Meeting of SC-02-02, 2003-10

[Last printing: 2003-11-19]

Report of the SC-02-02 Working Group on digital input/output interfacing of the SC-02 Subcommittee on Digital Audio, held in conjunction with the AES 115th Convention in New York, NY, US, 2003-10-08.

The meeting was convened by chair J. Grant.

The agenda was approved as written. Discussion of AES-X140 was taken as new business.

The report of the previous meeting, held in Amsterdam, Netherlands, 2003-03-20, was accepted with one amendment. Some proposed corrections had been posted to the reflector on 4th and 5th April without objection. The report was accepted as amended in that reflector dialog.

Open Projects

AES-R4-R: Review of AES-R4 2002: Guidelines for AES standard for digital audio - Digital input-output interfacing - Transmission of digital audio over asynchronous transfer mode (ATM) networks, AES47
Project scope: to review the informative report intended to to accompany AES47, transmission of digital audio over asynchronous transfer mode (ATM) networks.
Assigned to: SC-02-02 , Status: Review
Intent: Review, Initiated: 2002-06, Target: 2007
Current goal: Status report, Goal date: Continuing

No action was required or proposed

AES-2id-R: Review of AES-2id-1996: AES information document for digital audio engineering - Guidelines for the use of the AES3 interface
Assigned to: SC-02-02, Status: Draft revision to include AES-X50 elements
Intent: Revision, Initiated: 2001, Target: 2006
Current goal: PTD, Goal date: 2003-10

R. Caine reported that there has been no significant activity, and none planned until progress is made on the next revision of AES3, on the assumption that the clause numbers in the two documents need to be aligned; however, consensus at the meeting was that this was not necessary. New goal date 2004-5.

AES-3id-R: Review of AES-3id-2001: AES information document for digital audio engineering - Transmission of AES3 formatted data by unbalanced coaxial cable
Project scope: Review of AES-3id-2001
Assigned to: SC-02-02, Status: Review
Intent: Review, Initiated: 2001, Target: 2006
Current goal: Status report, Goal date: 2006

No action was required or proposed

AES-10id-R: Review of AES-10id-1995 (r2000): AES information document for digital audio engineering - Engineering guidelines for the multi-channel audio digital interface (MADI) AES10
Assigned to: SC-02-02, Status: Review pending revision of AES10
Intent: Review, Initiated: 2000, Target: 2005
Current goal: Status report, Goal date: 2005

Caine reported that a first draft for the revised document had recently been uploaded to the FTP site, but more work needs to be done on it and he would welcome input from others.

AES3-R: Revision of AES3-1992 (r1997): AES Recommended practice for digital audio engineering - Serial transmission format for two channel linearly represented digital audio data
Assigned to: SC-02-02, Status: CFC published 2003-06-02
Intent: Revision, Initiated: 1997, Target: 2003
Current goal: CFC, Goal date: 2003-09-03

This document has recently been revised and now the target for the next review is 2008. An important question is whether the document should be restructured along the lines of the ISO OSI 7-layer model, with separate sections for physical interface, electrical interface, signal coding, and higher-layer aspects such as channel status, which would make addition of, for instance, co-axial cable and fibre options easier - no conclusion at this point.

AES10-R: Review of AES10-1991 (r1997): AES Recommended Practice for Digital Audio Engineering - Serial Multi-channel Audio Digital Interface (MADI)
Assigned to: SC-02-02, Status: Revised 2003
Intent: Review, Initiated: 2003, Target: 2008
Current goal: Review, Goal date: continuing

This document has recently been revised; No new action was required or proposed

AES18-R: Review of AES18-1996 (r2002): AES recommended practice for digital audio engineering - Format for the user data channel of the AES digital audio interface
Project scope: Review of AES18-1996
Assigned to: SC-02-02, Status: Review
Intent: Review, Initiated: 2002-04, Target: 2007
Current goal: Status report, Goal date: Continuing

No action was required or proposed

AES41-R: Review of AES41-2000: AES standard for digital audio - Recoding data set for audio bit-rate reduction
Project scope: Review of AES41-2000
Assigned to: SC-02-02, Status: Review
Intent: Review, Initiated: 2000, Target: 2005
Current goal: Status report, Goal date: 2005

No action was required or proposed

AES47-R: Review of AES47-2002: Digital Audio in asynchronous transfer mode (ATM)
Project scope: to set a standard practice for mapping multiple channels of audio in linear PCM or AES3 format into an ATM transport system, for the purposes of interconnecting large numbers of sources and destinations, with best performance for latency, jitter and other relevant factors.
Assigned to: SC-02-02, Status: Review
Intent: Review, Initiated: 2002-04-19, Target: 2007
Current goal: Status report, Goal date: 2006

Grant mentioned a number of items that needed attention:

a) Organizationally Unique Identifier (OUI): Since the Amsterdam meeting of AES, the BBC has registered an OUI and it has been included in the draft for IEC 62365. AES47 should now be harmonized with IEC, so an amendment should follow. As an administrative matter and action item, a draft of such an amendment can and should be developed by the AESSC secretariat.

b) DSD audio: Some preliminary discussion on the reflector already took place, and was continued at this meeting. Consensus was that professional applications of DSD, just like those of other audio coding methods, should be supported in AES47. As action item, Grant will start this process.

