Blog

Publications

Here are a few published articles relating to my research work.

Focal - An Eye-Tracking Musical Expression Controller
Stewart Greenhill, Cathie Travers
In: Proceedings International Conference on New Interfaces for Musical Expression (NIME), 2016
Abstract: We present Focal, an eye-tracking musical expression controller which allows hands-free control over audio effects and synthesis parameters during performance. A see-through head-mounted display projects virtual dials and switches into the visual field. The performer controls these with a single expression pedal, switching context by glancing at the object they wish to control. This simple interface allows for minimal physical disturbance to the instrumental musician, whilst enabling the control of many parameters otherwise only achievable with multiple foot pedalboards. We describe the development of the system, including the construction of the eye-tracking display, and the design of the musical interface. We also present a comparison of a performance between Focal and conventional controllers.
TOBY - early intervention in autism through technology
Svetha Venkatesh, Dinh Phung, Thi Duong, Stewart Greenhill, Brett Adams
In: Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, 2013
Abstract: We describe TOBY Playpad, an early intervention program for children with Autism Spectrum Disorder (ASD). TOBY teaches the teacher - the parent - during the crucial period following diagnosis, which often coincides with no access to formal therapy. We reflect on TOBY's evolution from table- top aid for flashcards to an iPad app covering a syllabus of 326 activities across 51 skills known to be deficient for ASD children, such imitation, joint attention and language. The design challenges unique to TOBY are the need to adapt to marked differences in each child's skills and rate of development (a trait of ASD) and teach parents unfamiliar concepts core to behavioural therapy, such as reinforcement, prompting, and fading. We report on three trials that successively decrease oversight and increase parental autonomy, and demonstrate clear evidence of learning. TOBY's uniquely intertwined Natural Environment Tasks are found to be effective for children and popular with parents.
Pervasive multimedia for autism intervention
Svetha Venkatesh, Stewart Greenhill, D Phung, Brett Adams, Thi Duong
In: Pervasive and Mobile Computing, 2012
Abstract: There is a growing gap between the number of children with autism requiring early intervention and available therapy. We present a portable platform for pervasive delivery of early intervention therapy using multi-touch interfaces and principled ways to deliver stimuli of increasing complexity and adapt to a child's performance. Our implementation weaves Natural Environment Tasks with iPad tasks, facilitating a learning platform that integrates early intervention in the child's daily life. The system's construction of stimulus complexity relative to task is evaluated by therapists, together with field trials for evaluating both the integrity of the instructional design and goal of stimulus presentation and adjustment relative to performance for learning tasks. We show positive results across all our stakeholders - children, parents and therapists. Our results have implications for other early learning fields that require principled ways to construct lessons across skills and adjust stimuli relative to performance.
Towards a video browser for the digital native
Brett Adams, Stewart Greenhill, Svetha Venkatesh
In: International Conference on Multimedia and Expo Workshops (ICMEW), 2012
Abstract: Almost every aspect of how we create, transmit, and consume video has changed, but video interfaces still mimic those from videos inception. We extend Temporal Semantic Compression for interactive video browsing, which uses an arbitrary frame-by-frame interest measure to sub-sample video in real time, with user interface elements that visualize these measures and the effect of compressing on them. We experiment with a novel interest measure for popularity, and design novel visualizations for expressing interest measures and the compression interaction. We conduct the first formative evaluation of the TSC paradigm, with 8 subjects, and report design implications arising from it.
Cognitive Intervention in Autism using Multimedia Stimulus
S. Venkatesh and S. Greenhill and D. Phung and B. Adams
In: ACM International Conference on Multimedia, 2011
Abstract: We demonstrate an open multimedia-based system for delivering early intervention therapy for autism. Using flexible multi-touch interfaces together with principled ways to access rich content and tasks, we show how a syllabus can be translated into stimulus sets for early intervention. Media stimuli are able to be presented agnostic to language and media modality due to a semantic network of concepts and relations that are fundamental to language and cognitive development, which enable stimulus complexity to be adjusted to child performance. Being open, the system is able to assemble enough media stimuli to avoid children overlearning, and is able to be customised to a specic child which aids with engagement. Computer-based delivery enables automation of session logging and reporting, a fundamental and time-consuming part of therapy.
