Showing papers on "Impulse noise published in 1995"

Adaptive median filters: new algorithms and results

Abstract: Based on two types of image models corrupted by impulse noise, we propose two new algorithms for adaptive median filters. They have variable window size for removal of impulses while preserving sharpness. The first one, called the ranked-order based adaptive median filter (RAMF), is based on a test for the presence of impulses in the center pixel itself followed by a test for the presence of residual impulses in the median filter output. The second one, called the impulse size based adaptive median filter (SAMF), is based on the detection of the size of the impulse noise. It is shown that the RAMF is superior to the nonlinear mean L/sub p/ filter in removing positive and negative impulses while simultaneously preserving sharpness; the SAMF is superior to Lin's (1988) adaptive scheme because it is simpler with better performance in removing the high density impulsive noise as well as nonimpulsive noise and in preserving the fine details. Simulations on standard images confirm that these algorithms are superior to standard median filters. >

A signal-dependent rank ordered mean (SD-ROM) filter-a new approach for removal of impulses from highly corrupted images

Abstract: Proposes an efficient nonlinear algorithm to suppress impulse noise from highly corrupted images while preserving details and features. The method is applicable to all impulse noise models, including fixed valued (equal height or salt and pepper) impulses and random valued (unequal height) impulses, covering the whole dynamic range. The algorithm is based on a detection-estimation strategy. If a signal sample is detected as a corrupted sample, it is replaced with an estimation of the true value, based on neighborhood information. Otherwise it is kept unchanged. The technique achieves excellent tradeoff between the suppression of noise, and preserving the details and edges without undue increase in computational complexity. Extensive simulation tests indicate that the method performs better than other existing algorithms, including the well known median filters. Illustrative examples included in the paper verify the capability of the proposed approach.

Adaptive robust impulse noise filtering

Abstract: It is well known that when data is contaminated by non-Gaussian noise, conventional linear systems may perform poorly. The paper presents an adaptive robust filter (adaptive preprocessor) for canceling impulsive components when the nominal process (or background noise) is a correlated, possibly nonstationary, Gaussian process. The proposed preprocessor does not require iterative and/or batch processing or prior knowledge about the nominal Gaussian process; consequently, it can be implemented in real time and adapt to changes in the environment. Based on simulation results, the proposed adaptive preprocessor shows superior performances over presently available techniques for cleaning impulse noise. Using the proposed adaptive preprocessor to clean the impulsive components in received data samples, conventional linear systems based on the Gaussian assumption can work in an impulsive environment with little if any modification. The technique is applicable to a wide range of problems, such as detection, power spectral estimation, and jamming or clutter suppression in impulsive environments. >

Methods and apparatus for reducing the effect of impulse noise on receivers

Abstract: Methods and apparatus for detecting the presence of impulse noise in a signal representing digital data and for performing a limiting or blanking operation in a receiver in response thereto are disclosed. In accordance with the present invention, to detect the presence of impulse noise, in one embodiment, the instantaneous sliced error energy for each received symbol is estimated and compared to either a predetermined threshold level indicative of impulse noise or to an adaptive impulse noise threshold level. In an adaptive impulse noise threshold embodiment, an adaptive impulse noise threshold value is generated by averaging the instantaneous sliced error energy values over a period of many symbols and by then applying a preselected gain to the averaged sliced error energy value to obtain an impulse noise threshold value. When impulse noise is detected a signal is asserted to indicate the detection and presence of the impulse noise and carrier recovery phase error correction operations and other decision dependent operations blanked or left unchanged until the impulse noise is no longer detected or for a preselected period of time after impulse noise has been detected.

Method and apparatus for selecting an adaptive filter for image data

Abstract: A device and method for filtering out the noise generated due to coding of image data signals. The device has a threshold determining unit, a binary index unit, a filter selecting unit, and an adaptive filtering unit. The threshold determining unit 4 divides each pixel of the input image data into two gray levels. The binary indexes defined by the gray level are checked by a window with a prescribed size. If the region in the window is determined to be a homogeneous region, a heterogeneous region, or an impulse noise region (block 5), the filter selecting unit selects a filter corresponding to the determined region, and the image data is processed by the selected filter.

