Highdefinition video coding with supermacroblocks A high definition video coding technique using supermacroblocks is investigated in this work. Our research is motivated by the observation that the macroblockbased partition in H.264AVC may not be efficient for high definition video since the maximum macroblock size of 16 x 16 is relatively small against the whole image size. In the proposed supermacboblock based video coding scheme, the original block size M x N in H.264 is scaled to 2M x 2N. Along with the supermacroblock prediction framework, a lowcomplexity 16 x 16 discrete cosine transform (DCT) is proposed. As compared with the ID 8 x 8 DCT, only 16 additions are added for a ID 16 points 16 x 16 DCT. Furthermore, an adaptive scheme is proposed for the selection the best coding mode and best transform size. It is shown by experimental results that the supermacroblock coding scheme can achieve a higher coding gain.

Adaptive block transforms for hybrid video coding Todays standard video coders employ the hybrid coding scheme on a macroblock basis. In these coders blocks of 16xc3x9716, and 8 xc3x97 8 pixel are used for motion compensation of noninterlaced video. The Discrete Cosine Transform (DCT) is then applied to the prediction error on blocks of size 8xc3x978. The emerging coding standard H.26L employs a set of seven different block sizes for motion compensation. The size of these blocks varies from 4 x 4 to 16 x 16. The block sizes smaller than 8x8 imply that the 8x8 DCT cannot be used for transform coding of the prediciton error. In the current test model an integer approximation of the 4xc3x974 DCT matrix is employed. In this paper the concept of Adaptive Block Transforms is proposed. In this scheme, the transform block size is adapted to the block sizes used for motion compensation. The transform exploits the maximum possible signal length for transform coding without exceeding the compensated block boundaries. The proposed scheme is integrated into the H.26L test model. New integer approximations of the 8xc3x978 and the 16 x 16 DCT matrices are introduced. Like the TML 4xc3x974 transform the coefficient values of these matrices are restricted to a limited range. The results presented here are based on an entropy estimation. They reveal an increased ratedistortion performance of approximately 1.1 dB for high rates on the employed test sequences.