Adaptive interpolation with flexible filter structures for video coding

Two novel algorithms are proposed for improving the coding efficiency of adaptive interpolation schemes for video codecs, without increasing implementation complexity. Proposed algorithms utilize two different filter structures with equal tap length, but with complementary frequency responses. Depending on the content being coded, encoder selects which one of the two filter structure is optimal and signals this information to the decoder. In addition, the symmetry of filters is not pre-defined but is flexible. Encoder selects the optimal filter symmetry depending on the coding rate and the content and signals this information to the decoder. Experimental results show, that proposed improvements bring up to 7% of bit-rate reduction at high bit-rate over conventional adaptive interpolation. When compared to H.264/AVC, average gain over the test set is 11%. Coding efficiency is improved without increasing the complexity, thus proposed algorithms are suitable for mobile multimedia use-cases, where the computational resources are very limited.