40681921
Design of a memory-scalable wavelet-based image codec
The goal of this research is to develop a high performance image codec to be implemented in a digital signal processor (DSP). This DSP chip has only a small amount of internal memory that is fast enough to keep up with the clock cycle of CPU. A new wavelet image codec called the scalable binary description (S-BiD) codec is proposed to achieve this goal. S-BiD, consists of an external wavelet transform and the block-based quantization scheme. The external wavelet algorithm uses a DWT-specific pre-fetching technique to reduce the impact of large access delay of a bulk storage device. Wavelet coefficients are quantized into a set of interleaved multiple bit-streams that describe the three layers in the quantization hierarchy, i.e. blocks, subbands and coefficients, respectively. The codec can generate good compressed images even when the size of the cache memory is less than 4 Kbyte. With a cache memory of 16 Kbyte, its PSNR performance is comparable with all other codecs while its coding time is the shortest. If more resources are available, its performance will be even better.
28495632
Iterative signal extrapolation algorithms with wavelets
A generalized Papoulis-Gerchberg (PG) algorithm for signal extrapolation based on the wavelet representation has been recently proposed by Xia, Kuo and Zhang. In this research, we first show that the generalized PG algorithm converges to the minimum norm solution when the wavelet bases are semi-orthogonal (or known as the prewavelet). However, the generalized PG algorithm converges slowly in numerical implementation. To accelerate the convergence rate, we formulate the discrete signal extrapolation problem os a two-step process and apply the steepest descent and conjugate gradient methods for its solution. Numerical experiments are given to illustrate the performance of the proposed algorithms.<<ETX>>
9519178
Progressive image indexing and retrieval based on embedded wavelet coding
A complete wavelet-based image storage and indexing system is proposed in this research. The proposed indexing features take account of the color, brightness, texture, frequency, and spatial information of a given query image. All features can be naturally extracted as a byproduct during the image compression. Since coding and indexing are integrated in an unified framework in the proposed system, the database management is greatly simplified. Extensive experimental results are given to demonstrate the retrieval performance of the new approach.
448363
A multiscale error diffusion technique for digital halftoning
A new digital halftoning technique based on multiscale error diffusion is examined. We use an image quadtree to represent the difference image between the input gray-level image and the output halftone image. In iterative algorithm is developed that searches the brightest region of a given image via "maximum intensity guidance" for assigning dots and diffuses the quantization error noncausally at each iteration. To measure the quality of halftone images, we adopt a new criterion based on hierarchical intensity distribution. The proposed method provides very good results both visually and in terms of the hierarchical intensity quality measure.
14807272
Progressive compression of 3D graphic models
A progressive coding method which encodes a 3D graphic model into an embedded bit stream is investigated in this research. The coder first encodes the coarsest resolution of the model, and then includes the finer details gradually. The embedding property allows the decoder to terminate the decoding at an arbitrary position in the compressed bit stream, and a more accurate model can be obtained when more bits are decoded. Numerical experiments are provided to demonstrate the excellent rate distortion performance and progressive compression performance of the new method.
1584599
Embedded coding of 3D graphic models
A progressive compression method which encodes a 3D graphic models into an embedded bit stream is investigated. The coder first encodes the coarsest resolution of the model, and then includes the information of finer details gradually. A rate-distortion model is used in the integration of different types of bit streams into a single embedded bit stream to optimize the overall coding performance. This embedding property can be applied to progressive transmission, multi-resolution editing and level-of-detail control. Numerical experiments are provided to demonstrate the excellent rate-distortion performance of the proposed method.
12709015
Motion-compensated frame interpolation scheme for H.263 codec
A fast block-based motion-compensated frame interpolation (FMCI) scheme was proposed in our previous work. FMCI does not require any motion search in the decoder so that the complexity is low enough to achieve frame rate increase in real time. To further improve the visual quality, we propose two add-on schemes to enhance FMCI in this research. They are the adaptive frame skip (AFS) scheme applied at the encoder and the hybrid frame interpolation (HFI) scheme which incorporates both frame repetition and FMCI at the decoder. By adopting these two add-on features, the enhanced FMCI method is made more robust to allow smooth playback.
12549772
Designing an evaluation method for security user interfaces: lessons from studying secure wireless network configuration
: / 28 Ten or 20 years ago, evaluating security products was not as much of a problem as it is today. Systems were managed by people able—and willing—to master the complexities. However, with the proliferation of personal computing devices and network connectivity in the home, systems are now regularly managed by nonexperts. Each system needs to be secured by each user in each home. Therefore designing effective, unbiased evaluation methods for consumer products is one of the first steps in improving both users’ experiences and their security practices. Evaluating the usability of security is a challenge. A common question evaluators face is: “How do I test whether users will configure and use a product securely?” In this article, we outline problems we encountered in evaluating secure wireless network configuration and examine the assumptions many user study methods make, but which may not hold for security.