Showing papers on "Quadrature mirror filter published in 1994"

Rotation and gray scale transform invariant texture identification using wavelet decomposition and hidden Markov model

Abstract: In this correspondence, we have presented a rotation and gray scale transform invariant texture recognition scheme using the combination of quadrature mirror filter (QMF) bank and hidden Markov model (HMM). In the first stage, the QMF bank is used as the wavelet transform to decompose the texture image into subbands. The gray scale transform invariant features derived from the statistics based on first-order distribution of gray levels are then extracted from each subband image. In the second stage, the sequence of subbands is modeled as a hidden Markov model (HMM), and one HMM is designed for each class of textures. The HMM is used to exploit the dependence among these subbands, and is able to capture the trend of changes caused by rotation. During recognition, the unknown texture is matched against all the models. The best matched model identifies the texture class. Up to 93.33% classification accuracy is reported. >

Architectures for lattice structure based orthonormal discrete wavelet transforms

Abstract: This paper presents efficient single-rate architectures for the orthonormal discrete wavelet transform (DWT). Folded and digit-serial architectures are derived from an efficient lattice implementation of two-channel FIR paraunitary systems known as the quadrature mirror filter (QMF) lattice. Folded architectures are derived by applying systematic folding techniques to multirate systems. For digit-serial architectures, we show that any two-channel subband system can be implemented using digit-serial processing techniques by utilizing the polyphase decomposition. Using this result, we describe an orthonormal DWT architecture which uses the QMF lattice structure and digit-serial processing techniques. The number of multipliers and adders required for both the folded and digit-serial lattice-based architectures approaches one-half the number required to implement similar systems based on direct-form filter implementations as the order of the FIR filters becomes large. This makes folded and digit-serial QMF lattice structures attractive choices for applications of the orthonormal DWT which require low area and low power dissipation. >

Mathematics of adaptive wavelet transforms: relating continuous with discrete transforms

Abstract: We prove several theorems and construct explicitly the bridge between the continuous and discrete adaptive wavelet transform (AWT). The computational efficiency of the AWT is a result of its compact support closely matching linearly the signal's time-frequency characteristics, and is also a result of a larger redundancy factor of the superposition-mother s(x) (super-mother), created adaptively by a linear superposition of other admissible mother wavelets. The super-mother always forms a complete basis, but is usually associated with a higher redundancy number than its constituent complete orthonormal (CON) bases. The robustness of super-mother suffers less noise contamination (since noise is everywhere, and a redundant sampling by bandpassings can suppress the noise and enhance the signal). Since the continuous super-mother has been created off-line by AWT (using least-mean-squares neural nets), we wish to accomplish fast AWT on line. Thus, we formulate AWT in discrete high-pass (H) and low-pass (L) filter bank coefficients via the quadrature mirror filter (QMF), a digital subband lossless coding. A linear combination of two special cases of the complete biorthogonal normalized (Cbi-ON) QMF [L(z),H(z),L+(z),H+(z)], called α-bank and β-bank, becomes a hybrid aα + bβ-bank (for any real positive constants a and b) that is still admissible, meaning Cbi-ON and lossless. Finally, the power of AWT is the implementation by means of wavelet chips and neurochips, in which each node is a daughter wavelet similar to a radial basis function using dyadic affine scaling.

Method and apparatus for reducing correlated errors in subband coding systems with quantizers

Abstract: A method and apparatus for reducing correlated errors in subband coding systems with quantizers is disclosed. A subband coding system comprises a plurality of subband analysis filters to divide the frequency spectrum of the input signal into subbands, individual subband quantizers for coding each subband by a preselected number of quantization levels, corresponding subband decoders and subband synthesis filters. The transfer function of each of the subband synthesis filters is advantageously determined based on the transfer functions of the subband analysis filters as well as on the characteristics of the quantizer used to code the corresponding subband. Specifically, the synthesis filter transfer functions may be based on a perfect reconstruction filter bank or a quadrature mirror filter bank, as well as on the gain factors of a gain plus additive noise linear model for the Lloyd-Max quantizers used to code the corresponding subbands. That portion of the error between the input signal and the replica signal as reconstructed by the system which is correlated to the input signal may be advantageously reduced or eliminated, irrespective of that portion of the error which is uncorrelated to the input signal. Thus, the total error in a final signal may be advantageously reduced by the subsequent application of prior art techniques for the reduction of random, uncorrelated noise.

