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Signal Processing Letters, IEEE

Issue 4 • Date April 1995

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Displaying Results 1 - 6 of 6
  • Variable-rate predictive residual vector quantizer

    Page(s): 70 - 72
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (246 KB)  

    A major problem with a VQ-based image compression scheme is its codebook search complexity. Recently, a predictive residual vector quantizer (PRVQ) was proposed by Rizvi and Nasrabadi (see IEEE Int. Conf. Image Processing, Austin, vol.1, p.608-612, Nov. 13-16, 1994). This scheme has a very low search complexity, and its performance is very close to that of the predictive vector quantizer (PVQ). The article presents a new VQ scheme called variable-rate PRVQ (VR-PRVQ), which is designed by imposing a constraint on the output entropy of the PRVQ. The proposed VR-PRVQ is found to give an excellent rate-distortion performance and clearly outperforms the state-of-the-art image compression algorithm developed by the Joint Photographic Experts Group (JPEG).<> View full abstract»

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  • Reduced-rate block truncation coding of images using error diffusion

    Page(s): 68 - 69
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (210 KB)  

    We consider a simple modification to classical block truncation coding (BTC) that may permit the use of larger block sizes for some applications. although BTC is favored for its simple encoding and decoding, its disadvantage is the relatively low compression ratio achieved. Bit rates on the order of 1 bit/pixel require large block sizes, which generally produce unacceptable degradation. However, these undesirable effects can be reduced considerably by incorporating error diffusion, which is a technique used in halftoning, into the BTC encoding stage.<> View full abstract»

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  • Optimization result for constrained beamformer design

    Page(s): 66 - 67
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (151 KB)  

    The column-unitary matrix whose range space is closest, in the Frobenius norm metric, to the range of a given matrix and whose columns belong to the null space of another specified matrix is obtained. An application of the matrix optimization result derived herein to constrained beamformer design in array signal processing is briefly described.<> View full abstract»

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  • Improved parameter estimation with noisy data for linear models using higher order statistics and inverse filter criteria

    Page(s): 63 - 65
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (249 KB)  

    The problem of estimating the parameters of a non-Gaussian ARMA signal model using higher order statistics is considered. We propose and analyze a novel class of criteria involving explicit higher order whitening, where higher order cumulants of deconvolved data are exploited at a finite number of lags excluding the zero lag. In the presence of a class of measurement noise of unknown covariance/cumulant function, the proposed criteria are shown to yield strongly consistent parameter estimators unlike the Wiggins-Donoho-Shalvi-Weinstein class involving implicit higher order whitening, where higher order cumulants of deconvolved data are exploited only at zero lag.<> View full abstract»

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  • Accuracy aspects of DOA and angular velocity estimation in sensor array processing

    Page(s): 60 - 62
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (219 KB)  

    A sensor array processing algorithm for joint estimation of the directions of arrival (DOAs) and the corresponding angular velocities is presented, together with the Cramer-Rao bound (CRB) of the problem. An embedded movement model circumvents the problems of biased estimates or high measurement rates that occur when conventional DOA estimation algorithms are applied to moving targets.<> View full abstract»

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  • Lip synchronization using speech-assisted video processing

    Page(s): 57 - 59
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (298 KB)  

    We utilize speech information to improve the quality of audio-visual communications such as videotelephony and videoconferencing. In particular, the marriage of speech analysis and image processing can solve problems related to lip synchronization. We present a technique called speech-assisted frame-rate conversion. Demonstration sequences are presented. Other applications, including speech-assisted video coding, are outlined.<> View full abstract»

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Aims & Scope

The IEEE Signal Processing Letters is a monthly, archival publication designed to provide rapid dissemination of original, cutting-edge ideas and timely, significant contributions in signal, image, speech, language and audio processing.

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Meet Our Editors

Editor-in-Chief
Peter Willett
University of Connecticut
Storrs, CT 06269
peter.willett@uconn.edu