High Efficiency Rate Control for Versatile Video Coding Based on Composite Cauchy Distribution

TL;DR

This paper introduces a novel rate control algorithm for VVC that models transform coefficients with a composite Cauchy distribution, leading to more accurate RD modeling and improved bit allocation, resulting in BD-Rate savings.

Contribution

The paper presents a new rate control method based on composite Cauchy distribution modeling and adaptive bit allocation for VVC, enhancing accuracy and efficiency over existing algorithms.

Findings

Achieves 1.03% BD-Rate saving in low delay mode

Achieves 2.96% BD-Rate saving compared to fixed QP

Improves control accuracy in random access mode

Abstract

In this work, we propose a novel rate control algorithm for Versatile Video Coding (VVC) standard based on its distinct rate-distortion characteristics. By modelling the transform coefficients with the composite Cauchy distribution, higher accuracy compared with traditional distributions has been achieved. Based on the transform coefficient modelling, the theoretically derived R-Q and D-Q models which have been shown to deliver higher accuracy in characterizing RD characteristics for sequences with different content are incorporated into the rate control process. Furthermore, to establish an adaptive bit allocation scheme, the dependency between different levels of frames is modelled by a dependency factor to describe relationship between the reference and to-be-coded frames. Given the derived R-Q and D-Q relationships, as well as the dependency factor, an adaptive bit allocation scheme is developed for optimal bits allocation. We implement the proposed algorithm on VVC Test Model (VTM) 3.0. Experiments show that due to proper bit allocation, for low delay configuration the proposed algorithm can achieve 1.03% BD-Rate saving compared with the default rate control algorithm and 2.96% BD-Rate saving compared with fixed QP scheme. Moreover, 1.29% BD-Rate saving and higher control accuracy have also been observed under the random access configuration.