Rate distortion optimization for bidirectional scalable motion model

The fully scalable motion model (SMM) is proposed for scalable video codec by taking advantage of motion information scalability. In previous work, SMM has been improved to support hierarchical B frame and bidirectional or multidirectional motion estimation. It yields better results comparing to method using unidirectional motion estimation. However, the process of bidirectional or multidirectional rate distortion optimization motion estimation is very complex and is the most time-consuming task in the encoding process. We present several algorithms to reduce its complexity and show corresponding simulation to compare their performance.