Annex 4 to AVC-496R

Source:	REQUIREMENTS sub-group
Title:	Profile architecture

This document reports the outcome of discussion at the Sydney meeting to define subsets of the MPEG-2 Video standard.

1. Structure

       Level*

High

see 	
to be
considered	

see	

Main

	skeleton	
MP@ML
see WD	skeleton	

Low

to be 
considered		
	SIMPLE	MAIN	NEXT	
						Functionality

* Definition of Level is yet to be worked out.  See MPEG93/339.  Levels are not necessarily identical across profiles.  Preliminary view on the high and low levels of the Main Profile is that they correspond to HDTV and SIF resolution, respectively.

2. Documentation

Skeletons of NEXT and SIMPLE have been produced as attached.

3. Action points

- Specifications of each Profile at Level by elaborating skeletons
- Overall structure of Profile/Level
- See open issues listed in the NEXT skeleton.

Attachments

- Skeleton of NEXT Profile
- Skeleton of SIMPLE Profile

END

Attachment 1: Skeleton of NEXT Profile

We considered a profile called here NEXT as a first work of defining Profiles and Levels other than Main.

1. Purpose

To meet the requirements of major applications, such as outlined by CCIR (MPEG93/439) and the information technology industry, consisting of telecommunications, computer, and DSM groups (MPEG93/467), which are not fully addressed by Main Profile at Main Level.

2. Key functionalities

NEXT will support the following functionalities;

#	Functionality	NEXT	Main	
1	Chroma format	Receive 4:2:2
Decode 4:2:2 or 4:2:0	4:2:0	
2	Flexibility in bit rates (range of bit rates, CBR/VBR)	Control of bit rate on each layer is required.	yes	
3	Random access / Channel hopping / Low Delay	yes; much shorter channel hopping?	yes, but not necessarily at every frame	
4	Editability	yes as Main Profile	yes, but not necessarily at every frame	
5	Resilience	Graceful degradation is required.
Graceful degradation provides the ability for the progressive reduction of picture quality as the error rate  in the bit stream increases. The reduction in picture quality may be continuous or in discrete stages, and may be achieved by mechanisms such as reduction in picture resolution or picture PSNR.
Means of utilising transmission channels with the capability of unequal error protection is required. eg. B-ISDN ATM or Terrestrial Broadcasting.	yes	
6	Video windowing (e.g. 4:3 from 16:9 pictures)	yes	yes	
7	Low delay	yes;
much lower delay than Main?	yes	
8	Trick modes	Simple Fast Forward and Rewind are required.
Data rate in FF/FR mode less than normal mode rate.	yes; those automatically supported by the basic syntax	
9 	Scalability (Hierarchical)	Three resolution scales are required. See section 3.
It shall be possible to "not code" any scale, as required.
Scalable technique with better efficiency than simulcast is required.	no	
10	Compatibility	Backward / forward compatibility with H.261, MPEG1 and MPEG2 Main profile.
Downward / upward compatibility is inherent in scalable requirement.
Backward compatibility may not be an important consideration in some applications, particularly if it affects any other of the requirements.
Forward compatibility with MPEG2 MP@ML is required for conformance at corresponding level. Other levels may not require this functionality.
Forward compatibility with MPEG1 constrained parameter is required for conformance at this level. Other levels may not require this functionality.	yes, but only MPEG-1 forward compatibility 	
11	Quality	It should be possible to trade coding complexity with subjective picture quality on any scale.		
12	Flexibility in Implementation	Simple implementation is suggested.
Target of software decoding for lowest scale of a lower level is foreseen for IT applications.	yes	

NEXT will not support the following in the interest of "distribution" class quality;

	- 4:4:4,
	- 10 bits.

3. Performance

Example figures for three layer resolution;

1) At HDTV Level

Layer	Resolution	Aspect ratio	Bit rate	
Upper
(HDTV)	1920x1152x25, 1920x1035x30
1440x1152x25, 1440x1035x30; 1440x960x29.97	16:9	<~100? Mbit/s 	
Middle
(EDTV/SDTV)	960x576x25, 960x486x29.97
720x576x25, 720x486x29.97	16:9, 4:3	<~25? Mbit/s	
Low (LDTV)	480x288x25, 480x243x29.97
360x288x25, 360x243x29.97	16:9, 4:3	<~4? Mbit/s	
2) At Information Technology (IT) Level

Layer	Resolution	Aspect ratio	Bit rate	
Middle
(SDTV)	720x576x25, 720x496(480)x29.97	4:3	<~4? Mbit/s	
Low (SIF)	360x288x25, 360x248(240)x29.97	4:3	<~2? Mbit/s	
Very Low (QSIF)	180x144x25, 180x124(120)x29.97 	4:3	<~1? Mbit/s	

4. Some clarification
4.1 Compatibility
1) Definition of backward/forward compatibility

Figure 1  Definition of forward/backward compatibility
2) Interworking
There are several interworking combinations between scalable and non-scalable systems.  Figure 2 illustrates pictures which are reproduced by the MP@ML decoder.

Figure 2  Pictures decoded by the MP@ML decoder
3) Configuration
Figure 3 illustrates a configuration for the backward/forward compatible scheme.

Figure 3  Configuration of a forward/backward compatible scheme
5. Open issues (to be studied by the next meeting)
- further clarification of compatibility
- hierarchy with respect to interlace/progressive
- target value for "very low delay"
- target value for "very fast channel hopping"
- inherent difficulty in compatibility (relation between layers)

	* number of pels per line
	* number of lines
	* aspect ratio
	* chroma format (see a possible solution in Annex)
	* error resilience
	* bit rate ratio

- trade off between different functionalities (implication of constraints).
- interrelationship between multiple profile/levels.
-  additional levels in NEXT profile.
- further profiles other than Main, NEXT.

END

Attachment 2: Skeleton of SIMPLE Profile

1. Purpose

To define a profile that is able to operate with less memory and lower speed memory relative to the Main Profile, while at the same time maintaining a moderately high coding efficiency.

2. Definition

The feature set of the Simple Profile includes all those of the Main Profile, except B-frames and Dual Prime prediction.

Discussion of this Profile included application to two levels, namely the Main level and HDTV level.

END