Optimal bit allocation in HEVC for real-time video communications

Recently, the Lagrange multiplier λ based rate control has been developed in the latest HEVC (High Efficiency Video Coding) codec. It is revealed that while such a rate control approach successfully guarantees a designated bit-rate, the optimal bit allocation has not been investigated or established in the λ-domain. To enhance the overall performance, we propose a novel linear relationship between distortion and λ. With this distortion model, we deduce a closed-form solution to minimize the distortion while satisfying a given rate regulation at the coding tree unit level. Extensive simulation results show that our method can achieve an average 0.20 dB improvement in the low-delay communications.