Report of the meeting of the SC-02-02 working group on digital audio interfaces, of the subcommittee on digital audio, held in Berlin, Germany, 2017-05-20.
The meeting was convened at 14:10 by chair J. Grant, participating remotely from the UK.
The agenda, and the report of the previous meeting, held in New York, NY USA, 2015-10-29, were approved as written.
Projects assigned to this group but not mentioned here had no action requested or required - see www.aes.org/standards/meetings/project-status.cfm for details.
Open projects:
AES3-4-R: Review of AES3-4-2009 (r2014), AES standard for digital audio - Digital input-output interfacing - Serial transmission format for two-channel linearly represented digital audio data - Part 4: Physical and electrical
and AES-2id-R: Review of AES-2id-2006 (r2012): AES information document for digital audio engineering - Guidelines for the use of the AES3 interface
J Paul presented some of the proposals for revision, from his SMPTE paper and Convention tutorial. Cables need to support frequencies up to the 5th harmonic of the Manchester-coded signal, e.g. for 192 kHz sample rate the square wave is at 24.576 MHz so a bandwidth of 125 MHz is needed. The drawing of an eye diagram is confusing as it shows a lens-shape whereas the specification is for a rectangular opening.
There was a lengthy discussion regarding the best way to develop the material into a revision of the documents. A bibliography could be added to AES-2id, or the material from the paper developed into an informative annex; in either case consensus would only be required on the additional material, not on the whole document. However, the new material is likely to contradict some of the current text, so a full revision may be needed.
Secretariat to liaise with J Paul to decide the best way forward. Members were reminded that consideration of the new version does not need to wait for a physical meeting.
AES10-R: Review of AES10-2008: AES Recommended Practice for Digital Audio Engineering - Serial Multichannel Audio Digital Interface (MADI)
and AES-10id-R Review of AES-10id-2005 (r2011): AES information document for digital audio engineering - Engineering guidelines for the multichannel audio digital interface (MADI) AES10
There has been no activity recently in Task Group SC-02-02-M. Use of MADI is increasing, but mostly in situations where it does not interface between equipment from different manufacturers. Those who have experience of current practice are encouraged to join the Task Group and contribute.
AES53-R, Review of AES53-2006 (r2011), AES Standard for digital audio - Digital input-output interfacing - Sample-accurate timing in AES47
This standard is being revised to bring it into line with current SMPTE standards. There were no adverse comments to the recent draft.
AES55-R, Review of AES55-2012: AES standard for digital audio engineering - Carriage of MPEG Surround in an AES3 bitstream
This standard should be reaffirmed.
Development projects:
AES-X182: AES/Ethernet Simple Open Protocol
Secretariat reported that U Zanghieri no longer works for the company that proposed this project, and no further progress is expected. The project is to be retired.
AES-X196: Use of AES3 with high sampling rates to carry multi-channel audio
There has been no input from the organisation that originally requested this project, so it is to be retired. P Treleaven noted that some of the IEC proposals for surround sound in IEC 60958 may be similar.
AES-X213: MADI over twisted-pair cabling
The draft which is in the WG document area as x213-150506-ptd-mb.pdf has now achieved consensus in the TG, so is ready to proceed to Proposed Working-group Draft (PWD).
AES-X221: IEC 60958-4 Ed.3 revision
The drafts have been approved for publication by IEC, so the project has been completed and will be retired.
Liaisons:
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.2032, derived from AES11
All three projects have completed their work and should be retired.
New projects
No new projects were proposed.
New business
No new business was proposed.
The meeting closed at 16:10. The next meeting will be scheduled in conjunction with the AES 143rd Convention in New York, 2017.
