VideoWorks –Blueprint for the functioning of a National Video DataGrid
David Shotton, Danny Torbica and John Pybus [e-mail: david.shotton@zoo.ox.ac.uk, danny.torbica@zoo.ox.ac.uk, john.pybus@zoo.ox.ac.uk]
Image BioInformatics Laboratory, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS
Key words to describe the work: Video e-services, editing, format conversion, semantic content analysis
Key Objectives: To provide an integrated suite of video e-services to enable authorized users to analyse, edit, customize,
trans-code and repurpose digital video files located in distant video archives and databases
Motivation for the work (problems addressed): User authentication and access control between Grid services and third
party databases outside the Grid community; interactive processing and two-way database access; video streaming and file
transfer using GridFTP protocol; task scheduling in a client-server-slave processor farm system using Grid middleware.
VideoWorks Project Description
Grid stretching aspects of VideoWorks project
VideoWorks for the Grid is an Oxford e-Science
Centre project that will provide an integrated suite of
video e-services to enable authorized users to
analyse, edit, customize, trans-code and repurpose
digital video files located in distant video archives
and databases, thereby adding value to the holdings
in these databases. Each video file to be processed
is first uploaded into VideoWorks, and is then
analysed structurally to identify scene change key
frames, and converted into a low-resolution
streaming preview.
Subsequent interactive
processing can take two forms: the VANQUIS
service permits content analysis of the video,
generating semantic metadata to permit subsequent
query by content, while the VIDOS service permits
repurposing of the video by permitting spatial and
temporal editing and/or format conversion (transcoding) to create a customized output video file for
local use, for example in teaching material or
research. Industrial Partner software permits video
structural analysis, format conversion and steaming.
The VideoWorks for the Grid project combines the
data complexity of the Semantic Web with the
computational complexity of ‘classic’ Grid
applications. It involves gathering large video data
files from distant databases and initiating
computationally complex processing activities and
analyses upon them. Existing Grid middleware
meets few of the requirements for such a Grid
database project.
For the prototype, we will work with two academic
video databases: the BUFVC MAAS Media Online
archive of rights-cleared videos for UK academic
use (http://www.bufvc.ac.uk/maas/index.html), to be
located at the Edinburgh EDINA National Data
Centre (http://edina.ac.uk), and the BioImage
Database (www.bioimage.org), a database for
multidimensional images and videos of biological
specimens.
Both will be enabled to provide
VideoWorks services.
The complex series of
interactions that will occur between a user, the
BioImage Database, the VideoWorks system are
illustrated in Fig 1.
User authentication
Providing a unified authentication regime for users
of third-party video databases linking into
VideoWorks services, and security of the
VideoWorks services themselves, will require use of
an external gateway that triggers an appropriate
digital certificate, since the X509 digital certificate
system employed in GSI is only appropriate for
Grid-enabled participants, and it is unrealistic to
expect individual database users to rush off
individually to some Certification Authority. Such
authorised access must be sufficiently persistent to
enable a user to start a long conversion job, log off,
and then reconnect later to review progress or
download the customized video.
Database access
Unlike most Grid projects involving databases,
VideoWorks requires not just the passive extraction
of data, but the ability both to communicate
interactively with the VideoWorks system in order to
specify customisation or analysis parameters, and
also to write newly-created semantic metadata back
into the video database of origin, while ensuring the
security and integrity of that database.
Video streaming and file transfer
Existing Grid middleware cannot allocate bandwidth
to facilitate streamed video delivery, and GridFTP
does not permit data buffers, flow control and staged
delivery services that might assist the asynchronous
transfer of large video data files.
VideoWorks task scheduling
Within the VideoWorks system, Grid middleware or
Condor will be used to schedule and prioritise
concurrent users’ jobs having different requirements,
distributing them to the VideoWorks slave processors
in the most efficient manner depending upon their
individual capabilities with regard to disc space,
processing speed or access to particular video codec
implementations.
The presentation will include a live demonstration of
the VIDOS service within the VideoWorks prototype,
and discussion of our progress in integrating the
various other software components and in
surmounting some of the obstacles to Grid
integration mentioned above.
Figure 1
Interactions between a user, the
BioImage Database and the VideoWorks system
(Arrow widths approximate the
volumes of data being transferred)
1 A BioImage user selects a video in the BioImage
Database and chooses to use the VideoWorks services.
2 The selected video is uploaded from the distant
database to VideoWorks file store using GridFTP.
3 An interactive session is established between the user
and the VideoWorks server.
4 Video sent to both conversion and analysis slaves.
5 Video preview version passed to streaming server.
6, 7 Preview and keyframe storyboard sent to user to
permit interactive processing.
8 User’s customization parameters are sent to the VIDOS
conversion slave; customized video created and sent to
VideoWorks server.
9 Customized video is downloaded to the user.
10 And / or Interactive semantic analysis of video
content undertaken by user
11 Semantic content metadata written to VideoStore
12 Semantic metadata transferred to BioImage for longterm storage and subsequent Query by Content.
Current Status and Development
Substantial progress has been made with VideoWorks and
we now have a stable VIDOS video editing and
transcoding system that permits one to upload a file from
one’s local machine or from any Web site using ftp and
http through a Web interface. Extensive testing was
implemented, with testing the current system on the most
commonly used hardware platforms and also with the
most commonly used browsers. Bug fixes ensured that
the system is now reliable enough to use in conjunction
with BioImage and with EDINA, now that they have
digitized a substantial proportion of their videos from the
British Universities Film and Video Council
(http://www.bufvc.ac.uk/maas/).
Further developments with respect to accessing EDINA
through a SOAP interface using SOAP and WSDL
standards are to be implemented as the next phase of
VideoWorks development.
Publication is planned in the journal Animal Behaviour of
work that has led to the development of an automated
procedure for tracking fish in aquaria through a video
analysis module of VideoWorks.