Abstract: Video signals are coded at a first relatively low frame rate. One or more portions of the image area, for example, the mouth of a person speaker: recognised by feature extractor, are coded at a higher frame rate. Preferably the second coding operates by resolving the pixel values of the image portion--considered as a vector--relative to a set or orthogonal reference vectors to produce coefficients which are then transmitted. Preferably, the feature extractor normalises the image portion as regards scaling, position and rotation and sends data on these parameters as side information.

Abstract: A method of processing an image including the steps of: locating within the image the position of at least one predetermined feature; extracting from the image data representing each feature; and calculating for each feature a feature vector representing the position of the image data of the feature in an N-dimensional space, such space being defined by a plurality of reference vectors each of which is an eigenvector of a training set of like features in which the image data of each feature is modified to normalize the shape of each feature thereby to reduce its deviation from a predetermined standard shape of the feature, which step is carried out before calculating the corresponding feature vector.