Opened 9 years ago

Closed 9 years ago

#720 closed technical change (fixed)

candidate of intra prediction mode

Reported by: PhuongNguyen Owned by: bbross
Priority: minor Milestone:
Component: Text Version: D8 (J1003) d7
Keywords: candidate, intra, prediction, mode Cc: bbross, wjhan, jct-vc@…

Description

Hello,

I have two points concerning the candidate selection for intra prediction mode.

  1. In 8.4.2 (derivation process for luma prediction mode), when candIntraPredModeA == candIntraPredModeB and candIntraPredModeA >= 2,

(8-20) reads candModeList[2] = 2 + ((candIntraPredModeA - 2 + 1) % 32)

so when candIntraPredModeA == 33, this formula gives

candModeList[2] = 2 + ((33 - 2 + 1) % 32) = 2 + (32 % 32) = 2

I think that in this case, we should use the mode 34 for candModeList[2] instead of 2 because it is the neighbouring mode of 33.

If this suggestion is adopted, the new formula for (8-20) will be :

candModeList[2] = 3 + ((candIntraPredModeA - 2) % 32)

  1. Also in the same case candIntraPredModeA == candIntraPredModeB and candIntraPredModeA >= 2,

+ if candIntraPredModeA == 2, candModeList[1] and candModeList[2] are 3 and 33
+ if candIntraPredModeA == 34, candModeList[1] and candModeList[2] are 2 and 33

I am wondering in these two cases, instead of choosing the opposite direction (33 and 2 respectively), whether neighbouring modes (4 and 32) will be better. In other words,

+ if candIntraPredModeA == 2, candModeList[1] and candModeList[2] are 3 and 4
+ if candIntraPredModeA == 34, candModeList[1] and candModeList[2] are 32 and 33

Best regards,
Phuong Nguyen.

Change History (5)

comment:1 Changed 9 years ago by DefaultCC Plugin

  • Cc bbross wjhan jct-vc@… added

comment:2 Changed 9 years ago by bbross

  • Milestone D8 deleted
  • Priority changed from major to minor
  • Type changed from enhancement to technical change

Please correct me if I'm wrong but this seems more like a technical change than a bug to me.

Such normative changes can be brought to the next meeting as a proposal and then, when the group agrees to adopt this change, integrated in the draft text.

comment:3 Changed 9 years ago by PhuongNguyen

Yes, this should be considered as a technical change.

Please discuss this point during the next meeting.

comment:4 Changed 9 years ago by PhuongNguyen

In a second thought, the point 2 can be considered as a technical change but the point 1 might be considered as a defect. I am wondering there is a mismatch between the intention and the formula (8-20). I would like to ask the owner of this part to check it, i.e. the mode 34 should be used instead of 2 when candIntraPredModeA == candIntraPredModeB and candIntraPredModeA >= 2.

comment:5 Changed 9 years ago by bbross

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