Mode-dependent transform competition for HEVC

Transform coding plays a key role in state-of-the-art video coders, such as HEVC. However, transforms used in current solutions do not cover the varieties of video coding signals. This work presents an adaptive transform design method that enables the use of multiple transforms in HEVC. A different transform set is learnt for each intra prediction mode, allowing the video encoder to perform better decisions regarding block sizes, prediction modes and transforms. Different systems are proposed to accommodate trade-offs between complexity and performance. Bit rate reductions in the range of 2% to 7% are reported, depending on complexity.