Fast Hevc-to-Av1 Transcoding Based On Coding Unit Depth Inheritance

With the advent of the recently launched AOMedia Video 1 (AV1) bitstream specification, there is currently a need for converting legacy content encoded with the state-of-the-art High Efficiency Video Coding (HEVC) standard to the new format. However, transcoding is a complex task composed of a decoding and an encoding process in sequence, which requires long processing times and high energy consumption. This paper proposes the first HEVC-to-AV1 transcoding solution, which is based on the high correlation between block size decisions in HEVC and AV1. The solution allows the AV1 encoder to inherit Coding Unit (CU) depth information from the HEVC bitstream to constrain the AV1 re-encoding process. Experimental results show an average transcoding time reduction of 35.41% at the cost of a compression efficiency loss of 4.54%.