Intra Prediction Using In-Loop Residual Coding for the post-HEVC Standard

TL;DR

This paper introduces an In-Loop Residual coding Intra Prediction (ILR-IP) method for post-HEVC video compression, improving intra prediction accuracy by using inner-block reconstructed pixels, leading to slight bit rate savings.

Contribution

The paper proposes a novel ILR-IP algorithm that enhances intra prediction by utilizing inner-block pixels, with rate-distortion optimized ILR signal selection, without increasing decoder complexity.

Findings

Up to 0.45% bit rate savings with ILR-IP.

No additional complexity at the decoder.

Improved intra prediction accuracy in post-HEVC standards.

Abstract

A few years after standardization of the High Efficiency Video Coding (HEVC), now the Joint Video Exploration Team (JVET) group is exploring post-HEVC video compression technologies. In the intra prediction domain, this effort has resulted in an algorithm with 67 internal modes, new filters and tools which significantly improve HEVC. However, the improved algorithm still suffers from the long distance prediction inaccuracy problem. In this paper, we propose an In-Loop Residual coding Intra Prediction (ILR-IP) algorithm which utilizes inner-block reconstructed pixels as references to reduce the distance from predicted pixels. This is done by using the ILR signal for partially reconstructing each pixel, right after its prediction and before its block-level out-loop residual calculation. The ILR signal is decided in the rate-distortion sense, by a brute-force search on a QP-dependent finite codebook that is known to the decoder. Experiments show that the proposed ILR-IP algorithm improves the existing method in the Joint Exploration Model (JEM) up to 0.45% in terms of bit rate saving, without complexity overhead at the decoder side.