The Experts below are selected from a list of 2190 Experts worldwide ranked by ideXlab platform

Ja-ling Wu - One of the best experts on this subject based on the ideXlab platform.

  • Modified symmetrical reversible variable-length Code and its theoretical bounds
    IEEE Transactions on Information Theory, 2001
    Co-Authors: Chien-wu Tsai, Ja-ling Wu
    Abstract:

    Reversible variable length Codes (RVLCs) have been adopted in emerging video coding standards-H.263+ and MPEG-4-to enhance their error-resilience capabilities (which are important and essential) in error-prone environments. This study proposes an efficient algorithm to construct a symmetrical RVLC from a given Huffman Code. In addition, theoretical bounds on the maximum Codeword length for fixed-length Huffman Codes, and on the optimal average Codeword lengths for sources with exponential distribution are provided.

  • on constructing the Huffman Code based reversible variable length Codes
    IEEE Transactions on Communications, 2001
    Co-Authors: Chien-wu Tsai, Ja-ling Wu
    Abstract:

    In this letter, we propose a generic and efficient algorithm that can construct both asymmetrical and symmetrical reversible variable-length Codes (RVLCs). Starting from a given Huffman Code, the construction is based on two developed Codeword selection mechanisms, for the symmetrical case and the asymmetrical case, respectively; it is shown that the two mechanisms possess simple features and can generate efficient RVLCs easily. In addition, two new asymmetrical RVLCs are constructed and shown to be very efficient for further reducing the coding overheads in MPEG-4 when operating in the reversible decoding mode.

Chien-wu Tsai - One of the best experts on this subject based on the ideXlab platform.

  • Modified symmetrical reversible variable-length Code and its theoretical bounds
    IEEE Transactions on Information Theory, 2001
    Co-Authors: Chien-wu Tsai, Ja-ling Wu
    Abstract:

    Reversible variable length Codes (RVLCs) have been adopted in emerging video coding standards-H.263+ and MPEG-4-to enhance their error-resilience capabilities (which are important and essential) in error-prone environments. This study proposes an efficient algorithm to construct a symmetrical RVLC from a given Huffman Code. In addition, theoretical bounds on the maximum Codeword length for fixed-length Huffman Codes, and on the optimal average Codeword lengths for sources with exponential distribution are provided.

  • on constructing the Huffman Code based reversible variable length Codes
    IEEE Transactions on Communications, 2001
    Co-Authors: Chien-wu Tsai, Ja-ling Wu
    Abstract:

    In this letter, we propose a generic and efficient algorithm that can construct both asymmetrical and symmetrical reversible variable-length Codes (RVLCs). Starting from a given Huffman Code, the construction is based on two developed Codeword selection mechanisms, for the symmetrical case and the asymmetrical case, respectively; it is shown that the two mechanisms possess simple features and can generate efficient RVLCs easily. In addition, two new asymmetrical RVLCs are constructed and shown to be very efficient for further reducing the coding overheads in MPEG-4 when operating in the reversible decoding mode.

Shuchien Huang - One of the best experts on this subject based on the ideXlab platform.

  • Huffman Code strategies to improve mfcvq based reversible data hiding for vq indexes
    Journal of Systems and Software, 2011
    Co-Authors: Chenghsing Yang, Shengchang Wu, Shuchien Huang
    Abstract:

    Data hiding, which embeds secret data into cover media, is one type of technology used to achieve the multimedia security. A reversible data hiding method has the characteristic that the cover media can be completely reconstructed after secret data are extracted. Recently, some reversible data hiding schemes have focused on the vector quantization (VQ)-compressed format. Using the modified fast correlation vector quantization (MFCVQ) concept, Lu et al. proposed a reversible data hiding scheme for VQ-index tables. In this paper, a new MFCVQ-based scheme is proposed. Specifically, our method will enlarge the embedding capacities by embedding multiple bits into a VQ index, thereby reducing the compressed bit rates by applying the Huffman-Code concept and the 0-centered classification. Experimental results indicate that this method has greater pure embedding capacities and fewer compressed bit rates than that of previous MFCVQ-based methods.

Yuhjue Chuang - One of the best experts on this subject based on the ideXlab platform.

