Joint Video Exploration Team (jvet) of itu-t sg 6 wp and iso/iec jtc 1/sc 29/wg 11

9Encoder optimization (5)

Contributions in this category were discussed Sat 14th 1530–1615 (chaired by JRO).

JVET-E0023 AHG5: Improved fast encoding setting [Y. Yamamoto, T. Ikai, Y. Yasugi (Sharp)]

This contribution proposes a fast encoding setting, which changes the threshold for stopping further splitting. The threshold is determined by the distance between current and reference pictures. Simulation results reportedly show around 12% encoding speed up with 0.23% BD-rate loss.

The criterion is the minimum distance in the RPL, computed once per slice. In RA, this means that smaller value of skip depth (2) is used for higher hierarchy layers. For LDB, always a skip depth 2 would be used. This is a pure encoder change for early termination of checking QTBT splitting options.

Two configurations were investigated:

• 
  A – use skip depth 2 when minimum distance is <=2, otherwise use skip depth 3; this reduces encoder runtime by 12% for RA, 0.23% loss, for LDB, it saves 17% encoder time, loses 0.25%.
  
• 
  B - use skip depth 2 when minimum distance is <=1, otherwise use skip depth 3; this reduces encoder runtime by 8% for RA, 0.12% loss, for LDB, no results are presented, but likely same as configuration A.
  

Another result is given in the contribution where skip depth 2 is always used for RA; this reduces the encoder time by approx. 17% and gives a loss of 0.33%.

No results on LDP were provided.

JVET-E0054 Cross-check of AHG5: Improved fast encoding setting (Test A) [X. Chen, J. Zheng (HiSilicon)] [late]
JVET-E0118 Cross-check of AHG5: Improved fast encoding setting (test B) [V. Lorcy (bcom), P. Philippe (Orange), T. Biatek (TDF)] [late]
JVET-E0078 AHG5: improved fast algorithm in JEM-4.0 [P.-H. Lin, Y.-J. Chang, C.-L. Lin, C.-C. Lin (ITRI)]

This contribution proposes a fast algorithm for QTBT structure determination. The method skips some partition processing in QTBT to enhance the encoding efficiency. The simulation results reportedly show that up to 4% encoding time reduction over JEM-4.0 can be achieved in the RA test condition with less than 0.05% BD-rate loss.

This makes checking of further splitting dependent on the RD cost for the parent CU, and compares it to that of first child CU being larger than 0.55 * Cost of parent.

The reduction of runtime of 4% seems to be quite low. It was asked whether more reduction would be possible when the factor of 0.55 would be modified.

Several experts expressed an opinion that further reduction of encoding time would be desirable. From the figure below, the solution B from E0023 is the best tradeoff compared to the compression loss.

E0078

From E0023, always skip depth 2 in RA

E0023

E0023

Decision (SW): Adopt JVET-E0023 test case B (skip depth 2 always for LDB and LDP, skip depth 2 for highest temporal layer in RA, other layers skip depth 3).

JVET-E0116 Cross-check of AHG5: improved fast algorithm in JEM-4.0 [K. Choi (Samsung)] [late]

10Joint Meetings, BoG Reports, and Summary of Actions Taken

10.1Exploration Experiments

The setup of Exploration Experiments was discussed, and an initial draft of the EE document was reviewed in the plenary (chaired by JRO). This included the list of all tools that are intended to be investigated in EEs during the subsequent meeting cycle:

EE1: Intra prediction

JVET-E0068 Unequal Weight Planar Prediction and Constrained PDPC [K. Panusopone, S. Hong, L. Wang (ARRIS)]

EE2: Nonlinear in-loop filters

JVET-E0032 Bilateral filter strength based on prediction mode [J. Ström, P. Wennersten, K. Andersson, J. Enhorn (Ericsson)] (also test cases with reduced lookup table memory)

EE3: Decoder Side Motion Vector Derivation

JVET-E0028 EE3: bi-directional optical flow w/o block extension [A. Alshin, E. Alshina (Samsung)] (investigate version without block size dependent weighting)

JVET-E0035 Enhanced Template Matching in FRUC Mode [Y. Lin, X. Chen, J. An, J. Zheng (HiSilicon)]

Li Zhang was mandated to compile the EE document with remote assistance by Elena Alshina, to be circulated by Thursday and reviewed Friday.

It was agreed to give the editors the discretion to finalize the document during the two weeks after the meeting, and circulate/discuss it on the reflector appropriately.

10.2Joint meetings

Joint meeting on evaluation of projections, Tuesday 0900–1000, of JCT-VC, JVET, VCEG, and MPEG Systems

See the JCT-VC report and the summary report JCTVC-Z0050 / JVET-E0137.

Joint meeting on projection format extensibility, Tuesday 1400–1500, of JCT-VC, VCEG, and MPEG Requirements, Systems, and Video

See the JCT-VC report.

Joint meeting on CfE preparation, Wednesday 1400–1500, of JVET with the VCEG and MPEG parent bodies

A draft preliminary CfE was presented with selection of test sequences and bit rates.

Testing of submissions was planned to be conducted by expert viewing.

No commitment was made that we will review all input, as we could get swamped.

A significant goal of the CfE is refinement of plans for a CfP.

Testing the JEM at the CfE stage as well as some proposals could provide a valuable reference point (as an additional anchor or a response).

(Potentially use the JEM bit rates as what should be matched.)

No fee was planned to be charged at the CfE stage.

Binary decoder and bitstreams are not necessary at CfE stage.

Just using the RA configuration for the CfE stage seems adequate.

Pre-/post- processing allowance – post-proc is allowed if part of decoding process. Perhaps allow for HDR and 360. Further study of this is desired.

It was agreed not to add WVGA and 720p to keep the effort manageable.

Joint meeting on CfE preparation and future video standardization, Thursday 1400–1500, of JVET with the VCEG and MPEG parent bodies

Further review and refinement of the planned preliminary CfE was conducted jointly; see the output document JVET-E1002.