Coding of details in very low bit-rate video systems

In this paper, the importance of including small image features at the initial levels of a progressive second generation video coding scheme is presented. It is shown that a number of meaningful small features called details should be coded, even at very low data bit-rates, in order to match their perceptual significance to the human visual system. We propose a method for extracting, perceptually selecting and coding of visual details in a video sequence using morphological techniques. Its application in the framework of a multiresolution segmentation-based coding algorithm yields better results than pure segmentation techniques at higher compression ratios, if the selection step fits some main subjective requirements. Details are extracted and coded separately from the region structure and included in the reconstructed images in a later stage. The bet of considering the local background of a given detail for its perceptual selection breaks the concept ofPeer ReviewedPostprint (published version

A review of ride comfort studies in the United Kingdom

United Kingdom research which is relevant to the assessment of vehicle ride comfort was reviewed. The findings reported in approximately 80 research papers are outlined, and an index to the areas of application of these studies is provided. The data obtained by different research groups are compared, and it is concluded that, while there are some areas of general agreement, the findings obtained from previous United Kingdom research are insufficient to define a general purpose ride comfort evaluation procedure. The degree to which United Kingdom research supports the vibration evaluation procedure defined in the current International Standard on the evaluation of human exposure to whole-body vibration is discussed

The Role of Edges and Line-Ends in Illusory Contour Formation

Illusory contours can be induced along directions approximately collinear to edges or approximately perpendicular to the ends of lines. Using a rating scale procedure we explored the relation between the two types of inducers by systematically varying the thickness of inducing elements to result; in varying amounts of "edge-like" or "line-like" induction. Inducers for om illusory figures consisted of concentric rings with arcs missing. Observers judged the clarity and brightness of illusory figures as the number of arcs, their thicknesses, and spacings were parametrically varied. Degree of clarity and amount of induced brightness were both found to be inverted-U functions of the number of arcs. These results mandate that any valid model of illusory contour formation must account for interference effects between parallel lines or between those neural units responsible for completion of boundary signals in directions perpendicular to the ends of thin lines. Line width was found to have an effect on both clarity and brightness, a finding inconsistent with those models which employ only completion perpendicular to inducer orientation.Air Force Office of Scientific Research (F49620-92-J-0334, URI 90-0175, F49620-92-J-0334); National Science Foundation (Graduate Fellowship); Office of Naval Research (N00014-91-J-4100

Non-linear dependency of the subjective perceived intensity of steering wheel rotational vibration

This is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2009 ElsevierThe present study has established equal sensation curves for steering wheel hand-arm rotational vibration. Psychophysical response tests of 20 participants were performed in a steering wheel rotational vibration simulator using the category-ratio Borg CR10 scale procedure for direct estimation of perceived vibration intensity. The test stimuli used were sinusoidal vibrations at 22 third octave band centre frequencies in the range from 3 to 400 Hz, with acceleration amplitudes in the range from 0.06 to 30 m/s(2) r.m.s. A multivariate regression analysis was performed on the mean perceived intensity Borg CR10 values as a function of the two independent parameters of the vibration frequency and amplitude. The results suggested a non-linear dependency of the subjective perceived intensity on both the steering wheel rotational vibration frequency and amplitude. The equal sensation curves were found to be characterised by a decreased sensitivity to hand-arm vibration with increasing frequency from 10 to 400 Hz, but by an increased sensitivity with increasing frequency from 4 to 10 Hz. A 6th order polynomial model has been proposed as a best fit regression model from which the equal sensation curves for steering wheel rotational vibration are derived.Relevance to industry: For the manufactures of automobiles, steering systems and other automobile components this study provides a mathematical model from which one or more new frequency weightings for the use in evaluating the perceived intensity of steering wheel rotational vibration are derived. (C) 2008 Elsevier B.V. All rights reserved

Hand-arm equal sensation curves for steering wheel rotational vibration

The present study has established equal sensation curves for steering wheel handarm rotational vibration. Psychophysical response tests of 20 participants were performed using the category-ratio Borg CR10 scale procedure. The test stimuli used were sinusoidal vibrations at 22 third octave band centre frequencies in the range from 3 to 400 Hz, with amplitudes in the range from 0.06 to 30 m/s2 r.m.s. A multivariate regression analysis was performed on the mean Borg CR10 intensity values as a function of the two independent parameters of the vibration frequency and amplitude. The results suggested a nonlinear dependency of the perceived intensity on both the steering wheel rotational vibration frequency and amplitude. A sixth-order polynomial model has been proposed as a best fit regression model

