Evaluation of chroma subsampling for high dynamic range video compression
Subsampling chroma channels of video content is a processing performed in most video distribution pipelines. In such pipelines, chroma subsampled content also undergoes video coding, using a codec, before being distributed. Presently, it is common practice to optimize compression efficiency and visual quality of content with respect to its subsampled version rather than the original one. Although this may suffice for traditional imagery, it is unclear if emerging technologies such as Wide Color Gamut and High Dynamic Range are more sensitive to quality loss due to chroma subsampling. In this article, we assess the efficiency of chroma subsampling when compressing HDR content. We compare the performance of two different downsampling filters against the full chroma sampling. Objective results show that distributing 4:4:4 is more efficient than its 4:2:0 counterpart at medium to high bit-rates. For low bit-rates, this increase in efficiency is reduced and in some cases even reversed.