Organisation internationale de normalisation

Other depth intra coding (7)

(Chaired by JRO, Sat. afternoon)

13.0.1.1.1.1.1.1.13JCT3V-J0022 Syntax cleanup of depth dc offset [T. Tsukuba, T. Ikai (Sharp)]

This contribution proposes to clean up dc offset related syntax element by removing depth_dc_flag with a context model adjustment. Experimental result reportedly shows -0.02% and -0.04% bdrate changes for synthesis in the CTC and all-intra configuration, respectively. It is asserted that this proposed method can remove a syntax element and simplify dc offset decoding process with no coding loss.

First part identical to JCT3V-J0047. Small loss (0.04% on average) is observed when the flag is removed from the syntax and instead the value of 1 is added to DC offset. Loss is >0.1% for two sequences in CTC, whereas only two sequences have small rate reduction.

Second part proposes context coding instead of bypass for depth_dc_abs, which compensates for the loss.

The coding loss probably comes due to cases where zero values need to be signalled for depth_dc_abs.

Complexity advantage of removing the flag would be minor, and does not justify the loss.

13.0.1.1.1.1.1.1.14JCT3V-J0091 Crosscheck on Syntax cleanup of depth dc offset(JCT3V-J0022) [K. Zhang, X. Zhang (MediaTek)] [late]

13.0.1.1.1.1.1.1.15JCT3V-J0047 Removal of depth_dc_flag syntax [J. Nam, S. Yea (LGE)]

As per decision of the last meeting, depth_dc_flag syntax is no longer used for DMM mode. Therefore, current depth_dc_flag syntax specifies that depth residual is present only when SDC is applied. In the contribution, removal of depth_dc_flag syntax is proposed. depth_dc_flag syntax can be removed by modifying calculation of DC offset. The experimental results show no impact under the common test conditions.

Note: The equation for computing the DC offset in the draft text may be incorrect, the value of 1 should be added (not subtracted) in inter mode

13.0.1.1.1.1.1.1.16JCT3V-J0072 Cross check of Removal of depth_dc_flag syntax (JCT3V-J0047) [M. W. Park, C. Kim (Samsung)] [late]

13.0.1.1.1.1.1.1.17JCT3V-J0051 Advanced boundary chain coding for depth intra coding [J. Seo, J. Nam, S. Yoo, S. Yea (LGE)]

This proposal provides results of the advanced boundary chain coding (ABC) based on HTM-12.0. The ABC is an improved coding tool based on the region boundary coding which separates a block into two partitions following an arbitrary contour described by a chain code. This proposal presents the experimental results of ABC without CABAC. The proposed method shows 0.2% and 0.2% BDR gains in synthesized views under CTC and AI configurations, respectively.

Two different methods are proposed: Only first bin of chain code context coded, and entirely bypass coded. The first method would result in 8 context coded bins per 4x4 block.

Average BR reduction in CTC for first method is 0.18%, for the second method 0.16%

Additional text around 5 pages for specifying the mode.

Some concern is raised about the additional implementation complexity of this new mode, compared to the relatively low compression benefit.

No support by other experts – no action.

13.0.1.1.1.1.1.1.18JCT3V-J0094 Cross-check results of advanced boundary chain coding (JCT3V-J0051) [K. Kawamura, H. Sabirin, S. Naito (KDDI)] [late]

13.0.1.1.1.1.1.1.19JCT3V-J0105 Crosscheck on Advanced boundary chain coding for depth intra coding (JCT3V-J0051) [S. Shimizu (NTT)] [late]

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