Vector Quantisation

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E.a.b. Da Silva - One of the best experts on this subject based on the ideXlab platform.

  • convergent algorithms for successive approximation Vector Quantisation with applications to wavelet image compression
    IEE Proceedings - Vision Image and Signal Processing, 1999
    Co-Authors: Marcos Craizer, E.a.b. Da Silva, E.g. Ramos
    Abstract:

    Embedded wavelet coders have become very popular in image compression applications, owing to their simplicity and high coding efficiency. Most of them incorporate some form of successive approximation scalar Quantisation. Recently developed algorithms for successive approximation Vector Quantisation have been shown to be capable of outperforming successive approximation scalar Quantisation ones. In the paper, some algorithms for successive approximation Vector Quantisation are analysed. Results that were previously known only on an experimental basis are derived analytically. An improved algorithm is also developed and is proved to be convergent. These algorithms are applied to the coding of wavelet coefficients of images. Experimental results show that the improved algorithm is more stable in a rate/spl times/distortion sense, while maintaining coding performances compatible with the state-of-the-art.

  • Results on successive approximation Vector Quantisation
    Electronics Letters, 1998
    Co-Authors: Marcos Craizer, E.a.b. Da Silva, E.g. Ramos
    Abstract:

    Successive approximation Vector Quantisation is a new algorithm that has given very good results in coding wavelet coefficients of images. Results which had been previously obtained on an experimental basis are established analytically. After modifications derived from this analysis, the algorithm shows very good convergence properties, as well as an improved coding performance.

  • low bit rate video coding using wavelet Vector Quantisation
    IEE Proceedings - Vision Image and Signal Processing, 1995
    Co-Authors: Demetrios G Sampson, E.a.b. Da Silva, M Ghanbari
    Abstract:

    A method for low bit-rate video coding based on wavelet Vector Quantisation is proposed. Motion estimation/compensation using overlapped block matching (OBM) is employed to eliminate the blocking effects in the prediction error introduced by conventional block matching. It is shown that OBM significantly increases the efficiency of the wavelet transform coder. The motion-compensated interframe prediction error is decomposed using a wavelet transform and a method is employed for the efficient coding of the wavelet coefficients. In this technique, the coefficients are coded with a zero-tree multistage lattice Vector quantiser. Simulation results are provided to evaluate the coding performance of the described coding scheme for low bit-rate video coding. It provides constant bit rate, obviating the need for buffer, with just small fluctuations in PSNR. Moreover, comparison with the RM8 implementation of the standard H261 video coder shows that the presented codec provides improvements in both peak signal-to-noise ratio and picture quality.

  • wavelet Vector Quantisation scheme for image sequence coding at 64 kbit s
    Electronics Letters, 1995
    Co-Authors: Demetrios G Sampson, E.a.b. Da Silva, M Ghanbari
    Abstract:

    A new method for low bit rate video coding based on overlapped block matching and successive approximation wavelet Vector Quantisation is described. The main advantage of this scheme is that the most important data of the motion compensated interframe prediction error image are given priority coding, resulting in excellent coding performance. Simulation results show that at 64kbit/s, the proposed method outperforms the RM8 implementation of H.261 by 2-3 dB.

  • wavelet transform image coding using lattice Vector Quantisation
    Electronics Letters, 1994
    Co-Authors: Demetrios G Sampson, E.a.b. Da Silva, M Ghanbari
    Abstract:

    A novel method for the efficient coding of image wavelet coefficients using zerotree multistage lattice Vector Quantisation is presented. This method achieves high compression ratios with good picture quality, maintaining a very simple implementation. Simulation results demonstrate that the coding performance of this algorithm favourably compares to some of the best reported image compression results.

J.t.h. Chung-how - One of the best experts on this subject based on the ideXlab platform.

  • Robust image and video coding with pyramid Vector Quantisation
    1999 IEEE International Symposium on Circuits and Systems (ISCAS), 1999
    Co-Authors: J.t.h. Chung-how
    Abstract:

    Most current image and video coding standards use variable length codes to achieve compression, which renders the compressed bitstream very sensitive to channel errors. In this paper, image and video coders based on Pyramid Vector Quantisation (PVQ) and using only fixed length codes are proposed. Still image coders using PVQ in conjunction with DCT and wavelet techniques are described and their robustness to random channel errors are investigated. This work is then extended to video coding. A novel fixed rate motion compensated wavelet/PVQ video coder suitable for low bit-rate applications and generating only fixed length codewords is presented. Its compression performance and robustness to random bit errors is compared with H.263.

E.g. Ramos - One of the best experts on this subject based on the ideXlab platform.

  • convergent algorithms for successive approximation Vector Quantisation with applications to wavelet image compression
    IEE Proceedings - Vision Image and Signal Processing, 1999
    Co-Authors: Marcos Craizer, E.a.b. Da Silva, E.g. Ramos
    Abstract:

    Embedded wavelet coders have become very popular in image compression applications, owing to their simplicity and high coding efficiency. Most of them incorporate some form of successive approximation scalar Quantisation. Recently developed algorithms for successive approximation Vector Quantisation have been shown to be capable of outperforming successive approximation scalar Quantisation ones. In the paper, some algorithms for successive approximation Vector Quantisation are analysed. Results that were previously known only on an experimental basis are derived analytically. An improved algorithm is also developed and is proved to be convergent. These algorithms are applied to the coding of wavelet coefficients of images. Experimental results show that the improved algorithm is more stable in a rate/spl times/distortion sense, while maintaining coding performances compatible with the state-of-the-art.

