Differential Coding Using Enhanced Inter-Layer Reference Picture for the Scalable Extension of H.265/HEVC Video Codec

Differential coding methods improve coding efficiency of scalable video codecs by adding the high-frequency component present in the previously coded enhancement layer (EL) pictures to the base layer (BL) picture. This paper proposes a method to enable differential coding in a scalable codec design without affecting the core coding tools, thus allowing a practical implementation to reuse single-layer hardware or software components. This is achieved by creating an additional reference picture called enhanced inter-layer reference (EILR) and inserting it to the EL decoded picture buffer and reference picture lists. An EILR picture is generated by adding differential information to the current inter-layer reference picture. The differential information is calculated using the previously decoded pictures of the BL and EL and the motion information of the BL picture. The proposed method reduces luma total bitrate on average by 2.2% and 2.8% for random access and low-delay test cases, respectively. The improvements are more significant for chroma components with the average bitrate reduction of 6.5%. The measured decoding time increase for a reference software implementation is similar to 16% with negligible overhead on encoding time.