Design of linear-phase quadrature mirror filters with powers-of-two coefficients

Abstract: This paper considers the design of linear-phase quadrature mirror filters (QMF's) with powers-of-two coefficients. A design method based on a recently developed weighted least-squares (WLS) algorithm is presented. First, we design QMF's with continuous coefficients using the WLS algorithm. This design process provides two favorable design results that the prototype analysis filter has quasi-equiripple stopband response and the resulting QMF bank shows quasi-equiripple reconstruction error behavior. To avoid the effect of nonuniformly distributed coefficient grid due to discretization of the filter coefficients, a procedure is then performed for obtaining an appropriate filter gain factor. Finally, utilizing the resulting error weighting function obtained by the WLS algorithm, we propose an efficient discrete optimization process to obtain a discrete solution in the minimax optimal sense. Design examples demonstrating the effectiveness of the proposed method are included. >

Biorthogonal wavelets for image compression

Abstract: Biorthogonal wavelets or filterbanks are shown to be superior in coding gain performance than orthogonal ones for logarithmic subband decompositions (limited to iterative decomposition of the downsampled output of the analysis low-pass filter). As a consequence, for logarithmic decompositions, the optimal filter is not an ideal filter. This is shown for maximally regular biorthogonal and orthogonal filters, as well as filters designed to optimize the subband coding grain.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A simple design method for nonuniform multirate filter banks

Abstract: The theory and design of perfect-reconstruction uniform-band QMF banks have been extensively studied. For nonuniform-band filter banks, there is a lack of efficient design methods. We propose a simple design method for nonuniform integer-decimated filter banks (near perfect reconstruction). The approach is to transform the nonuniform filter bank design problem to a corresponding uniform filter bank design problem. Therefore, only one prototype filter needs to be designed. The analysis and synthesis filters are simple combinations of the cosine modulated versions of the prototype filter. An example is given to demonstrate the proposed method. >

Multi-scale wavelet modulation

Abstract: The purpose of this paper is to provide the fundamental characterization of a general multidimensional modulation format which utilizes wavelet basis functions as pulse shapes. This type of modulation is particularly effective in distorting channels since it allows for frequency selective processing. In addition to developing the signal format, power spectral density, bandwidth efficiency and error rate performance, an efficient digital implementation utilizing digital filter banks is put forth. Finally, the use of wavelets in communication is seen to generate new pulse shape designs. A practical solution discussed in the paper applies the Smith-Barnwell two-channel filter bank design. >

Novel efficient approach for the design of equiripple quadrature mirror filters

Abstract: Quadrature mirror filters have been used extensively in subband coding of speech signals. The authors introduce a novel efficient approach for the design of equiripple quadrature mirror filters. The new approach is more efficient than the previously proposed design method in terms of computer time and memory requirement.

Apparatus for suppressing ghosts in signals modulating a carrier in quadrature phasing with a video carrier

Abstract: Composite video signal and a relatively low power phase-shift-keyed (PSK) signal encoding digital information are transmitted on respective phases of a video carrier in quadrature with each other. Selected scan lines of the composite video signal contain ghost-cancellation reference (GCR) signals. A digital signal receiver performs a first detection of the video carrier modulated in the two phases, down-converting to an intermediate-frequency (IF) signal. This IF signal is selectively amplified prior to respective second detection of the down-converted video carrier by in-phase and quadrature-phase synchronous video detectors. A first cascade filter connection of a first ghost-cancellation filter and a first equalization filter follows the in-phase video detector, and a second cascade filter connection of a second ghost-cancellation filter and a second equalization filter follows the quadrature-phase video detector. Gating circuitry selects scan lines containing GCR signals from the video signal response of the first cascade filter connection for accumulation, which generates separated ghosted GCR signal for use by a computer such as a microcomputer. Adjustable parameters of the ghost-cancellation filters are adjusted in parallel responsive to computer calculations, while adjustable parameters of the equalization filters are also adjusted in parallel responsive to further computer calculations. Iterative feedback reduces ghosts in the response of the first cascade filter connection. Ghosts in the response of the second cascade filter connection are reduced in an analogous manner.

Eigen design of quadrature mirror filters

Abstract: The paper presents a method for the design of quadrature mirror filters. A new frequency weighted stopband energy function is introduced, which leads to considerable flexibility in the design process. Unlike other techniques which involve searches and nonlinear optimization, the formulation reduces the design equations to an eigenvector problem. The resulting filters are regular and have additional desirable properties as discussed in the paper. Also considered is application to pyramidal coding of images, which together with DPCM and PCM, leads to high compression ratios. >

Cosine-modulated 2 dimensional FIR filter banks satisfying perfect reconstruction

