Enhancement of direct mode selection in B pictures for bit rate reduction of compressed video sequences

In this paper, we propose a method for direct mode enhancement in B pictures in the framework of H.264 (MPEG-4/Part 10), which employs reduction of outliers, clustering of the Lagrangian values and specification of smaller values of the Lagrangian multiplier in the rate-distortion optimization for mode selection. Experimental results using high quality video sequences show that bit rate reduction and no subjective visual loss in the decoded pictures are obtained using our method. Moreover, we verify that our method achieves further bit rate reduction without introducing visible distortion in the decoded sequences when other solutions would introduce inadmissible artifacts. Last but not least, the proposed method is a simple and useful add-on, which is applicable in any video coding system that employs rate-distortion optimization for coding mode selection.