  • Results on successive approximation Vector Quantisation
    Electronics Letters, 1998
    Co-Authors: Marcos Craizer, E.a.b. Da Silva, E.g. Ramos
    Abstract:

    Successive approximation Vector Quantisation is a new algorithm that has given very good results in coding wavelet coefficients of images. Results which had been previously obtained on an experimental basis are established analytically. After modifications derived from this analysis, the algorithm shows very good convergence properties, as well as an improved coding performance.

M Ghanbari - One of the best experts on this subject based on the ideXlab platform.

  • low bit rate video coding using wavelet Vector Quantisation
    IEE Proceedings - Vision Image and Signal Processing, 1995
    Co-Authors: Demetrios G Sampson, E.a.b. Da Silva, M Ghanbari
    Abstract:

    A method for low bit-rate video coding based on wavelet Vector Quantisation is proposed. Motion estimation/compensation using overlapped block matching (OBM) is employed to eliminate the blocking effects in the prediction error introduced by conventional block matching. It is shown that OBM significantly increases the efficiency of the wavelet transform coder. The motion-compensated interframe prediction error is decomposed using a wavelet transform and a method is employed for the efficient coding of the wavelet coefficients. In this technique, the coefficients are coded with a zero-tree multistage lattice Vector quantiser. Simulation results are provided to evaluate the coding performance of the described coding scheme for low bit-rate video coding. It provides constant bit rate, obviating the need for buffer, with just small fluctuations in PSNR. Moreover, comparison with the RM8 implementation of the standard H261 video coder shows that the presented codec provides improvements in both peak signal-to-noise ratio and picture quality.

  • wavelet Vector Quantisation scheme for image sequence coding at 64 kbit s
    Electronics Letters, 1995
    Co-Authors: Demetrios G Sampson, E.a.b. Da Silva, M Ghanbari
    Abstract:

    A new method for low bit rate video coding based on overlapped block matching and successive approximation wavelet Vector Quantisation is described. The main advantage of this scheme is that the most important data of the motion compensated interframe prediction error image are given priority coding, resulting in excellent coding performance. Simulation results show that at 64kbit/s, the proposed method outperforms the RM8 implementation of H.261 by 2-3 dB.

  • wavelet transform image coding using lattice Vector Quantisation
    Electronics Letters, 1994
    Co-Authors: Demetrios G Sampson, E.a.b. Da Silva, M Ghanbari
    Abstract:

    A novel method for the efficient coding of image wavelet coefficients using zerotree multistage lattice Vector Quantisation is presented. This method achieves high compression ratios with good picture quality, maintaining a very simple implementation. Simulation results demonstrate that the coding performance of this algorithm favourably compares to some of the best reported image compression results.

  • fast lattice based gain shape Vector Quantisation for image sequence coding
    IEE Proceedings I Communications Speech and Vision, 1993
    Co-Authors: Demetrios G Sampson, M Ghanbari
    Abstract:

    A fast lattice-based gain/shape Vector-Quantisation method (FLGSVQ) is presented. The proposed technique combines the basic ideas of gain/shape Vector Quantisation (GSVQ) with lattice codes to offer an encoding process which is extremely fast compared with the conventional GSVQ. The main aim is to show how Vector quantisers designed using the LBG algorithm can be substituted by lattice-based ones with vast reductions in encoding complexity, at a competitive image quality. A simple single-/two-stage coding system based on lattice Quantisation is tested for interframe predictive coding of image sequences. Simulation results are provided to compare the performance of the proposed method with the conventional LBG-designed Vector Quantisation. These results, along with subjective evaluations, clearly demonstrate that lattice Quantisation can be competitive with Vector Quantisation in terms of signal-to-noise performance, only at a very small fraction (4%) of the Vector-quantiser complexity.

S.x. Chen - One of the best experts on this subject based on the ideXlab platform.

  • Fast codebook design of Vector Quantisation
    Electronics Letters, 2012
    Co-Authors: S.x. Chen
    Abstract:

    To reduce the computational overhead of the codebook design of Vector Quantisation, a fast codebook design method is proposed. In this method, the energy distribution of Vectors is improved by rearranging the elements of Vectors based on the information of the energy distribution at each dimension of the initial codebook. Then using the subVectors and their characteristic values, a three-step elimination criterion is introduced to efficiently reduce computational overheads. Experimental results demonstrate the effectiveness of the proposed method in terms of arithmetical operations and search space.

  • fast encoding method for Vector Quantisation of images using subVector characteristics and hadamard transform
    Iet Image Processing, 2011
    Co-Authors: S.x. Chen
    Abstract:

    In a framework of Vector Quantisation (VQ), the encoding speed is a key issue for its practical applications. To speed up the VQ encoding process, a fast encoding method in the Hadamard transform domain is presented. In the proposed method, a five-step test flow based on two characteristic values, the first element and variance of the transformed subVector, is introduced to reject a large number of unlikely codewords. In order to make full use of the energy–compaction property of an orthogonal transform, the partial distance search (PDS) method is used in its Steps 4 and 5. Experimental results show that the proposed algorithm outperforms most of the existing algorithms, especially in case of larger codebook size and high-detail images.

  • initial codebook method of Vector Quantisation in hadamard domain
    Electronics Letters, 2010
    Co-Authors: S.x. Chen
    Abstract:

    To deal with the problem that the initialisation method based on random selection may provide a suboptimal codebook of Vector Quantisation (VQ); an improved method is proposed. In the proposed method, Hadamard transform is performed on training Vectors, and then the transformed Vectors are sorted according to their first elements. The ordered transformed Vectors are partitioned into groups. The initial codebook is composed of the mid Vector of each ordered group. This method has a better performance and can be used as the initialisation method of VQ to improve and speed up codebook design.