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Annex 4 to Doc. AVC-177R
Annex 4 to Doc. AVC-177R

DEFINITION OF END TO END DELAY


1. Introduction

The following description of the end to end coding delay is proposed to 
allow comparison between coding schemes regarding what end to end delay is 
concerned.

A this stage the transmission delay is neglected and the end to end delay is 
defined as a back to back delay (see Figure 1).


           ------     -------     -------     -------
          |CAMERA|---|ENCODER|---|DECODER|---|DISPLAY|
           ------     -------     -------     -------

                      Figure 1

2. Description of end to end delay

The different delay in encoder and decoder are described in Figure 2.

The expression for the total end to end delay is 

              6            6
       Dtot = ƒ°Die + D7 + ƒ°Djd
             i=1          i=1

A more precise explanation of frame reordering is given in Figure 3.


3. Conclusion

The above definition has to be adopted to the specific coding.  Mainly 
examples are given.

It can be pointed out that the main elements for delay are 

     -	format conversion
     -	frame reordering
     -	buffer delay

For simplicity reasons, D6e+D7+D6d can be neglected when comparing coding 
schemes.

It should however be noticed that this factor must be added to when the end 
to end delay is calculated to meet the requirements (low end to end delay).


References

AVC-124 (Japan) Considerations on processing delay with hybrid coding 
AVC-115 (PTT Research - NL) Features of MUPCOS