一种自适应的关键帧量化参数确定方法

Adaptive quantization parameter determination for key frames

以JVT-AA029提出的适用于基于分层B帧的分层预测结构的码率控制方案为基础,提出了一种自适应确定关键帧量化参数(Quantization Parameter,QP)的方法.根据起始QP、可用信道带宽和信源特性的经验关系式,计算用于编码视频序列中第一个关键帧的QP.对于其他关键帧,首先根据已编码帧的编码特性确定参考QP和目标比特预算值,然后使用率失真模型计算QP,并以参考QP为依据进一步调整计算所得的QP.实验结果表明,提出的关键帧量化参数确定方法使原JVT-AA029的码率控制性能平均提高了0.14 dB;同时,基于提出方法的码率控制方案能够更准确地达到目标比特率,与已有码率控制方案相比,平均性能提高了0.77 dB.

Based on the rate control scheme in JVT-AA029 for the video encoders using hierarchical B frames, a quantization parameter （QP） determination method is proposed to adaptively determine the QP for key frames. This method firstly utilizes an empirical equation expressing the relation among the starting QP, the available channel bandwidth and the source characteristics to calculate the starting QP for the first key frame of the video sequence. For the other key frames, the target bit budgets and reference QPs are determined based on the actual coding properties of the previous frames. Then the QPs are calculated by employing a rate-distortion model and further adjusted according to the reference QPs. Experimental results show that the proposed method leads to an average improvement of 0.14 dB over the performance of the original rate control scheme in JVT-AA029, and by integrating the proposed method, the rate control scheme outperforms the existing state-of-the art one by 0.77 dB on average.