System for controlling the effects of noise in television receivers

Abstract: A television receiver having a microprocessor controlled disturbance control system that can operate totally under user control or automatically. The microprocessor generates an on-screen menu which presents noise control options to the user. In the preferred embodiment, the menu options allow the user to ameliorate the effects of impulse noise disturbances, longer duration disturbances, continuous wave form (CW) disturbances, or some combination of the three, without requiring the user to understand the nature of these disturbances. The present invention also provides compensation circuitry for reducing the effects of impulse noise in the video signal that is controlled by responding to the high frequency luminance signal produced by a comb filter, and also responding to the composite video picture signal. High frequency luminance and amplitude variations that are outside of the composite video signal range are indicative of the presence of impulse noise. These variations are detected and used to produce a control signal for activating tracking and hold circuitry for reducing the effect of the impulse.

Comfort noise generator for echo cancelers

Abstract: The invention describes a method and device of comfort noise generation for echo cancelers. The invention stores the actual background noise of a channel in a noise buffer. When the echo suppressor is activated by the echo canceler to suppress any unwanted signals on the channel, the buffer provides the stored noise to the channel to provide continuous background noise. To ensure that neither speech nor impulse noise enters the buffer, hangover delays and energy threshold levels are provided such that signals within the delay period or signals which exceed the energy threshold level are screened from entering the buffer.

Partial discharge signal generation transmission and acquisition

Abstract: The phase resolved partial discharge detection technique (or 'PD pattern recording technique') is applicable to field measurements, particularly if combined with disturbance rejection techniques and non-conventional pick-up circuits. Electromagnetic disturbances can be eliminated by filtering in the time domain (impulse noise gating) and/or in the frequency domain (down-mixing). The PD patterns not only reveal the PD physics and thus help to identify the defect type, but also serve to evaluate the efficiency of the disturbance rejection procedure.

Two-dimensional rank-conditioned median filter

Abstract: A version of 2-D median filter specialized to impulse noise removal introducing negligible distortion in noise-free pixels is proposed Only pixels of prefixed ranks are replaced with the local median When extreme ranks (min and max) are chosen, spikes are selectively suppressed, more efficiently than by median filter Error probability for salt/pepper noise is theoretically derived MAE and visual comparisons with median filter attest increased accuracy >

Noise, impulse noise, and other physical factors: combined effects on hearing.

Abstract: In most of the epidemiologic studies conducted during the last 20 years, impulse noise caused increased risk of hearing loss in comparison to continuous noise with the same acoustical energy. The interaction between noise exposure (broadband at 100 dB(A)) and hand-arm vibration (125 Hz at 2 ms-2 acceleration level) has been proven for people having vibration-induced white finger symptoms. This interaction is evidenced as a permanent hearing loss. However, why the interaction is seen only in people with VWF is not known. The mechanisms may be related to individual susceptibility, and hypotheses are given on the role of the autonomous nervous system regulating the peripheral vascular reaction. Whole-body vibration (2-10 Hz, at 10 ms-2 level) seems to increase the TTS when noise (broadband at 90 dB(A)) is present. This effect is more pronounced at higher temperatures. The hypothermia protects hearing against the effects of noise in animal studies. The interaction between noise and temperature decrease seems obvious in animal studies. Exercise has both increased and decreased the TTS during noise exposure. The effects have been successfully explained as the depression of the stapedius reflex. Thus, less protection against noise is provided for the inner ear in exercise conditions. The increase of the blood temperature also has been suggested to increase noise-induced TTS during exercise. Electromagnetic fields have been found to cause acoustical interactions in the inner ear. Animal studies and human studies have given contradictory results on the effects of magnetic coil devices on hearing. The MR imaging devices produce noise levels of 82-93 dB, which is not sufficient to produce the risk of permanent hearing loss when short exposure durations are taken into consideration. More systematic research is needed with accurately defined electromagnetic characteristics to reveal the potential interactions. The interactions seem to exist, but relatively high levels and durations of exposure are needed to produce an observable effect on hearing. More investigations are still needed on the permanent hearing loss in humans caused by simultaneous long-term exposures to interacting environmental factors.

Adaptive noise transformation system

Abstract: A system for suppressing the effects of undesirable noise from an annoying noise source contains a plurality of transformation sounds which, when combined with the noise form a sound that is pleasing to the ear. The transformation sounds are stored in the digital memory of the system or on a CD-ROM. The incident noise is detected and converted to signals which are dynamically analyzed, filtered and monitored to control the transformation sound selection process. The transformation sounds are modulated by a filtered signal derived from these noise signals that tracks the average energy in the noise. The transformation sounds include a primary transformation sound that is selected substantially continuously. The transformation sounds include also secondary transformation sounds that are selected for combination with the noise in periods when the primary transformation sound does not completely suppress the undesirable effects of the noise, and when the primary transformation sound is decreasing in volume. The system is especially effective in abating the traffic noise from freeways at nearby locations.

