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Backward compatible enhancement of chroma format in HEVC

First version of the latest video coding standard, High Efficiency Video Coding (HEVC), only supports coding of video in YUV 4:2:0 chroma format. An extension of the standard that will support other chroma formats is currently under development, however, version 1 decoders will not be able to handle the bitstreams created using this extension. In this paper, we propose a novel method to create scalable bitstreams that involve a backward compatible base layer in 4:2:0 format that can be handled by HEVC version 1 decoders and code additional layers to enhance the chroma resolution. The proposal codes 4:2:0 video in the base layer and the high resolution chroma components as auxiliary pictures as separate enhancement layers. The high resolution chroma components could optionally be predicted from the upsampled 4:2:0 chroma components of base layer. The simulations show that the proposed method achieves scalability with 9.5% coding efficiency penalty on average compared to single layer coding of 4:4:4 video. When compared to simulcast of 4:2:0 and 4:4:4 video, proposed method provides 38% gain on average. Proposed method makes services using high chroma fidelity easier to be deployed, due to the backwards compatibility to existing HEVC implementations with high coding efficiency.