Getting the picture

A surveillance system based on artificial intelligence promises to give clear, unequivocal pictures of those caught on CCTV committing crimes. The system, developed at the University of Portsmouth, improves CCTV image quality by ‘selectively’ enhancing sequences of video footage.

CCTV images seen on television often appear fuzzy or blurred because they are captured on video. ‘Take a CCTV camera that costs £20,000,’ said Dr David Brown from the university’s Institute of Industrial Research. ‘It has excellent optical lenses but once the image goes to video the tape can stretch or it ages and is nowhere near the quality you need.’

When prosecutors present CCTV footage in court they are usually working off a small number of images that mitigate against the defendant or defendants. These single frames are found in the miles of tape police have at their disposal.

The images are usually of poor quality and have to be enhanced using interpolation, a mathematical method of creating missing data. An image can be increased from 100 to 200 pixels through interpolation. While there are many methods of interpolation — one simple way is to generate a new pixel by using the average of the value of the two pixels on either side of the one to be created.