effectiveness of the proposed technique. Finally, the results of a study of statistical properties of block motion-compensated frame difference signals are also summarized, to assist in future choice of a coding strategy for such signals.

Predictive Vector Quantization of Images

The purpose of this paper is to present new image coding schemes based on a predictive vector quantization (PVQ) approach. The predictive part of the encoder is used to partially remove redundancy, and the VQ part further removes the residual redundancy and selects good quantization levels for the global waveform. Two implementations of this coding approach have been devised, namely, sliding block PVQ and block tree PVQ. Simulations on real images show significant improvement over the conventional DPCM and tree codes using these new techniques. The strong robustness property of these coding schemes is also experimentally demonstrated.

A comparison of block-matching algorithms mapped to systolic-array implementation

This paper presents an evaluation of several well-known block-matching motion estimation algorithms from a system-level very large scale integration (VLSI) design viewpoint. Because a straightforward block-matching algorithm (BMA) demands a very large amount of computing power, many fast algorithms have been developed. However, these fast algorithms are often designed to merely reduce arithmetic operations without considering their overall performance in VLSI implementation. Three criteria are used to compare various block-matching algorithms: (1) silicon area, (2) input/output requirement, and (3) image quality. A basic systolic array architecture is chosen to implement all the selected algorithms. The purpose of this study is to compare these representative BMAs using the aforementioned criteria. The advantages/disadvantages of these algorithms in terms of their hardware tradeoff are discussed. The methodology and results presented provide useful guidelines to system designers in selecting a BMA for VLSI implementation.

Interpolative vector quantization of color images

Interpolative vector quantization has been devised to alleviate the visible block structure of coded images plus the sensitive codebook problems produced by a simple vector quantizer. In addition, the problem of selecting color components for color picture vector quantization is discussed. Computer simulations demonstrate the success of this coding technique for color image compression at approximately 0.3 b/pel. Some background information on vector quantization is provided. >

Advances in the scalable amendment of H.264/AVC

To support clients with diverse capabilities, ISO/IEC MPEG and ITU-T form a joint video team (JVT) to develop a scalable video coding (SVC) technology that uses single bitstream to provide multiple spatial, temporal, and quality (SNR) resolutions, thus satisfying low-complexity and low-delay constraints. It is an amendment of the emerging standard H.264/AVC and it provides an H.264/AVC-compatible base layer and a fully scalable enhancement layer, which can be truncated and extracted on-the-fly to obtain a preferred spatio-temporal and quality resolution. An overview of the adopted key technologies in the SVC and a comparison in coding efficiency with H.264/AVC are presented

Layered access control schemes on watermarked scalable media

Intellectual Property (IP) protection is a critical element in multimedia transmission and delivery systems. Conventional IP protection on multimedia data can be categorized into encryption and watermarking. In this paper, a structure to perform layered access control on scalable media by combining encryption and robust watermarking is proposed, implemented, and verified. By taking advantages of the nature of both encryption and watermarking, copyrights of multimedia contents can be well protected and at the same time, multiple-grade services can be provided. In the summated examples, we assume a scalable transmission scheme over the broadcasting environment and use it to test the effectiveness of proposed method. When the embedded watermark is extracted with high confidence, the key to decrypt the next layer can be perfectly recovered. Then, the media contents are reconstructed and the copyrights are assured. The application examples also demonstrate the practicality of the proposed system.

H.264/AVC motion estimation implmentation on Compute Unified Device Architecture (CUDA)

Due to the rapid growth of graphics processing unit (GPU) processing capability, using GPU as a coprocessor to assist the central processing unit (CPU) in computing massive data becomes essential. In this paper, we present an efficient block-level parallel algorithm for the variable block size motion estimation (ME) in H.264/AVC with fractional pixel refinement on a computer unified device architecture (CUDA) platform, developed by NVIDIA in 2007. The CUDA enhances the programmability and flexibility for general-purpose computation on GPU. We decompose the H.264 ME algorithm into 5 steps so that we can achieve highly parallel computation with low external memory transfer rate. Experimental results show that, with the assistance of GPU, the processing time is 12 times faster than that of using CPU only.

Fast mode decision algorithm for Residual Quadtree coding in HEVC

High Efficiency Video Coding (HEVC) is an in-progress next generation video coding standard. It has a similar basic structure to the ITU/MPEG H.264/AVC coder but with further enhancement on each coding tool to increase compression efficiency. Thus, a Residual Quadtree (RQT) coding scheme is adopted in the conventional transform coding procedure. The cost is the additional computation complexity when compared to the fixed-size transform. In this paper, we design a fast algorithm for Residual Quadtree mode decision. Considering the Rate-Distortion efficiency, we replace the original depth-first mode decision process by a Merge-and-Split decision process. Furthermore, because a substantial numbers of zero-blocks are produced after quantization and mode decision, we reduce the unnecessary computation by using the inheritance property of zero-blocks. In addition, for nonzero-blocks, two early termination schemes are developed for both TU Merge and TU Split procedures, respectively. Comparing to HM 2.0, our method saves the RQT encoding time from 42% to 55% for a number of test videos with negligible coding loss.