Abstract: Fast intra mode determination schemes based on an image region correlation and the Rate-Distortion (RD) cost are proposed for interframes in the H.264/AVC video standard. With the inter mode search procedure with 7 block types, an intra mode search causes a significant increase in the complexity and computational load for an inter-frame. At first, we adopt a Macro-Block (MB) tracking scheme to obtain the most correlated image region in the reference picture. To reduce the computational load of the intra mode search at the inter-frame, the Rate-Distortion (RD) costs of a tracked MB or image region for the current MB is used and we propose adaptive thresholding algorithms for skipping the intra mode search. For the IPPP sequence type, the overall encoding time can be reduced up to 52% based on comparative analysis of experimental results with JM reference software.