Yuh-Ming Huang

A refined fast 2-D discrete cosine transform algorithm

An index permutation-based fast two-dimensional discrete cosine transform (2-D DCT) algorithm is presented. It is shown that the N/spl times/N 2-D DCT, where N=2/sup m/, can be computed using only N 1-D DCTs and some post additions.

AN EFFICIENT JPEG TO MPEG-11 TRANSCODING ALGORITHM

From the view points of media editing, it is desired that pictures in an video sequence could be coded in a picture-by-picture sense. But, in order to increase the compression ratio, the temporal correlation among pictures must be taken into account. Instead of using JPEG or MPEG alone, a transform-domain transcoding approach is proposed to achieve the above goal. Based on the proposed transcoding algorithm, a low-cost and low-bit-rate editing system, which produces MPEG-1 decodable bitstreams, has been constructed.

An A*-Based Algorithm for Constructing Reversible Variable Length Codes with Minimum Average Codeword Length

Variable length codes (VLCs) are widely adopted in many compression standards due to their good coding efficiency on average codeword length. However, an inherent problem with a VLC is that an error of even one bit can cause serious error propagation and thus loss of synchronization at the receiver, which would lead to a series of non-correctly decoded symbols. Reversible variable length codes (RVLCs) were introduced to significantly mitigate this phenomenon. In this work, a method to find an optimal RVLC in terms of the minimum average codeword length is first formulated as a tree-searching problem, and then, instead of performing an exhaustive search, an A*-based construction algorithm is proposed to find an optimal RVLC. The proposed algorithm has been applied to several benchmarks for sources and has found respective optimal symmetric and asymmetric RVLCs.

A refined fast 2-D discrete cosine transform algorithm with regular butterfly structure

A fast computation algorithm for the two-dimensional discrete cosine transform (2-D DCT) is derived based on index permutation. As a result, only the computation of N N-point 1-D DCTs and some post-additions are required for the computation of an (N/spl times/N)-point 2-D DCT. Furthermore, as compared with the method of Cho and Lee (1992), the derivation of the refined algorithm is more succinct, and the associated post-addition stage possesses a more regular butterfly structure. The regular structure of the proposed algorithm makes it more suitable for VLSI and parallel implementations.

Two improved data hiding schemes

The meaning of data (information) hiding is to embed the secret information into a cover host, such as an image. Usually, the naked eye of the people cannot perceive any change when the image is modified slightly. The evaluation of data hiding schemes should be measured by the distortion (or called Mean Square Error; MSE) and the embedding rate (the average number of bits embedded in a cover pixel). In this paper, we propose two improved data hiding schemes. One is to improve the EMD (Exploiting Modification Direction)-based data hiding algorithm to have higher stego-image quality. The other is to improve the Matrix encoding-based data hiding algorithm by using the idea of Hamming+1 to further improve the stego-image quality. Both proposed improved schemes are verified to be correct through the theoretical analysis and the experiment.

Soft-decision priority-first decoding algorithms for variable-length error-correcting codes

Joint source-channel decoding has recently received extensive attention due to the rise in the applications of multimedia wireless communication. Based on a code trellis rather than on a code tree, this work presents a maximum a posteriori (MAP) soft-decision priority-first decoding algorithm and its approximations for variable-length error-correcting codes. Simulation results indicate that for the code with average codeword length 6.269 bits and free distance 3, under moderate signal-to-noise ratio, one of the proposed algorithms almost reaches the lowest decoding complexity, and has nearly the same performance on symbol error probability as the MAP decoding.

Shortest synchronizing codewords of a binary Huffman equivalent code

The inherent problem of a variable-length code is that even a single bit error can cause loss of synchronization and may lead to error propagation. Synchronizing codewords have been extensively studies as a mean to overcome the drawback and efficiently stop error propagation. First we prove the restatement of a result originally given by B. Ruder (1971) in a more straightforward way. Next, we present the necessary conditions for the existence of a binary Huffman equivalent code with shortest synchronizing codeword(s). Finally, with the help of derived conditional equations, a unified approach for constructing a binary Huffman equivalent code with most shortest synchronizing codeword(s) and most other synchronizing codewords is proposed also.

A novel modularized fast polynomial transform algorithm for two-dimensional convolutions

Abstract This paper presents a novel modularized fast polynomial transform (FPT) algorithm for computing two-dimensional (2-D) convolutions. In this new method, only FPTs, FFTs or NTTs of the same length are required. As a result, the modularity and regularity of the proposed algorithm makes it suitable for a concurrent implementation of the 2-D convolver.

Two-variable modularized fast polynomial transform algorithm for 2-D discrete Fourier transforms

A novel two-variable modularized fast polynomial transform (FPT) algorithm is presented. In this method, only fast polynomial transforms and fast Fourier transforms of the same length are required. The modularity, regularity, and easy extensibility of the proposed algorithm make it of great practical value in computing multidimensional discrete Fourier transforms (DFTs). >

An H.263-compatible Video Coder With Content-based Bit-rate Control

For very low bit-rate video coding applications, the ITU-T H.263 coding scheme has been adopted as the video coding kernel of the ITU- T H.324 niultimedia communication standard. In this paper, an H.263-compatible video coder with a content-based bit-rate control scheme is proposed. It is shown by simulation results that the proposed coder outperforms the traditional H.263 coder.