Noise elimination circuit

Abstract: PROBLEM TO BE SOLVED: To eliminate only impulse noise by leaving vertical and horizontal edges in the case of animation and still images SOLUTION: A video signal SI of a current field is sequentially stored in frame memories 1, 2, and a motion vector detection circuit 3 detects a motion vector S3 A motion correction circuit 4 reads the pixel of a preceding field corresponding to a noted pixel of a current field from the frame memory 2 An inter-frame difference arithmetic operation circuit 5 accumulates the absolute value of differences of the pixel of the current field and the preceding field for each block Horizontal and vertical edge detection circuits 6, 7 outputs signals S6, S7 representing horizontal and vertical edges Delay circuits 8-1 to 8-3 are used to make time matching A discrimination circuit 9 generates a selection signal S10 to select a filter and a delay circuit 10 is used to make time matching Vertical, horizontal and spatial media filter 11, 12, 13 apply filter processing to the video signal and delay circuits 14-1 to 14-3 are used to make time matching and a selection circuit 15 selects the signal

Coded 64-CAP ADSL in an impulse-noise environment-simulation results

Abstract: This paper describes performance results of E1-ADSL (2.048 Mb/s asymmetrical digital subscriber line) transmission based on carrierless amplitude/phase modulation (CAP) in an impulse-noise environment. Various coding schemes for error protection are investigated. Code options are Reed Solomon code with interleaving, array code and trellis coding, or interleaved trellis coding. The simulation results are based on real measured impulses from an impulse-noise measurement campaign carried out by German Telekom. The inter-arrival times between impulses were either assumed to be constant (worst-case scenario) or were delivered from a distinctive stochastic generator with an inter-arrival time density according to a model also derived in the German campaign. It was found that the RS codes, even with a quite small error-correcting capability, achieved acceptable error performance. Array codes can also be a low-complexity alternative. Trellis coding alone, as expected, was not very effective against the impulse noise.

Minimum mean squared error impulse noise estimation and cancellation

Abstract: Impulses are infrequent bursts of high amplitude noise. A wide-band communications or data acquisition receiver has a fast sampling rate, so it can capture many samples of each impulse waveform. The arrival of an impulse can be identified by its distinct waveform and amplitude. The paper models impulse waveforms as a vector subspace of low dimension. Formulas are derived for the minimum mean squared error (MMSE) estimation of the arrival time and amplitudes of impulses, given that a set of vectors that spans the subspace is known. Formulas are also derived for the adaptive MMSE estimation of a set of vectors that spans the subspace. The values of the mean squared error (MSE) of the amplitude estimates are determined. It is shown how the theory can be used to cancel impulse noise. Correlated impulse noise arriving at a reference input can be used to estimate and cancel the primary input impulse noise. The MMSE coefficients for impulse noise cancellation are derived and presented. Simulations are presented that use the equations and methods derived in the paper for modeling and canceling impulse noise measured on copper telephone loops for asymmetric digital subscriber lines (ADSL). >

Modified 2D median filter for impulse noise suppression in a real-time system

Abstract: A new modified 2D (3*3) multi-shell median filter (MMMF) for restoration of images corrupted with impulse noise is presented. This filter can not only reduce impulse noise but alleviate missing line errors. The hardware of MMMF can be easily implemented using standard TTL ICs. In fact, we realize the circuit by the Field Programmable Gate Array (FPGA). This novel median filter can be used in a real time system for noise suppression. >

Vector median filters for processing of color images in various color spaces

Abstract: The paper presents a comparative study of performance of 2D vector median filters which calculate in various color coordinates the distances between the vectors corresponding to pixels of color images. The paper deals with the problem of the best choice of the color space for vector median calculations. The problem is considered for the task of restoration of color images corrupted with impulse noise. The comparison has been made experimentally, using 4 test images and 3 types of impulse noise. The results have been evaluated by consideration of quadratic errors in the Munsell space as well as by comparing their subjective quality.

