Organisation internationale de normalisation

Constant decoder delay. The presenter noted that implementations are much simpler if all possible processing paths have the same effective signal delays. While there is already a coreQmfDelayCompensation, this does not apply to all processing paths. Furthermore, the management of “encoder delay compensation” is complex and a significant likelihood of errors in encoder implementation. The contribution proposes to mandate a constant, deterministic delay in decoder processing, as shown in the following figure (lower hatch-shading in the following figure):

The presenter noted one open issue: the delay is from encoder signal input to where in the decoder?

• 
  Final output signal
  
• 
  Point at which potential configuration change occurs.
  

Experts discussed and agree that the only requirement is that there be a constant delay from encoder signal input to decoder mixing block and to decoder output signal.

The contribution proposes to

• 
  Include a table of actual decoder delay for all signal paths, plus the delay values that must be added (e.g. delay line) in order to achieve a constant delay for all operating modes. This involves a change to the normative “rule set” for determining processing domains.
  
• 
  Syntax bits that previously dealt with decoder delay are revised as follows:
  
  • 
    coreQmfDelayCompensation) is now reserved
    
  • 
    receiverDelayCompensation is now re-interpreted to signal the new constant delay mode of operation.
    

The presenter noted that a Phase 2 PDAM text will have an editing period, and proposed that the table of delays be reviewed in light of technology added to Phase 2 at this meeting. This can be done in the editing period.

It was the consensus of the Audio subgroup to incorporate the Constant Decoder Delay technology into MPEG-H Phase 2.