Rate distortion optimization for hybrid video coding

In modern hybrid video coding, rate-distortion optimization (RDO) plays a critical role. Basically, it aims at minimizing the distortion for a coding unit under a constraint over the rate, which is achieved by optimally selecting the related coding parameters. The granularity of the coding unit is important in the optimization. Theoretically, the global optimality can be obtained when the granularity of coding unit is increased to the whole video sequence. However, it is computationally infeasible because the space of control parameters for a whole sequence is too huge to be optimized. Following a strategy of “divide and conquer”, the RDO algorithms proposed in this book are in three stages.