Unequal-arm adaptive rood pattern search for fast block-matching motion estimation in the JVT/H.26L

The adaptive rood pattern search (ARPS) algorithm proposed by Nie and Ma has shown two to three times of search speed-up improvement over that of diamond search (DS) based on the MPEG4 Verification Model encoding platform. In this paper, first we have shown that the distribution of motion vectors bears a rood shape. An improved ARPS algorithm, called ARPS-3 or unequalarm ARPS, is then proposed and experimented on the JVT/H.26L JM encoding platform. Due to complex modes and multi-frame prediction, a new normalized computational cost metrics is also proposed for objectively measuring the computational gain or search speed-up. Experimental results show that ARPS-3 has achieved superb performance on many accounts while maintaining fairly close rate-distortion performance compared with that of the full search. It also outperforms its predecessors, ARPS and ARPS-2 (or equal-arm ARPS).