The Image Library for Intelligent Detection Systems (i-LIDS) provides benchmark surveillance datasets for analytics systems. This paper proposes a methodology to investigate the effect of compression and frame-rate reduction, and to recommend an appropriate suite of degraded datasets for public release. The library consists of six scenarios, including Sterile Zone (SZ) and Parked Vehicle (PV), which are investigated using two different compression algorithms (H.264 and JPEG) and a number of detection systems. PV has higher spatio-temporal complexity than the SZ. Compression performance is dependent on scene content hence PV will require larger bit-streams in comparison with SZ, for any given distortion rate. The study includes both industry standard algorithms (for transmission) and CCTV recorders (for storage). CCTV recorders generally use proprietary formats, which may significantly affect the visual information. Encoding standards such as H.264 and JPEG use the Discrete Cosine Transform (DCT) technique, which introduces blocking artefacts. The H.264 compression algorithm follows a hybrid predictive coding approach to achieve high compression gains, exploiting both spatial and temporal redundancy. The highly predictive approach of H.264 may introduce more artefacts resulting in a greater effect on the performance of analytics systems than JPEG. The paper describes the two main components of the proposed methodology to measure the effect of degradation on analytics performance. Firstly, the standard tests, using the ‘f-measure’ to evaluate the performance on a range of degraded video sets. Secondly, the characterisation of the datasets, using quantification of scene features, defined using image processing techniques. This characterization permits an analysis of the points of failure introduced by the video degradation.
KEYWORDS: Cameras, Video, Video surveillance, Detection and tracking algorithms, Process modeling, Calibration, RGB color model, Surveillance, Data modeling, Algorithm development
In the wake of an increasing number of terrorist attacks, counter-terrorism measures are now a main focus
of many research programmes. An important issue for the police is the ability to track individuals and groups
reliably through underground stations, and in the case of post-event analysis, to be able to ascertain whether
specific individuals have been at the station previously.
While there exist many motion detection and tracking algorithms, the reliable deployment of them in a large
network is still ongoing research. Specifically, to track individuals through multiple views, on multiple levels
and between levels, consistent detection and labelling of individuals is crucial. In view of these issues, we have
developed a change detection algorithm to work reliably in the presence of periodic movements, e.g. escalators
and scrolling advertisements, as well as a content-based retrieval technique for identification.
The change detection technique automatically extracts periodically varying elements in the scene using Fourier
analysis, and constructs a Markov model for the process. Training is performed online, and no manual intervention
is required, making this system suitable for deployment in large networks. Experiments on real data shows
significant improvement over existing techniques.
The content-based retrieval technique uses MPEG-7 descriptors to identify individuals. Given the environment
under which the system operates, i.e. at relatively low resolution, this approach is suitable for short
timescales. For longer timescales, other forms of identification such as gait, or if the resolution allows, face
recognition, will be required.
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