Hardware-Decoder-Friendly High Throughput String Prediction for SCC Implemented in AVS3

Abstract

String prediction (SP) is a highly efficient screen content coding technique adopted into international and China video coding standards. However, SP requires a high number of SRAM fetches to decode and output a block for display, leading to low throughput (T). Low T results in a high decoder and SRAM clock frequency to output the required number of display pixels, which is determined by the specific display resolution and frame rate. To achieve hardware-decoder-friendly high throughput SP (HTSP), this paper exploits specific SRAM fetch rate constraints for five SRAM-cell sizes commonly used in hardware decoder designs. Additionally, the optimal reference string selection process is formulated as a multi-constraint rate-distortion optimization (MCRDO) problem and a novel reference string searching method is presented. HTSP boosts throughput by up to 4 times compared to the state-of-the- art SP, with only a negligible impact on coding efficiency.