Opened 9 years ago Closed 9 years ago #700 closed defect (fixed)Derivation process of chroma offset in WP when an input bit depth is beyond 8bit
Description
When an input bit depth is beyond 8bit, the derivation process of chroma offset in the weighted prediction is incorrect. Since the value of chroma offset is always held in 8bit (see equations (8224) and (8225)), the predicted value of chroma offset must be also held in 8bit.
Original;
Modified;
The modified patch is provided in this ticket. Attachments (2)Change History (7)comment:1 Changed 9 years ago by DefaultCC Plugin
Changed 9 years ago by Tanizawacomment:2 Changed 9 years ago by ksuehring
I think I cannot follow this problem: Equation 752 contains:
bdShift = 1 << ( BitDepthC − 1 )
which looks like the original code. Is the implementation somehow diverging from the draft text? comment:3 followup: ↓ 4 Changed 9 years ago by Tanizawa
The derivation process of ChromaOffsetLx in equation (752) is described as follows:
Reflecting Ticket#699, the bdShift was modified to "128".
Therefore, the shift value must be modified to "128", too.
original:
modified:
The new patch is provided in this ticket. Changed 9 years ago by Tanizawacomment:4 in reply to: ↑ 3 Changed 9 years ago by yanye
I verified that the attached patch file is correct. For >8 bits video, the WP weights should still be represented in 8bit precision.
Yan
Replying to Tanizawa:
comment:5 Changed 9 years ago by fbossen
Fixed in r3116 Note: See
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Patch file for chroma offset