Temporally Adaptive Quantization Algorithm in Hybrid Video Encoder

In video coder, inter-frame prediction results in distortion propagation among adjacent frames, and this distortion dependency is a crucial factor for rate control and video coding algorithm optimization. The macroblock tree (MBTree) is a typical temporal quantization control algorithm, in which a quantization offset delta is employed for adjustment according to the amount of distortion propagation measured by the relative propagation cost rho Appropriate delta-rho model is the key to the MBTree-like adaptive quantization algorithm. The default delta-rho model in MBTree algorithm is designed in an empirical way with rough model accuracy and insufficient universality to different input source. This paper focuses on this problem and apply the competitive decision mechanism in exploring optimal delta-rho model, and then proposes an improved delta-rho model with rate distortion optimization. The simulation results verify that the improved MBTree algorithm with the proposed model achieves up to 0.14 dB BD-PSNR improvement, and 0.29 dB BD-SSIM improvement. The proposed algorithm achieves better temporal bit allocation and reduces the distortion fluctuation in temporal domain, achieving in adaptive quantization control.