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Vision, Image and Signal Processing, IEE Proceedings -

Issue 1 • Date Feb 2002

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Displaying Results 1 - 7 of 7
  • Robust authentication scheme for protecting copyrights of images and graphics

    Page(s): 43 - 50
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1290 KB)  

    Watermarking techniques are primarily used for copyright protection. A simple and robust watermark-like digital authentication scheme is proposed. This work has two major merits. First, the watermark used in the proposed authentication scheme is the same type used in the original image, e.g. grey level images. Second, the proposed scheme meets the requirements for watermarking techniques. Illegal users cannot perceive and break the watermark signed from the original image. Furthermore, the signed watermark is robust against attacks by many image altering algorithms, such as filtering, lossy compression, rotation and scaling. The proposed scheme is not only suitable for ordinary natural images, but also for cartoon graphics View full abstract»

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  • Robust microphone arrays using subband adaptive filters

    Page(s): 17 - 25
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (874 KB)  

    A new adaptive beamformer which combines the idea of subband processing and the generalised sidelobe canceller structure is presented. The proposed subband beamformer has a blocking matrix that uses coefficient-constrained subband adaptive filters to limit target cancellation within an allowable range of direction of arrival. Simulations comparing the fullband and subband adaptive beamformers show that the subband beamformer has better performance than the fullband beamformer when the target and/or interfering signals are coloured. In reverberant environments, the proposed subband beamformer also performs better than its fullband counterpart View full abstract»

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  • Psychophysically derived quantisation model for efficient DWT image coding

    Page(s): 51 - 56
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (687 KB)  

    An efficient method for the optimum quantisation of the luminance and chrominance components for discrete wavelet transform (DWT) still image coding, based on current psychophysical evidence, is described. Its practical application to image compression is presented. This new approach is further supported by experimental work which compares perceived DWT image quality with conventional JPEG-encoding, that is block-based discrete cosine transform (DCT) coding, on the basis of quantisation distortion View full abstract»

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  • Bayesian multivariate autoregressive models with structured priors

    Page(s): 33 - 41
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1290 KB)  

    A variational Bayesian (VB) learning algorithm for parameter estimation and model-order selection in multivariate autoregressive (MAR) models is described. The use of structured priors in which subsets of coefficients are grouped together and constrained to be of a similar magnitude is explored. This allows MAR models to be more readily applied to high-dimensional data and to data with greater temporal complexity. The VB model order selection criterion is compared with the minimum description length approach. Results are presented on synthetic and electroencephalogram data View full abstract»

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  • Candidate scheme for fast ACELP search

    Page(s): 10 - 16
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (745 KB)  

    The algebraic code excited linear prediction (ACELP) algorithm has been adopted by many speech coding standards, due to low complexity and high quality in its analysis-by-synthesis optimisation. For further computational complexity reduction, the authors propose a fast ACELP algorithm using a designed pilot function to predict the predetermined candidate pulses. With candidate pulses, it is possible to not only reduce the number of search loops but also to avoid the computation of unnecessary correlation functions. The proposed candidate position scheme can be applied to all ACELP coders such as the ITU G-723.1 and G.729 as well as the GSM enhanced full rate (EFR) speech coding standards. Simulation results show that the computational load can be reduced by about 50-80% with almost imperceptible degradation in performance View full abstract»

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  • Design and implementation of a fast algorithm for modulated lapped transform

    Page(s): 27 - 32
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (569 KB)  

    A new fast algorithm for the computation of the modulated lapped transform (MLT) is proposed and its efficient implementation using pipelining techniques and complex programmable logic device (CPLD) is presented. The new algorithm computes a length-M MLT via the length-M/2 fast Fourier transform (FFT). Computational overhead due to data shuffling in pre-processing and post-processing is offset in hardware realisation. Hence the overall throughput of the MLT computation for real-time applications is significantly improved. The pipelined CPLD architecture and circuitry are described in detail. Computational complexity of the proposed algorithm is analysed, and throughput improvement is verified by experimental results View full abstract»

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  • Alternating fixed-point algorithm for stereophonic acoustic echo cancellation

    Page(s): 1 - 9
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (817 KB)  

    A novel algorithm for use in stereophonic acoustic echo cancellation is introduced. The alternating fixed-point structure of the algorithm descends each of the channels alternatively and avoids nonuniqueness in the solutions by employing inter- and intra-channel orthogonal projections. For a noisy environment, the algorithm is shown to provide improved misalignment performance and echo cancellation over leading competitors at a low computational cost. The inherent noise robustness is uncovered using H estimation techniques and noise-error bounds are derived View full abstract»

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