Automated removal of overshoot artefact from images

This paper presents a simple but robust technique for overshoot removal from video sequences. The artefact of overshoot is modelled as a filter which distorts the step response of edges within the affected image. By detecting strong vertical edges in an image and measuring the distorted step response, an equalising filter can be designed to restore the step response closer to the ideal response and hence minimise the overshoot visible in the picture. The algorithm is presented along with results for both real archived images and images with known distortions. This allows performance in terms of Peak Signal to Noise Ratio to be assessed. The performance is shown to be good both quantitatively and qualitatively. The limitation of the approach is shown to be the lack of preservation of finer detail in some cases. Performance could be enhanced by first assigning areas of fine detail in the image which should not be processed. Application to video sequences is also considered where the equaliser update is weighted between the current and previous frame to reduce flicker artefacts.