The present invention relates to the field of image encoding. In particular, it relates to methods and devices where the concept of auxiliary frames may be employed to reduce or remove the need of copying data, for reference encoding purposes, between encoders which encode different parts of an image frame. This purpose is achieved by spatially modifying (S104) original image data before encoding (S106, S108) it using the encoders, and using (S110) the encoded image data as image data of an auxiliary frame. The auxiliary frame is referenced by an inter frame comprising motion vectors corresponding to a restoration of the auxiliary frame image data back to a spatial arrangement of the original image data.