Optimized bit allocation algorithm for coding tree unit level

doi:10.11772/j.issn.1001-9081.2022091410

Journal of Computer Applications ›› 2023, Vol. 43 ›› Issue (10): 3195-3201.DOI: 10.11772/j.issn.1001-9081.2022091410

Special Issue: 网络与通信

• Network and communications • Previous Articles Next Articles

Optimized bit allocation algorithm for coding tree unit level

Xu YANG¹^,²(), Hongwei GUO³^,⁴, Wanxue LI¹

^1.School of Physics and Engineering Technology，Chengdu Normal University，Chengdu Sichuan 611130，China
^2.School of Communication and Information Engineering，Chongqing University of Posts and Telecommunications，Chongqing 400065，China
^3.School of Engineering，Honghe University，Mengzi Yunnan 661199，China
^4.School of Information and Communication Engineering，University of Electronic Science and Technology of China，Chengdu Sichuan 611731，China

Received:2022-09-22 Revised:2022-11-28 Accepted:2022-12-07 Online:2023-02-28 Published:2023-10-10
Contact: Xu YANG
About author:GUO Hongwei， born in 1980， Ph. D.， professor. His research interests include video coding and communication， image processing.
LI Wanxue， born in 1992， Ph. D.， lecturer. Her research interests include image processing， video coding.
Supported by:
National Natural Science Foundation of China(62061015);Special Scientific Research Project of Chengdu Normal University(ZZBS2020-11)

优化编码树单元级比特分配算法

杨栩¹^,²(), 郭红伟³^,⁴, 李婉雪¹

^1.成都师范学院物理与工程技术学院，成都 611130
^2.重庆邮电大学通信与信息工程学院，重庆 400065
^3.红河学院工学院，云南蒙自 661199
^4.电子科技大学信息与通信工程学院，成都 611731

通讯作者: 杨栩
作者简介:郭红伟（1980—），男，云南金平人，教授，博士，CCF高级会员，主要研究方向：视频编码及通信、图像处理
李婉雪（1992—），女，四川成都人，讲师，博士，主要研究方向：图像处理、视频编码。
基金资助:
国家自然科学基金资助项目(62061015);成都师范学院专项科研项目(ZZBS2020?11)

Abstract

Abstract:

It the rate control algorithms of the new generation video coding standard H.266/VVC （Versatile Video Coding）， the rate-distortion optimization technique with independent coding parameters is adopted. However， the Coding Tree Units （CTUs） within the same frame affect others in the spatial domain， and there are global coding parameters. At the same time， in the CTU-level bit allocation formulas， approximated coding parameters for bit allocation are used， resulting in the reduction of rate control accuracy and coding performance. To address these issues， a spatial-domain global optimization algorithm for CTU-level bit allocation called RTE_RC （Rate Control with Recursive Taylor Expansion） was proposed， and the global coding parameters were approximated by using a recursive algorithm. Firstly， a globally optimized bit allocation model in spatial-domain was established. Secondly， a recursive algorithm was used to calculate the global Lagrange multiplier in the CTU-level bit allocation formula. Finally， the bit allocation of coding units was optimized and the coding units were coded. Experimental results show that under the Low-Delay Prediction frame （LDP） configuration， compared with the rate control algorithm VTM_RC （Rate Control algorithm Versatile Test Model）， the proposed algorithm has the rate control error decreased from 0.46% to 0.02%， the bit-rate saved by 2.48 percentage points， and the coding time reduced by 3.52%. Therefore， the rate control accuracy and rate distortion performance are significantly improved by the proposed algorithm.