  • two algorithms for constructing efficient Huffman Code based reversible variable length Codes
    IEEE Transactions on Communications, 2007
    Co-Authors: Chiawei Lin, Yuhjue Chuang
    Abstract:

    In this paper, Huffman-Code-based reversible variable length Code (RVLC) construction algorithms are studied. We use graph models to represent the prefix, suffix, and Hamming distance relationships among RVLC candidate Code words. The properties of the so-obtained graphs are investigated in detail, based on which we present two efficient RVLC construction algorithms: Algorithm 1 aims at minimizing the average Code word length while Algorithm 2 jointly minimizes the average Code word length and maximizes the error-detection probability at the same time.

Nieves R. Brisaboa - One of the best experts on this subject based on the ideXlab platform.

  • Lightweight natural language text compression
    Information Retrieval, 2007
    Co-Authors: Nieves R. Brisaboa, Antonio Farina, Gonzalo Navarro, José R. Paramá
    Abstract:

    Variants of Huffman Codes where words are taken as the source symbols are currently the most attractive choices to compress natural language text databases. In particular, Tagged Huffman Code by Moura et al. offers fast direct searching on the compressed text and random access capabilities, in exchange for producing around 11% larger compressed files. This work describes End-Tagged Dense Code and ( s , c )-Dense Code, two new semistatic statistical methods for compressing natural language texts. These techniques permit simpler and faster encoding and obtain better compression ratios than Tagged Huffman Code, while maintaining its fast direct search and random access capabilities. We show that Dense Codes improve Tagged Huffman Code compression ratio by about 10%, reaching only 0.6% overhead over the optimal Huffman compression ratio. Being simpler, Dense Codes are generated 45% to 60% faster than Huffman Codes. This makes Dense Codes a very attractive alternative to Huffman Code variants for various reasons: they are simpler to program, faster to build, of almost optimal size, and as fast and easy to search as the best Huffman variants, which are not so close to the optimal size.

  • s c dense coding an optimized compression Code for natural language text databases
    String Processing and Information Retrieval, 2003
    Co-Authors: Nieves R. Brisaboa, Antonio Farina, Gonzalo Navarro, Maria F Esteller
    Abstract:

    This work presents (s,c)-Dense Code, a new method for compressing natural language texts. This technique is a generalization of a previous compression technique called End-Tagged Dense Code that obtains better compression ratio as well as a simpler and faster encoding than Tagged Huffman. At the same time, (s,c)-Dense Code is a prefix Code that maintains the most interesting features of Tagged Huffman Code with respect to direct search on the compressed text. (s,c)-Dense Coding retains all the efficiency and simplicity of Tagged Huffman, and improves its compression ratios.

  • an efficient compression Code for text databases
    European Conference on Information Retrieval, 2003
    Co-Authors: Nieves R. Brisaboa, Gonzalo Navarro, Eva Lorenzo Iglesias, José R. Paramá
    Abstract:

    We present a new compression format for natural language texts, allowing both exact and approximate search without decompression. This new Code -called End-Tagged Dense Code- has some advantages with respect to other compression techniques with similar features such as the Tagged Huffman Code of [Moura et al., ACM TOIS 2000]. Our compression method obtains (i) better compression ratios, (ii) a simpler vocabulary representation, and (iii) a simpler and faster encoding. At the same time, it retains the most interesting features of the method based on the Tagged Huffman Code, i.e., exact search for words and phrases directly on the compressed text using any known sequential pattern matching algorithm, efficient word-based approximate and extended searches without any decoding, and efficient decompression of arbitrary portions of the text. As a side effect, our analytical results give new upper and lower bounds for the redundancy of d-ary Huffman Codes.

  • s c dense coding an optimized compression Code for natural language text databases
    Lecture Notes in Computer Science, 2003
    Co-Authors: Nieves R. Brisaboa, Antonio Farina, Gonzalo Navarro, Maria F Esteller
    Abstract:

    This work presents (s,c)-Dense Code, a new method for compressing natural language texts. This technique is a generalization of a previous compression technique called End-Tagged Dense Code that obtains better compression ratio as well as a simpler and faster encoding than Tagged Huffman. At the same time, (s,c)-Dense Code is a prefix Code that maintains the most interesting features of Tagged Huffman Code with respect to direct search on the compressed text. (s, c)-Dense Coding retains all the efficiency and simplicity of Tagged Huffman, and improves its compression ratios. We formally describe the (s, c)-Dense Code and show how to compute the parameters s and c that optimize the compression for a specific corpus. Our empirical results show that (s, c)-Dense Code improves End-Tagged Dense Code and Tagged Huffman Code, and reaches only 0.5% overhead over plain Huffman Code.