When performing an inter predictive encoding on any image frame x is required, a reference image frame is determined for image x; image x is a P-frame image or a B-frame image; for each reference image frame, following processes are respectively performed: whether resolution of a reference image frame is the same as resolution of image x is determined; if resolution of the reference image frame is different from resolution of image x, resolution of reference image frame is adjusted to be the same as resolution of image x; if resolution of each reference image frame is the same as resolution of image x, inter predictive encoding is performed on image x based on each reference image frame.