Human comfort in relation to sinusoidal vibration

An investigation was made to assess the overall subjective comfort levels to sinusoidal excitations over the range 1 to 19 Hz using a two axis electrohydraulic vibration simulator. Exposure durations of 16 minutes, 25 minutes, 1 hour, and 2.5 hours have been considered. Subjects were not exposed over such durations, but were instructed to estimate the overall comfort levels preferred had they been constantly subjected to vibration over such durations

Boundary, Brightness, and Depth Interactions During Preattentive Representation and Attentive Recognition of Figure and Ground

This article applies a recent theory of 3-D biological vision, called FACADE Theory, to explain several percepts which Kanizsa pioneered. These include 3-D pop-out of an occluding form in front of an occluded form, leading to completion and recognition of the occluded form; 3-D transparent and opaque percepts of Kanizsa squares, with and without Varin wedges; and interactions between percepts of illusory contours, brightness, and depth in response to 2-D Kanizsa images. These explanations clarify how a partially occluded object representation can be completed for purposes of object recognition, without the completed part of the representation necessarily being seen. The theory traces these percepts to neural mechanisms that compensate for measurement uncertainty and complementarity at individual cortical processing stages by using parallel and hierarchical interactions among several cortical processing stages. These interactions are modelled by a Boundary Contour System (BCS) that generates emergent boundary segmentations and a complementary Feature Contour System (FCS) that fills-in surface representations of brightness, color, and depth. The BCS and FCS interact reciprocally with an Object Recognition System (ORS) that binds BCS boundary and FCS surface representations into attentive object representations. The BCS models the parvocellular LGN→Interblob→Interstripe→V4 cortical processing stream, the FCS models the parvocellular LGN→Blob→Thin Stripe→V4 cortical processing stream, and the ORS models inferotemporal cortex.Air Force Office of Scientific Research (F49620-92-J-0499); Defense Advanced Research Projects Agency (N00014-92-J-4015); Office of Naval Research (N00014-91-J-4100

Optic nerve head segmentation

Reliable and efficient optic disk localization and segmentation are important tasks in automated retinal screening. General-purpose edge detection algorithms often fail to segment the optic disk due to fuzzy boundaries, inconsistent image contrast or missing edge features. This paper presents an algorithm for the localization and segmentation of the optic nerve head boundary in low-resolution images (about 20 /spl mu//pixel). Optic disk localization is achieved using specialized template matching, and segmentation by a deformable contour model. The latter uses a global elliptical model and a local deformable model with variable edge-strength dependent stiffness. The algorithm is evaluated against a randomly selected database of 100 images from a diabetic screening programme. Ten images were classified as unusable; the others were of variable quality. The localization algorithm succeeded on all bar one usable image; the contour estimation algorithm was qualitatively assessed by an ophthalmologist as having Excellent-Fair performance in 83% of cases, and performs well even on blurred image

Effects of gender differences on the subjective perceived intensity of steering wheel rotational vibration based on a multivariate regression model

This is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2009 ElsevierThe aims of this study were to determine equal sensation curves for hand-arm steering wheel rotational vibration and to investigate the effect of gender on the subjective perceived intensity of steering wheel hand-arm vibration. Psychophysical response tests of 40 participants (20 mates and 20 females) were performed using a steering wheel rotational vibration simulator using the category-ratio Borg CR10 scale procedure for direct estimation of perceived intensity. The test stimuli were sinusoidal vibrations at 22 third octave band centre frequencies in the range from 3 to 400 Hz, with acceleration amplitudes in the range from 0.04 to 27 m/s(2) r.m.s. Multivariate regression procedures were applied to the experimentally acquired data in order to establish a regression model expressing the Borg CR10 perceived intensity values as a function of the two independent parameters of the frequency and amplitude of vibration. The equal sensation curves suggested a non-linear dependency of the subjective perceived intensity on both frequency and amplitude. Females were found to provide higher Borg CR10 perceived intensity values than males (p < 0.05), particularly at the higher intensity levels above approximately 1.0 m/s(2) r.m.s and at the higher frequencies above approximately 20 Hz.Relevance to industry: For the manufacturers of steering systems and of other automobile components this study provides vibration perception curves and identifies the possible importance of gender towards the perception of vibration which arrives at the steering wheel. (C) 2009 Elsevier B.V. All rights reserved