Abstract: Considers the theory of cosine-modulated 2 dimensional (2-D) perfect reconstruction (PR) filter banks. First, a 2-D digital filter design with half passband, obtained by the sampling matrix, is discussed. Next, 2-D analysis filter banks are realized by cosine-modulating this prototype 2-D digital filter. It is shown that the modulation in the 2-D frequency plane is equivalent to the 1-D modulation. A necessary and sufficient condition for 2-D perfect reconstruction filter banks is derived. If the polyphase filter pairs of the prototype filter have a double-complement, the resulting 2-D filter bank satisfies the condition of perfect reconstruction. >

Progressive optimality in hierarchical filter banks

Abstract: The concept of progressive optimization is proposed for the design of hierarchical subband transforms. The time and frequency properties of the product filters in subband trees are discussed and evaluated. It is shown that the performance improvements in image coding are possible by using different PR-QMF banks at different nodes of a subband tree. >

On multidimensional linear phase perfect reconstruction filter banks

Abstract: We consider the multidimensional version of the problem of linear phase perfect reconstruction filter bank design. We give conditions for linear phase property of the filter bank, enumerate the number of symmetric and antisymmetric filters in the bank and give results on the possibility of construction of the entire filter bank if all filters in the bank except one are specified without any restriction other than the linear phase property. >

The design of 2-D nonseparable directional perfect reconstruction filter banks

Abstract: In this paper, we develop a directional 2-D nonseparable filter bank that can perfectly reconstruct the downsampled subband signals. The filter bank represents two powerful image and video processing tools: directional subband decomposition and perfect reconstruction. The directional filter banks consist of (1) the input signal and the subband signals modulation, (2) diamond shape prefilter, and (3) four different parallelogram shape prefilters. This paper addresses the design and implementation of a two-band filter bank that is proved to be able to provide perfect reconstruction of the downsampled subband signals. Finally, we use a conventional 1-D half-band filter as a prototype and then apply the McClellan transform for the specific 2-D diamond shape and parallelogram shape subfilters. This method is extremely simple in designing the analysis/synthesis subfilters for the filter bank.

Quadrature modulated filter banks

Abstract: This paper proposes a new family of perfect reconstruction (PR) filter banks called quadrature modulated filter banks (QMFB) by imposing structural constraints in the polyphase matrix. The single stage orthonormal QMFB is a complete modulated version of the two channel conjugate quadrature filters (CQF) because it is identical to the CQF when M=2. More general cascade linear phase orthogonal and nonorthogonal PR systems are also derived. In particular, we are able to obtain more general orthogonal and nonorthogonal versions of the Lapped Orthogonal Transform (LOT). >

A subband adaptive filter with two types of analysis filter bank

Abstract: Conventional subband ADFs (adaptive digital filters) using filter banks have shown degradation in performance because of the non-ideal nature of filters. For this problem, we propose a new type of subband ADF incorporating two types of analyses filter bank. We show that we can design the optimum filter bank which minimizes the LMSE (least mean squared error). In other words, we can design a subband ADF with less MSE than that of conventional subband ADFs. >

N-parallel filter bank equivalent to tree structure

Abstract: This paper presents the equivalent polyphase implementations of an N-channel filter bank based on an s-level tree structured filter bank. The realization employs a cascade of the filter's polyphase components with distributed decimation followed by the NxN Hadamard matrix realizing a filter bank with real computations (real-valued filter coefficients) only, which is simple to realize. >

Efficient multirate adaptive beamforming technique

Abstract: An efficient beamforming technique based on the recently proposed quadrature mirror filter based multirate sub-band adaptive beamformer (QMF-MSAB), is presented. The improved technique uses only one adaptive processor for all sub-bands, resulting in a considerable reduction in hardware requirements. In addition, the new structure maintains the overall superiority of the multirate approach over full-band beamforming.

Improved methods for the design of 1-D and 2-D QMF banks

Abstract: An iterative procedure proposed by Chen and Lee for the design of quadrature mirror filter (QMF) banks is extended to the design of two types of filter banks, i.e., l-D QMF banks with low reconstruction delay and 2-D nonseparable hexagonal QMF banks. Our simulations show that the extended methods are very efficient and yield good designs. >

A novel time-domain approach for the design of quadrature mirror filter banks

Abstract: A novel approach for the design of two-channel QMF banks is proposed. In the design, instead of minimizing the objective function directly, an iterative procedure is used in each step in which the objective function is modified into a quadratic function whose minimum point can be obtained analytically. Compared with the iterative method proposed recently by Chen and Lee (1992) in which the perfect reconstruction condition is formulated in the frequency domain, the perfect reconstruction condition in our method is formulated in the time domain. This avoids calculating large matrices and leads to reduced computation complexity in the design. A case study is included which demonstrates that the proposed method needs only a fraction of the computation time required by the method of Chen and Lee.

