1. A New Rate-Complexity-QP Algorithm for HEVC Intra-Picture Rate Control LING TIAN, YIMIN ZHOU, AND XIAOJUN CAO 2014 INTERNATIONAL CONFERENCE ON COMPUTING, NETWORKING AND COMMUNICATIONS, MULTIMEDIA COMPUTING AND COMMUNICATIONS SYMPOSIUM 1

2. Outline 1.Introduction 2.Related Work (Rate distortion models for rate control) 3.Proposed R-D model for HEVC 4.QP calculation for rate control 5.Experimental Result 6.Conclusion 2

3. Introduction To take advantage of the limited network bandwidth while maintaining optimized visual quality of video streams, rate control schemes play an indispensable role in video compression and communication. Superabundant bits stream may result in network traffic jam or unexpected frame loss. Over-reduced bits stream may lead to the underutilization of network bandwidth and unnecessary video quality degradation. 3

4. Introduction(cont.) In this paper, different Rate-Complexity-QP model and a RCQA algorithm is proposed. This algorithm effectively takes the picture content complexity, intra picture rate control and QP into consideration. The algorithm is implemented in HM 9.1. 4

5. Introduction 5

6. Outline 1.Introduction 2.Related Work (Rate distortion models for rate control) 3.Proposed R-D model for HEVC 4.QP calculation for rate control 5.Experimental Result 6.Conclusion 6

7. Related Work 7

8. Related Work (cont.) 1.ρ-domain model 2.Quadratic model After observing the relationship between Qstep and quantization, the equation is modified by [8] ρ is the percentage of zeros among the quantized transform coefficient. 8

9. Related Work (cont.) intra-picture complexity similar to MAD, may lead to the model error 9

10. Related Work (cont.) [4] B. Li, H. Li, L. Li, and et al. “Rate Control by Rr-lambda Model for HEVC,” in Joint Collaborative Team on Video Coding (JCT-VC) 11 th Meeting, JCTVC-K0103, Shanghai, China, 2012. [6] Z. He, Y.K. Kim and S.K. Mitra, “Low Delay Rate Control for DCT Video Coding via ρ-domain Source Modeling,” IEEE Transactions on Circuits and Systems for Video Technology, vol.11, pp.928–940, 2001. [7] T. Chiang and Y. Q. Zhang, “A New Rate Control Scheme Using Quadratic Rate-Distortion Modeling” IEEE Transactions on Circuits System and Video Technology, vol.7, pp 246-250, Feb.1997. [9] L. Tian, Y. Sun, Y. Zhou, and et al., “Analysis of Quadratic R-D Model in H.264/AVC Video Coding,” 17th IEEE International Conference on Image Processing, pp. 2853-2856, China, 2010. [10] Y. Zhou, Y. Sun, Z. Feng, and et al., “New Rate-Distortion Modeling and Efficient Rate Control for H. 264/AVC video coding,” Signal Processing: Image Communication, vol. 24, pp 345-356, 2009. 10

11. Outline 1.Introduction 2.Related Work (Rate distortion models for rate control) 3.Proposed R-D model for HEVC 4.QP calculation for rate control 5.Experimental Result 6.Conclusion 11

12. Proposed R-D model for HEVC 12

13. Proposed R-D model for HEVC (cont.) By the relationship mentioned above, four model should be discussed below 1.Linear distortion-quantization (D-Q) model 2.Exponential rate-quantization (R-Q) model 3.Linear rate-complexity (R-C) model 4.Uniform rate-complexity-quantization model 13

14. Proposed R-D model for HEVC (cont.) 1.Linear distortion-quantization (D-Q) model  By observing Y-axis in Fig.1.a, we can see a linear relationship between D and Q. 14

15. Proposed R-D model for HEVC (cont.) 2.Exponential rate-quantization (R-Q) model  By observing Y-axis in Fig.1.a, based on the curves shape and the exponential model for H.264 in [9], the model can be as 15

