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Annex 4 to Doc. AVC-355R
Annex 4 to Doc. AVC-355R

Report of the discussion on "Profile"

Adhoc Group on Video Test Model had a session on Wednesday to discuss how to 
structure the generic standard MPEG-2, paying attention to the notion of 
"profile".  Before the discussion, MPEG Convenor presented the background, 
referring to the related decisions to date;

    - 	Our policy is to take the "toolkit with maximum core" approach to MPEG-
2.
    - 	Performance and functional requirements from various applications have 
been collected and now being integrated into a single document covering 
system, video and audio.
    - 	The generic standard and specific applications may be liaised by use of 
the "profile" notion given in ISO/IEC Technical Report DTR 10000.  Its 
terminology is as attached.
    - 	"Profile" is currently used rather liberally, thus clarification and 
common understanding of the members are necessary.

Activities on video requirements so far have identified features to be 
developed, and these have been reflected in various experiments of the Test 
Model.  If these experiments are successfully carried out, we will be able to 
provide sufficient tools in the new MPEG-2 standard to meet those requirements 
from a wide range of applications. 

The issue is that one specific application may use a particular combination of 
features and parameters conforming to MPEG-2 for its optimization and another 
specific application may choose another combination also conforming to MPEG-2 
for the same reason; possible examples mentioned were use/non-use of B-
pictures, new predictions (such as intelligent prediction, leaky prediction).  
The result may be that two MPEG-2 conforming equipment cannot talk each other 
(i.e. incompatibility inside MPEG-2).  Since implementation technology will 
evolve, there may happen interoperability problems between different 
generation equipment. 

The policy of "toolkit with maximum core" is intended as a compromise between 
meeting as many requirements as possible (i.e. generic) and keeping 
interoperability as widely as possible.  The boundary of the core should be 
clarified at some point of time (hopefully in November).

Toward this direction, application of "profile" may help us.  Dr. LeGall 
provided the attached diagram as a basis of further elaboration, to which a 
particular application (or group of applications) may be mapped.  Another of 
his suggestions is to define a couple of "target profiles" similar to the 
"constrained bitstream" in MPEG-1, according to this diagram.

One of the suggestions raised during the discussion was to work out a matrix 
relating functionalities provided in the TM to specific or group of 
applications.  The purpose of this is to clarify application attributes, 
maximum core, interoperability and interface issues.  There was a concern 
expressed against this approach, however, that there may be a risk to get 
involved in business aspects for which this engineering group is not 
responsible.  

Members are requested to contribute to clarifying this issue and the way to 
reflect the outcome in the standard.

                              -----------
                             | The Works |
                             |-----------|
                             |     |     |
                 |-----------|---| | |---|------------|
                 |            ---|---|---             |
                 |               |   |                |
          ---------------    --------------    -------------
         | Compatibility |  |   No Frill   |  | Scalability |
         |   Extension   |  |     Core     |  |  Extension  |
         |               |  |    Syntax    |  |             |
          ---------------    --------------    -------------
                                   |    ---------
                                   |---|  Normal |
                                   |    ---------
                                   |    ---------
                                   |---|Low Delay|
                                   |    ---------

           Figure   Link between features and syntactic subset


*  *  *  *

Definitions given in DTR 10000


International Standardised Profile

An internationally agreed-to, harmonized document which identifies a standard 
or group of of standards, together with options and parameters, necessary to 
accomplish a function or set of functions.


Profile

A set of one or more base standards, and, where applicable, the identification 
of chosen classes, subsets, options and parameters of those base standards, 
necessary for accomplishing a particular function.

Profiles provide a basis for the development of uniform, internationally 
recognized, conformance tests.

Note: An International Standardised Profile includes the specifications of one 
or more Profiles


Base Standard

An approved International Standard or CCITT Recommendations which is used in 
the definition of a Profile.


END