1,721,071 research outputs found
Wavelet Atoms Approximation for Simultaneous Image Compression and Denoising
No full textWISDOW-Comp is a scheme for simultaneous image compression and denoising. Its key issue consists of firstly expanding the input image in a basis of wavelets. The corresponding coefficients can be then seen as waves that travel through both space and scales. Thus the overlapping effects principle can be applied to manage waves interference. Each atom is characterized by the amplitude and the location of its absolute modulus maximum. This powerful representation allows us to sent to the decoder just the low pass component of the image and the significance map of atoms absolute maxima for achieving a denoised image. Experimental results show that the proposed comp-denoiser outperforms the state of the art in terms of both rate and distortio
Signal Denoising via Overlapping Atoms in a Wavelet Domain
No full textIn this paper a novel approach to signal denoising in a wavelet domain is proposed. The signal is adapted to an a priori selected basis considering its details as the result of overlapping elementary atoms at different scale levels. This new proposal is supported by experimental observations along with some preliminary theoretical results
A WAVELET BASED CODING SCHEME VIA ATOMIC APPROXIMATION AND ADAPTIVE SAMPLING OF THE LOWEST FREQUENCY
No full textIn this paper1 a new wavelet based coding scheme exploiting Wavelet Atoms and a Non Uniform Sampling (WANUS) of the lowest frequency band is presented. The encoder only sends the lowest frequency band (LFB) to the decoder. This latter exploits atomic approximation for predicting wavelet details band from LFB. Since this strategy only works in an undecimated wavelet domain, we prove here that an effective adaptive downsampling of the LFB can be reached using the minimax technique. The proposed scheme outperforms available coders in terms of rate-distortion results requiring a moderate computational effort
SSIM based signature of facial micro-expressions
No full textFacial microexpressions (MEs) play a crucial role in the non verbal communication. Their automatic detection and recognition on a real video is a topic of great interest in different fields. However, the main difficulty in automatically capturing this kind of feature consists in its rapid temporal evolution, i.e. MEs occur in very few frames of video acquired by a conventional camera. In this paper a first study concerning the perceptual characteristics of ME is performed. The study is based on the observation that MEs are visible by a human observer, even though they are very rapid, and almost independently of the context. The Structural SIMilarity index (SSIM), which is a common perception-based metric, has been then used to detect a sort of fingerprint of MEs, that will be indicated as PES (Perceptual Expression Signature). The latter is able to efficiently guide the preprocessing step for MEs recognition procedure, as it allows for a fast video segmentation by providing only those frames where a ME occurs with high probability. Preliminary empirical studies on MEs in the wild have confirmed the feasibility of such an approach
Scratch Detection via Underdamped Harmonic Motion
No full textThis paper presents SDHO (scratch detection via harmonic oscillator), a generalized model to detect line scratches on digital images. The line scratch profile is now a solution of a second order homogeneous differential equation, depending exclusively on the width and the brightness of the scratch. This method performs noticeably better than the other existing techniques with a lower computing time
An entropy based approach for SSIM speed up
No full textThis paper focuses on an entropy based formalism to speed up the evaluation of the Structural SIMilarity(SSIM) index in images affected by a global distortion. Looking at images as information sources, avisualdistortion typical setcan be defined for SSIM. This typical set consists of just a subset of information belongingto the original image and the corresponding one in the distorted version. As side effect, some general theoreticalcriteria for the computation of any full reference quality assessment measure can be given in order to maximizeits computational efficiency. Experimental results on various test images show that the proposed approachallows to estimate SSIM with a considerable speed up (about 200 times) and a small relative error (often lowerthan 5%
TRANSIENTS DETECTION IN THE TIME SCALE DOMAIN
No full textIn this paper a novel model for transients detection in piecewise stationary signals is presented. A hybrid representation is assumed for the signal and the different behavior of each component (stationary, transient and stochastic) in the time-scale plane is exploited. Experimental results on both shape contours, described by a differential chain code, and audio signals show the generality of the proposed model
IMAGE DENOISING USING SIMILARITIES IN THE TIME SCALE PLANE
No full textThis paper presents a de-noising method that recognizes similarities in the image through the time scale behaviour of wavelet coefficients. Wavelet details are represented as linear combination of predefined atoms whose center of mass traces trajectories in the time scale plane (from fine to coarse scale). These trajectories are the solution of a proper ordinary differential equation and characterize atoms corresponding to groups of not isolated singularities in the signal. The distances among atoms, the ratio of their amplitudes and the difference of their decay along scales are the parameters to use for defining similarities in the image. Experimental results show the potentialities of the method in terms of visual quality and mean square error, reaching the most powerful and recent de-noising schemes
A fast preprocessing method for micro-expression spotting via perceptual detection of frozen frames
Full text linkThis paper presents a preliminary study concerning a fast preprocessing method for facial microexpression (ME) spotting in video sequences. The rationale is to detect frames containing frozen expressions as a quick warning for the presence of MEs. In fact, those frames can either precede or follow (or both) MEs according to ME type and the subject’s reaction. To that end, inspired by the Adelson–Bergen motion energy model and the instinctive nature of the preattentive vision, global visual perception-based features were employed for the detection of frozen frames. Preliminary results achieved on both controlled and uncontrolled videos confirmed that the proposed method is able to correctly detect frozen frames and those revealing the presence of nearby MEs—independently of ME kind and facial region. This property can then contribute to speeding up and simplifying the ME spotting process, especially during long video acquisitions
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