Opened 12 years ago

Closed 12 years ago

Derivation process error for luma intra prediction mode

Reported by: Owned by: sunnykr bbross minor WD6 Text D6 (H1003) dI/dJ/dK bbross, wjhan, jct-vc@…

Description

candModeList[0] = candIntraPredModeA (8 24)
candModeList[1] = 2 + ( ( candIntraPredModeA − 2 − 1 ) % 32 (8 25)
candModeList[2] = 2 + ( ( candIntraPredModeA − 2 + 1 ) % 32 (8 26)

In Intra_Angular (33) mode, candModeList[0] is 33, candModeList[1] = 32, and candModeList[2] = 2 (instead of 34).
In Intra_Angular (34) mode, candModeList[0] is 34, candModeList[1] = 33, and candModeList[2] = 3 (instead of 0 or 1 : non-angular modes).

Mod 32 operator is correct for those cases?

comment:1 Changed 12 years ago by DefaultCC Plugin

• Cc bbross wjhan jct-vc@… added

comment:2 Changed 12 years ago by chung

Another issue concerning (8 25) formula :
it does not work for candIntraPredModeA=2, since in this case we get
-1 % 32
This is not supported in the modulus definition

comment:3 Changed 12 years ago by tyamamoto

According to the definition of mod operation in spec, it actually does not support negative values. So (8-25) could be fixed as HM implementation.

candModeList[1] = 2 + ( ( candIntraPredModeA － 2 － 1 + 32 ) % 32) (8-25)

On 'Mod 32' correctness, it seems, by using 'Mod 32' instead of 'Mod 33', (8-25) and (8-26) are handling the fact that Intra_Angular(2) and Intra_Angular(34) are the 'same' direction (directions of 180 degrees opposite). So current equation seems fine unless it is not what original proposal intended.

comment:4 Changed 12 years ago by bbross

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

Fixed in JCTVC-I1003_d9.

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