Report of the meeting of the SC-02-02 working group on Digital audio interfaces, of the subcommittee on Digital audio, held in New York on 2011-10-20
The meeting was convened by chair J. Grant.
The agenda was approved as written, and the report of the previous meeting, which had previously been approved via the e-mail reflector, was reviewed.
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.
Open Projects
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 is still awaiting secretariat formatting with a new title.
AES55-R: Review of AES55-2007; AES standard for digital audio engineering - Carriage of MPEG Surround in an AES3 bitstream
This standard is due for review. Any proposals for to amend it should be sent to this reflector before 2012-03-01.
AES-2id-R: Review of AES-2id-2006: AES information document for digital audio engineering - Guidelines for the use of the AES3 interface
There had been no progress on reviewing 7.4.9 (Jitter accumulation). Subclause 5.2.2.13 was discussed (see Standards Manager's e-mail to the group reflector on 28 September), and it was felt that the best solution would be to remove the first paragraph entirely, just retaining the paragraph relating to bit 7, and amend the title accordingly.
Secretariat to prepare a new draft, changing 5.2.2.13 and switching references to AES3 so that the main reference is to the current (2009) version and references to the previous version are 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-R8: AES standards project report - Synchronisation of digital audio over wide areas
This report is due for review. Any proposals for to amend it should be sent to this reflector before 2012-03-01.
Development projects
AES-X139: Liaison with EBU ECA (Expert Committee on Audio)
A. Mason reported that there had been further changes to the EBU structure. Most of the 300 members of ECA are from industry, so there is a risk of diluting the influence of EBU members. Strategic Programme Groups (SPGs) have been created, consisting only of EBU members and a few co-opted experts, and the SPG on Audio & Radio Systems has taken over all ECA's projects. However, ECA still exists as a forum in which audio issues can be raised. PLOUD has completed its standardisation work, which is the subject of two sessions in the AES 131st Convention.
AES-X182: AES/Ethernet Simple Open Protocol
U. Zanghieri reported that the new drafts referred to in the previous SC-02-02 meeting had been produced, though somewhat later than originally planned. There have been some comments on the reflector, and further drafts are expected in November. The LED indications which are currently in the companion Report are to be moved to the Standard, as the meeting felt that it was useful to standardise these indications because it would be confusing for users if different products used the LEDs in different ways.
AES-X186B: Liaison with ITU-R re draft BS.647, derived from AES3-2009
There had been no response from ITU-R to the secretariat's report to them of minor errors in their draft.
AES-X186C: Liaison with ITU-R re draft BS.[sync], derived from AES11
The ITU-R text had still not been received. A new group in ITU-R is writing a standard for synchronisation of video frame rate and audio sample rate.
AES-X196: Revision of AES3 to use high sampling rates to carry multi-channel audio
The initial draft is still awaited. C. Gaunt proposed that the 8-channel version should not be called AES3 because it would not be compatible with the current AES3, and should be regarded as a new standard carrying AES3 subframes, in a similar way to AES10. The project's intent has been changed to "standard".
Liaisons
J. Yoshio reported that there had been no activity related to IEC 60958 etc since the previous SC-02-02 meeting. IEC TC100, including TA4, would be meeting in Melbourne, Australia, the following week. An extension mechanism is needed for the coding of the data type of compressed audio carried over 60958, because most of the code points currently available have been used by either SMPTE 338 or IEC 61937. USB is expected to become an IEC standard; this will allow the precise synchronisation needed for high-quality audio in consumer equipment to be standardised. S. Harris observed that lower-cost USB chips add or drop samples to achieve synchronization, whereas for professional use there are de facto standards for Windows and MAC OS.)
New Project
S. Lyman has submitted a Project Initiation Form on replay gain, to normalise playback levels; if this results in a project it will be AES-X202. It would use ITU-R BS.1770-2 (the same scheme as in EBU R128) instead of the current ad hoc loudness measure, and transport the information using ID3v2 tags.
The next meeting will be held in conjunction with the 132nd Convention in Budapest.
