Quality Enhancement in H.264 Transform Domain Downsizing

In the H.264 coding standard, an integer cosine transform (ICT) is adopted for transform coding. As the ICT is an integer approximation to the discrete cosine transform (DCT), its performance is different from that of the DCT. When the scheme of discarding high frequency coefficients is employed in the ICT domain downsizing, the output quality is worse than when done in the DCT domain. In this paper, the authors propose a scheme to enhance the output quality by converting the downsizing operation back to the DCT domain. The experimental results show that the proposed schemes present quality enhancement over the ICT domain downsizing.