Interactively Browsing Movies In Terms Of Action, Foreshadowing and Resolution
Stewart Greenhill, Brett Adams, Svetha Venkatesh
In: IEEE/ACM Joint Conference on Digital Libraries (JCDL 2010), 2010
Abstract: We describe a novel video player that uses Temporal Semantic Compression (TSC) to present a compressed summary of a movie. Compression is based on tempo which is derived from film rhythms. The technique identifies periods of action, drama, foreshadowing and resolution, which can be mixed in different amounts to vary the kind of summary presented. The compression algorithm is embedded in a video player, so that the summary can be interactively recomputed during playback.
Method of Analysing Data
Stewart Greenhill, Svetha Venkatesh, Peter Lee, Geoff West, Chiou Peng Lam
Abstract: A computer assisted method of analysis suitable for process control, comprises the steps of: receiving first data streams representing values from a process; receiving second data streams representing states of the process; recording metadata about the data streams; calculating relationships between pairs of the data streams; and recording relationship data resulting from the calculating step together with an association between at least one relationship datum and its corresponding meta-data.
Geode - A Framework for Social and Context-Driven Browsing for Personal Multimedia
Stewart Greenhill, Svetha Venkatesh
In: unpublished, 2008
Abstract: We present a system that harvests readily available context information (GPS, bluetooth, user) when multiple media such as photos, video, audio, or activity streams (eg. from Twitter, Facebook, etc.) are acquired through cell phones and uses it for multimedia navigation, search and sharing. Separate context streams are recorded on the phone, and related to media captured (on the phone or other devices) based on recorded time. Our framework integrates and unifies all time-based media and uses contextual meta-data to construct novel, rich browsers, facilitating the sharing of both data and meta-data across users. This includes location, co-presence and activity, which are used in new ways for navigation and search in the aggregated media. By considering the meta-data tuple {media, place, time, activities, friends}, rich queries can be made by selecting subsets of available meta-data. Further, synchronous media streams can be played back in parallel, allowing of media aggregation in novel ways. Our implementation and experiments demonstrate the efficacy of this paradigm.
Temporal semantic compression for video browsing
Brett Adams, Stewart Greenhill, Svetha Venkatesh
In: Proceedings 13th International Conference on Intelligent User Interfaces, 2008
Abstract: Temporal Semantic Compression is a novel paradigm for browsing and playing video data, which satisfies dynamic compression levels via time-based measures of interest to guide where to resample a video. This enables interaction with a dynamic zoom factor, which is mapped to a scroll wheel or alternative 2D gesture. The result fuses automatic semantic analysis and human attention applied to the activity of browsing. We implement one version of a TSC browser, the Temporoscope - temporal analogue to a telescope - which uses movie tempo or its derivative to infer interest and drive compression, and a 2D interface to simultaneously control position and compression. The screen footprint contains a level of context that varies with compression level, and sits taxonomically between parameter-heavy expert workbenches and dumb VCR-like linear subsampling.
Contextual Navigation in a Multimedia Journal
Stewart Greenhill, Svetha Venkatesh
In: ACM International Conference on Multimedia, 2008
Abstract: This work presents a framework for multimedia journaling, maintaining strong relationships between the document and embedded media. This enables media archives that are robust to changes in software environments, such as changes in web-sharing services, proprietary file formats and enables portability across operating system. We develop a journaling application using an existing multimedia framework, and show the power of the paradigm with specific case studies.
Multi-modal Emotive Computing in a Smart House Environment
Simon Moncrieff, Svetha Venkatesh, Stewart Greenhill, Geoff West
In: Pervasive and Mobile Computing, Special issue on Design and Use of Smart Environments, 2007
Abstract: We determine hazards within a smart house environment using an emotive computing framework. Representing a hazardous situation as an abnormal activity, we model normality using the concept of anxiety, using an agent based probabilistic approach. Interactions between a user and the environment are determined using multi-modal sensor data. The anxiety framework is a scalable, real-time approach that is able to incorporate data from a number of sources, or agents, and able to accommodate interleaving event sequences. In addition to using simple sensors, we introduce a method for using audio as a pervasive sensor indicating the presence of an activity. The audio data enabled the detection of activity when interactions between a user and a monitored device didn't occur, successfully preventing false hazardous situations from being detected. We present results for a number of activity sequences, both normal and abnormal.
