[Show abstract][Hide abstract] ABSTRACT: For dictionary-based decompositions of certain types, it has been observed that there might be a link between sparsity in the dictionary and sparsity in the decomposition. Sparsity in the dictionary has also been associated with the derivation of fast and efficient dictionary learning algorithms. Therefore, in this paper we present a greedy adaptive dictionary learning algorithm that sets out to find sparse atoms for speech signals. The algorithm learns the dictionary atoms on data frames taken from a speech signal. It iteratively extracts the data frame with minimum sparsity index, and adds this to the dictionary matrix. The contribution of this atom to the data frames is then removed, and the process is repeated. The algorithm is found to yield a sparse signal decomposition, supporting the hypothesis of a link between sparsity in the decomposition and dictionary. The algorithm is applied to the problem of speech representation and speech denoising, and its performance is compared to other existing methods. The method is shown to find dictionary atoms that are sparser than their time-domain waveform, and also to result in a sparser speech representation. In the presence of noise, the algorithm is found to have similar performance to the well established principal component analysis.
IEEE Journal of Selected Topics in Signal Processing 10/2011;
[Show abstract][Hide abstract] ABSTRACT: Most design procedures for a digital parametric equalizer begin with analog design techniques, followed by applying the bilinear transform to an analog prototype. As an alternative, an approximation to the parametric equalizer is sometimes designed using pole-zero placement techniques. In this paper, we present an exact derivation of the parametric equalizer without resorting to an analog prototype. We show that there are many solutions to the parametric equalizer design constraints as usually stated, but only one of which consistently yields stable, minimum phase behavior with the upper and lower cutoff frequencies positioned around the center frequency. The conditions for complex conjugate poles and zeros are found and the resultant pole zero placements are examined.
IEEE Transactions on Audio Speech and Language Processing 09/2011;
[Show abstract][Hide abstract] ABSTRACT: Multichannel signal processing techniques are usually concerned with extracting information about sources from several received signals. In this paper, we describe an emerging field of multichannel audio signal processing where the inter-channel relationships are exploited in order to manipulate the multichannel content. Applications to real-time, automatic audio production are described and the necessary technologies and the architecture of such systems are presented. The current state of the art is reviewed, and directions of future research are also discussed.
Digital Signal Processing (DSP), 2011 17th International Conference on; 08/2011
[Show abstract][Hide abstract] ABSTRACT: In this study, we propose a heuristic methodology for modeling the end-to-end distortion characteristics of an error resilient broadcast system for 3D video over Digital Video Broadcasting - Handheld (DVB-H). We also use this model to optimally select the parameters of the video encoder and the error correction scheme, namely, Multi Protocol Encapsulation - Forward Error Correction (MPE-FEC), minimizing the overall distortion. The proposed method models the RQ curve of video encoder and performance of channel codec to jointly derive the optimal encoder bit rates and unequal error protection (UEP) rates specific to the 3D video broadcast. Moreover, the distortion on the 3D video quality caused by packet losses and the loss rate of the channel is estimated. Finally, with the use of analytical models and estimated single packet loss distortions, end-to-end distortions are minimized and optimal encoder bit rates and UEP rates are obtained.
3DTV Conference: The True Vision - Capture, Transmission and Display of 3D Video (3DTV-CON), 2011; 06/2011
[Show abstract][Hide abstract] ABSTRACT: The problem of energy-efficient multi-target tracking (MTT) in wireless sensor networks is considered for sensor nodes with limited energy resources and sharp manoeuvring targets of different classes. A distributed multi-sensor multi-target tracking scheme is proposed for energy-efficient MTT with adaptive sampling. Behavioural data obtained while tracking the target including the target's previous locations are recorded as metadata to compute the sampling interval so that the tracking continuity and energy efficiency are improved. Following this, the next tasking sensors group is selected proactively according to the predicted target location probability distribution. A 'main node' is elected from the selected tasking sensors so that the energy efficiency is improved. Sensor nodes that detect more than one target at the same time determine their preferred target according to the target importance and the distance to the target. Simulation results show that compared to other well-known target tracking schemes, the proposed scheme can provide a significant improvement in energy efficiency while maintaining acceptable accuracy and seamless tracking, even with sharp manoeuvring targets. Additionally, more important targets experience better tracking accuracy.
[Show abstract][Hide abstract] ABSTRACT: The work reported in this paper is in support of applications of ferrites in measurement systems operating at frequencies in the range 100-600 GHz. Measurements of the magneto-optical characteristics of selected grain-oriented hexaferrite ceramics from 75 to 600 GHz are described; a quasi-optical transmissometer driven by a multiband vector-network-analyser is used to provide the required high dynamic range, spectral-resolution, and scan-speeds. The implications of the results of the measurements are examined.
IEEE Transactions on Microwave Theory and Techniques 01/2011;
[Show abstract][Hide abstract] ABSTRACT: Scalable Video Coding (SVC) enables low complexity adaptation according to transmission and display requirements, providing an efficient solution for video content delivery through heterogeneous networks. However, legacy video and most commercially available content capturing devices use conventional non-scalable coding, e.g., H.264/AVC, to compress and store video streams. As a consequence and in order to fully exploit the advantages of SVC technology, efficient transcoding from conventionally coded to scalable content is urgently needed. In this paper an efficient transcoder from H.264/AVC to a wavelet-based SVC is proposed. The complexity of the transcoder is kept very low by using information extracted directly from the decoded H.264/AVC bitstream, such as motion vectors and the presence of residual data. The proposed approach has been tested with well known benchmarking sequences, showing a good performance in terms of decoded video quality and system complexity.
Image Processing (ICIP), 2010 17th IEEE International Conference on; 10/2010
[Show abstract][Hide abstract] ABSTRACT: The discrete coordinated transformation provides us a scheme to design flat all-dielectric devices. Such novel devices have flat profiles and are easy to be controlled and set up in the antenna systems. A flat reflector and a flat lens are designed as examples. The FDTD based simulation results have proved good agreement between the transformed devices and the conventional ones.
Antennas and Propagation Society International Symposium (APSURSI), 2010 IEEE; 08/2010
[Show abstract][Hide abstract] ABSTRACT: An actively-loaded magnetoinductive media was presented and fully investigated analytically. Stability bounds were derived, along with an expression for the effective magnetic permeability. Mutual coupling interactions and periodicity were accounted for, and it was shown that these properties have a critical effect on both stability, as well as the effective material parameters. The bandwidth of negative-μ and μnz materials are significantly increased as compared to passive media. This could have a significant impact on applications in which these classes of materials may be of benefit.
Antennas and Propagation Society International Symposium (APSURSI), 2010 IEEE; 08/2010
[Show abstract][Hide abstract] ABSTRACT: Coordinate transformation is applied to design an all-dielectric device for Extraordinary Transmission (ET) in a single sub-wavelength slit. The proposed device has a broadband feature and can be applied from microwave to visible frequency bands. Finite-Difference Time-Domain (FDTD) simulations are used to verify the device's performance. The results show that significantly increased transmission is achieved through the sub-wavelength aperture from 4 GHz to 8 GHz when the device is applied. In contrast with previously reported systems, the frequency sensitivity of the new device is very low.
Optics Express 08/2010; 18(16):16946-54.
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