Inter-Block Dependency-Based CTU Level Rate Control for HEVC
| Autor: | Ce Zhu, Hongwei Guo, Shuai Li, Mai Xu |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Computer science
Rate control 020206 networking & telecommunications 02 engineering and technology Coding tree unit Video compression picture types Constraint algorithm symbols.namesake Lagrange multiplier 0202 electrical engineering electronic engineering information engineering Media Technology symbols Electrical and Electronic Engineering Performance improvement Encoder Algorithm Coding (social sciences) |
| Zdroj: | IEEE Transactions on Broadcasting. 66:113-126 |
| ISSN: | 1557-9611 0018-9316 |
| Popis: | Although high efficiency video coding (HEVC) has achieved high coding performance, it has been shown that dependent rate-distortion optimization (RDO) can still further improve the coding performance at the encoder side. Inspired by our previous work on temporal-dependent RDO, this paper proposes a rate control method at coding tree unit (CTU) level to obtain both higher rate-distortion (R-D) performance and lower bitrate errors. We first formulate the global optimization problem in hybrid video coding and present a general solution framework based on a weighted Lagrange multiplier, where the weighted coefficient is related to the strength of temporal dependency among coding units, and a propagation factor is introduced for quantitative measurement of the temporal dependency. Second, an estimation method of CTU level R-D model is proposed to characterize R-D relationship more accurately. Finally, under the constraint of frame level bit budget, a formulation combining inter-block dependency and R-D characteristic is developed for optimal bit allocation at the CTU level. In the process of encoding a frame, a relaxed constraint algorithm (RCA) and a strict constraint algorithm (SCA) are employed to reduce the difference between numbers of actual and target bits for the current frame, respectively. Experimental results demonstrate that, on the HEVC test model (HM-16.7), our methods including RCA and SCA achieve considerable R-D performance improvement with lower bitrate errors, outperforming the state-of-the-art schemes. It is worth mentioning that even compared with HEVC without rate control, the RCA can still achieve bitrate savings of 5.4% and 5.1% on average under configurations of low delay P and B frames, respectively. |
| Databáze: | OpenAIRE |
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