In this disclosure, a novel method for
direct mode enhancement in B-pictures and
skip mode enhancement in P-pictures in the framework of H.264 (MPEG-4 / Part 10) is disclosed.
Direct mode and
skip mode enhancements are achieved by clustering the values of the Lagrangian, removing outliers and specifying smaller values of the Lagrangian multiplier in the rate-
distortion optimization for encoding
mode selection. Experimental results using high quality video sequences show that
bit rate reduction is obtained using the method of the present invention, at the expense of a slight loss in peak
signal-to-
noise ratio (PSNR). By conducting two different experiments, it has been verified that no subjective visual loss is visible despite the peak
signal-to-
noise ratio change. In relationship to the existing ratedistortion optimization methods currently employed in the (non-normative) MPEG4 / Part 10
encoder, the method of the present invention represents a simple and useful add-on. More importantly, when other solutions such as further increasing the values of the quantization parameter are not applicable, as inadmissible artifacts would be introduced in the decoded pictures, the method of the present invention achieves
bit rate reduction without introducing visible
distortion in the decoded sequences. Even more, despite the fact that the present document makes use of the H.264 framework, the proposed method is applicable in any
video encoding system that employs ratedistortion optimization for encoding
mode selection.