JVET-AJ0090 AHG12: temporal ALF [L. Xu, Y. Yu, H. Yu, D. Wang (OPPO)]

This contribution proposes an adaptive loop filter that uses temporal reconstructed information as the input to a filter whose output will enhance the current picture. The proposed temporal adaptive loop filter (TALF) is implemented on top of ECM-14.0 reference software. The simulation results show that the proposed method can achieve the following BD-rates gain over the anchor:

RA: -0.13%/0.26%/0.25%, 100.6%/102.6%EncT/DecT

LDB: -0.16%/0.54%/0.21%, 102.2%/104.2%EncT/DecT

The input samples to TALF are retrieved from the reference pictures as identified by the motion vectors. Motion is clipped to integer precision to fetch corresponding samples.

Another mode of filtering uses collocated samples from the closest reference picture in the reference picture list.

The proposed TALF is applied to inter coded blocks (using samples from refernce pictures) and IBC blocks (using samples from current picture before ALF).

No fixed filters. Up to 8 history TALF sets can be stored for use by future pictures.

Currently, the TALF coefficients are signalled in the slice header, instead of using APS. It was commented that using an APS like other ALF filters is more desirable.

It was commented that this proposal would introduce some latency, the gain may not sufficient to justify the latency.

Multiple experts expressed interest in the proposal.

It was agreed to investigate this in an EE. The proposal needs to be modified to carry the coefficients in an APS.

JVET-AJ0318 Crosscheck of JVET-AJ0090 (AHG12: temporal ALF) [Z. Dai (Alibaba)]

JVET-AJ0372 BoG Report: Group of ECM tools with large memory access [X. Li (BoG chair)]

This was presented Thu 7 Nov. 1515

This document contains the report of the BoG on group of tools with large memory access. The BoG met on 11/6 Wednesday 10:15am –11:35am.

Mandates

With regard to AHG7 activities, it was agreed to establish a new group of tools with large memory access, e.g by needing large lookup tables. It is however also necessary to take into account the granularity of usage, e.g. it is different if a large amount of coefficient values needs to be reloaded for every 4x4 block or for an entire CTU.

This BoG was to further work on criteria, and set up a list of tools that would be added to such a group.

Recommendations

• Tool list
  • PDP
  • Enhanced MTS
  • LFNST extension
  • NSPT
  • Fixed filter in ALF
• Cfg Options (For tools which extended the tools in VVC, the group off test should only turn off the extended part while leaving the VVC tool unchanged)
  • PDP control is available
  • The proponents of Enhanced MTS and LFNST extension will try to
  • The proponents NSPT and Fixed filter in ALF will implement the control
• Summary table

Note that the lookup table sizes are counted based on the ECM-14 implementation, which has not been fully optimized for memory usage.

The tools with lookup table size larger than 64Kbytes. Note that Kbytes =1000bytes in the following discussions.