Distributed Query Processing for Mobile Surveillance
Stewart Greenhill and Svetha Venkatesh
In: ACM Internactional Conference on Multimedia, 2007
Abstract: Addressing core issues in mobile surveillance, we present an architecture for querying and retrieving distributed, semi-permanent multi-modal data through challenged networks with limited connectivity. The system provides a rich set of queries for spatio-temporal querying in a surveillance context, and uses the network availability to provide best quality of service. It incrementally and adaptively refines the query, using data already retrieved that exists on static platforms and on-demand data that it requests from mobile platforms. We demonstrate the system using a real surveillance system on a mobile 20 bus transport network coupled with static bus depot infrastructure. In addition, we show the robustness of the system in handling different conditions in the underlying infrastructure by running simulations on a real, but historic dataset collected in an offline manner.
Browsing personal media archives with spatial context using panoramas
Brett Adams, Stewart Greenhill, Svetha Venkatesh
In: ACM International Conference on Multimedia, 2006
Abstract: This paper presents novel techniques for using panoramas as spatial context to enhance browsing of personal media archives. This context, scenes where frequent media capture takes place, is present in the disparate photos and videos, but not leveraged by traditional browsing techniques (e.g. thumbnails or zoomable interfaces). Coarse geo-position is often an insufficient index at such media capture hotspots. We experiment with panoramic video, which presents archive video organically blended with panoramas of media capture hotspots; Immersive browsing and filtering with media items projected onto spherical panoramas; and Detection and representation of links between panoramas to enable browsing of situated media in quasi-3D. We present proof-of-concept implementations and observations of their effectiveness, limitations, and open problems. Experiments confirm the intuition that each holds promise for augmenting traditional browsing environments.
Virtual Observers in a Mobile Surveillance System
Stewart Greenhill and Svetha Venkatesh
In: ACM International Conference on Multimedia, 2006
Abstract: Conventional wide-area video surveillance systems use a network of fixed cameras positioned close to locations of interest. We describe an alternative and flexible approach to wide area surveillance based on observation streams collected from mobile cameras mounted on buses. We allow a "virtual observer" to be placed anywhere within the space covered by the sensor network, and reconstruct the scene at these arbitrary points. Use of such imagery is challenging because mobile cameras have variable position and orientation, and sample a large spatial area but at low temporal resolution. Additionally, the views of any particular place are distributed across many different video streams. Addressing this problem, we present a system in which views from an arbitrary perspective can be constructed by indexing, organising, and transforming images collected from multiple streams acquired from a network of mobile cameras. Our system supports retrieval of raw images based on constraints of space, time, and geometry (eg. visibility of landmarks). It also allows the synthesis of wide-angle panoramic views in situations where the camera motion produces suitable sampling of the scene and metaphors for query and presentation that overcome the complexity of the data.
A quantification of differences of soil moisture under perennial and annual pastures
Bill Scott, Gary Patterson, Dave Nicholson, Wayne Parker, Angela Stuart-Street, Ahmed Hasson, Tim Wiley, Stewart Greenhill, Ross Lantzke, John Horgan
In: Grain and Graze project report, Department Of Agriculture and Food, Western Australia, 2006
Abstract: The Neutron Moisture Meter NMM is used to quantify the water in the soil profile of six pastures on the coastal, NW wheatbelt region of Western Australia. Most sites show a large difference in water use by perennials, some 50 to 150 mm in the upper 1.4 m of the profile, a significant extra water use in a ~500 mm rainfall region. That use is a climatic trend combined with cropping. The decreased rainfall has had a significant effect and the annuals and cropping are lowering soil moisture levels. The perennials take more water upper and lower in the profile depending on the situation; but they tend to even out the water use over the year.
Testing Surveillance Camera Installations
Stewart Greenhill, Seng C. Tan, Geoffrey West, Svetha Venkatesh
Abstract: This invention concerns the testing of surveillance camera installations. In particular, the invention involves an automatic testing system for surveillance camera installations, and a method for testing. The invention involves receiving test or 'probe' images from at least one camera in the installations. Storing a reference image from at least the one camera. Comparison of the probe image with a reference image from the same camera, and production of an output when maintenance is required for that camera. The comparison involves the steps of: Extracting salient features from both the probe and reference images. Calculating matching factors between the salient features extracted from both images. And, computing a decision about whether maintenance is required from the matching factors.
