This paper proposes a new motion compensation method using "sliced blocks" in DCT-based hybrid video coding. In H.264 | MPEG-4 Advance Video Coding, a brand-new international video coding standard, motion compensation can be performed by splitting macroblocks into multiple square or rectangular regions. In the proposed method, on the other hand, macroblocks or sub-macroblocks are divided into two regions (sliced blocks) by an arbitrary line segment. The result is that the shapes of the segmented regions are not limited to squares or rectangles, allowing the shapes of the segmented regions to better match the boundaries between moving objects. Thus, the proposed method can improve the performance of the motion compensation. In addition, adaptive prediction of the shape according to the region shape of the surrounding macroblocks can reduce overheads to describe shape information in the bitstream. The proposed method also has the advantage that conventional coding techniques such as mode decision using rate-distortion optimization can be utilized, since coding processes such as frequency transform and quantization are performed on a macroblock basis, similar to the conventional coding methods. The proposed method is implemented in an H.264-based P-picture codec and an improvement in bit rate of 5% is confirmed in comparison with H.264.
In this paper, we propose a new method to improve the coding efficiency of B-pictures by applying the motion compensated frame rate up-conversion technique. In B-Picture coding in H.264, the direct mode is used for one of the prediction modes. In the direct mode, B-picture is constructed without transmitted motion vector information.
Therefore the direct mode is the most effective coding mode in B-pictures. On the other hand, in motion compensated frame rate up-conversion technique, interpolated frames which are similar to B-pictures, can be constructed with the motion vectors by detecting motion between coded images.
In our proposed method, the same motion estimation algorithm is used for detecting motion vectors between coded P-pictures in both of encoder side and decoder side. Therefore, our proposed decoder can use the detected motion vectors without transmitted motion vector information for B-picture coding.
In the experiment, we selected prediction modes for each block by using conventional rate distortion optimization algorithm. The proposed method provides B-picture coding efficiency nearly 30% over than that of H.264.