Showing papers on "Impulse noise published in 1997"

Minimum-maximum exclusive mean (MMEM) filter to remove impulse noise from highly corrupted images

Abstract: The minimum-maximum exclusive mean (MMEM) filter is presented to remove impulse noise from highly corrupted images. Simulation results show that even if the occurrence rate of the impulse noise is very high (70%), the restoration performance is still acceptable.

Blotch and Scratch Detection in Image Sequences based on Rank Ordered Differences

Abstract: Publisher Summary Old movies are often valuable historical records, but most of them progressively deteriorate in visual quality during the years, decreasing their usefulness. To avoid distortions in the unaffected parts of the image, first the locations of the blotches and scratches have to be detected before the restoration algorithm can be applied. This chapter proposes an algorithm based on rank ordered differences (ROD) that are calculated from the data of the current image flame, and the preceding and succeeding motion-compensated frame. The ROD detector presented in the chapter is a modified form of the signal-dependent rank ordered mean filter (SD-ROM) used for restoration of an impulse noise corrupted image. While the SD-ROM filter works exclusively in the spatial area of one image frame and is only able to remove one or two pixel wide distortions, the ROD filter is designed to work on image sequences. It is able to detect both thin scratches and blotches. The chapter also compares the new algorithm to existing detection algorithms in the form of probability plots and images indicating the correct, false, and missing detections.

Adaptive threshold nonlinear algorithm for adaptive filters with robustness against impulse noise

Abstract: A new adaptation algorithm for adaptive filters is proposed, introducing "adaptive threshold" in the nonlinear correlation function. The adaptive threshold controlled by the long-term average of the error signal power makes the filtering system highly robust against impulse noise, which is demonstrated by the results of simulation and theoretical calculation.

Impulse noise detection and removal using fuzzy techniques

Abstract: A new algorithm is presented which can remove impulse noise from corrupted images while preserving details. The algorithm is based on fuzzy impulse detection and fuzzy noise cancellation techniques. Experimental results show that the algorithm is capable of providing significant improvement over many published techniques in terms of both subjective and objective evaluations.

Adaptive nonlinear RLS algorithm for robust filtering in impulse noise

Abstract: An adaptive nonlinear RLS algorithm for robust filtering in impulse noise is presented. The analysis of the mean and mean-square behaviours is carried out and verified by simulation. It is shown that the new algorithm can provide a robust performance against impulse noise and outperform the LMS counterpart and the RLS algorithm particularly when there is impulse noise.

A multirate wireless transmission system using wavelet packet modulation

Abstract: A new OFDM transmission version for multirate integrated service based on wavelet packet transform (WPT), named orthogonal wavelet division multiplexing (OWDM), is proposed. Carrying multirate services and restraining non-stationary noise are the two novel aspects of this system. The principle of WPT and the transceiver structure using WPT are presented. The performance of the system under impulse noise and single tone interference is analyzed.

Noise-immune automatic gain control for QAM radio receivers

Abstract: Automatic gain control (AGC) for a quadrature-amplitude-modulation (QAM) digital radio receiver, such as used for receiving digital high-definition television transmissions, is provided immunity to the effects of the ringing of intermediate-frequency (IF) amplifiers at carrier frequency in response to impulse noise. The energy associated with the ringing of the IF amplifiers is at frequencies relatively close to the carrier of the IF signal as compared to data modulation. Filtering that suppresses the energy associated with the ringing of the IF amplifiers is used to recover information concerning the envelope variations of the QAM signal free from accompanying ringing energy, which envelope variations are then peak detected to develop AGC signals for the QAM digital radio receiver.

