This paper proposes a sub-frame layer RDO algorithm to further improve coding performance of low-delay hierarchical prediction structure in High Efficiency Video Coding. In the proposed algorithm, each frame is segmented into two sub-frames according to motion intensity, and a sub-frame layer is taken as a basic optimizing unit. An inter-frame dependency model is proposed to quantify inter-frame dependency of a frame or a sub-frame. The proposed inter-frame dependency model is composed of two parts, Laplace distribution based direct inter-frame dependency model and distortion propagation chain. The direct inter-frame dependency model is used to evaluate dependency caused by direct reference, and the distortion propagation chain shows the relationship between direct reference and indirect reference. With quantified inter-frame dependency, Lagrange optimization is then used to solve the optimal $\lambda $ -QP pair for each sub-frame layer in frame layer 1 (L1) to frame layer 4 (L4). For frame layer 0 (L0), additional L0 frames are adaptively inserted according to inter-frame dependency of the previous L0 frame, and the optimal $\lambda $ -QP pair for each sub-frame in L0 is solved using Lagrange optimization. When peak signal to noise ratio is used as quality criterion, the proposed algorithm achieves 7.0% and 7.0% bit-rate reduction with lowdelay_P_main (LDP) and lowdelay_main (LDB) configurations respectively; when structural similarity is used as quality criterion, the proposed algorithm achieves 13.3% and 13.1% bit-rate reduction with LDP and LDB configurations respectively.

中文翻译：

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高效视频编码的子帧层速率失真优化

本文提出了一种子帧层RDO算法，以进一步提高高效视频编码中低延迟分层预测结构的编码性能。该算法根据运动强度将每一帧分割为两个子帧，以子帧层为基本优化单元。提出了帧间依赖性模型来量化帧或子帧的帧间依赖性。所提出的帧间依赖模型由两部分组成，基于拉普拉斯分布的直接帧间依赖模型和失真传播链。直接帧间依赖模型用于评估直接引用引起的依赖，失真传播链显示直接引用和间接引用之间的关系。具有量化的帧间依赖性，然后使用拉格朗日优化来求解帧层 1 (L1) 到帧层 4 (L4) 中每个子帧层的最优 $\lambda $ -QP 对。对于帧层 0 (L0)，根据前一 L0 帧的帧间依赖性自适应插入额外的 L0 帧，并使用拉格朗日优化求解 L0 中每个子帧的最佳 $\lambda $ -QP 对。当峰值信噪比作为质量标准时，所提出的算法分别在lowdelay_P_main（LDP）和lowdelay_main（LDB）配置下实现了7.0%和7.0%的比特率降低；当使用结构相似性作为质量标准时，所提出的算法在 LDP 和 LDB 配置下分别实现了 13.3% 和 13.1% 的比特率降低。