A Probabilistic Approach to the Anxious Home for Activity Monitoring
Geoff West, Stewart Greenhill, Svetha Venkatesh
In: Proceedings 29th Annual International Computer Software and Applications Conference, 2005
Abstract: This paper describes an approach to representing normal activities in a smart house based on the concept of anxiety. Anxiety is computed as a function of time and is kept low by interactions of an occupant with the various devices in a house. Abnormality is indicated by a lack of activity or the wrong activity which will cause anxiety to rise ultimately raising an alarm, querying the occupant and/or alerting a carer in real-time. Anxiety is formulated using probabilistic models that describe how people interact with devices in combinations. These models can be learnt interactively as the smart house acts pessimistically enquiring of the occupant if what they are doing is normal. Results are presented for a number of kitchen scenarios and for different formulations of anxiety.
Estimation of the Surface Stress from the Streamwise Pressure Gradient - The Karman Integral Momentum Equation Revisited
Paul Findlater, William Scott, Stewart Greenhill, Jenny Hopwood
In: Journal of Environmental Fluid Mechanics, 2004
Abstract: A method is developed to estimate the stress at the surface in a portable wind tunnel for wind erosion studies. The boundary layer height and the pressure gradient are used in a simple expression from the Karman Integral Momentum Equation. Values of friction velocity u* are within 10% of experimental values obtained through correlation techniques, including measurements of differential pressures with the Murdoch Turbulence Probe MTP and the X-wire, hot-wire anemometer XWA. Wind velocity and stress profiles reveal logarithmic trends and a 'constant stress layer' near the surface in the DAWA portable wind tunnel. Realignment of the statistics with the mean wind is essential.
Adaptive Model for Foreground Extraction in Adverse Lighting Conditions
Stewart Greenhill, Svetha Venkatesh, Geoff West
In: Proceedings PRICAI2004 8th Pacific Rim International Conference on Artificial Intelligence, 2004
Abstract: Background elimination models are widely used in motion tracking systems. Our aim is to develop a system that performs reliably under adverse lighting conditions. In particular, this includes indoor scenes lit partly or entirely by diffuse natural light. We present a modified "median value" model in which the detection threshold adapts to global changes in illumination. The responses of several models are compared, demonstrating the effectiveness of the new model.
Design and Testing of a Turbulence Probe for Harsh Flows
Paul Findlater, Stewart Greenhill, William D Scott
In: Environmental Fluid Mechanics, 2001
Abstract: The force of wind on the ground created by turbulent eddies is commonly used to describe the horizontal flux of material during wind erosion. Here we present the Murdoch Turbulence Probe, an instrument for use in both clean and eroding flows which uses pressure differences to measure the three components of wind velocity. Correlation techniques calculate the forces near the ground and turbulence statistics in nearly real time, including turbulent velocity fluctuations from less than 0.1 Hz to 200 Hz, mean flow velocities, Reynolds stresses as well as the integral length and time scales. In the portable wind-tunnel used by Agriculture Western Australia, turbulence statistics were recorded over stable surfaces and in blowing sand from the initiation of erosion up to the time the sand supply was exhausted. Estimates of the friction velocity derived from the turbulence probe were compared with estimates obtained from the wind speed profile measured with a rake of pitot and static tubes. The Murdoch Turbulence Probe appears to work well in sandblasting conditions. Relative turbulence intensities ranged from 0.11 to 0.2 and are in close agreement with values in the literature. The ratio of the turbulence to the friction velocity (3 to 3.2) is at the high end of the reported range. The Reynolds stress measurements agree closely with predictions of the threshold friction velocities of the sand and estimates from the wind speed profile with a von Karman constant of about 0.3, lower than the commonly accepted value of 0.4. We suggest that the wind-tunnel profile represents the 'outer layer' of the boundary-layer that may best be described by a 'Wake Law' or 'Defect Law'. At about 54 mm above the surface, the friction velocity decreases from 0.64 m/s to 0.39 m/s and the mean velocity increases from 9.6 m/s to 11.6 m/s as the supply of sand is depleted. In addition to the friction velocity, other scales may be necessary to characterise the overriding effect of the wind and in extending wind-tunnel results to the field.