Scene-based KLT for Intra Coding in HEVC

Transform coding and quantization are part of the cornerstones in the current High Efficiency Video Coding (HEVC) standard. They are applied on the residuals from inter-frame or intra predictions. With specified transform matrices, HEVC enhances the coding efficiency vastly compared to Advanced Video Coding (AVC). However, there is still room for improvement. It is observed that the coding of transform coefficients occupies the majority of the bit rate in the stream, since transform matrices in HEVC can not offer the best energy compaction for prediction errors, especially for diagonal features. We introduce scene-based Karhunen-Loeve transform (KLT) in place of the conventional transform for the intra-predicted data for 8 × 8 and 16 × 16 Transform Units (TU). The transform matrices are adaptively designed and later applied according to the prediction modes, quantization steps as well as sizes. The simulation shows great prospect of reducing the bit rate further with KLT, as we gain 3.23%, 7.18% and 6.25% in terms of BD-Rate against HM-16.15 on average for class B, class C and BVI textures respectively, with All-Intra configuration.