Image compression method and apparatus

Controlling compression of image or video data by a quality controller, the method including selecting a discrete quantisation level from a plurality of predetermined discrete quantisation levels for compression of a current image frame 90; and determining an average of the discrete quantisation level used for each image area of a plurality of previous image areas forming one or more previous image frames 92, 94. An updated discrete quantisation level is determined for the current image frame from the determined average value and the discrete quantisation level selected for the current image frame 96. The method then provides to an encoder information to enable the encoder to determine compression parameters associated with the updated discrete quantisation level for compressing the current image frame using a predetermined compression protocol 98. Preferably, the updated discrete quantisation level may be determined based on a comparison 104 of a first difference 100 between the selected quantisation level for the frame and a selected quantisation level for a previous frame, and a second difference 102 between the selected quantisation level for the frame and the determined average.