Opened 9 years ago

Closed 9 years ago

#684 closed defect (fixed)

Weighted Prediction Formula Bug in 8.5.2.2.3.2 Weighted sample prediction process

Reported by: yul Owned by: bbross
Priority: critical Milestone: D8
Component: Text Version: D8 (J1003) d7
Keywords: weighted prediction Cc: bbross, wjhan, jct-vc@…

Description

In Section 8.5.2.2.3.2 Weighted sample prediction process, Equations (8-227) and (8-229),
predSamples[ x ][ y ] = Clip3( 0, ( 1 << bitDepth ) − 1, predSamplesL0[ x ][ y ] * w0 + o0 ) (8-227)
predSamples[ x ][ y ] = Clip3( 0, ( 1 << bitDepth ) − 1, predSamplesL1[ x ][ y ] * w1 + o1 ) (8-229)
have fatal errors that predSamplesL0 and predSamplesL1 are not right-shifted by "shift1". Those errors result in predSamples are always equal to ( 1 << bitDepth ) − 1.

The correct equations are given as follows:
predSamples[ x ][ y ] = Clip3( 0, ( 1 << bitDepth ) − 1, (predSamplesL0[ x ][ y ] + offset1 ) >> shift1 ) * w0 + o0 ) (8-227)
predSamples[ x ][ y ] = Clip3( 0, ( 1 << bitDepth ) − 1, (predSamplesL1[ x ][ y ] + offset1 ) >> shift1 ) * w1 + o1 ) (8-229)

Change History (4)

comment:1 Changed 9 years ago by DefaultCC Plugin

  • Cc bbross wjhan jct-vc@… added

comment:2 Changed 9 years ago by yul

Sorry, the correct equations should as follows:
predSamples[ x ][ y ] = Clip3( 0, ( 1 << bitDepth ) − 1, (predSamplesL0[ x ][ y ] * w0 + offset1 ) >> shift1 ) + o0 ) (8-227)
predSamples[ x ][ y ] = Clip3( 0, ( 1 << bitDepth ) − 1, (predSamplesL1[ x ][ y ] * w1 + offset1 ) >> shift1 ) + o1 ) (8-229)

comment:3 Changed 9 years ago by pandrivon

I think that original equations are right.
Please correct me if I am wrong, but equations (8-227) and (8-229) of J1003 d7 are only used when log2WD = 0 (as specified by the condition in equations (8-226) and (8-228) and min(log2WD) = 0). It means as log2WD = luma_log2_weight_denom + shift1 and as min(luma_log2_weight_denom) = 0 and as min(shift1) = 0 that both luma_log2_weight_denom and shift1 should be equals to 0 so that not shift (shift1=0) is required in that case (same for chroma component).

comment:4 Changed 9 years ago by bbross

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