Abstract: The refinement of a lower-pel resolution motion estimation vector is made more effective by preceding the actual refinement with a determination of a context out of a set of context candidates based on coding costs of a set of lower-pel resolution vectors within a neighborhood of the lower-pel resolution motion estimation vector, wherein each context candidate is associated with a ranking among a set of higher-pel resolution candidate vectors surrounding the lower-pel resolution motion estimation vector. The actual refinement of the lower-pel resolution motion estimation vector to obtain the higher-pel resolution motion estimation vector may thus use the ranking associated with the context determined: sequentially arranged accordingly, the set of higher-pel resolution candidate vectors may be tested sequentially.

Abstract: Techniques for image recompression. In one implementation, the techniques are implemented to recompress a baseline joint photographic experts group (JPEG) image with compression savings. The techniques replace the Huffman coding of baseline JPEG with an arithmetic coding that uses a sophisticated adaptive probability model. The arithmetic coding techniques avoid global operations such as global sorting that would prevent distributed and multithreaded decompression operations when recovering the original JPEG image from the recompressed image. At the same time, the techniques realize substantial compression savings relative to baseline JPEG, on average 23% compressing savings in some implementations.