Annex 2 to AVC-674R

Source: 	Chia-Chang Li, AT&T Bell Laboratories
Title: 	Norway Meeting of MPEG-2 DSM-CC Extension
Purpose: 	Report

1.	Introduction
The 28th meeting of MPEG-2 was held in Grimstad, Norway on July 18-22, 1994.  One of the most important activities is the Digital Storage Medium Control Command Extension (DSM-CC Extension), which will become Part 6 of MPEG-2, i.e., ISO/IEC 13818-6, in the form of Working Draft (WD) by 11/94, Committee Draft (CD) by 7/95, Draft International Standard (DIS) by 11/95, and finally International Standard (IS) by 7/96.  The scope of the this new MPEG-2 work item is to extend beyond the existing DSM-CC specification, which is now a normative annex of MPEG-2 Systems (ISO/IEC 13818-1) and provides only “VCR-like” controls in a single-user-single-server environment, to cover more diverse and heterogeneous network environments for many more applications.
2.	General Information of the Meeting
2.1	Participants
The following is an incomplete list of the attendees of the meeting.  Some people did not sign in on the attendance sheet.

	Tom Lookabaugh(Chairman)		DiviCom
	Matthew Goldman			DEC
	Thomas Werner				R.I.C
	Dieter Scherer				Hewlett-Packard
	Kwangkee Lee				Samsung
	Mark Porter				Oracle
	Phil Roberts				AT&T
	Vince Guaglianone			Mitsubishi
	S. J. Huang				Matsushita
	Chia-Chang Li (Editor)			AT&T
	Guy Cherry				Tektronix
	Michel Fortier				BNR
	Frederic Bompard			MATRA
	Leonardo Chiariglione(Convenor)	CSELT
	Franco Prampolini			IBM (Italy)
	Jeff Hamilton				General Instrument
	Bill Helms				Scientific Atlanta
	Chris Adams				Hewlett-Packard
	Tony Wasilewski				Scientific Atlanta
	Andria Wang				Bellcore
	Bahman Amin-Saleh			Bell Atlantic
2.2	Submissions
The following list contains all the contributions discussed in the meeting.  The first two contributions were submitted in the Paris meeting in March/94 and re-introduced in this meeting.

MPEG 94/083 (Paris)	Protocols for DSM-CC Connection-Oriented Service (Wasilewski, SA)	
MPEG 94/087 (Paris)	Philosophy for Command and Control Protocols (Leach, Microsoft)	
MPEG 94/213 (Norway)	Proposal for Multi-media Scripting Language (Minakata, Matsushita)	
MPEG 94/214 (Norway)	Necessary Provision for Applying H.222.0 to the H.32X Terminals (Japan)	
MPEG 94/216 (Norway)	Use of X.500 in RPC Standards for DSM-CC (Rodi, IBM)	
MPEG 94/217 (Norway)	Overview of X.500 (Rodi, IBM)	
MPEG 94/225 (Norway)	Communication Procedure for H.222.1 (Japan)	
MPEG 94/234 (Norway)	DSM-CC Extension Using Remote Procedure Calls (Goldman, DEC)	
MPEG 94/262 (Norway)	Support for ITU-T Control and Indication Signals (ITU-T EG ATM/Video)	
MPEG 94/273 (Norway)	Stream Service I/F (Porter, Oracle)	
MPEG 94/274 (Norway)	MediaNet RPC Proposal (Porter, Oracle)	
MPEG 94/276 (Norway)	DSM-CC Extension Protocol and Multimedia (Chakrabarti, AT&T)	
SC29/N825	Liaison Statement from ITU-T SG15 to JTC 1/SC 29 on Comments on the DSM-CC Work in MPEG (ITU-T SG15)	
MPEG 94/288 (Norway)	Set-top Boot Protocol (Porter, Oracle)	
3.	Summary of Major Outcomes
3.1	Revision of Requirements
The requirements document was revised slightly.  The major change is to include synchronization as one of the functionalities supported by DSM-CC Extension.
3.2	Preliminary Working Draft (PWD)
A baseline document was produced at the end of the meeting and was called the Preliminary Working Draft.  A caveat was included at the beginning to indicate the preliminary nature of the document.  The following sections summarize the major elements of the document.
3.2.1	Protocol Model
Figure 1 shows the relationship between DSM-CC and other protocols.

