Chung-Chieh Jay Kuo

Moving cast shadow elimination for robust vehicle extraction based on 2D joint vehicle/shadow models

A new algorithm to eliminate moving cast shadow for robust vehicle detection and extraction in a vision-based highway monitoring system is investigated. The proposed algorithm is based on a simplified 2D vehicle/shadow model of six types projected on to a 2D image plane. Parameters of the joint 2D vehicle/shadow models can be estimated from the input video without light source and camera calibration information. Simulations are performed to verify that the proposed technique is effective for vision-based highway surveillance systems.

Robust video transmission over wideband wireless channel using space-time coded OFDM systems

A space-time coded orthogonal frequency-division multiplexed (STC-OFDM) system is proposed to transmit layered video signals over wireless channels. The space-time coding can provide a diversity gain for the multiple-antenna system while OFDM can alleviate the frequency-selective fading effect. An input video sequence is compressed and partitioned into layers with different priorities. Then, an unequal error protection scheme based on the product Reed-Solomon (RS) codes is employed to provide different levels of protection to different layers. At the receiver, a minimum mean square error (MMSE) detector with interference cancellation (IC) is integrated with the space-time decoder to reconstruct the desired signal effectively. We derive an analytic bound for the error probability, and conduct experiments for the transmission of the H.263 video bitstream. It is shown that the proposed scheme enhances the PSNR performance significantly in the environment with a moderate signal-to-noise ratio.

Power control for packet-based wireless communication systems

A power control scheme for packet-based wireless communication systems is proposed in this paper. The proposed power control scheme aims at minimizing the total number of transmissions that a packet needs before it is received successfully over a Rayleigh fading channel subject to two constraints. One is that the transmission power should be greater than zero. The other is imposed by the constraint on the total transmission power at the base station. We use the augmented Lagrangian multiplier method to solve this problem and provide a theoretical solution. The simulation results show that, with the proposed power control scheme, the number of re-transmission can be reduced and the delay of a packet wasted in the channel can be decreased as well.

Pixel- and compressed-domain color matching techniques for video mosaic applications

Several color matching algorithms are proposed to merge two or more video inputs of smaller sizes into one single video output of a larger size with a wider field of view for the video mosaic application. The main challenge is to remove apparent seam lines between image boundaries. All developed algorithms share the same basic idea with different implementation details. That is, color differences between input images are first compensated using either histogram equalization or polynomial-based contrast stretching techniques. Then, a linear filtering technique is adopted to remove seam lines between image boundaries. The algorithms are developed in both the pixel and the DCT domains. The compressed-domain processing is attractive since it reduces the computational complexity. It is shown by experimental results that the color matching problem can be solved satisfactorily even in the compressed domain.

Joint mesh-texture optimization for progressive transmission

Progressive coding of 3D textured graphic models using a joint mesh-texture optimization technique is investigated in this work. The mesh and texture data of a model are first fed into their respective compression modules to result in a series of levels of details. Then, for a given viewpoint, a rate-distortion surface is generated using these mesh and texture data. Afterwards, an optimal path over the rate-distortion surface is determined by the steepest descent algorithm. To achieve progressive transmission, the mesh and texture are transmitted in a certain ratio along the optimal path to provide the best visual quality for the given viewpoint. For further generalization, a layered sampling algorithm is proposed to deal with an arbitrary viewing angle. The performance of the proposed joint mesh-texture progressive coding algorithm is demonstrated by experimental results.

Analysis of multihypothesis motion-compensated prediction for error resilient video transmission

Multi-hypothesis motion compensated prediction (MHMCP) predicts a block from a weighted sum of multiple reference blocks in the frame buffer. By efficiently combining these reference blocks, MHMCP can provide less prediction errors so as to reduce the coding bit rates. Although MHMCP was originally proposed to achieve high coding efficiency, it has been observed recently that MHMCP can also enhance the error resilient property of compressed video. In this work, we investigate the error propagation effect in the MHMCP coder. More specifically, we study how the multi-hypothesis number as well as hypothesis coefficients influence the strength of propagating errors. Simulation results are given to confirm our analysis. Finally, several design principles for the MHMCP coder are derived based on our analysis and simulation results.

Efficient implementation of elliptic curve cryptography (ECC) on embedded media processors

Elliptic curve cryptography (ECC) is an excellent candidate for secure embedded multimedia applications due to its small key size and high security protection. The performance profiling of the ECC implementation, such as execution time and data cache stalls, on TriMedia TM1300 and Intel Pentium 4 is conducted in this research. Based on this study, we identify the main bottlenecks of the EEC implementation, and propose some favorable micro-architecture for this application. Moreover, several integer multiplication schemes are presented for the TM1300 processor for performance enhancement. In particular, the FIR-based multiplication is built with the special FIR instruction provided by TM1300. The performance improvement of the proposed schemes is reported and discussed. Overall, we aim at providing a good understanding of the system architecture of secure embedded multimedia applications, hardware and software cryptography implementation with ECC as an example.

An enhanced fast variable block-size motion estimation scheme for H.264

An enhanced version of the fast inter-prediction mode decision and variable block size motion estimation scheme for the H.264 video encoder is proposed in this work. In particular, we focus on the rate estimation model and thresholds for early termination. They are adaptively updated to enhance the coding speed and the rate-distortion performance. More details about the threshold setting and the mode decision processes are also provided. The improved algorithm can achieve a speed-up factor ranging from 70 to 150 times as compared to the full-search algorithm.

Progressive geometry encoder based on the octree structure

A progressive 3D geometry coding scheme based on the octree structure is proposed in this work, which achieves better coding efficiency than the state-of-the-art geometric codec known as the kd-tree-based codec. Given a 3D mesh, the quantized 3D vertices are first partitioned into an octree structure. The octree is then traversed from the root and gradually to the leaves and, during the traversal, each 3D cell in the tree front is subdivided along three orthogonal directions. For each cell subdivision, the order of subdivision directions is adaptively chosen, the neighborhood-prediction is used and the vertex number distribution is efficiently encoded. The final output bit stream contains relevant information associated with each cell subdivision. It is shown in experimental results that the coding cost is around 15.6 bits per vertex (bpv) for 12-bit coordinate quantization and 5.6 bpv for 8-bit coordinate quantization on average.

Multistage mode decision for intraprediction in H.264 codec

A multistage mode decision method to reduce the complexity of Intra prediction in H.264/JVT is proposed in this work. The rate-distortion optimized (RDO) mode decision is adopted by H.264 to achieve the optimal coding gain at the cost of a very high computational complexity. Our research goal is to reduce the complexity of intra prediction without significant RD performance loss. The proposed fast intra prediction algorithm uses two features, i.e. the sum of absolute residual coefficients (SATD) and the sum of absolute gradients (SAG), and a simplified RDO method to determine the best mode for 4x4 blocks. It incorporates an early termination mechanism at various intermediate decision steps to avoide unnecessary computations when a good decision can be made at an earlier stage. It is demonstrated by experimental results that the proposed scheme performs approximately 10 to 30 times faster than the current RDO mode decision (JM7.3a) with little degradation in the coding gain.