Hardware Implementation of a High-Accuracy and High-Throughput Rate Estimation Unit for VVC Residual Coding

In High Efficiency Video Coding standard, rate estimation based on context-based adaptive binary arithmetic coding (CABAC) typically achieves high accuracy. However, due to serial data dependencies, hardware implementation solutions suffer from lower throughput. When it comes to the latest generation video coding standard, namely Versatile Video Coding (VVC), the increased data dependency and computational complexity during the coding process pose more challenges for the hardware design of rate estimation. To solve these problems, this paper presents a hardware implementation of high-accuracy and high-throughput rate estimation unit for VVC. In terms of throughput improvement, we propose two optimization algorithms to eliminate the majority of data dependencies in coefficient coding with nearly negligible loss in Bjontegaard Delta (BD)-rate performance. To save hardware resources, we introduce a rate estimation table compression algorithm and an optimized local statistical information storage strategy. Based on these optimizations, we present a hardware implementation for the rate estimation unit and a parallel scheme for the rate-distortion optimization process. The proposed algorithm shows an increase of 0.29% in the BD-rate compared to the VVC test model 19.2. Synthesis results show that the proposed design supports real-time coding of $7680\times 4320$ @30fps at 500MHz operating frequency. These results indicate that our proposed design performs well in terms of BD-rate performance and throughput. To the best of our knowledge, this is the first hardware implementation of rate estimation for VVC.