Conventional video encoders typically employ a fixed chroma subsampling format, such as YUV420, which may not optimally reflect variations in chroma detail across different types of content. This can lead to suboptimal chroma quality and inefficiencies in bitrate allocation. We propose an Adaptive Resolution-Chroma Subsampling (ARCS) framework that jointly optimizes spatial resolution and chroma subsampling to balance perceptual quality and decoding efficiency. ARCS selects an optimal (resolution, chroma format) pair for each bitrate by maximizing a composite quality-complexity objective, while enforcing monotonicity constraints to ensure smooth transitions between representations. Experimental results using x265 show that, compared to a fixed-format encoding (YUV444), on average, ARCS achieves a 13.48 % bitrate savings and a 62.18 % reduction in decoding time, which we use as a proxy for the decoding energy, to yield the same colorVideoVDP score. The proposed framework introduces chroma adaptivity as a new control dimension for energy-efficient video streaming.

翻译：传统视频编码器通常采用固定的色度下采样格式，如YUV420，这可能无法最优地反映不同类型内容中色度细节的变化。这会导致色度质量欠佳以及比特率分配效率低下。我们提出了一种自适应分辨率-色度下采样（ARCS）框架，该框架联合优化空间分辨率和色度下采样，以平衡感知质量与解码效率。ARCS通过最大化质量-复杂度复合目标函数，为每个比特率选择最优的（分辨率，色度格式）组合，同时施加单调性约束以确保不同表示之间的平滑过渡。使用x265的实验结果表明，与固定格式编码（YUV444）相比，ARCS平均可节省13.48%的比特率，并将解码时间（我们将其作为解码能耗的代理指标）降低62.18%，同时保持相同的colorVideoVDP评分。所提出的框架将色度自适应性作为节能视频流传输的新控制维度。