Opened 3 years ago

Last modified 3 years ago

#1309 new defect

Potential for reference pictures to be reactivated across a CVS boundary

Reported by: jackh Owned by:
Priority: minor Milestone: D10
Component: Text Version: D10 (L1003) v33
Keywords: Cc: bbross, wjhan, jct-vc@…

Description

Section 8.3.2 of L1003 v34 says:

When the current picture is an IRAP picture with NoRaslOutputFlag equal to 1, all reference pictures currently in the DPB (if any) are marked as "unused for reference".

the clear intention being that there may be no pictures in a CVS that reference pictures from a preceding CVS. This is fine. However, later in the same section, it says this:

All reference pictures that are included in RefPicSetLtCurr and RefPicSetLtFoll are marked as "used for long-term reference".

This gives the potential for a BLA picture which has been spliced from another stream to reactivate a reference picture from the preceding CVS if it has an entry in its long term RPS which happens to have the same POC (or LSB thereof) as a picture remaining in the DPB from the preceding CVS. This has potential to subsequently mess up the DPB output process.

As such reference pictures will never be actually used (they can only be used by RASLs which will not be decoded in this case anyway), I suggest that the second section above be modified to say:

When the current picture is not an IRAP picture or NoRaslOutputFlag is equal to 0, all reference pictures that are included in RefPicSetLtCurr and RefPicSetLtFoll are marked as "used for long-term reference".

Change History (3)

comment:1 Changed 3 years ago by DefaultCC Plugin

  • Cc bbross wjhan jct-vc@… added

comment:2 Changed 3 years ago by adarsh

"Reference pictures" are those that are marked as "used for reference" - short-term or long-term. The process described in subclause 8.3.2 is processed in the order it is specified in that subclause. Before the RPS of the current picture is decoded, if the current picture is an IRAP picture with NoRaslOutputFlag = 1, all reference pictures X (i.e. pictures marked as "used for reference" - short-term or long-term) are marked as "unused for reference". At the end of this step, these pictures X are no longer "reference pictures". Therefore "re-activation" would not happen because "All reference pictures that are included in RefPicSetLtCurr and RefPicSetLtFoll are marked as "used for long-term reference." only applies to reference pictures.

Note that even when populating RefPicSetLtCurr and RefPicSetLtFoll, only "reference pictures" (or "no reference picture") are considered.

comment:3 Changed 3 years ago by jackh

Ah, I see - that clears it up. Many thanks.

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  • Adarsh Krishnan Ramasubramonian(Participant)
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