Video summarisation: A conceptual framework and survey of the state of the art

This is the post-print (final draft post-refereeing) version of the article. Copyright @ 2007 Elsevier Inc.Video summaries provide condensed and succinct representations of the content of a video stream through a combination of still images, video segments, graphical representations and textual descriptors. This paper presents a conceptual framework for video summarisation derived from the research literature and used as a means for surveying the research literature. The framework distinguishes between video summarisation techniques (the methods used to process content from a source video stream to achieve a summarisation of that stream) and video summaries (outputs of video summarisation techniques). Video summarisation techniques are considered within three broad categories: internal (analyse information sourced directly from the video stream), external (analyse information not sourced directly from the video stream) and hybrid (analyse a combination of internal and external information). Video summaries are considered as a function of the type of content they are derived from (object, event, perception or feature based) and the functionality offered to the user for their consumption (interactive or static, personalised or generic). It is argued that video summarisation would benefit from greater incorporation of external information, particularly user based information that is unobtrusively sourced, in order to overcome longstanding challenges such as the semantic gap and providing video summaries that have greater relevance to individual users

Access to recorded interviews: A research agenda

Recorded interviews form a rich basis for scholarly inquiry. Examples include oral histories, community memory projects, and interviews conducted for broadcast media. Emerging technologies offer the potential to radically transform the way in which recorded interviews are made accessible, but this vision will demand substantial investments from a broad range of research communities. This article reviews the present state of practice for making recorded interviews available and the state-of-the-art for key component technologies. A large number of important research issues are identified, and from that set of issues, a coherent research agenda is proposed

Long-Term Consequences of Early Eye Enucleation on Audiovisual Processing

A growing body of research shows that complete deprivation of the visual system from the loss of both eyes early in life results in changes in the remaining senses. Is the adaptive plasticity observed in the remaining intact senses also found in response to partial sensory deprivation specifically, the loss of one eye early in life? My dissertation examines evidence of adaptive plasticity following the loss of one eye (unilateral enucleation) early in life. Unilateral eye enucleation is a unique model for examining the consequences of the loss of binocularity since the brain is completely deprived of all visual input from that eye. My dissertation expands our understanding of the long-term effects of losing one eye early in life on the development of audiovisual processing both behaviourally and in terms of the underlying neural representation. The over-arching goal is to better understand neural plasticity as a result of sensory deprivation. To achieve this I conducted seven experiments, divided into 5 experimental chapters, that focus on the behavioural and structural correlates of audiovisual perception in a unique group of adults who lost one eye in the first few years of life. Behavioural data (Chapters II-V) in conjunction with neuroimaging data (Chapter VI) relate structure and function of the auditory, visual and audiovisual systems in this rare patient group allowing a more refined understanding of cross sensory effects of early sensory deprivation. This information contributes to us better understanding how audiovisual information is experienced by people with one eye. This group can be used as a model to learn how to accommodate and maintain the health of less extreme forms of visual deprivation and to promote overall long-term visual health

The role of multisensory integration in the bottom-up and top-down control of attentional object selection

Selective spatial attention and multisensory integration have been traditionally considered as separate domains in psychology and cognitive neuroscience. However, theoretical and methodological advancements in the last two decades have paved the way for studying different types of interactions between spatial attention and multisensory integration. In the present thesis, two types of such interactions are investigated. In the first part of the thesis, the role of audiovisual synchrony as a source of bottom-up bias in visual selection was investigated. In six out of seven experiments, a variant of the spatial cueing paradigm was used to compare attentional capture by visual and audiovisual distractors. In another experiment, single-frame search arrays were presented to investigate whether multisensory integration can bias spatial selection via salience-based mechanisms. Behavioural and electrophysiological results demonstrated that the ability of visual objects to capture attention was enhanced when they were accompanied by noninformative auditory signals. They also showed evidence for the bottom-up nature of these audiovisual enhancements of attentional capture by revealing that these enhancements occurred irrespective of the task-relevance of visual objects. In the second part of this thesis, four experiments are reported that investigated the spatial selection of audiovisual relative to visual objects and the guidance of their selection by bimodal object templates. Behavioural and ERP results demonstrated that the ability of task-irrelevant target-matching visual objects to capture attention was reduced during search for audiovisual as compared to purely visual targets, suggesting that bimodal search is guided by integrated audiovisual templates. However, the observation that unimodal targetmatching visual events retained some ability to capture attention indicates that bimodal search is controlled to some extent by modality-specific representations of task-relevant information. In summary, the present thesis has contributed to our knowledge of how attention is controlled in real-life environments by demonstrating that spatial selective attention can be biased towards bimodal objects via salience-driven as well as goal-based mechanisms

