| 1. |
- Andersson, Kenneth, 1970-, et al.
(author)
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Prediction from off-grid samples using continuous normalized convolution
- 2007
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In: Signal Processing. - : Elsevier BV. - 0165-1684 .- 1872-7557. ; 87:3, s. 353-365
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Journal article (peer-reviewed)abstract
- This paper presents a novel method for performing fast estimation of data samples on a desired output grid from samples on an irregularly sampled grid. The output signal is estimated using integration of signals over a neighbourhood employing a local model of the signal using discrete filters. The strength of the method is demonstrated in motion compensation examples by comparing to traditional techniques.
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| 2. |
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| 3. |
- Christensen, M, et al.
(author)
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Multi-pitch estimation
- 2008
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In: Signal Processing. - : Elsevier BV. - 0165-1684 .- 1872-7557. ; 88:4, s. 972-983
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Journal article (peer-reviewed)abstract
- In this paper, we formulate the multi-pitch estimation problem and propose a number of methods to estimate the set of fundamental frequencies. The proposed methods, based on the nonlinear least-squares (NLS), Multiple Signal Classification (MUSIC) and the Capon principles, estimate the multiple fundamental frequencies via a number of one-dimensional searches. We also propose an iterative method based on the Expectation Maximization (EM) algorithm. The statistical properties of the methods are evaluated via Monte Carlo simulations for both the single- and multi-pitch cases.
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| 4. |
- Enqvist, Per
(author)
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On the simultaneous realization problem - Markov-parameter and covariance interpolation
- 2006
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In: Signal Processing. - : Elsevier BV. - 0165-1684 .- 1872-7557. ; 86:10, s. 3043-3054
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Journal article (peer-reviewed)abstract
- An efficient algorithm for determining the unique minimal and stable realization of a window of Markov parameters and covariances is derived. The main difference compared to the Q-Markov COVER theory is that here we let the variance of the input noise be a variable, thus avoiding a certain data consistency criterion. First, it is shown that maximizing the input variance of the realization over all interpolants yields a minimal degree solution-a result closely related to maximum entropy. Secondly, the state space approach of the Q-Markov COVER theory is used for analyzing the stability and structure of the realization by straightforward application of familiar realization theory concepts, in particular the occurrence of singular spectral measures is characterized.
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| 5. |
- Lindgren, David, et al.
(author)
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Rank Reduction and Volume Minimization Approach to State-Space Subspace System Identification
- 2006
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In: Signal Processing. - : Elsevier. - 0165-1684 .- 1872-7557. ; 86:11, s. 3275-3285
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Journal article (peer-reviewed)abstract
- In this paper we consider the reduced rank regression problemsolved by maximum-likelihood-inspired state-space subspace system identification algorithms. We conclude that the determinant criterion is, due to potential rank-deficiencies, not general enough to handle all problem instances. The main part of the paper analyzes the structure of the reduced rank minimization problem and identifies signal properties in terms of geometrical concepts. A more general minimization criterion is considered, rank reduction followed by volume minimization. A numerically sound algorithm for minimizing this criterion is presented and validated on both simulated and experimental data.
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| 6. |
- Lindström, Fredric, et al.
(author)
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A hybrid acoustic echo canceller and suppressor
- 2007
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In: Signal Processing. - : Elsevier. - 0165-1684. ; 87:4, s. 739-749
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Journal article (peer-reviewed)abstract
- Wideband communication is becoming a desired feature in telephone conferencing systems. This paper proposes a computationally efficient echo suppression control algorithm to be used when increasing the bandwidth of an audio conferencing system, e.g. a conference telephone. The method presented in this paper gives a quality improvement, in the form of increased bandwidth, at a negligible extra computational cost. The increase in bandwidth is obtained through combining a conventional acoustic echo cancellation unit and an acoustic echo suppression unit, i.e. a hybrid echo canceller and suppressor. The proposed solution was implemented in a real-time system. Frequency analysis combined with subjective tests showed that the proposed method extends the bandwidth, while maintaining high quality.
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| 7. |
- Schüldt, Christian, et al.
(author)
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Adaptive filter length selection for acoustic echo cancellation
- 2009
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In: Signal Processing. - AMSTERDAM : Elsevier. - 0165-1684 .- 1872-7557. ; 89:6, s. 1185-1194
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Journal article (peer-reviewed)abstract
- The number of coefficients in an adaptive finite impulse response filter-based acoustic echo cancellation setup is an important parameter, affecting the overall performance of the echo cancellation. Too few coefficients give undermodelling and too many cause slow convergence and an additional echo due to the mismatch of the extra coefficients. This paper proposes a method to adaptively determine the filter length, based on estimation of the mean square deviation. The method is primarily intended for identifying long non-sparse systems, such as a typical impulse response from an acoustic setup. Simulations with band limited flat spectrum signals are used for verification, showing the behavior and benefits of the proposed algorithm. Furthermore, off-line calculation using recorded speech signals show the behavior in real situations and comparison with another state-of-the-art variable filter length algorithm shows the advantages of the proposed method.
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| 8. |
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| 9. |
- Stoica, Peter, 1949-, et al.
(author)
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On maximum likelihood estimation in factor analysis : an algebraic derivation
- 2009
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In: Signal Processing. - : Elsevier BV. - 0165-1684 .- 1872-7557. ; 89:6, s. 1260-1262
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Journal article (peer-reviewed)abstract
- The maximum likelihood estimate in factor analysis is typically obtained as the solution of the stationary point equation of the likelihood function. This type of derivation suffers from two problems: it is rather cumbersome and, in fact, it is incomplete as it does not include a proof that the so-obtained estimate is indeed a global maximum point of the likelihood function. In this note we present a simple algebraic derivation of the maximum likelihood estimate in factor models with spherical noise that applies to the general complex-valued data case.
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| 10. |
- Tran Viet, Linh, 1973-, et al.
(author)
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Compact colour descriptors for colour-based image retrieval
- 2005
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In: Signal Processing. - : Elsevier BV. - 0165-1684 .- 1872-7557. ; 85:2, s. 233-246
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Journal article (peer-reviewed)abstract
- In many colour-based image retrieval systems the colour properties of an image are described by its colour histogram. Histogram-based search is, however, often inefficient for large histogram sizes. Therefore we introduce several new, Karhunen-Loève transform (KLT)-based methods that provide efficient representations of colour histograms and differences between two colour histograms. The methods are based on the following two observations, Ordinary KLT considers colour histograms as signals and uses the Euclidian distance for optimization, KLT with generalized colour distance measures that take into account both the statistical properties of the image database and the properties of the underlying colour space should improve the retrieval performance. Image retrieval applications compare similarities between different images. Relevant for the decision is only the local structure of the image space around the current query image since the task is to find those images in the database that are most similar to this given query image. Therefore only the local topology of the feature space is of interest and compression methods should preserve this local topology as much as possible. It is therefore more important to have a good representation of the differences between features of similar images than good representations of the features of the images themselves. The optimization should therefore be based on minimizing the approximation error in the space of local histogram differences instead of the space of colour histograms. In this paper we report the results of our experiments that are done on three image databases containing more than 130,000 images. Both objective and subjective ground truth queries are used in order to evaluate the proposed methods and to compare them with other existing methods. The results from our experiments show that compression methods based on a combination of the two observations described above provide new, powerful and efficient retrieval algorithms for colour-based image retrieval. © 2004 Elsevier B.V. All rights reserved.
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