Opened 10 years ago Closed 6 years ago #1302 closed enhancement (fixed)WP unnecessary condition for log2Wd < 1
Description
The else branch for the condition on (log2Wd >= 1) in "8.5.3.3.3.7 Explicit weighted sample prediction process" is never entered, e.g in Eq (8‑247) but the issue is the same for v1 too:
if( log2Wd >= 1 )
else
When looking at the derivation of log2Wd, it cannot be <1 so the else part can be removed as an editorial change on both v1 and v2:
luma:
shift1 is set equal to Max( 2, 14 − bitDepth ) or (14- bitDepth) in v1
-> shift is ranging from 4 to 6 for v1 and from 2 to 6 for Rext, so it never gets to 0 and since luma and chroma log2WeightDenominator range from 0 to 7, log2Wd can never be smaller than 2. Change History (3)comment:1 Changed 10 years ago by DefaultCC Plugin
comment:2 Changed 7 years ago by bbross
comment:3 Changed 6 years ago by bbross
fixed in v5 (2018/02) Note: See
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Agreed by the authors of the AHG2 report JCTVC-AD0002 (checked 2016/12 release of the HEVC specification).
Fix:
In Equations 8-277 and 8-278, remove the condition checks “if( log2Wd >= 1 )” and the associated “else” clauses.