Research On Directional Dct And Its Applications In H.264 Video Coding

Obviously, digital images and videos play a major role on the multimedia data services undoubtedly. Currently, many developed international standards for image and video coding, such as JPEG, H.261/263/264, and MPEG1/2/4, almost have chosen the two-dimensional DCT block-based orthogonal transform. This traditional DCT transform is applied on the N N image blocks, and it consists of two identical one-dimensional N-points DCTsThis paper primarily studies a new block-based image coding framework - the directional DCT, its first transform may be along another direction (eg. the diagonal direction) other than the vertical or horizontal direction. The coefficients, generated by all directional transforms, are arranged according to certain rules in the first step, then the second transform can be implemented through the coefficients. For the image blocks with many directional edges, the directional DCT framework can acquire a better coding performance in comparison with the conventional DCT. By adopting the best suited one through all directional DCTs for each image block, the paper results demonstrated that it could indeed improve coding gain prominently.Another research of this paper is all phase biorthogonal transform (APBOT), which can also provide a better coding performance and subjective effects. By choosing uniform quantization of APBOT, the quantization process can reduce computational complexity instead of using DCT quantization table, and in the low-bit-rate, block effects can also be improved in some degree. Base on the research of directional DCT, This paper developed directional APBOT algorithm that is also able to acquire some coding gain by applying on the images with more directional detail information.In the end, this paper described the characteristics of the core technology of H.264. In order to remove the overhead bits used to present the directional DCT mode, the transform modes can get combination with the best intra prediction of H.264. This paper tentatively proposed intra coding framework based on directional DCT.