Multi-lambda search for improved rate-distortion optimization of H.265/HEVC

Lagrangian Rate Distortion Optimization (RDO) is widely employed in modern video encoders such as H.265/HEVC for mode decision. For each encoding stage, this approach involves minimizing a cost, which is a function of rate, distortion and a multiplier called lambda. This paper explores multi-lambda search and its impact on RDO by using more than one value of lambda. Simulations show an average bit rate saving up to 13.0% can be achieved for the H.265/HEVC codec. Moreover, the extra added complexity is contained to a certain level and is also adjustable according the processing resources available.