Perception-Based CTU Level Bit Allocation for Intra High Efficiency Video Coding

Xiaoyan Liu,Yun Zhang,Huanhua Liu,Linwei Zhu

doi:10.1109/access.2019.2948709

Abstract

The conventional rate control algorithm does not fully consider the characteristics of the Human Visual System (HVS). To address this problem, in this paper, a perception based Coding Tree Unit (CTU) level bit allocation algorithm for intra High Efficiency Video Coding (HEVC) is proposed, which aims to minimize the perceptual distortion of each CTU under a given bit rate constraint. Firstly, to better represent perceptual distortion, Perceptually Weighted Mean Squared Error (PWMSE) is adopted instead of Mean Squared Error (MSE). Then, the relationship between Rate (R) and Perceptually Weighted Distortion (Dr) is formulated by the proposed R-Dr model. Finally, the perceptual weighting factor derived from the R-Dr model is used to guide CTU level bit allocation. Experimental results show that the proposed algorithm achieves 6.27% bit rate reduction and 0.38 dB Bjontegaard Delta Perceptually Weighted Peak Signal to Noise Ratio (BD-PWPSNR) gain on average. Under other seven quality evaluation metrics, the proposed algorithm achieves from 1.57% to 8.95% average bit rate reduction while maintaining the perceptual quality, which significantly outperforms the benchmark schemes. Moreover, the proposed perception-based CTU level bit allocation algorithm also maintains a high rate control accuracy, which reaches 99.997%.

Highlights

With the development of multimedia video technology, Ultra High Definition (UHD), Three-Dimensional (3D), and Virtual Reality (VR) videos are becoming more and more popular
Many coding algorithms in High Efficiency Video Coding (HEVC) encoder, such as motion estimation, rate control, intra and inter prediction, were all developed based on the Mean Squared Error (MSE), it is easier and more compatible to integrate the Perceptually Weighted Mean Squared Error (PWMSE) to the encoder than other perceptual metrics
EXPERIMENTAL SETUP To testify the effectiveness of the proposed algorithm, JCTVC-K0103 [5], JCTVC-M0257 [7], HEVC test Model (HM)-16.7 default anchor algorithm and Wang-SPL [19] are adopted as the benchmark schemes

Summary

INTRODUCTION

With the development of multimedia video technology, Ultra High Definition (UHD), Three-Dimensional (3D), and Virtual Reality (VR) videos are becoming more and more popular. Guo et al [10] proposed an effective frame-level bit allocation method to improve video coding performance and maintain high precision of bit rate control in HEVC. Texture complexity and motion information were used to measure the temporal-spatial masking effect, which were used to guide the rate control algorithm in [22] These mentioned metrics could remove the perceptual redundancy to some extent, the performance can be further improved for the compressed image or video from the perceptual quality perspective. A perception based CTU level bit allocation algorithm for intra High Efficiency Video Coding (HEVC) is proposed. The associated perceptual weighting factor is derived and utilized in HEVC to guide the bit allocation in CTU level for rate control.

PROBLEM AND MOTIVATIONS

RATE-PERCEPTUALLY WEIGHTED DISTORTION MODEL

PERCEPTUAL WEIGHTING FACTORS DETERMINATION FOR CTUS

Repeat process