Low-complexity merge candidate decision for fast HEVC encoding

1. Low-complexity merge candidate decision for fast HEVC encoding Muchen LI, Keiichi Chono, Satoshi Goto Multimedia and Expo Workshops (ICMEW), 2013 IEEE International Conference on

2. outline • Introduction • Low-complexity merge candidate decision • A. GMV Based Merge Candidate Decision • B. Position-Priority Based Merge Candidate Decision • Simulation Results

3. Introduction #1 • Although the Merge mode brings significant coding efficiency improvements, the complexity of its Merge candidate decision associated with Rate-Distortion cost computation is proportional to the number of Merge candidates. • The investigation shows that redundant and unnecessary RD cost computation for particular Merge candidates between Ground-truth MVs (GMVs) obtained by motion estimation (ME) and Merge candidates.

4. Introduction #2 • For each PU, the Merge mode utilizes up to 5 MVP candidates and selects the best one based on computationally expensive Rate-Distortion (R-D) cost check for each Merge candidate. • Sun of absolute transformed difference (SATD) • 8-tap filter

5. Introduction #3 • Merge mode allows at most 5 Merge MV candidates from the previously inter-coded blocks located in the positions described. • 5 spatial • 2 temporal

6. Introduction #4

7. Introduction #5 • As well as Merge mode, AMVP mode also introduces MVP competition technology and predicts the MV of current PU as one of the MVPs. • Ground-truth MV

8. Introduction #6

9. Introduction #7 • In the study, it is found that the Merge candidates are typically distributed in the SR and the Merge candidate decision is based on the R-D cost that also uses the SATD measurement. • Checking the SATD for all the Merge candidates is redundant and excessive in some cases.

10. Low-complexity merge candidate decision #A1GMV Based Merge Candidate Decision • The ME in the AMVP mode check and the merge candidate decision employ the same SATD measurement and there is a correlation between them. • Basically, the GMV has the minimum SATD in the SR and it can be taken as a reference for the Merge candidate decision.

11. Low-complexity merge candidate decision #A2GMV Based Merge Candidate Decision

12. Low-complexity merge candidate decision #A3GMV Based Merge Candidate Decision • In Case (2), the GMV is identical to the BMMV, including the prediction direction, reference picture index and MV components. Case (2) can also be called as equal case. • The GMV represents the true MV of the current PU better than or equal to the BMMV (up to 88.38% for LP and 72.91% for RA).

13. Low-complexity merge candidate decision #A4GMV Based Merge Candidate Decision

14. Low-complexity merge candidate decision #B1Position-Priority Based Merge Candidate Decision

15. Low-complexity merge candidate decision #B2Position-Priority Based Merge Candidate Decision • A1, B1, and T are always the dominant positions for all the cases. When the CU size becomes larger, the total proportion of A1, B1 and T becomes smaller and the order of them is varying a little for different partitions. • A1, B1 and T are available • A1, B1 and T are not available

16. Low-complexity merge candidate decision #B3Position-Priority Based Merge Candidate Decision

17. Simulation Results #1

18. Simulation Results #2

19. Simulation Results #3

20. Simulation Results #4