Arbitrary Block-size Transform Video Coding

Transform is a very important coding tool in video coding. It decorrelates the pixel data and removes the redundancy among pixels so as to achieve compression. Traditionally, order-S transform is used in video and image coding. Latest video coding standards, such as H.264/AVC, adopt both order-4 and order-8 transforms. The adaptive use of more than one transforms of different sizes is known as Arbitrary Block-size Transform (ABT). Transforms other than order-4 and order-8 can also be used in ABT. It is expected larger transform size such as order-16 will benefit more in video sequences with higher resolutions such as nap and 1a8ap sequences. As a result, order-16 transform is introduced into ABT system.;In this thesis, the development of simple but efficient order-16 transforms will be shown. Analysis and comparison with existing order-16 transforms have been carried out. The proposed order-16 transforms were integrated to the existing coding standard reference software individually so as to achieve a new ABT system. In the proposed ABT system, order-4, order-8 and order-16 transforms coexist. The selection of the most appropriate transform is based on the rate-distortion performance of these transforms. A remarkable improvement in coding performance is shown in the experiment results. A significant bit rate reduction can be achieved with our proposed ABT system with both subjective and objective qualities remain unchanged.;Three kinds of order-l 6 orthogonal DCT-like integer transforms are proposed in this thesis. The first one is the simple integer transform, which is expanded from existing order-8 ICT. The second one is the hybrid integer transform from the Dyadic Weighted Walsh Transform (DWWT). It is shown that it has a better performance than simple integer transform. The last one is a recursive transform. Order-2N transform can be derived from order-N one. It is very close to the DCT. This recursive transform can be implemented in two different ways and they are denoted as LLMICT and CSFICT. They have excellent coding performance. These proposed transforms are investigated and are implemented into the reference software of H.264 and AVS. They are also compared with other order-16 orthogonal integer transform. Experimental results show that the proposed transforms give excellent coding performance and ease to compute.;Besides ABT with higher order transform, a transform based template matching is also investigated. A fast method of template matching, called Fast Walsh Search, is developed. This search method has similar accuracy as exhaustive search but significantly lower computation requirement.;Prior knowledge of the coefficient distribution is a key to achieve better coding performance. This is very useful in many areas in coding such as rate control, rate distortion optimization, etc. It is also shown that coefficient distribution of predicted residue is closer to Cauchy distribution rather than traditionally expected Laplace distribution. This can effectively improve the existing processing techniques.