Implicit Transform Selection based on Cross Color Component Prediction for Future Video Coding In the study of video coding technologies, Discrete Cosine Transform type II (DCTII) has been employed for energy compaction. To improve coding efficiency, Multiple Transform Selection (MTS) scheme is recently proposed where Discrete Sine Transform type VII (DSTVII) and DCTVIII are newly introduced with explicit signaling. MTS is not applied for chroma components due to the limitation of computation complexity at an encoder side. This paper proposes implicit transform selection to apply DSTVII for the chroma blocks based on the intra prediction mode applied to the chroma block. The experimental results show 0.45% and 0.48% BDrate gain in all intra configuration for Cb and Cr components compared to the conventional method with negligible impact of encoding and decoding complexity.

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.