Image texture classification using Quadrature Mirror Filter bank in combination with Co—occurrence matrices

Abstract: This paper presents a method for the classification of textures using Quadrature Mirror Filter (QMF) bank subband decomposition in combination with statistical descriptors. In our combined method the QMF bank splits the input image into four subbands, and statisti-cal descriptors based on co-occurrence matrices are computed from the subsanzpled low-low band. The experiments demonstrate that the combined method have better classification performance than that of statistical descriptors computed from the co-occurrence matrices of the whole texture image. In addition, the experiments demonstrate that the combined method based on computationally efficient IIR QMF banks yields approximately the sameclassification results as the combined method based on classical FIR QMF banks. 1 Introduction Texture analysis plays an important role in such areas as medical diagnosis, remote sensing and industrial inspection. One important usage of texture analysis is to distinguish among various classes of textures. That is, given a sample texture, identify to which of a finite number of textureclasses the sample belongs.For the texture discrimination problem several texture descriptors have been proposed: Fourierpower spectrum [1], autocorrelation function [2], autoregressive moving average models [3], Markovrandom field models [4], digital filter banks [5] and spatial gray-level co-occurrence matrices [6].Among the different texture descriptors spatial gray-level co-occurrence matrices are cited in theliterature most frequently. A co-occurrence matrix is a second-order statistical measure of imagevariation. It contains information on the spatial relationship between pairs of gray levels of pixels.Co-occurrence matrices are seldomly used directly. Instead, features based on them are com-puted. Haralick eL al. [6] have suggested 14 textural features, which include both statistical andinformation theoretic measures.

Design of low-delay FIR QMF banks using the Lagrange-multiplier approach

Abstract: A new approach for the design of two-channel perfect reconstruction FIR filter banks with short reconstruction delays is presented. A low-order filter is first designed and the objective function of the filter bank is formulated as a quadratic programming problem with linear constraints. The Lagrange-multiplier method is then used to design a higher-order filter. The method is simple, efficient, and flexible and leads to a closed-form solution. A design example is included to illustrate the advantages of the method.

The Detection and Extraction of Features of Low Probability of Intercept Signals Using Quadrature Mirror Filter Bank Trees.

Abstract: : A new type of spread spectrum intercept receiver is described which uses orthogonal Wavelet techniques and a Quadrature Mirror Filter (QMF) bank tree to decompose a waveform into components representing the energy in rectangular "tiles" in the time frequency plane By simultaneously examining multiple layers of the tree, the dimensions of concentrations of energy can be estimated with a higher resolution than is normally associated with linear transform techniques This allows detection and feature extraction even when the interceptor has little knowledge of specific parameters of the signal being detected In addition, the receiver can intercept and distinguish between multiple signals For each category of spread spectrum, the receiver estimates the energy cells' positions in the time frequency plane, the cells' bandwidths, time widths and signal to noise ratios, and the energy distribution within each cell With this information, a classifier can then determine how many transmitters there are, and which cells belong to each In this report, algorithms are described for detecting and extracting features for each of the spread spectrum signal formats These algorithms are analyzed mathematically and the results are verified with simulation The detection abilities of these algorithms are compared with other spread spectrum detectors hat have been described in the literature

Least square filters for approximating perfect reconstruction filter banks

Abstract: This paper presents a least squares (LS) design methodology for approximating perfect reconstruction filter banks. A filter bank can be represented as a multi-input multi-output (MIMO) LTI system whose transfer function is described by the filter bank polyphase matrix. Rising this MIMO system representation, we frame a general least squares filter design problem. Then given an arbitrary set of rational analysis filters we find the causal synthesis filters for a filter bank which achieves the best causal LS approximation to perfect reconstruction. >

A new approach for the design of low-delay quadrature mirror filter banks

Abstract: An iterative approach is proposed for the design of two-channel QMF banks with low reconstruction delays. The perfect reconstruction condition is formed in the time-domain and the design efficiency is significantly improved by formulating a quadratic objective function in each step of an iterative process whose minimum point can be obtained in closed form. The proposed method is demonstrated by a design example. >

Design and implementation of linear-phase 2-channel perfect reconstruction FIR filter banks with equiripple stopband

Abstract: This paper presents a design and implementation method for linear phase 2-channel perfect reconstruction FIR filter banks with arbitrary filter length. In this method, which we call the weighted Lagrange-Newton method, by introducing the least squares weighting function into Horng's method (Lagrange-Newton method), QMF (Quadrature Mirror Filters) with good stopband attenuation can be designed. Furthermore, we show the construction of a 2-channel perfect QMF that achieves perfect reconstruction in spite of coefficient quantization.