Compressed domain video compositing with HEVC

Video compositing such as blending of user interfaces or advertisements on top of video content is used in many applications. Compositing is usually carried out in the pixel domain either after decoding on the end device or based on transcoding before or during transport, e.g. on cloud resources. This paper proposes a novel method to create a composition of several coded input videos in the compressed domain, i.e. without performing entropy coding at runtime. The method entails merging of input video bitstreams into a single output video bitstream and insertion of pre-encoded inter-predicted composition pictures. Such a lightweight approach is computationally much less demanding than transcoding-based compositing and can be beneficial for service scalability. This paper explores the coding performance of the proposed method though experiments with the composition of a transparent ticker overlay on top of video sequences. The proposed method is reported to outperform transcoding-based pixel domain compositing in rate distortion and quality.