Detection and removal of impulse noise by a neural network guided adaptive median filter

Abstract: We introduce a novel adaptive median filter for the removal of impulse noise in images Using pixel classification by a self-organising neural network to detect the positions of the noisy pixels, we are able to effectively eliminate the impulses while retaining image integrity Detailed statistical analysis and comparison of the proposed method with traditional median filters are provided A visual example is given to demonstrate the performance of the proposed filter

Novel filter algorithm for removing impulse noise in digital images

Abstract: In this paper, we present a novel filter algorithm that is more capable in removing impulse noise than some of the common noise removal filters The philosophy of the new algorithm is based on a pixel identification concept Rather than processing every pixel in a digital image, this new algorithm intelligently interrogates a subimage region to determine which are the 'corrupted' pixels within the subimage With this knowledge, only the 'corrupted' pixels are eventually filtered, whereas the 'uncorrupted' pixels are untouched Extensive testing of the algorithm over a hundred noisy images shows that the new algorithm exhibits three major characteristics First, its ability in removing impulse noise is better visually and has the smallest mean-square error compared with the median filter, averaging filter and sigma filter Second, the effect of smoothing is minimal As a result, edge and line sharpness is retained Third, the new algorithm is consistently faster than the median filter in all our test cases In its current form, the new filter algorithm performs well with impulse noise© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering Downloading of the abstract is permitted for personal use only

A recursive nonlinear filter for removal of impulse noise

Abstract: We present a new algorithm for suppression of impulse noise which is based on a special combination of impulse detection and nonlinear filtering. The nonlinear filter possesses a recursive structure and provides an estimate of the original sample and the impulse height. The impulse detector is realized as a radial basis function network and yields a fuzzy decision about the impulsivity of a sample. Due to the special combination of both systems, we need only a small number of parameters which can be computed recursively using a procedure derived from a joint optimality criterion. Thereby, we achieve a dramatic gain in performance over other existing methods for both weakly and highly corrupted signals. Further, the algorithm preserves signal details and edges and is applicable to arbitrary impulse distributions.

Picture noise elimination device

Abstract: PURPOSE:To eliminate the impulse noise in a flat picture part without degrading the picture quality at an contour part CONSTITUTION:Since this device is provided with a rank order filter for outputting the value of the order of a certain determined size inside a certain determined area on a field or on a frame for input picture signals 1 and a picture output circuit 3 for outputting picture signals based on the output of the rank order filter and input picture signals and the picture signals are outputted based on the input signals and output signals of the rank order filter, the impulse noise of the flat picture part is eliminated without degrading the picture quality at the contour part of an object

Impulse noise correction in TV transmission

Abstract: We describe a real-time digital image processing approach for correcting the impulse noise impairment in television transmission. The described algorithm identifies the pixels impaired with impulse noise and subsequently corrects them. A real-time processing board is constructed to demonstrate the algorithm. >

Mitigating impulse noise over HFC networks for telephony-over-cable

Abstract: This paper deals with the design of impulse noise resistant receivers for providing telephony-over-cable (ToC) services over hybrid fiber coax (HFC) networks. We first discuss the overall scenario of ToC services and the impulse noise problems faced by such systems in HFC networks. We then briefly describe the time-frequency characteristics of impulse interference and derive the probability of error for binary and quadrature PSK signalling schemes for impulse noise afflicted channels. In light of the constraints imposed by the ToC problem, the performance of the proposed solution strategies which make use of non-linear processing and channel coding, is evaluated in detail along with simulation results.

State-conditioned rank-ordered filtering for removing impulse noise in images

Abstract: A new framework for removing impulse noise from images is presented in which the nature of the filtering operation is conditioned on a state variable. As part of this state-based framework, several sliding-window algorithms are examined, each of which is applicable to fixed and random-valued impulse noise models. First, a simple two-state approach is described in which the current state is computed according to the output of a simple classifier that operates on the differences between the input pixel and the remaining rank-ordered pixels in the current window. Based on the value of the state variable, the algorithm switches between the output of an identity filter and an order-statistic (OS) filter. For a small additional cost in memory, this simple strategy is easily generalized into a multi-state approach using weighted combinations of the identity and OS filters in which the weighting coefficients can be optimized using image training data. Extensive simulations indicate that these methods perform significantly better in terms of noise suppression and detail preservation than a number of existing nonlinear techniques with as much as thirty percent impulse noise. Finally, the method is shown to be extremely robust with respect to the training data and the percentage of impulse noise.

