Can small be beautiful? assessing image resolution requirements for mobile TV

Mobile TV services are now being offered in several countries, but for cost reasons, most of these services offer material directly recoded for mobile consumption (i.e. without additional editing). The experiment reported in this paper, aims to assess the image resolution and bitrate requirements for displaying this type of material on mobile devices. The study, with 128 participants, examined responses to four different image resolutions, seven video encoding bitrates, two audio bitrates and four content types. The results show that acceptability is significantly lower for images smaller than 168×126, regardless of content type. The effect is more pronounced when bandwidth is abundant, and is due to important detail being lost in the smaller screens. In contrast to previous studies, participants are more likely to rate image quality as unacceptable when the audio quality is high

To catch a thief - You need at least 8 frames per second: The impact of frame rates on user performance in a CCTV detection task

The new generation of digital CCTV systems can be tailored to serve a wide range of security requirements. However, many digital CCTV systems produce video which is insufficient in video quality to support specific security tasks, such as crime detection. We report a study investigating the impact of lowering frame rates on an observer's ability to distinguish between crime and no crime events from post-event recorded video. 80 participants viewed 32 video scenes at 1, 5, 8, and 12 frames per second (fps). The task required observers to determine if one of three possible events had occurred. Results showed that the number of correct detections, task confidence decreased significantly at 8 fps and lower. Our results provide CCTV practitioners with a minimum frame rate level (8 fps) for event detection, a task performed by CCTV users of varying skill and experience

Do people trust their eyes more than their ears? media bias while seeking expert advice

Enabling users to identify trustworthy actors is a key design concern in online systems and expertise is a core dimension of trustworthiness. In this paper, we investigate (1) users' ability to identify expertise in advice and (2) effects of media bias in different representations. In a laboratory study, we presented 160 participants with two advisors-one represented by text-only; the other represented by one of four alternate formats: video, audio, avatar, or photo+text. Unknown to the participants, one was an expert (i.e. trained) and the other was a non-expert (i.e. untrained). We observed participants' advice seeking behavior under financial risk as an indicator of their trust in the advisor. For all rich media representations, participants were able to identify the expert, but we also found a tendency for seeking video and audio advice, irrespective of expertise. Avatar advice, in contrast, was rarely sought, but-like the other rich media representations-was seen as more enjoyable and friendly than text-only advice. In a future step we plan to analyze our data for effects on advice uptake

Rich Media, Poor Judgement? A Study of Media Effects on Users’ Trust in Expertise

In this paper, we investigate how interpersonal cues of expertise affect trust in different media representations. Based on a review of previous research, richer representations could lead either to a positive media bias (P1) or increased sensitivity for cues of expertise (P2). In a laboratory study, we presented 160 participants with two advisors - one represented by text-only; the other represented by one of four alternate formats: video, audio, avatar, orphoto+text. Unknown to the participants, one was an expert (i.e. trained) and the other was a non-expert (i.e. untrained). We observed participants' advice seeking and advice uptake to infer their sensitivity to correct advice in a situation of financial risk. We found that most participants preferred seeking advice from the expert, but we also found a tendency for seeking audio and in particular video advice. Users' self-reports indicate that they believed that video in particular would give them the most detailed insight into expertise. Data for advice uptake, however, showed that all media representation, including text-only, resulted in good sensitivity to correct advice

Getting the big picture on small screens: Quality of experience in mobile TV

This chapter provides an overview of the key factors that influence the quality of experience (QoE) of mobile TV services. It compiles the current knowledge from empirical studies and recommendations on four key requirements for the uptake of mobile TV services: (1) handset usability and its acceptance by the user, (2) the technical performance and reliability of the service, (3) the usability of the mobile TV service (depending on the delivery of content), and (4) the satisfaction with the content. It illustrates a number of factors that contribute to these requirements ranging from the context of use to the size of the display and the displayed content. The chapter highlights the interdependencies between these factors during the delivery of content in mobile TV services to a heterogeneous set of low resolution devices