Opened 9 years ago

Closed 9 years ago

#410 closed defect (fixed)

Lossless coding is not guaranteed

Reported by: kugur Owned by: bbross
Priority: major Milestone:
Component: Text Version: D6 (H1003) dI/dJ/dK
Keywords: Cc: bbross, wjhan, jct-vc@…

Description

At the San Jose meeting, lossless coding mode (H0530) and sign bit hiding (H0481) are adopted. In the lossless coding mode, lowest QP value is used to switch to lossless mode for CU's. However, when lossless coding mode is enabled , current design does not anymore guarantees a lossless operation due to sign bit hiding technique.

This is because sign bit is not signaled but derived from the magnitude of the levels and some combinations of level and sign are not allowed.

Suggested fix: Disable sign bit hiding for the blocks where lossless coding mode is applied.

Attachments (1)

JCTVC-H1003_dK_data_hiding_fix_for_lossless.docx (26.3 KB) - added by wen.gao 9 years ago.

Download all attachments as: .zip

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 wen.gao

The issue has been addressed in HM6.1 software. Specifically, the data hiding operation is disabled when the lossless coding mode is used in a CU.

The CD text (JCTVC-H1003_dK) will also need modificaiton to reflect the change. We propose the following change:

(1) In 7.3.10 Residual coding syntax

if (qpprime_y_zero_transquant_bypass_flag ==1 && QP’Y ==0) 
    signHidden=0
 else
    signHidden = ( lastNZPosInCG – firstNZPosInCG >= sign_hiding_threshold) ? 1 : 0

(2) In 7.4.2.1

qpprime_y_zero_transquant_bypass_flag equal to 1 specifies that, when QP′Y is equal to 0, a lossless coding process shall be applied. In lossless coding operation, the scaling and transform process as specified in subclause 8.6 and the in-loop filter process as specified in subclause 8.7 are bypassed, and the sign bit hiding in residual_coding() is not applied.

The modified text is also attached.

comment:3 Changed 9 years ago by bbross

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

Fixed by integration of JCTVC-I0529 in JCTVC-I1003 d2

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