Artefact Characterisation for JPEG and JPEG 2000 Image Codecs: Edge Blur and Ringing

This paper presents a method of objective evaluation of the edge blur and ringing artefacts produced by image codecs. It is difficult to detect and measure individual artefacts in coded images. A synthetic test pattern is developed to separate and measure edge blur and ringing artefacts due to image compression. The influence of contrast on the quality metrics is investigated. The performance of five JPEG and JPEG2000 codec implementations is compared. All five codecs show an increasing level of artefacts with increasing compression ratio. Different implementations of a codec have different artefact characteristics. The objective artefact measures can be used in the image and video codec development process and in parameter optimisation of codec performance. These metrics can also be used to select suitable parameters for video codecs such as MPEG-1, MPEG-2 and MPEG-4 while creating video streams for the Internet applications and in any multimedia application in general.