Key words: bit allocation, global Lagrange multiplier, rate control, Recursive Taylor Expansion (RTE), Versatile Video Coding (VVC)

摘要：

新一代视频编码标准H.266/VVC（Versatile Video Coding）的码率控制算法采用编码参数相互独立的率失真优化技术。然而，同一帧内的编码树单元（CTU）间在空域上相互影响，且存在全局编码参数；同时，CTU级比特分配公式采用近似的编码参数分配比特，进而降低了码率控制精度和编码性能。针对上述问题，提出空域全局优化CTU级比特分配算法RTE_RC（Rate Control with Recursive Taylor Expansion），并通过递归算法逼近全局编码参数。首先，建立空域全局优化比特分配模型；其次，应用递归算法求解CTU级比特分配模型中的全局拉格朗日乘子；最后，优化编码单元的比特分配并对编码单位进行编码。实验结果表明，在低延时P（Prediction）帧（LDP）配置下，与码率控制算法VTM_RC相比，所提算法的码率控制误差由0.46%下降至0.02%，码率节省了2.48个百分点，编码时间下降了3.52%，显著提升了码率控制精度和率失真性能。

关键词: 比特分配, 全局拉格朗日乘子, 码率控制, 递归泰勒展开, VVC

CLC Number:

TN919.81

Xu YANG, Hongwei GUO, Wanxue LI. Optimized bit allocation algorithm for coding tree unit level[J]. Journal of Computer Applications, 2023, 43(10): 3195-3201.

杨栩, 郭红伟, 李婉雪. 优化编码树单元级比特分配算法[J]. 《计算机应用》唯一官方网站, 2023, 43(10): 3195-3201.

Figures/Tables 4

Tab. 1 Performance comparison of different bit allocation optimization algorithms

类别	视频序列	VTM_RC		文献［22］算法		文献［23］算法		文献［16］算法		RTE_RC
类别	视频序列	BD-rate（Y）	$Δ R$	BD-rate（Y）	$Δ R$	BD-rate（Y）	$Δ R$	BD-rate（Y）	$Δ R$	BD-rate（Y）	$Δ R$
ClassB	Kimono	12.10	0.12	-10.50	1.90	-10.70	1.40	-5.93	0.07	11.20	0.02
	ParkScene	2.60	0.01	1.10	0.10	1.30	0.00	-1.44	0.06	2.60	0.01
	Cactus	-0.80	0.11	-0.10	0.10	1.00	0.10	-1.76	0.07	-3.80	0.02
	BasketballDrive	6.90	0.09	6.40	0.10	6.20	0.10	-1.42	0.06	6.90	0.04
	BQTerrace	2.40	0.18	3.20	0.10	5.90	0.10	-4.24	0.11	0.90	0.00
	平均值	4.64	0.10	0.02	0.46	0.74	0.34	-2.96	0.07	3.50	0.02
ClassC	BasketballDrill	-9.70	0.29	-2.90	0.20	-4.10	0.20	-0.33	0.21	-11.00	0.01
	BQMall	-1.30	0.31	0.80	0.40	-0.50	0.20	-0.53	0.23	-1.60	0.01
	PartyScene	0.60	0.17	0.00	0.10	-3.30	0.10	-1.50	0.13	1.00	0.03
	RaceHorses	0.50	0.14	0.40	0.30	1.30	0.10	-1.13	0.11	3.60	0.01
	平均值	-1.05	0.23	0.40	0.25	-1.65	0.15	-0.87	0.17	-2.00	0.01
ClassD	BasketballPass	-3.10	0.53	-2.20	0.40	-3.00	0.40	-1.01	0.45	-3.60	0.07
	BQSquare	10.00	0.93	3.90	0.80	1.30	0.30	1.95	0.79	5.70	0.02
	BlowingBubbles	3.50	0.62	0.10	0.90	-2.30	0.40	-0.51	0.52	2.50	0.12
	RaceHorses	1.90	0.47	2.50	0.40	2.20	0.50	0.48	0.36	4.40	0.01
	平均值	2.25	0.64	2.17	0.63	-1.33	0.40	0.23	0.53	2.30	0.05
ClassE	FourPeople	6.20	0.58	4.10	0.50	5.40	0.40	-2.81	0.48	-0.90	0.00
	Johnny	10.30	1.23	8.30	1.10	5.70	1.10	-2.67	1.09	-0.20	0.01
	KristenAndSara	4.20	0.76	6.30	1.30	3.90	0.70	-4.30	0.66	-3.60	0.01
	平均值	4.97	0.86	6.23	0.97	5.00	0.73	-3.26	0.74	-1.60	0.01
总体平均		3.03	0.46	2.21	0.58	0.69	0.41	-1.71	0.37	0.55	0.02

