Report of the SC-02-02 Working Group on Digital Input/Output Interfacing of the SC-02 Subcommittee on Digital Audio meeting, held in conjunction with the AES 113th Convention in Los Angeles, CA, US, 2002-10-03

Vice Chair R. Finger convened the meeting in the absence of Chair J. Dunn.

The agenda as posted on the Web site was approved with the addition of Liaisons as item 7. The report of the previous meeting posted to the web site was accepted as written.

Open projects.

AES-2id-R Review of AES-2id Guidelines for the use of AES3 interface
A draft needs to be written. R. Caine volunteered, for the time being, to coordinate various inputs and to also write new sections covering the various amendments to AES3. J. Brown indicated that he has some input already prepared and simply needs to send them to Caine for coordination. In order to start a broader WG discussion, Caine will post these inputs to the reflector as soon as practical.

AES-3id-R Review of AES-3id Transmission of AES3 formatted data by unbalanced coaxial cable
Caine asked whether at some point it would be logical and useful to include the coaxial version directly into AES3, but added that he felt it was not appropriate to do this at the present (since AES3 was recently revised). Others also supported this view.

No action was taken.

AES-10id-R Review of AES-10id Engineering guidelines for the multichannel audio digital interface (MADI) AES10
This document will be reviewed following completion of AES10-R.

AES3-R Revision of AES3 Serial transmission format for two-channel linearly represented digital audio data
The secretariat needs to complete the check that the present PWG includes all necessary style changes. Because it is getting near the end of the year this needs to be done as soon as practical.

A target date of 2002-11 was agreed for the PWD.

AES10-R Review of AES10 Serial multichannel audio digital interface (MADI)
Caine reported that a new PCFC was completed and available. He also reported that there was e-mail correspondence regarding an issue related to a portion of the document referencing NRZI. To remove the concerns so mentioned, Caine proposed that Section 4.3, �Transmission format,� be re-worded to reference the ISO/IEC FDDI specification mentioned in the Normative References, and delete Section 4.3.4, �NRZI Encoding.� It was agreed that Caine will post this proposal to the reflector as soon as practical, and the secretariat will cross-check the mentioned normative reference to be sure there are no hidden conflicts and that the concern discussed has been remedied.

The PCFC needs to be revised per above, and a CFC is now anticipated end of 2002-11.

AES18-R Review of AES18 Recommended Practice for Digital Audio Engineering�Format for the User Data Channel of the AES Digital Audio Interface
No action was taken.

AES41-R Review of AES41 Recoding data set for audio bit-rate reduction
No action was taken.

AES47-R Review of AES47 Digital input-output interfacing�Transmission of asynchronous transfer mode (ATM) networks
No action was taken.

AES-X50 Guidelines for Development of Specifications Which Reference or Use AES3 Formatted Data
This project is suspended pending availability of resources. Caine suggested that the WG consider the possibility of including the content of the draft into a revised AES-2id. The meeting discussed the proposal with no disagreement. No action was taken.

AES-X92 Digital Audio in Asynchronous Transfer Mode (ATM)
This project is actually in regard to AES47 and is a companion report that was published as AES-R4. The meeting recommends to SC-02 that this project be deleted and another be created as AES-R4-R.

AES-X94 Presto: Audio via Synchronous Digital Hierarchy (SDH)
Because the project has been suspended for a long time and no prospects for forwarding it further are apparent, the meeting recommends to SC-02 that it should be terminated.

AES-X111 Transmission of the Unique Material Identifier (UMID) on AES3
This project is the subject of a Task Group G meeting, chaired by C. Chambers and scheduled for the following day.

AES-X119 Connector for AES3 Interfaces
Brown reported that, as requested at the meeting in Munich, he posted a report of the Task Group to that reflector and gave discussion during the WG meeting. The basic conclusion of the report is that completely separate lines are needed for the different signal types under discussion, therefore there should be 6 connector types (half are male and half female) used to maintain this separation, and selection is dependent on the degree of compatibility of the equipment or installation so involved. Further, the Task Group�s view, expressed by Brown during the meeting, is that there are issues in regard to how readily these connectors should be modifiable from one type to another by a regular user in the field, as compared with changes made by a manufacturer or a skilled technician.

J. Nunn and Caine pointed out that completely different and unchangeable connectors, while more readily understandable in the field, would also be a burden on manufacturers or could present complications to purchasers when dealing with multiple equipment options and wishing to insure compatibility. This situation might be found unacceptable as a matter of standardization in a document that has been in existence for a long time and one that covers a very large installed base. So the issue is still whether the XLD connector (or variant) should be included in the AES3 standard, and if so then how to word any such amendment or change. This was not addressed in the Task Group report. The chair observed that since the present Task Group report seemed to be making a negative recommendation as to adoption of the XLD in AES3, the WG needed to give further guidance to the Task Group or seek assistance from SC-05. The WG members present at the meeting felt that there is benefit to having a compatible connector for digital use and interoperable with that already adopted in AES3 (i.e., XLR). But there are still important issues that need to be resolved that have been identified in the Task Group report. The WG recommends to SC-02 that this conclusion be conveyed to SC-05.

New projects

A project regarding standardizing a method of Playback Volume Adjustment Calculation for CDs was requested from D. Prince via the secretariat. The WG held a good discussion with many follow-up questions and felt there was need to better define the request. Also, the secretariat will forward it to other AESSC groups for consideration. At present this does not seem to be a matter for SC- 02-02 action.

New business

There was no new business.

Liaison

Mr. Yoshio reported activity of the IEC groups and status of the various IEC60958 documents. He reported that the Japanese Committee has submitted a proposal for the inclusion of an optical connector for consumer use. The next meeting of IEC is scheduled for San Francisco during the week of October 14. Nunn reported that EBU have recently expressed interest in becoming more active in matters associated with AES3. Nunn needs to discuss this subject further with J. Emmett of EBU.

The next meeting is scheduled to be held in conjunction with the AES 114th Convention in Amsterdam, The Netherlands.