The role of multisensory integration in the bottom-up and top-down control of attentional object selection

Selective spatial attention and multisensory integration have been traditionally considered as separate domains in psychology and cognitive neuroscience. However, theoretical and methodological advancements in the last two decades have paved the way for studying different types of interactions between spatial attention and multisensory integration. In the present thesis, two types of such interactions are investigated. In the first part of the thesis, the role of audiovisual synchrony as a source of bottom-up bias in visual selection was investigated. In six out of seven experiments, a variant of the spatial cueing paradigm was used to compare attentional capture by visual and audiovisual distractors. In another experiment, single-frame search arrays were presented to investigate whether multisensory integration can bias spatial selection via salience-based mechanisms. Behavioural and electrophysiological results demonstrated that the ability of visual objects to capture attention was enhanced when they were accompanied by noninformative auditory signals. They also showed evidence for the bottom-up nature of these audiovisual enhancements of attentional capture by revealing that these enhancements occurred irrespective of the task-relevance of visual objects. In the second part of this thesis, four experiments are reported that investigated the spatial selection of audiovisual relative to visual objects and the guidance of their selection by bimodal object templates. Behavioural and ERP results demonstrated that the ability of task-irrelevant target-matching visual objects to capture attention was reduced during search for audiovisual as compared to purely visual targets, suggesting that bimodal search is guided by integrated audiovisual templates. However, the observation that unimodal targetmatching visual events retained some ability to capture attention indicates that bimodal search is controlled to some extent by modality-specific representations of task-relevant information. In summary, the present thesis has contributed to our knowledge of how attention is controlled in real-life environments by demonstrating that spatial selective attention can be biased towards bimodal objects via salience-driven as well as goal-based mechanisms

Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

The COGs (context, object, and goals) in multisensory processing

Our understanding of how perception operates in real-world environments has been substantially advanced by studying both multisensory processes and “top-down” control processes influencing sensory processing via activity from higher-order brain areas, such as attention, memory, and expectations. As the two topics have been traditionally studied separately, the mechanisms orchestrating real-world multisensory processing remain unclear. Past work has revealed that the observer’s goals gate the influence of many multisensory processes on brain and behavioural responses, whereas some other multisensory processes might occur independently of these goals. Consequently, other forms of top-down control beyond goal dependence are necessary to explain the full range of multisensory effects currently reported at the brain and the cognitive level. These forms of control include sensitivity to stimulus context as well as the detection of matches (or lack thereof) between a multisensory stimulus and categorical attributes of naturalistic objects (e.g. tools, animals). In this review we discuss and integrate the existing findings that demonstrate the importance of such goal-, object- and context-based top-down control over multisensory processing. We then put forward a few principles emerging from this literature review with respect to the mechanisms underlying multisensory processing and discuss their possible broader implications

An Object-Based Interpretation of Audiovisual Processing

Visual cues help listeners follow conversation in a complex acoustic environment. Many audiovisual research studies focus on how sensory cues are combined to optimize perception, either in terms of minimizing the uncertainty in the sensory estimate or maximizing intelligibility, particularly in speech understanding. From an auditory perception perspective, a fundamental question that has not been fully addressed is how visual information aids the ability to select and focus on one auditory object in the presence of competing sounds in a busy auditory scene. In this chapter, audiovisual integration is presented from an object-based attention viewpoint. In particular, it is argued that a stricter delineation of the concepts of multisensory integration versus binding would facilitate a deeper understanding of the nature of how information is combined across senses. Furthermore, using an object-based theoretical framework to distinguish binding as a distinct form of multisensory integration generates testable hypotheses with behavioral predictions that can account for different aspects of multisensory interactions. In this chapter, classic multisensory illusion paradigms are revisited and discussed in the context of multisensory binding. The chapter also describes multisensory experiments that focus on addressing how visual stimuli help listeners parse complex auditory scenes. Finally, it concludes with a discussion of the potential mechanisms by which audiovisual processing might resolve competition between concurrent sounds in order to solve the cocktail party problem