With the advancement of generative models, the assessment of generated images becomes increasingly more important. Previous methods measure distances between features of reference and generated images from trained vision models. In this paper, we conduct an extensive investigation into the relationship between the representation space and input space around generated images. We first propose two measures related to the presence of unnatural elements within images: complexity, which indicates how nonlinear the representation space is, and vulnerability, which is related to how easily the extracted feature changes by adversarial input changes. Based on these, we introduce a new metric to evaluating image-generative models called anomaly score (AS). Moreover, we propose AS-i (anomaly score for individual images) that can effectively evaluate generated images individually. Experimental results demonstrate the validity of the proposed approach.

The video-based action recognition task has been extensively studied in recent years. In this paper, we study the structural vulnerability of deep learning-based action recognition models against the adversarial attack using the one frame attack that adds an inconspicuous perturbation to only a single frame of a given video clip. Our analysis shows that the models are highly vulnerable against the one frame attack due to their structural properties. Experiments demonstrate high fooling rates and inconspicuous characteristics of the attack. Furthermore, we show that strong universal one frame perturbations can be obtained under various scenarios. Our work raises the serious issue of adversarial vulnerability of the state-of-the-art action recognition models in various perspectives.

Electroencephalography (EEG) has attracted much attention because it allows to monitor user states in real time and is applicable to applications for improvement of multimedia user experience. The repeatability of EEG-based perceptual response analysis is critical for the reliability of such applications, which has not been sufficiently addressed in previous studies. In this paper, we evaluate the repeatability of EEG-based image quality assessment. We repeatedly perform the same experiment for three successive days. Then, we design a classification system that discriminates the quality of images based on EEG, whose performance is examined across the data collected in different days. We reveal that the repeatability of image quality evaluation using EEG decreases as time goes and the memory effect intensifies the loss of repeatability.