This paper presents a transform domain allocation method for watermarking of digital multimedia content;specific analytical results are obtained for audio watermarking. To solve the problem, the watermarking transmitt...
详细信息
ISBN:
(纸本)0819435899
This paper presents a transform domain allocation method for watermarking of digital multimedia content;specific analytical results are obtained for audio watermarking. To solve the problem, the watermarking transmitter, channel and receiver are formally defined and watermarking is described in a detection theory framework. Describing the channel by a generic attack model and using detection theory, the challenge is to minimize the probability of detection error at the receiver. Using strong assumptions an the original and watermark signals to derive analytical results, an optimal allocation method is deduced. The allocation strategy is compared to strategies in most present systems. Moreover, the assumptions on the signals reveal to be realistic in a given implementation of the watermarking system. The allocation method is being patented for digital multimedia content.
Recently, most background modeling approaches represent distributions of background changes by using parametric models such as Gaussian mixture models. Because of significant illumination changes and dynamic moving ba...
详细信息
Recently, most background modeling approaches represent distributions of background changes by using parametric models such as Gaussian mixture models. Because of significant illumination changes and dynamic moving backgrounds with time, variations of background changes are hard to be modeled by parametric background models. Moreover, how to efficiently and effectively update parameters of parametric models to reflect background changes remains a problem. In this paper, we propose a novel coarse-to-fine detection theory algorithm to extract foreground objects on the basis of nonparametric background and foreground models represented by binary descriptors. We update background and foreground models by a first-in-first-out strategy to maintain the most recent observed background and foreground instances. As shown in the experiments, our method can achieve better foreground extraction results and fewer false alarms of surveillance videos with lighting changes and dynamic backgrounds in both collected and CDnet 2012 benchmark data sets.
Experimental methods and statistics derived from signal detection theory are frequently used to compare two imaging techniques, to predict human performance under different parameterizations of an imaging system, and ...
详细信息
Experimental methods and statistics derived from signal detection theory are frequently used to compare two imaging techniques, to predict human performance under different parameterizations of an imaging system, and to distinguish variables related to human visual perception from variables related to decision making. We review recent experimental results suggesting that the assumptions of signal detection theory are fundamentally unsound Instead of shifting decision criteria under different priors, humans appear to alter the information assimilation process, representing images from categories with high prior probability more accurately (less variance) than images from categories with low prior probability. If this hypothesis is correct, detection theory measures such as d' and area under the receiver operating characteristic may be misleading or incomplete. We propose an alternative approach that can be used to quantify the effects of suboptimal decision making strategies without relying on a model of detection structure. (C) 2001 SPIE and IS&T.
Objective: To evaluate the F-wave dilution hypothesis;which implies that absolute F-wave latencies obscure the much smaller delay associated with slow intra-lesion conduction, such is caused by nerve root compression ...
详细信息
Objective: To evaluate the F-wave dilution hypothesis;which implies that absolute F-wave latencies obscure the much smaller delay associated with slow intra-lesion conduction, such is caused by nerve root compression in lumbosacral radiculopathy. A corollary objective is to determine how F-wave measurement and pathological factors influence diagnostic accuracy. Methods: An analytical model is developed based on signal detection theory and a number of simplifying assumptions. Diagnostic accuracy, quantified by the area under the receiver operating characteristic (ROC) curve, is determined for various model realizations derived from the clinical and experimental neurophysiology literature. A preliminary experimental validation of model predictions is also performed. Results: Absolute F-wave latency does not influence the accuracy of focal lesion detection. F-wave latency variance and lesion pathology are the determinant factors. F-wave latencies and distal latencies are estimated to have qualitatively similar detection characteristics, although distal latencies have quantitatively better diagnostic efficacy for comparable focal pathology. Preliminary experimental results support the modeled dependence of diagnostic accuracy on latency variance and lesion severity. Conclusions: Absolute F-wave latency does not dilute slow conduction within focal lesions, such as in lumbosacral radiculopathy. The dominant measurement factor is F-wave latency variance. Significance: To maximize the diagnostic utility of F-wave latencies, focus must be placed on reducing latency variance, such as through correction for demographic covariates. This model calls into question the F-wave dilution hypothesis. (c) 2006 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.
Vestibular perceptual thresholds are defined by a dynamic sensory system. To capture these dynamics, thresholds were previously fit as a function of frequency. In this paper, we compare fits using two published models...
