Interlaced asymmetric search range assignment for bidirectional motion estimation

Bidirectional motion estimation significantly enhances video coding efficiency, but its huge complexity is also a critical problem for implementation. This paper presents an interlaced asymmetric search range assignment (IASRA) algorithm. By applying a large and a small search ranges to two reference directions and switching the assignment of these two search ranges once per macroblock, total complexity for bidirectional motion estimation can be reduced by near half with slight coding efficiency drop. IASRA also has the flexibility to be combined with existing fast algorithms and architectures for further complexity saving. We demonstrate this feature by combining IASRA with the state-of-the-art IMNPDR and PMRME architectures, which results in 33% to 42% complexity reduction with less than 1% bit rate increase.