Opened 16 months ago

Closed 16 months ago

Last modified 16 months ago

#1092 closed defect (fixed)

Bug on signalling of some partitioning layouts in VTM-9.0 encoder

Reported by: vdrugeon Owned by:
Priority: minor Milestone: VTM-9.1
Component: VTM Version: VTM-9.0
Keywords: Cc: ksuehring, XiangLi, fbossen, jvet@…

Description

The VTM encoder initialises the value of the variable numExpSliceInTile in function HLSWriter::codePPS to pcPPS->getNumSlicesInTile(i) - 1. This variable is then used to determine the syntax element num_exp_slices_in_tile[i] written in the bitstream.

But initialising this variable to pcPPS->getNumSlicesInTile(i) - 1 can lead to issues when a tile contains several slices for which the last slice is bigger than the previous one: for example, if a tile has a height of 5 CTUs and contains two slices with the first slice having a height of 2 CTUs and the second a height of 3 CTUs. In that case, the current VTM encoder will set the value of num_exp_slices_in_tile to 1 instead of 2, which means that the decoder will derive a tile having 3 slices instead of 2 with the first two slices having a height of 2 CTUs and the last one a height of only 1 CTU.

Initialising the variable numExpSliceInTile as follows would solve the problem for the above described configuration:
uint32_t numExpSliceInTile = (pcPPS->getNumSlicesInTile(i) == 1) ? 0 : pcPPS->getNumSlicesInTile(i);

Change history (8)

comment:2 Changed 16 months ago by biaowang

I think the title is somehow misleading.
According to your description, it is a bug of tile/slice implementation, but not subpicture.
If subpicture is disable, is the bug still valid?

comment:3 Changed 16 months ago by vdrugeon

The bug is probably still valid if subpictures are disabled, but I have only tested it with subpictures.
Can you confirm that you are happy with the bug fix or otherwise propose another fix?

comment:4 Changed 16 months ago by biaowang

could you share the configuration file?
I can test for the case when subpicture is disabled.
If the bug is still valid, I request to change the name of the title, since it is not true.

comment:5 Changed 16 months ago by vdrugeon

  • Summary changed from Bug on signalling of some subpictures layouts in VTM-9.0 encoder to Bug on signalling of some partitioning layouts in VTM-9.0 encoder

I don't have a strong opinion about the title of the bug to be honest, so I have changed it since it seems to be so important to you...
Configuration file will follow

comment:6 Changed 16 months ago by biaowang

Thanks for sharing the configuration file.
Just tested and the bug is still valid when subpicture is disabled, and your MR fix the issue.

Don't get me wrong.
If a bug occurs to slice/tile implementation but subpicture is complained, it sends wrong message to the community.
IMHO, we shall keep the bug track description as precise as possible, as we do for the meeting note.

comment:7 Changed 16 months ago by ksuehring

  • Resolution set to fixed
  • Status changed from new to closed

The MR is merged

comment:8 Changed 16 months ago by ksuehring

  • Milestone set to VTM-9.1
  • Version set to VTM-9.0
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