c) ATM service over Ethernet physical layer: ATM has been standardized over telecom networks, but not over local area networks such as those using Ethernet processing chips - a potentially useful professional audio application. The specifics in AES47 are independent of physical layer, so such standardization or guideline for use, if any, should be properly a separate document. As action item, Grant will complete a project initiation request.

d) Table of required formats: Consensus of the meeting is that the format with 2-channels and overhead bits is the most important to be supported at the receiver. Need to add the necessary language in AES47 to encourage such support at the receiver.

e) Applications that might otherwise comply but which technically violate Section 4.3.2 for receivers: An ID document should be developed to handle such applications, and make recommendations if appropriate. C. Chambers will develop a draft.

f) "Absolute" time reference/stamp: Including a time reference is best if it is inserted as early as practical in the process, such as in the AES3 signal, and then it can be carried throughout the system, including via AES47. Including such a reference directly in AES47 might not be worthwhile. No further action anticipated.

Development projects

AES-X119: Standard, Connector for AES3 interfaces
Project scope: to consider the specification of an alternative connector for AES3 interfaces.
Assigned to: SC-02-02-F,
Status: Questionnaire to establish need/desire for digital connector rationale.
Intent: Amendment of AES3, Initiated: 2001-03, Target: 2004
Current goal: Status report, Goal date: 2003-10

J. Brown reported on progress. Regarding the proposed XLD connector situation a rather extensive draft questionnaire, with explanations, was developed but has not progressed as fast as was predicted in Amsterdam. He asked that the WG give comments on the questionnaire portion and also the Appendix-A. The AESSC secretariat suggested that the background portion of the document be separated into a report. Other comments on the questionnaire were also made. A revised draft needs to be developed and circulated to the WG; anyone who wants changes is requested to suggest alternative wording. Once approved by the WG, the questionnaire can be circulated as proposed at the Amsterdam meeting. New goal date 2004-05.

AES-X111: Transmission of the unique material identifier (UMID) on AES3
Project scope: to study and recommend a standard to implement an imbedded unique identifier into the AES3 data stream.
Assigned to: SC-02-02-G, Status: PTD has been revised
Intent: Standard, Initiated: 2000-09, Target: 2003
Current goal: PWD, Goal date: 2003-10

C. Chambers mentioned that a draft document dated 2003-03-21 was posted to the web site soon after the SC-02-02-G Task Group meeting in Amsterdam. He reviewed some of the basics of the document for the benefit of the WG. As an action item, editorial drafting needs to be finished jointly by C. Chambers and the secretariat after which the document will be posted to the WG for review. New goal date 2003-12.


AES-X139: Liaison with EBU P/AGA
Project scope: Liaison with EBU P/AGA
Assigned to: SC-02-02, Status: Continuing
Intent: Liaison, Initiated: 2002-03, Target: Continuing
Current goal: Liaison, Goal date: Continuing

The EBU P/AGA group is considering to reference AES3, AES5, and AES11 instead of maintaining their own parallel texts. The meeting agreed that having a single text is very desirable, and that EBU should be kept informed of any proposed amendments to these three standards.

IEC MT60958-1
J. Yoshio reported that MT60958-1 would meet on the Friday during the Convention, and optical connectors for consumer use and professional use would be on the agenda. The AESSC secretariat reported that SC-05-02-F would discuss professional use on the Thursday, so would be able to provide input.

DVD Forum WG-10
Yoshio also reported on DVD Forum WG-10, which would also hold a meeting (which would be an open meeting) on the Friday. A new category code will be defined for a DVD recorder with hard disc. Ad-hoc group 10-1 has started work on use of DVD for professional audio (probably to be called DVD-AR).

New Projects

AES-X140: High Resolution Multichannel Audio Interconnection (HRMAI)
Project scope: To specify a bi-directional, point-to-point connection for up to 48 channels of digital audio in a variety of formats. The link uses a single Category 5 (or better) structured-wiring data cable, and is designed for use in a studio environment. The system uses the 100Base-TX physical layer of Fast Ethernet (IEEE 802.3) to transfer framed audio data. Audio synchronisation is maintained by transmitting an audio clock signal in parallel with the audio data using available signal pairs on the cable.

Assigned to: SC-02-02, Status: Initiated
Intent: Standard, Initiated: 2003-09, Target: 2004-10
Current goal: Draft, Goal date: 2003-10

M. Page reported that the current draft needs some editing to produce a standard and possibly also a companion Report. The system should be seen as a next-generation equivalent to MADI, i.e. a point-to-point link and not a network. The emphasis is on high reliability and low latency. There are plans for a later version that would be based on Gigabit Ethernet hardware, but this should be considered as a later amendment so as not to delay publication of the standard as currently intended. A Task Group to develop the draft was requested; Page, P. Eastty, J. Grant, S. Harris, and T. Thompson volunteered to join the TG. [NOTE: Task group SC-02-02-H has since been formed for this purpose]

New Business

There was no new business.

The next meeting is scheduled to be held in conjunction with the AES 116th Convention, Berlin, Germany, in 2004-05.

AES - Audio Engineering Society