Lossless Intra Coding in HEVC with Adaptive 3-tap Filters

TL;DR

This paper introduces an adaptive 3-tap filter prediction method for lossless intra coding in HEVC, achieving significant bit rate reductions through offline training and online fine-tuning.

Contribution

It proposes a novel adaptive 3-tap filter prediction approach with offline training and online optimization for lossless intra coding in HEVC.

Findings

Average bit rate reduction of 12.02% over default HEVC lossless coding.

Average bit rate reduction of 3.28% over Sample-based Angular Prediction (SAP).

Effective online adaptation improves coding efficiency.

Abstract

In pixel-by-pixel spatial prediction methods for lossless intra coding, the prediction is obtained by a weighted sum of neighbouring pixels. The proposed prediction approach in this paper uses a weighted sum of three neighbor pixels according to a two-dimensional correlation model. The weights are obtained after a three step optimization procedure. The first two stages are offline procedures where the computed prediction weights are obtained offline from training sequences. The third stage is an online optimization procedure where the offline obtained prediction weights are further fine-tuned and adapted to each encoded block during encoding using a rate-distortion optimized method and the modification in this third stage is transmitted to the decoder as side information. The results of the simulations show average bit rate reductions of 12.02% and 3.28% over the default lossless intra coding in HEVC and the well-known Sample-based Angular Prediction (SAP) method, respectively.