16. Proposed R-D model for HEVC (cont.) 3.Linear rate-complexity (R-C) model  Using the variation of picture content to determined the complexity of the picture  The author use the average gradient per pixel to denote the picture content complexity 16

17. Proposed R-D model for HEVC (cont.) 3.Linear rate-complexity (R-C) model  By observing Y-axis in Fig.1.b, based on the dot on the figure, the model can be as 17

18. Proposed R-D model for HEVC (cont.) 4.Uniform Rate-Complexity-Quantization (RCQ) Model  Since C is independent of Q, we propose a uniform RCQ model to depict the relationships among rate, complexity and quantization 18

19. Outline 1.Introduction 2.Related Work (Rate distortion models for rate control) 3.Proposed R-D model for HEVC 4.QP calculation for rate control 5.Experimental Result 6.Conclusion 19

20. QP calculation for rate control To get more efficient and fine-granulate rate control, the authors further derive the total differential of the RCQ model to obtain the incremental QP for the encoding process in HEVC. 1.Total differential of the uniform RCQ model 2.Incremental QP calculation 3.RCQ model update 4.RCQ based rate control algorithm 20

21. QP calculation for rate control (cont.) 1.Total differential of the uniform RCQ model ( 全微分 dR 為對應於 c 和 q 小變化時 R 變化量的近似值。 ) 21

22. QP calculation for rate control (cont.) 22

23. QP calculation for rate control (cont.) 2.Incremental QP calculation  Since the content and motion complexity of the successive pictures have a high correlation, the bitrate difference between two successive pictures can be  Hence, QP value of the current frame can be obtained according to the feedback of rate control buffer 23

24. QP calculation for rate control (cont.) 24

25. QP calculation for rate control (cont.) 25

26. QP calculation for rate control (cont.) 4.RCQ based rate control algorithm 26

27. Outline 1.Introduction 2.Related Work (Rate distortion models for rate control) 3.Proposed R-D model for HEVC 4.QP calculation for rate control 5.Experimental Result 6.Conclusion 27

28. Experimental Result The authors implement RCQA to control bit-rate under the platform of HEVC reference software HM 9.1, which is compared with HM 9.1 RC and the normal HM 9.1 fixed QP (FIXQP) rate control schemes. Video sequences are coded in an all intra configuration with high efficiency coding parameters as described in “encoderintra-main.cfg”. 28

29. Experimental Result (cont.) The proposed RCQ model is implemented in HM 9.1, which is compared with HM 9.1 RC and the normal HM 9.1 fixed QP rate control schemes. 29

30. Experimental Result (cont.) Table III shows the results of rate control accuracy, which is calculated by |TBR − ABR | /TBR, where TBR is obtained from the FIXQP scheme. 30

31. Experimental Result (cont.) Fig.3 shows the simulation results of the buffer size during the coding process. The X-axis is the picture index and Y-axis denotes the relative buffer size minus the standard buffer threshold. Buffer occupancy for fixed QP, HM9.1 rate control and RCQA rate control. (a): B : Cactus, target bit rate 105.423mbps, initial QP = 22. (b): C : RaceHorsesC, target bit rate 5.106Mbps, initial QP = 32. 31

32. Outline 1.Introduction 2.Related Work (Rate distortion models for rate control) 3.Proposed R-D model for HEVC 4.QP calculation for rate control 5.Experimental Result 6.Conclusion 32

33. Conclusion Pros : 1.This paper has proposed a linear distortion-quantization model, an exponential rate quantization model and a linear rate complexity model, which are integrated into a novel Rate-Complexity-QP (RCQ) model for HEVC intra-picture rate control. 2.Experimental results show that RCQA outperforms the HM 9.1 RC and the normal HM 9.1 fixed QP (FIXQP) rate control schemes. Cons : 1.The proposed method only apply rate control on frame level. 2.The proposed method only deals with “encoderintra-main.cfg” configuration. 33