Preparing high-quality 360-degree video for HTTP Adaptive Streaming requires encoding each sequence into multiple representations spanning different resolutions and quantization parameters (QPs). For ultra-high-resolution immersive content such as 8K 360-degree video, this process is computationally intensive due to the large number of representations and the high complexity of modern codecs. This paper investigates fast multirate encoding strategies that reduce encoding time by reusing encoder analysis information across QPs and resolutions. We evaluate two cross-resolution information-reuse pipelines that differ in how reference encodes propagate across resolutions: (i) a strict HD -> 4K -> 8K cascade with scaled analysis reuse, and (ii) a resolution-anchored scheme that initializes each resolution with its own highest-bitrate reference before guiding dependent encodes. In addition to evaluating these pipelines on standard equirectangular projection content, we also apply the same two pipelines to cubemap-projection (CMP) tiling, where each 360-degree frame is partitioned into independently encoded tiles. CMP introduces substantial parallelism, while still benefiting from the proposed multirate analysis-reuse strategies. Experimental results using the SJTU 8K 360-degree dataset show that hierarchical analysis reuse significantly accelerates HEVC encoding with minimal rate-distortion impact across both equirectangular and CMP-tiled content, yielding encoding-time reductions of roughly 33%-59% for ERP and about 51% on average for CMP, with Bjontegaard Delta Encoding Time (BDET) gains approaching -50% and wall-clock speedups of up to 4.2x.

翻译：为HTTP自适应流媒体准备高质量的360度视频，需要将每个序列编码为覆盖不同分辨率和量化参数（QP）的多种表示形式。对于8K 360度视频等超高分辨率沉浸式内容，由于表示形式数量众多且现代编解码器复杂度高，此过程计算密集。本文研究了快速多码率编码策略，通过在不同QP和分辨率间复用编码器分析信息来减少编码时间。我们评估了两种跨分辨率信息复用流水线，其区别在于参考编码如何在分辨率间传播：(i) 严格的HD -> 4K -> 8K级联，配合缩放分析复用；(ii) 分辨率锚定方案，该方案在指导依赖编码之前，用其自身的最高码率参考初始化每个分辨率。除了在标准等距柱状投影内容上评估这些流水线外，我们还将相同的两种流水线应用于立方体贴图投影（CMP）分块编码，其中每个360度帧被划分为独立编码的图块。CMP引入了显著的并行性，同时仍能从所提出的多码率分析复用策略中受益。使用SJTU 8K 360度数据集的实验结果表明，分层分析复用能显著加速HEVC编码，且对等距柱状投影和CMP分块内容的率失真影响极小，使ERP的编码时间减少约33%-59%，CMP平均减少约51%，Bjontegaard Delta编码时间（BDET）增益接近-50%，实际运行速度提升高达4.2倍。