基于失真反向传播的时域依赖率失真优化

Temporal dependent rate-distortion optimization based on distortion backward propagation

率失真优化是基于块的混合视频编码器中一项关键技术,然而广泛采用的独立率失真优化远未取得最优编码性能。为提升高效视频编码的率失真性能,提出了一种时域依赖率失真优化算法。首先,采用指数形式率失真函数,推导出时域失真传播因子的计算式;然后,通过预编码获得编码失真和运动补偿预测误差,并采用失真反向传播估算时域失真传播因子;最后,自适应地调节编码树单元的拉格朗日乘子和量化参数,以优化编码比特资源分配。实验结果显示,在低时延编码配置下,相比于高效视频编码的率失真优化算法,所提算法在获得同等重建视频质量的前提下,将所有测试视频码率平均节省4.4%,BasketballDrill序列码率最高节省13.0%。

Rate-distortion optimization(RDO) is a crucial technique in block based hybrid video encoders. However, the widely used independent RDO is far from obtaining optimal coding performance. To improve the rate-distortion(R-D)performance of high efficiency video coding(HEVC), a temporal dependent RDO algorithm was proposed. Firstly, the formula to calculate temporal distortion propagation factor was derived by using an exponential R-D function. Then, the coding distortion and motion compensation predicted error were obtained by pre-encoding, and the temporal distortion propagation factor was estimated by using distortion backward propagation. Finally, the Lagrange multiplier and quantization parameter of coding tree unit were adaptively adjusted to optimize bit resources allocation. Experimental results show that compared with the original RDO method in HEVC under the low-delay configuration, the proposed algorithm achieves an average 4.4% bit rate reduction for all test sequences, and up to 13.0% bit rate reduction for test sequence BasketballDrill, at the same reconstructed video quality.