Abstract
Video is used as recording media in surveillance system and also more frequently by the Swedish Police Force. Methods for analyzing video using an image processing system have recently been introduced at the Swedish National Laboratory of Forensic Science, and new methods are in focus in a research project at Linkoping University, Image Coding Group. The accuracy of the result of those forensic investigations often depends on the quality of the video recordings, and one of the major problems when analyzing videos from crime scenes is the poor quality of the recordings. Enhancing poor image quality might add manipulative or subjective effects and does not seem to be the right way of getting reliable analysis results. The surveillance system in use today is mainly based on video techniques, VHS or S-VHS, and the weakest link is the video cassette recorder, (VCR). Multiplexers for selecting one of many camera outputs for recording is another problem as it often filters the video signal, and recording is limited to only one of the available cameras connected to the VCR. A way to get around the problem of poor recording is to simultaneously record all camera outputs digitally. It is also very important to build such a system bearing in mind that image processing analysis methods becomes more important as a complement to the human eye. Using one or more cameras gives a large amount of data, and the need for data compression is more than obvious. Crime scenes often involve persons or moving objects, and the available coding techniques are more or less useful. Our goal is to propose a possible system, being the best compromise with respect to what needs to be recorded, movements in the recorded scene, loss of information and resolution etc., to secure the efficient recording of the crime and enable forensic analysis. The preventative effective of having a well functioning surveillance system and well established image analysis methods is not to be neglected. Aspects of this next generation of digital surveillance systems are discussed in this paper.
