The efficiency of the H.264/AVC video coding standard (the latest in the MPEG family) can be further improved by advancing new prediction key-techniques. However, generally these techniques also lead to an extremely high complexity encoding process. As a solution to this problem, we focused on a fast technique to avoid the exhaustive search on the numerous prediction methods available in the standard. Exploiting the high spatial correlation in the natural video, we introduce a new measure of conformance (MC), which is based on the similarity of performance produced by the encoder on the neighbour blocks. This MC makes it possible to select automatically the sub-optimal prediction mode for intra coding as well as to safely avoid the full-scale search for motion compensation applied to variable block-size throughout multiple reference pictures. The MC is updated during the encoding process of the considered block. Therefore, it does not expose any serious additional computation. The experimental results obtained by the new technique are discussed in the paper. In average, the H.264 encoder is speeded up by 23 % at a slight decrease in compression efficiency (5.8 %) for all most the same PSNR quality (-0.08 %)