SC-02-02 meeting, London, 2011-05

Report of the meeting of SC-02-02 Working Group on digital input/output interfacing of the SC-02 Subcommittee on Digital Audio held in London, UK., 2011-05-13.

The meeting was convened by chair J. Grant.

The agenda, and the report of previous meeting held in San Francisco 2010-11-04, were approved.

Open Projects

NOTE 1 Unless stated otherwise, the status of open review projects is, "No action requested or required".
NOTE 2 This report will be deemed to be approved if there are no unresolved issues by 10th June 2011.

AES41-R: Review of AES41-2009: AES standard for digital audio - Recoding data set for audio bit-rate reduction
The draft of the revised text (dividing the standard into five parts, one specifying the transport and four specifying different data sets) from 2011-03-25 is still awaiting secretariat formatting. The title should be changed because the data sets are no longer restricted to audio bit-rate reduction.

AES47-R: Review of AES47-2006: AES standard for digital audio - Digital input-output interfacing - Transmission of digital audio over asynchronous transfer mode (ATM) networks
The meeting proposed this standard should be reaffirmed. C. Chambers reported that the technique is still in use at the BBC; no amendments are required.

AES50-R: Review of AES50-2005, AES standard for digital audio engineering - High-resolution multi-channel audio interconnection (HRMAI), also AES-R6: Guidelines for AES50 (HRMAI)
The PCFC for the revised version of the standard was posted on 2011-05-05. A marked-up version showing changes is also on the SC-02-02 document site. The changes include clarification of the functionality of the green light on the interface, and of the interpretation of the M bit.

AES51-R: Review of AES51-2006: AES standard for digital audio - Digital input-output interfacing - Transmission of ATM cells over Ethernet physical layer
The meeting proposed this standard should be reaffirmed, with references updated (as an editorial change) for the latest version of IEEE802.3

AES52-R: Review of AES52-2006, AES standard for digital audio engineering - Insertion of unique identifiers into the AES3 transport stream
The meeting proposed this standard should be reaffirmed.

AES53-R: Review of AES53-2006, AES Standard for digital audio - Digital input-output interfacing - Sample-accurate timing in AES47
The meeting proposed this standard should be reaffirmed.

AES-2id-R: Review of AES-2id-2006: AES information document for digital audio engineering - Guidelines for the use of the AES3 interface
C. Chambers and R. Caine to review 7.4.9 (Jitter accumulation) and decide whether a revision is required. The current text makes reference to AES3-2003, with references to the four parts of AES3-2009 having been added in brackets; this should be reversed, so that the references in the main text are to AES3-2009 with references to AES3-2003 in brackets. (Note: this will also require revision of 5.2.1, because "minimum" implementation level is not supported in AES3-2009, and maybe other parts of the text.)

AES-10id-R: Review of AES-10id-2005: AES information document for digital audio engineering - Engineering guidelines for the multichannel audio digital interface (MADI) AES10
This information document was reaffirmed on 26th April.

Development Projects

AES-X139: Liaison with EBU ECA (Expert Committee on Audio)
A. Mason reported that ECA had met the previous afternoon, hosted by the BBC in London W12, and discussed the following three existing projects. PLOUD has published R128 and Tech Docs 3341-3344, and will review them in September. BWF is being revised, the revisions including: loudness metadata in Tech 3285; multi-channel without specific loudspeaker assignments (e.g. for ambisonics); some other clarifications; and incorporation of XML. There is also a review of all the EBU audio-related recommendations, technical documents, position statements, etc.; EBU has not enforced a formal review period for all its publications. Other items discussed included: upmixing, e.g. from stereo to surround; 3D sound and wave field synthesis; time-aligning signals from different microphones; revision of the lip-sync cookbook (though there had been little enthusiasm for lip-sync work); and the use of telecom networks for delivery to the listener. Mason also pointed out that non-members of the EBU, as well as members, may join the EC-A by going to the EBU Technical web site,

AES-X182: AES/Ethernet Simple Open Protocol
U. Zanghieri reported that a 500-node system is now in operation, and some minor changes to the specification are expected as a result of experience with that system. New drafts are expected by the end of July.

AES-X186A: Liaison with ITU-R re BS.1873, derived from AES10-2008 (MADI)
AES-X186B: Liaison with ITU-R re draft BS.647, derived from AES3-2009
AES-X186C: Liaison with ITU-R re draft BS.[sync], derived from AES11

The version of ITU-R BS.647-2 which was received for review in November was discussed. The text has been substantially rearranged to fit the ITU-R house style; for instance, the definitions which in the AES text are in clause 3 of each Part have been collected together into Part 1 of BS.647, while the remaining text of Parts 1-4 of AES3 corresponds to Parts 2-5 respectively of BS.647.

Grant pointed out that when the wording of clause 4 of Part 2 of AES3 was rephrased to form clause 2 of Part 3 of BS.647, the word "audio" was lost from the second sentence. The secretariat will check through the text and notify ITU-R of this and any other discrepancies.


J. Yoshio reported that the following IEC TC100 groups would meet on the following day: TA4: MT60958-1 and -3 and MT61937-6; TA11: new projects on measurement of delays in display equipment for the purpose of synchronising audio and video, and on loudness normalisation. The new edition of IEC60958-3 will include multi-channel and loudness metadata.

New Projects

8-channel digital audio interface
No new projects were introduced.

New Business

It was noted that the Project Initiation Form for the carriage of 8 (instead of 2) audio channels in AES3 has not yet been submitted.

There was some discussion what sequence of preambles should be used: whether to use the current sequence with the Z preamble marking the first channel, or to use the X or Z preamble for the first channel and Y for all the other seven. Stefan Heinzmann and Chris Dunn to be included in the Task Group.

This project could be relevant to digital microphones, so SC-04-04 will need to be kept informed.

The next meeting will be held in conjunction with the AES 131st Convention in New York, NY., US., 20 to 23 October 2011.

AES - Audio Engineering Society