详细信息
Vestibular perceptual thresholds are defined by a dynamic sensory system. To capture these dynamics, thresholds were previously fit as a function of frequency. In this paper, we compare fits using two published models with two new models. Furthermore, a new fitting method that utilizes vestibular perceptual dynamics is developed to improve fit quality and overcome problems associated with the conventional approach. Combinations of the four models and two fitting methods are tested using both simulated data and previously published experimental data. Simulations reveal that the conventional approach underestimates thresholds when the number of trials at each frequency is limited (circa 50);this underestimation is reduced fivefold by the new fitting method that simultaneously utilizes data across frequencies. The new fitting method also scored best for goodness of fit for both the simulations and experimental data. In fact, the new approach of fitting simultaneously across frequencies proved more accurate, more precise, more robust, and more efficient than the conventional approach of fitting the responses at each frequency individually and then fitting these threshold data across frequency. The revised fit of published yaw rotation threshold data shows that these are best fit by a first-order high-pass filter having a plateau of 0.5A degrees/s (roughly a factor of 4 higher than the motion platform vibration) at frequencies above the cutoff frequency of 0.26 Hz, which is well above the cutoff frequency of the semicircular canals (circa 0.03 Hz). This dynamic analysis suggests the contributions of a velocity leakage mechanism to human yaw rotation thresholds.
作者：
Barton, JJSHarvard Univ
Sch Med Beth Israel Deaconess Med Ctr Dept Neurol Boston MA 02215 USA Harvard Univ
Sch Med Beth Israel Deaconess Med Ctr Dept Ophthalmol Boston MA 02215 USA
Many reports in the literature describe a variety of ocular signs in myasthenia gravis. To determine the utility of laboratory recordings of ocular signs in the evaluation for myasthenia, we reviewed all previous stud...
详细信息
Many reports in the literature describe a variety of ocular signs in myasthenia gravis. To determine the utility of laboratory recordings of ocular signs in the evaluation for myasthenia, we reviewed all previous studies of quantitative measures of eye movements or intra-ocular pressures. We selected those studies with data presented for both myasthenic and non-myasthenic ocular palsies. Signal detection theory was used to evaluate the discriminative power of each variable. The characteristics of saccades and quick phases of optokinetic nystagmus at the start of recording were poor at distinguishing between myasthenic and non-myasthenic palsies, except when the comparison was solely between myasthenia and chronic progressive external ophthalmoplegia. The effects of fatigue on saccadic parameters were also not discriminative, though there was insufficient data to evaluate this adequately. Changes induced by edrophonium in the amplitude or peak velocity of saccades or optokinetic quick phases were good diagnostic tests, retaining high sensitivities when criteria were set to yield a specificity of 95%, Most of these parameters were less efficient as screening tests, with modest specificities when criteria were set to yield a sensitivity of 95%. The change in optokinetic quick phase amplitude recorded by infrared oculography was the best test, with ideal characteristics of 97% specificity and sensitivity at a criterion of zero change. This analysis suggests that eye movement recordings of saccades or optokinetic nystagmus have potential as useful and inexpensive tests for myasthenia, and warrant further study. (C) 1998 Elsevier Science B.V.
detection theory has been applied to the measurement of vestibular thresholds and vestibular sensory integration. Yet, a formal detection theory analysis of vestibular responses has not been published. Such a de novo ...
详细信息
detection theory has been applied to the measurement of vestibular thresholds and vestibular sensory integration. Yet, a formal detection theory analysis of vestibular responses has not been published. Such a de novo analysis seems warranted because the vestibular system has characteristics that differ from other sensory systems, which impacts the application of detection theory. For example, the physical stimuli evoking vestibular responses are typically bidirectional (e.g., leftward/rightward);this bidirectional nature of vestibular responses leads to another characteristic-what is sometimes called vestibular bias-that must also be considered, since it can impact threshold measurements, including thresholds found using staircase procedures. This paper develops a basic model of vestibular noise and then analyzes this model for four standard paradigms-one-interval recognition, one-interval detection, two-interval detection, and two-interval recognition. While any of these paradigms might be justified for a specific application, it is concluded that one-interval recognition paradigms have advantages over other paradigms for many vestibular applications. One-interval recognition is favored over one-interval detection because it lends itself to a fixed detection boundary, is more efficient, and is less impacted by device vibration. One-interval recognition is generally favored over two-interval recognition because it assesses vestibular bias and can require substantially less time than two-interval tasks.
暂无评论