Adaptive noise reduction and image sharpening for digital video compression

Abstract: This paper presents a framework of digital video preprocessing for digital video compression The purpose of this preprocessing is to reduce the noise and thus improve the video compression efficiency A four stage processing system has been proposed The first process is a median filter to remove the 2D impulse noise The second process is a 2D spatial filter that is controllable by the video encoder parameters The third process is an image sharpening operation to enhance the image resolution or details so that the decoded video from the encoded bitstream still gives high resolution content The last process is a recursive temporal filter that is used to reduce the temporal noise The recursive filter is designed to adapt to the video content so that high quality temporal filtering is achieved

Adaptive comb filter and decision feedback equalizer for noise suppression

Abstract: An improvement to a half duplex multipoint communication environment wherein a digital subscriber line (DSL) receiver employs an adaptive comb filter and a decision feedback equalizer (DFE) to efficiently suppress or eliminate low frequency periodic impulse noise and crosstalk generated in the vicinity of the device receiver.

Error performance of OFDM-QAM in subcarrier multiplexed fiber-optic transmission

Abstract: Error performance of OFDM-QAM signals is analyzed for subcarrier multiplexed (SCM) fiber-optic video transmission, particularly for hybrid AM/OFDM systems. In comparison with conventional M-QAM signals, it is shown that the OFDM system provides significant performance improvements in terms of bit-error rate (BER), channel capacity, and operating range of the optical modulation depth, in the lightwave SCM environment where both the clipping impulse noise and Gaussian noise are present. As a result, the OFDM signals will introduce less interference effects on the nominal AM channels than the M-QAM signals under the same operating conditions.

Applications of real-time median filtering with fast digital and analog sorters

Abstract: This paper explores applications of digital and analog hardware realizations of median filters suitable for potential use in real-time control and monitoring applications in power electronic circuits and drives. Median filters have the ability to suppress impulse noise in signals, while preserving underlying edges. Filter performance is demonstrated with results from two prototypes.

Noise cancellation using nonlinear fuzzy filters

Abstract: Noise cancellation is a key task in the area of digital processing of measurement data. In this framework, the role of emergent techniques is rapidly growing. This paper aims at presenting the latest advances in the field of 2-D filters based on fuzzy reasoning. First, a classification of most significant approaches is proposed. Then, a collection of methods is analyzed focussing on their similarities and differences. A new filtering technique is proposed in the second part of the paper. The new filter belongs to the class of FIRE filters: it combines in the same structure rules for different noise statistics. Experimental results show that the proposed method is able to restore data corrupted by mixed Gaussian and impulse noise outperforming other techniques in the literature.

Robust impulse noise suppression using adaptive wavelet de-noising

Abstract: It is widely acknowledged that the effect of impulsive noise is a major source of performance degradation within a wide range of communication systems. This is due to the fact that non-Gaussian interference is neglected within the system design philosophy for reasons of complexity and tractability. We directly address this problem using a novel 'de-noising' technique in which significant performance gains are achieved with low-complexity.

Selective vector median filtering of colour images

Abstract: The vector median filter (VMF) has proved to be a highly effective tool for removing impulse noise from colour images [1]. However, when images are highly corrupted [2], or when high fidelity is required [3], the application of a vector median filter may lead to unacceptable levels of colour image distortion. In this paper we present a development of the VMF, which divides the filtering process into two distinct stages: noise detection; and noise removal. This allows selective application of the VMF to only those neighbourhoods which contain 'noisy pixels' and subsequently allows these pixels to be excluded from the calculation of the vector median. It is therefore possible to substantially improve the performance of the VMF when operating on highly corrupted images or when an application requires a high level of fidelity.

Apparatus for reducing impulse noise in high-frequency digital receivers

Abstract: A high-frequency radio signal receiving apparatus for digital communication includes a receiving antenna for receiving a high-frequency radio wave, a frequency converter for converting a signal supplied from the receiving antenna through a wide-band bandpass filter into a signal of an intermediate frequency band, an impulsive noise detecting unit for detecting impulsive noise on the basis of a signal outputted from the frequency converter. The apparatus further includes an impulsive noise correcting unit for correcting the signal outputted from the frequency converter in dependence on a signal outputted from the impulsive noise detecting unit, and a demodulating unit for demodulating a signal outputted from the impulsive noise correcting unit and supplied by way of a narrow-band bandpass filter.