Tab. 1 Performance comparison of different bit allocation optimization algorithms

类别	视频序列	VTM_RC		文献［22］算法		文献［23］算法		文献［16］算法		RTE_RC
类别	视频序列	BD-rate（Y）	$Δ R$	BD-rate（Y）	$Δ R$	BD-rate（Y）	$Δ R$	BD-rate（Y）	$Δ R$	BD-rate（Y）	$Δ R$
ClassB	Kimono	12.10	0.12	-10.50	1.90	-10.70	1.40	-5.93	0.07	11.20	0.02
	ParkScene	2.60	0.01	1.10	0.10	1.30	0.00	-1.44	0.06	2.60	0.01
	Cactus	-0.80	0.11	-0.10	0.10	1.00	0.10	-1.76	0.07	-3.80	0.02
	BasketballDrive	6.90	0.09	6.40	0.10	6.20	0.10	-1.42	0.06	6.90	0.04
	BQTerrace	2.40	0.18	3.20	0.10	5.90	0.10	-4.24	0.11	0.90	0.00
	平均值	4.64	0.10	0.02	0.46	0.74	0.34	-2.96	0.07	3.50	0.02
ClassC	BasketballDrill	-9.70	0.29	-2.90	0.20	-4.10	0.20	-0.33	0.21	-11.00	0.01
	BQMall	-1.30	0.31	0.80	0.40	-0.50	0.20	-0.53	0.23	-1.60	0.01
	PartyScene	0.60	0.17	0.00	0.10	-3.30	0.10	-1.50	0.13	1.00	0.03
	RaceHorses	0.50	0.14	0.40	0.30	1.30	0.10	-1.13	0.11	3.60	0.01
	平均值	-1.05	0.23	0.40	0.25	-1.65	0.15	-0.87	0.17	-2.00	0.01
ClassD	BasketballPass	-3.10	0.53	-2.20	0.40	-3.00	0.40	-1.01	0.45	-3.60	0.07
	BQSquare	10.00	0.93	3.90	0.80	1.30	0.30	1.95	0.79	5.70	0.02
	BlowingBubbles	3.50	0.62	0.10	0.90	-2.30	0.40	-0.51	0.52	2.50	0.12
	RaceHorses	1.90	0.47	2.50	0.40	2.20	0.50	0.48	0.36	4.40	0.01
	平均值	2.25	0.64	2.17	0.63	-1.33	0.40	0.23	0.53	2.30	0.05
ClassE	FourPeople	6.20	0.58	4.10	0.50	5.40	0.40	-2.81	0.48	-0.90	0.00
	Johnny	10.30	1.23	8.30	1.10	5.70	1.10	-2.67	1.09	-0.20	0.01
	KristenAndSara	4.20	0.76	6.30	1.30	3.90	0.70	-4.30	0.66	-3.60	0.01
	平均值	4.97	0.86	6.23	0.97	5.00	0.73	-3.26	0.74	-1.60	0.01
总体平均		3.03	0.46	2.21	0.58	0.69	0.41	-1.71	0.37	0.55	0.02

Fig. 1 Comparison of R-D performance of different algorithms in different test sequences

Tab. 2 Comparison of BD-rate for each component between VTM_RC and RTE_RC

类别	VTM_RC				RTE_RC
类别	Y	U	V	YUV	Y	U	V	YUV
平均值	3.03	3.40	3.63	3.19	0.55	-2.10	-1.98	-0.31
ClassB	4.60	1.50	0.90	3.47	3.50	0.58	-1.32	2.21
ClassC	-2.50	-6.20	-4.20	-3.40	-2.00	-8.28	-6.20	-3.75
ClassD	3.10	6.20	7.20	4.30	2.30	1.30	2.70	2.20
ClassE	6.90	12.10	10.60	8.38	-1.57	-1.27	-2.17	-1.62

Tab. 3 Comparison of coding time of different algorithms

算法	编码时间
FIXED_QP	830.31
VTM_RC	831.89
RTE_RC	802.59

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Optimized bit allocation algorithm for coding tree unit level

优化编码树单元级比特分配算法

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