SC-02-02 meeting 2004-05

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 116th Convention in Berlin, Germany, 2004-05-06.

J. Grant, chairman of SC-02-02 convened the meeting.

The Agenda was approved with the addition of Project AES-X143. The report of the previous meeting, held in New York, NY, USA, 2003-10-08 was approved.

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 accompany AES47, transmission of digital audio over asynchronous transfer mode (ATM) networks.
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
Draft revision to include elements from retired project AES-X50
R. Caine reported that he has recovered the AES-X50 text. This and other text has been incorporated in the PTD, but it is not yet ready to submit to the working group. New goal date 2004-10.

AES-3id-R: Review of AES-3id-2001: AES information document for digital audio engineering -- Transmission of AES3 formatted data by unbalanced coaxial cable
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
Caine will incorporate the revisions in the e-mail from C Travis of 2004-04-29, and issue the revised draft as a PWD. A PCFC is anticipated by 2004-10.

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
The meeting felt that the current document should be restructured to separate the specifications of the different different layers (e.g. electrical, subframe format, channel status). A new task group is required; initial members R Caine (leader), M. Yonge, C. Chambers, S. Harris, J.Yoshio, and J. Brown. PTD to propose a new structure to be discussed at the San Francisco meeting, 2004-10.

AES10-R: Review of AES10-1991 (r1997): AES Recommended Practice for Digital Audio Engineering -- Serial Multi-Channel Audio Digital Interface (MADI)
The errors listed in the e-mail from Travis of 2004-04-29 were discussed. None of them was considered to be urgent enough to warrant a revision at this time. but all should be included in any future revision.

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
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
Mandatory review is due in 2005. There was some discussion as to whether this standard requires active maintenance. Chambers to investigate within the BBC. Caine to enquire of International Association of Broadcast Manufacturers (IABM).

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.

An amendment to incorporate the OUI from IEC 62365 remains to be done. A Task Group meeting is required to develop a draft revision to clause 4.3.2 and Table 2.

Noted that related projects AES-X143 and AES-X144 (see below) have been initiated.

Development Projects

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.
Secretariat-formatted PTD to include editorial changes. New goal date 2004-07.

AES-X119: Standard, Connector for AES3 interfaces
Project scope: to consider the specification of an alternative connector for AES3 interfaces.
The Task Group has provided two drafts of the questionnaire. Brown recommended that the document should appear in the AES Journal, on the website (with responses able to be submitted on-line), and in non-AES press which would be read by studio people, which was supported by the meeting. Yonge offered to produce a secretariat draft as a matter of urgency, so that it could be approved by the Task Group and then the Working Group in time to be published in the July/August Journal. Responses will be requested by 15th October, so that they can be collated in time for the San Francisco meeting.

AES-X139: Liaison with EBU P/AGA
Project scope: Liaison with EBU P/AGA
Secretary reported that in December 2003 the EBU P/AGA felt that it no longer needed its own text parallel to AES3-2003; a draft which simply makes reference to AES3 is believed to be in progress but has not yet been received. R Chalmers will be the new liaison.

AES-X140: High Resolution Multichannel Audio Interconnection Project
Scope: To specify a bi-directional point-to-point connection for up to 24 channels of digital audio in a variety of formats.

There is one outstanding item in the draft, which is to insert the same OUI that is used in IEC 62365. Also, Annex A should be deleted to eliminate dependence on AES-X130. M. Page will make those changes and then pass the draft to the Working Group by 1st August. New goal: CFC, date 2004-09.

AES-X143: Transmission of asynchronous transfer mode (ATM) over an Ethernet physical layer
Project scope: to specify an encapsulation of ATM cells in Ethernet packets, so that ATM equipment may be connected using hardware specified for Ethernet networks.

Grant presented the current Task Group draft. The specification of how the ATM cells are carried in Ethernet packets is substantially complete, but more work needs to be done on negotiation of various aspects of the service between endpoints. The packet format includes the Ethernet MAC layer so that it can be carried by standard network interfaces in personal compauters, for example. If current proposals to form an IEEE 802.3 study group on Synchronous Ethernet are realised, a liaison will be sought with that group; this may result in a Quality of Service adequate to allow AES-X143 packets to share links with conventional Ethernet traffic.

R Caine reported that a BBC patent concerning looped-back timing, which has now been released, may be relevant to A.3.4. New goal: PTD, date 2004-09.

AES-X144: Carriage of DS audio data in AES47
Project scope: to amend AES47-2002 clauses, and 6 to provide the option of transmitting DSD audio instead of linear PCM

A Task Group draft is anticipated. New goal date 2004-10.


SC-05-02 is formally requested to specify a fibre connector for AES3 and AES10, with a recommendation in favour of the LC type.

Yoshio reported that IEC MT60958-1 and -3 would meet on the Saturday; their concern is what would be the professional optical connectors: Part 1 includes all connections and connectors of IEC60958 families.

Yoshio invited members to attend the DVD Forum WG-10 meeting (which would be an open meeting) on the Sunday. Grant reported that IEC PT62379 would meet on the Saturday to further progress the Common Control Interface draft.

New Projects

Grant will submit a Project Initiation Form based on his e-mail to the Working Group of 1st May.

New Business

The meeting requested SC-02 to retire Task Group SC-02-02-A.

Next meeting in conjunction with the 117th AES Convention, San Francisco, October 2004.

AES - Audio Engineering Society