New Computational Methods for the Prediction and Analysis of Helicopter Noise

Abstract: : This paper describes several new methods to predict and analyze rotorcraft noise. These methods are 1) a combined computational fluid dynamics and Kirchholt scheme for far-field noise predictions, 2) parallel computer implementation of the Kirchhoff integrations 3) audio and visual rendering of the computed acoustic predictions over large far-field regions, and 4) acoustic tracebacks to the Kirchhoff surface to pinpoint the sources of the rotor noise. The paper describes each method and presents sample results for three test cases. The first case consists of in-plane high-speed impulsive noise and the other two cases show idealized parallel and oblique blade-vortex interactions. The computed results show good agreement with available experimental data but convey much more information about the far-field noise propagation. When taken together, these new analysis methods exploit the power of new computer technologies and offer the potential to significantly improve our prediction and understanding of rotorcraft noise.

Learning algorithms for audio signal enhancement. Part 2 : Implementation of the rough-set method for the removal of hiss

Abstract: Learning algorithms were implemented for the elimination of strong hiss found in old records and of impulse noise affecting transmitted audio signals. The rough-set method was tested with regard to the automatic setting of the cutoff threshold in the spectral filtration of noisy audio. Applied methods, results of musical signal processing, and conclusions are presented.

Robust modelling of noisy ARMA signals

Abstract: In this paper methods are developed for enhancement and analysis of autoregressive moving average (ARMA) signals observed in additive noise which can be represented as mixtures of heavy-tailed non-Gaussian sources and a Gaussian background component. Such models find application in systems such as atmospheric communications channels or early sound recordings which are prone to intermittent impulse noise. Markov chain Monte Carlo (MCMC) simulation techniques are applied to the joint problem of signal extraction, model parameter estimation and detection of impulses within a fully Bayesian framework. The algorithms require only simple linear iterations for all of the unknowns, including the MA parameters, which is in contrast with existing MCMC methods for analysis of noise-free ARMA models. The methods are illustrated using synthetic data and noise-degraded sound recordings.

Nonlinear filtering of noisy images using neuro-fuzzy operators

Abstract: A neuro-fuzzy approach to nonlinear filtering of noisy images is presented. A new filter is proposed which aims at combining the advantages of neural and fuzzy paradigms. The network structure of the neuro-fuzzy operator implements a particular mechanism based on fuzzy reasoning which specifically addresses noise cancellation and preservation of image details. The learning method is based on the genetic algorithms (GAs) and yields an effective training of the network in presence of data even if highly corrupted by noise. The results of computer simulations show that the neuro-fuzzy filter is very effective in removing impulse noise and is able to outperform a number of methods in the literature.

Equalizer, reception system having an equalizer, data conversion method and apparatus thereof

Abstract: Apparatus and method for minimizing a data error, in case of fault, by detecting a sudden level fluctuation by hit or impulse noise of an input signal, level recovery, and error variance based on the error judged from the equalized signal, and updating a tap coefficient of an adaptive tap coefficient in accordance with the result of detection.

A wavelet-domain algorithm for denoising in the presence of noise outliers

Abstract: A wavelet domain robust denoising algorithm is presented, which efficiently removes both Gaussian as well as Gaussian mixed with impulse noise. Several wavelet domain operators are developed which help in the denoising process. The superiority of the new algorithm is firmly established by simulation over a variety of images.