DSM-CC provides access for general applications, MHEG applications, and scripting languages to primitives for establishing or deleting a network connection (User-Network Primitive) and communication between a client and a server across a network (User-User Primitive).  U-U and U-N primitives may use a Remote Procedure Call (RPC) protocol.  Naming, addressing, authorization, and authentication are provided by an X.500 distributed directory service to both RPC and User-Network primitives.

Figure 1: DSM-CC Protocol Model

DSM-CC may be carried as a stream within an MPEG 1 System Stream, an MPEG 2 Transport Stream, or an MPEG 2 Program Stream.  Alternatively, DSM-CC may be carried over other transports, such as TCP or UDP.

The dotted line between DSM-CC and ITU-T Control and Indication Signaling indicates their relationship is for  further study. The ITU-T Control and Indication Signals may be carried in a completely different mechanism, and hence outside the scope of DSM-CC, or, alternatively an integrated mechanism may be defined for the controls for all the audiovisual communication connections.
3.2.2	DSM-CC Primitives
As shown in Figure 1, there are two categories of primitives: User-to-Network, and User-to-User.
3.2.2.1	DSM-CC User-to-Network Primitives
DSM-CC User-to-Network Primitives describes network control operations.  The syntax for the primitives is written in the style of function calls for an application programmer interface.  These control operations assume a very high level end-to-end architecture in order to provide a very generic interface.

There were significant differences of opinion about the implementation of the function calls.  Three possibilities have been mentioned: (1) translated into an existing message-based network control protocol (e.g., Q.2931 for ATM), (2) translated into other message-based protocol and (3) implemented as RPCs.  A combination of them is also possible.  The subgroup agreed on the disagreement and decided to present both the message-based and RPC-based approaches in the PWD.
3.2.2.2	DSM-CC User-to-User Primitives
Four groups of functions were proposed for this category of primitives.  They are Playback, Record and Edit Assembly, File System Access, and Database Access.  All the groups contain a set of functions with their syntax and semantics described except the group of Record and Edit Assembly, which serves currently as a place holder to invite contributions.  The purpose of Playback group is self-evidenced in its name.  The initial application of the File System Access and Database Access groups is for service logic download and navigation.  However, their definitions are generic enough to support other applications.
3.2.3	Service/Network Boot Procedures
The subgroup, after significant amount of discussion, recognized the benefits to standardize such procedures but also understood the difficulties, especially for the network boot procedure.  It was decided that the service boot procedure should be covered in the File System Access part of the User-to-User Primitives and a section was created as a place holder to invite contributions for the network boot procedure.
3.2.4	Directory Service
X.500 was proposed and accepted without much debate as the basis for naming, addressing, authentication and authorization.
3.2.5	Mapping to Transport
DSM-CC is intended for use over multiple transport protocols.  On links which are carrying MPEG streams, DSM-CC may be embedded in the system streams or may be carried on a separate transport mechanism.  When mapping DSM-CC protocol into MPEG System streams, the PES packet structure shall be used with certain packet header fields restricted to certain values.  The associated PES packets shall have a stream_id value of 5 as specified in Table 2-18 of ITU-T Rec. H.222.0 | ISO/IEC 13818-1 and the elementary stream formed by these packets must have a stream type value of 0x08 as defined in Table 2-35 of ITU-T Rec. H.222.0 | ISO/IEC 13818-1.  The mapping to other types of transport is for further study.
3.3	Liaison Statement
A liaison statement to ITU-T SG15 was drafted by the subgroup and approved by MPEG to recognize the existing work in ITU-T for end-to-end control and indication signaling, indicate MPEG’s view of  its relationship with DSM-CC, and express the desire to collaborate.

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