Opened 12 years ago

Closed 12 years ago

# 14-bit issues in Weighted Prediction

Reported by: Owned by: pandrivon bbross major D7 Text D7 (I1003) d4 bbross, wjhan, jct-vc@…

### Description

In 8.5.2.2.3 Weighted sample prediction process, variable offset1 is set equal to 1<<(shift1-1) but shift1 is set equal to 14 - bitDepth. If bitDepth equals to 14 then we have a negative shift. Basic non-invasive lightweight solution would be to set offset1 to 0 when bitDepth equals to 14. Another hardcore one would be to shift all MC (WP, IF...) precision on 15 bits instead of 14 bits that would be very invasive in the code. Btw, the same issue happens in HM7.0. (WP, IF).
Any thoughts?

### comment:1 Changed 12 years ago by DefaultCC Plugin

• Cc bbross wjhan jct-vc@… added

### comment:2 Changed 12 years ago by pandrivon

Quoted in 8.5.2.2.3:
"– The variable offset1 is set equal to 1 << ( shift1 − 1 ) and the variable offset2 is set equal to 1 << ( shift2 − 1 ). "

Suggestions:
"– The variable offset1 is derived as follows.

• If shift1 is greater than 0, offset1 = 1 << ( shift1 − 1 ) (8-201)
• Otherwise, offset1 = 0 (8-202)
• The variable offset2 is set equal to 1 << ( shift2 − 1 )."

or all could be written as a text (it allows removing to equation figures) like:
"- If shift1 is greater than 0, the variable offset1 is set equal to 1<<( shift1 - 1 ), otherwise shift 1 is set equal to 0.

• The variable offset2 is set equal to 1 << ( shift2 − 1 )."

HM should be fixed accordingly Cf. ticket #595.

### comment:3 Changed 12 years ago by bbross

• Milestone set to D7

### comment:4 Changed 12 years ago by bbross

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

Fixed in JCTVC-I1003_d6.

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