JVET-E0121 AHG4: Evaluation report of Netflix HDR test sequences [T. Lu, F. Pu, P. Yin, T. Chen, W. Husak (Dolby)] [late]

This was presented in the BoG JVET-E0132 (presented by A. Norkin).

This report provides compression results of HM-16.13 for some of the HDR test sequences that have been under study in the AHG4. The performance is evaluated using Rate-Distortion curves and subjective viewing on HDR displays.

Preferred candidates are:

• HDR2K: Cosmos1 and Cosmos6
• HDR4K: Meridian1, Chimera3, Chimera6

A side comment is that Cosmos7, Chimera5 and Chimera8 are not given high preference because they contain chaotic/fast motion that may make viewers uncomfortable under repetitive viewing in a typical subjective test.

QP37 is used to check visual quality.

Further discussion on HDR testing:

In a follow-up activity, the BoG performed informal viewing of sequences (original and coded), and on this basis suggested modifications of common testing conditions, as well as conditions for the HDR/WCG part of the planned Call for Evidence.

The BoG reconvened on January 18, 2017, to review and discuss comments from the HD-HDR viewing sessions. There were three viewing sessions conducted as part of the activity. The first was an informal viewing session performed during the setup of the content. The second and third viewing sessions were announced on the reflector.

Sessions one and two consisted of viewing the compressed representation of the Cosmos_6, Cosmos_7 and Cosmos_1 sequences, where the compressed representation corresponded to the HM anchor configuration in JVET-D1020 with the “master QP” set equal to 37. Session three also included viewing the uncompressed presentation of the sequences.

The comments from the viewing are below:

Cosmos_6 sequence (or “vortex” sequence)

• Comment that the sequence was a difficult sequence to perform visual assessment
• Comment that the sequence contained two scene cuts
• Comment that there was noise in the “vortex” that may be due to the computer rendering process
• Recommendation: do not include this sequence in the CTC

Cosmos_7 sequence (or “caterpillar” sequence):

• Comment that the sequence looked interesting and with details
• Comment that the sequence had high colours
• Comment that there was some de-colourization on the bubbles. It was noted that it was possible that this may be related to the display.
• Comment that the original sequence contained noise on the face of the “caterpillar”.
  • One participant suggested that the noise may be due to the computer rendering process
  • More than one participant observed that the noise appeared to change from frame to frame, and that this temporal variation was creating a so-called pulsing artefact.
• Comment that there was noise across the entire picture
• Comment that the sequence was very colourful
• Recommendation: Encourage further study of the sequence and source of the issues identified above. Do not include in the CTC at this time.

Cosmos 1 sequence (or “tree trunk” sequence):

• Comment that the compressed version had a lot of artefacts
• Comment that the grass was challenging for compression
• Comment that the grass in the original sequence had high texture
• Comment that there was noise in the upper right corner of the sequence. It was suggested by multiple participants that this may be an artefact due to the computer rendering process.
• Comment that there was noise in the grass in the original sequence
• Comment that the noise characteristics appears to be temporally and spatially consistent
• Recommendation: Include the sequence in the CTC

After the above discussion, the current state of the CTC was:

One participant suggested that FireEater could be removed from the CTC.

One participant commented that FireEater is the only dark sequence in the CTC.

One participant commented that the first part of ShowGirl is also dark

For the CfE, it was commented that it could be desirable to select 3–4 sequence from the CTC list.

The following ranked preference for selection was discussed:

1. Market (Agree)
2. ShowGirl (Agree)
3. EBU_06_Starting
4. EBU_04_Hurdles
5. Cosmos_1_Tree_Trunk

This order was agreed by the group.

For rate selection, several participants noted that rates had been identified as part of the verification tests in JCTVC-X1018. The rates are copied below:

One participant commented that the group should anticipate that responses to the CfE may have better coding efficiency than the anchors in JCTVC-X1018.

One participant suggested that the group could reduce the rates by 10% to account for the potential of improved coding efficiency, as the visual quality of the lowest rate had been observed to be quite poor.

One participant noted that the rates above are substantially lower than the previous HDR CfE. This statement applies to Market3 and Showgirl, as the EBU sequences were not used.

It was reported that for Cosmos_1_Tree_Trunk, the rates for QP22–37 were: 9207, 5118, 1212, and 472.

One participant commented that the lower bit rates had significant visible artefacts

One participant suggested to reduce the bit rate of the highest rate point for Cosmos_1_Tree_Trunk to 6000, 3000 1200, 500.

Agreed: Reduce the bit rate of the highest rate point for Cosmos_1_Tree_Trunk to 6000, 3000 1200, 500.

Agreed: For the other sequences, it was suggested to reduce the rate by 10% and round the resulting rate.

The recommendations of the BoG were reported to the JVET plenary and approved.

Exploration experiments (40)

General EE results reporting (1)

Contributions in this category were discussed Thursday 1600–1650 (chaired by JRO and GJS).