JVET-Y0159 EE2-related: inter MTS refinement on adaptive intra MTS (EE2-4.4) [T. Hashimoto, T. Ikai (Sharp)]
This contribution proposes to change the inter MTS aspect of Adaptive intra MTS (AMTS) in EE2-4.4a by restricting AMTS’s candidate number increase in the case of inter MTS. It is noted that AMTS (EE2-4.4a) extends the number of MTS (Multiple transform selection) candidate up to 6:
- VVC 4
- ECM 4 (but the MTS candidate can be chosen from more transforms)
- AMTS 6
It is reported the simulation results of proposed method compared to the ECM-3.1 with inter MTS is:
- RA: BD-rate YUV: -0.06%, -0.12%, -0.02%; EncT: 99%; DecT: 100%
- LDB: BD-rate YUV: -0.23%, -0.22%, -0.47%; EncT: 103%; DecT: 100%
It is recommended to adopt method1 because it is asserted to show best performance without any encoder time increase.
In v2, results are updated.
It is reported that the AMTS software from EE has an encoder/decoder mismatch when enabled for inter, beyond a bug in ECM (for which a ticket was issued)
Method 1 keeps the number of candidates for inter MTS fixed as currently (4).
Question: Which are the 6 candidates in method 3 for inter MTS? Not clear. Probably the selection of candidates would require more investigation. Currently method 3 performs worse than method 1.
Currently inter MTS is not used in CTC
Method 1 provides 0.37%/0.59% in RA/LB, with 20%/30% encoder run time increase.
Decision (SW/BF): Adopt JVET-Y0159 method 1.