A hierarchical classification-based approach to Inter Mode Decision in H.264/AVC

The H.264/AVC standard achieves a high coding efficiency compared with previous standards. However, it does so at a very high computational cost, with motion estimation being one of the most demanding subsystems. In this paper a hierarchical classification-based approach to the inter mode decision (MD) problem is proposed. A first classifier detects SKIP/Direct modes while a second one is able to decide whether using a large (16times16, 16times8 and 8times16) or a small mode (8times8, 8times4, 4times8 and 4times4). The same procedure is applied at SubMacroblock level. The suggested classifiers are binary and linear. The input features that feed both classifiers have been carefully selected. A novel cost function that pays more attention to the most critical samples during the classifier training process has been designed. The results are very promising: a 64 % computational saving of the total encoding time with respect to JM10.2 is achieved with negligible degradation in the rate-distortion performance.