A low delay rate control method for screen content coding
- PDF / 2,936,005 Bytes
- 26 Pages / 439.642 x 666.49 pts Page_size
- 1 Downloads / 180 Views
A low delay rate control method for screen content coding Tong Tang1 · Ling Li2,3 Received: 19 October 2018 / Revised: 24 April 2019 / Accepted: 20 June 2019 / © Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract Unlike conventional camera captured video (CCV), the screen content video (SCV) is generated by computer, like text, animation, or graphics. The SCV contents are discontinuous, as one abrupt frame is often followed by many static frames. These distinct characteristics bring challenges to the implementation of rate control in screen content coding (SCC). This paper proposes a low delay rate control method for SCC in HEVC (High Efficiency Video Coding). Firstly, a bit allocation scheme considering buffer status and picture complexity is proposed. Then, an R − MAD (Rate-Mean Absolute Difference)model is built to estimate frame QP (quantization parameter) according to allocated bits. Finally, a dynamical adjusting scheme is designed to fix the error of the estimated frame QP. Experimental results show that the proposed method could effectively avoid buffer overflow and improve the coding efficiency over the recommended rate control scheme in HEVC. Keywords Rate control · Screen content · HEVC · Buffer · Low delay
1 Introduction HEVC [6, 29] is the latest video coding standard developed by JCT-VC (Joint Collaborative Team of Video Coding), and it can save about 50% bitrate at similar quality compared with H.264/AVC [36]. Rate control (RC) plays an important role in the process of video coding. RC helps to adopt proper coding parameters, aiming at minimizing the distortion of compressed videos with bitrate constraint. It has been acknowledged that RC can be divided into two steps. Tong Tang
[email protected] Ling Li [email protected] 1
Communication Institute, Chongqing University of Posts and Telecommunications, Chongqing, China
2
Institute of Software, Chinese Academy of Sciences, Beijing, China
3
University of Chinese Academy of Sciences, Beijing, China
Multimedia Tools and Applications
The first step is bit allocation. Appropriate bits are allocated to each level in the hierarchical video coding structure, including group of picture (GOP) level, frame level and coding unit (CU) level. The second step is bit control. Appropriate coding parameters (such as coding mode, quantization parameter (QP), etc.) are adopted to achieve the target bitrate. In general, optimal bit allocation achieves minimal distortion, and accurate coding parameter setting ensures RC accuracy. Therefore, the objective of RC schemes in video coding is two-fold: • •
Objective I: Optimal bit allocation to achieve minimal distortion. Objective II: Accurate coding parameter estimation to ensure RC accuracy.
For conventional camera captured video (CCV), researchers have proposed many RC methods, which can be mainly classified into three types: Q-domain methods, ρ-domain methods and λ-domain methods. Q-domain methods [7, 21, 24] investigate relationship between rate (R) and QP, i.e. R − Q relationshi
Data Loading...