Impulse noise removing circuit

Abstract: PURPOSE:To reduce the deterioration of a signal by removing an impulse noise from an FM demodulated signal in the case of a weak electric field CONSTITUTION:An impulse noise a' is extracted from an input signal 1 through an HPF 2, a gate pulse (b) is generated from an MV 5 by delaying the noise a', the input signal is also applied to delay circuits 3, 4 to delay it, the gain of the impulse part is turned to '0' through gate circuits 11 to 13, and the amplitude values E1, E2 of the leading edges of signals are extracted On the other hand, a slowly rising rectangular wave (h) is extracted from the gate pulse through a saw tooth generating circuit 8 and a gate circuit 9 and a slowly falling triangular wave (m) is extracted through an MV 7 and a subtraction circuit 10 so that the amplitude values of both the signals (h), (m) are set up to E1 and E2 Then outputs (f), (l) from the gate circuits 11, 12 are held by respective box cars 14, 15 as pulses f', l' with width tau2, signals (i), (n) with amplitude E1, E2 are obtained respectively through multiplier circuits 16, 17 and added to the output (k) of the gate circuit 13 through a synthesizing circuit 18 to execute the linear interpolation of the leading and trailing edges of the part lacked as the impulse part by the gate circuit 13

Median and neural networks hybrid filters

Abstract: In this paper we present a new nonlinear filter with neural networks for signal processing in a mixed noise environment, where both Gaussian noise and impulsive noise may be present. Mean filters can effectively remove the Gaussian noise and order statistics filters can effectively remove the impulsive noise. However it is difficult to combine these filters to remove the mixed noise in an image processing environment without blurring the image details or edges. In order to remove a mixed noise while preserving edges and details, we develop a novel prototype filter which is composed of two stages. The purpose of the first and second stages is to remove the impulse noise and Gaussian noise, respectively. The prototype filter can be shown by a network structure. This network can be extended and generalized to the median and neural networks hybrid (MNNH) filter. The coefficients of the MNNH filter are learned by the backpropagation algorithm.

A wide-band impulse-noise survey on subscriber lines and inter-office trunks - Modeling and simulation

Abstract: Alternatives of a simulation model for impulse noise on subscriber lines are proposed and their statistical properties are outlined. Several pseudo-noise generators are combined with spectral shaping operations to approximate the desired statistics of the non-stationary disturbance. Although the considerations are based on the special statistical properties of impulse noise, the applied methods may as well be applicable to other modeling purposes. Especially, a proposal that allows to generate samples that fulfill the required amplitude statistics and bring forth a prescribed power density spectrum may be suitable elsewhere, too.

Impulse noise performance of an asymmetric digital subscriber lines passband transmission system

Abstract: This letter presents an analytical method to numerically evaluate the bit error Probability (BEP) performance of a quadrature amplitude modulation (QAM) transmission system in the presence of impulse noise. This work facilitates characterization of the two-wire twisted-pair loop plant for high-speed digital communications. Simulation results are presented to demonstrate the effectiveness of this approach using parameters that are typical of the recently proposed Asymmetric Digital Subscriber Lines (ADSL) for high-speed digital transmission over local copper telephone loops. >

The modified probabilistic neural network as a nonlinear correlator detector

Abstract: A nonlinear correlator detector for the detection of a signal class with some intra class variance is developed using the modified probabilistic neural network and the general regression neural network. An application, involving the detection of regular tone bursts transmitted over a poor and noisy radio channel subjected to fading, random noise and impulse noise effects, is used to show the effectiveness of the method as compared to a linear correlator.

Method of interlaced/progressive scanning changing method including double smoothing function and video signal processing device based thereon

Abstract: PURPOSE: To effectively remove an impulse noise and a Gaussian noise, and to suppress a step edge phenomenon by operating double smoothing constituted of median filtering, censoring, and OSF for an interlacing scanning signal, and converting it into a progressive scanning signal. CONSTITUTION: An interlacing scanning signal XK having noise components is processed by a double smoothing part 30 and an interlacing/progressive converting part 40. At first, a bias error depending on the size of a noise power and a signal edge is permitted so that the edge of the signal XK can be prevented from being damaged by using media filters 31 and 35 in the double smoothing part 30. Then, a smoothing filter in which censoring parts 32 and 36 are connected with OSF 33 and 38 is used. At that time, the censored pixel data are aligned in the order of the size by the OSF parts 33 and 38, and weight is added to each pixel data so that the smoothing of remaining noise components can be attained.

A study of impulse noise caused by connecting or disconnecting coaxial cable between equipment

Abstract: This paper describes the characteristics of impulse noise that is generated when a coaxial cable linking pieces of equipment at different ground potentials is connected or disconnected. The potential difference of equipment with a DC power supply system in a telecommunications center is simulated with an experimental model. The measured peak value of the impulse noise current is almost independent of any DC current on the coaxial cable produced by potential differences between the equipment and earth. An analysis model for adopting a SPICE program has been developed and the calculated waveforms agree well with the experimental results. A countermeasure to prevent the impulse noise current is also clarified.