Image pre-processing for content-based image coding in a teleteaching system

Image pre-processing for content-based image coding scheme in an experimental teleteaching system, which is built on ISDN by BRI, is described. To realize better image quality of projected teaching materials, e.g. films, and to make better use of the available data rate, special consideration is given to the document image preprocessing, such as change detection, change type classification and change area extraction, as well as coding mode selection. Experiments demonstrate the effect of the scheme with the pre-processing