A VVC Intra Rate Control With Small Bit Fluctuations Using a Lagrange Multiplier Adjustment

Abstract

Since the emergence of high-quality multimedia processing applications such as video streaming, digital editing, archiving, etc. these days, an intra coding rate control (RC) is becoming an indispensable and important technology. In this article, a frame-level intra RC scheme for Versatile Video Coding (VVC) using a Lagrange multiplier adjustment (LMA) is proposed. The VVC test model (VTM) uses an R-lambda model-based rate control. However, the estimation performance of target bits based on an R-lambda-QP relation is decreased because the distortion dependencies among consecutive frames are not considered especially for intra RC. Thus, in a rate-distortion optimization (RDO) based encoding, the lambda values determined for given quantization parameter (QP) values should be elaborately controlled to increase the target bits estimation performance. In our work, we focus on the intra RC scheme by taking advantage of particle-filtering-based prediction (PFP) for distortion estimates, and precise per-frame lambda values can be derived for an appropriate RDO process that can lead to small bit-fluctuations. Our extensive experimental results demonstrate that our RC scheme using the per-frame LMA is superior to the default RC (VTM-16.0rc1) method and the state-of-the-art RC methods with significant margins of average 15.57%, 15.31% and 31.13% improvements in terms of the normalized root mean square error (NRMSE) for All Intra (AI) configuration of VVC, respectively.