Use of Animal Test Data in the Development of a Human Auditory Hazard Criterion for Impulse Noise, Part 1

Abstract: : Hearing loss and sensory cell loss data, obtained from 909 chinchillas exposed to one of 137 different impulse noise or blast wave exposure paradigms, were statistically analyzed. The objective was to extract relations between the effects of the exposure on the auditory system (effects metrics) and metrics used to characterize the blast wave exposure. Specifically the following two questions were asked: (a) What is the best indicator of the amount of hazard associated with an impulse noise exposure? (b) How does the hazard of an impulse noise exposure accumulate with increasing numbers of impulses? Two analytical approaches were used. Both approaches indicated that the P-weighting functions or one of its derivatives (P1-, P2- or R-weighting) best organized the effects metrics. Depending on the analytical approach, either an energy trading rule of 10 log(10) N or 6 log(10) N; where N is the number of impulses, best organized the data for N between 10 and 100. For exposures of between 1 and 10 impulses, a region of the parametric space that is of considerable practical significance, there is insufficient data to form any conclusions. For this region the limited data suggest that an energy trading rule i.e., 10 log N, does not work.

Hit-noise reduction in portal images: a comparison between wavelet- and rank-order-based methods

Abstract: The system we have been investigating is a real-time portal imager which incorporates an x-ray-to-light converter and a CCD sensor. When the high-energy X-rays of the radiation therapy beam circumvent the converter and impinge directly on the CCD sensor they cause artifacts in the image that have the appearance of scattered bright points of light. It is as if salt has been shaken onto a photograph. In therapy imaging the artifact is termed 'direct hit' noise. The generic name impulse noise. The goal of this investigation has been to determine an efficient method for eliminating 'direct hit' artifacts produced on a CCD camera in a portal imaging system. Because the photon energies for portal imaging are so high, it is very difficult to prevent the hits. For that reason, we have investigated post-processing methods to remove the noise from captured images. Two families of filtering algorithms are applied in the images: A wavelet-based family and a rank-order based family.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Non-intrusive measurement of impulsive noise in telephone-type networks

Abstract: An in-service, non-intrusive technique for the characterization of stationary and impulsive noise in a telecommunication system is presented. It is based on the segmentation of the signal observed during a telephone call in speech and noise periods by means of a Bayesian classifier. The signal observed during noise periods is further processed by means of a hypothesis testing procedure in order to detect noise-impulses. Experimental results that show the effectiveness of the proposed technique are discussed.

Removal of impulse noise in highly corrupted digital images using a relaxation algorithm

Abstract: A relaxation algorithm for removing impulse noise from highly corrupted images is proposed, where a nonlinear probabilistic model is used to reduce the ambiguity of each pixel based on the contextual information. Each pixel is given three labels which stand for ‘‘positive corruption,’’ ‘‘no corruption,’’ and ‘‘negative corruption.’’ The initial probabilities of a pixel whose gray level lies in the middle intensity range of the whole image are simply given some fixed values. Those of a pixel whose gray level lies in the upper or lower part of the intensity range are determined by its gray level and the difference with the median value in a 3×3 window. To display the image after each iteration, the gray level of a pixel with high no-corruption probability is set to its original value approximately, while the gray level of a pixel with high corruption probability will be replaced by the average value of its neighbor pixels with high no-corruption probabilities. Experimental results show that this algorithm can effectively remove both positive and negative impulse noise with very high probability and is superior in performance to some other methods for highly corrupted images.

Two-stage nonlinear detector in DS/SSMA communications with impulse noise

Abstract: A new two-stage nonlinear detector for synchronous DS/SSMA communications in impulsive channels is presented and analysed. In the detector, an interference cancellation scheme is used such that the effect of the multiple-access on the system performance can be alleviated. For a multiuser system with long spreading sequences an approximate error probability is derived and shows that the new detector is insensitive to the 'near-far' effect and gives a near-single-user performance. For cases with short spreading sequences Monte-Carlo simulations are carried out to estimate the error probability and the results show that the detector performs robustly in various mixtures of noise.

Joint amplitude and delay estimation for CDMA systems in impulsive channels

Abstract: A nonlinear extended recursive least square algorithm for the joint estimation of the amplitude and delay of the user signals in CDMA system over impulsive channels is presented. Simulation results show that by using a nonlinear function to palliate the effect of the impulse noise, the new algorithm can provide a robust performance quite close to the Cramer-Rao lower bound.