SC-02-02 meeting, New York, 2005-10

Report of the SC-02-02 Working Group on digital input/output interfacing of the SC-02 Subcommittee on Digital Audio meeting, held in New York, US., 2005-10-06.

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

The agenda and the report of the previous meeting, held in Barcelona, Spain, 2005-05-26, were approved.

Open Projects

AES-2id-R: Review of AES-2id-1996: AES information document for digital audio engineering -- Guidelines for the use of the AES3 interface
Assigned to: SC-02-02, Status: Draft revision
Intent: Revision, Initiated: 2001, Target: 2006
Current goal: PTD, Goal date: 2005-10

R. Caine presented the draft that was posted on 12th September.

J. Siau reported that some equipment will mute if the "unlocked" bit (bit 5 of byte 0 of channel status) is set. Caine to add guidance on the interpretation of the 1 state to the description of this bit in 5.2.2.

New goal: PWD, date: 2006-04.

AES3-R: Review of AES3-2003: AES Recommended practice for digital audio engineering -- Serial transmission format for two channel linearly represented digital audio data
Assigned to: SC-02-02, Status: Revision to restructure this complex document anticipated
Intent: Revision, Initiated: 2003, Target: 2005
Current goal: PTD, Goal date: 2005-10

Caine presented the draft that was posted on 24th September, and reviewed the questions in his E-mail of that date. The meeting preferred "content" to "essence", and "physical" to "electrical". Each part will be a separate standard, so will need its own foreword, references, etc.

Caine also proposed withdrawing the "minimal" channel status (1 in the first bit, zero everywhere else) and the use of bits 4-7 of the subframe for the AUX channel. The "minimal" channel status was intended to simplify interface design by removing the need to calculate a CRC, but this is not a problem with present-day designs. It was thought that the use of the AUX channel described in annex A of AES3-2003 had never been implemented, but if it is to be withdrawn a form of words would have to be found that left code point 010 for bits 0-2 of byte 2 of channel status safe. S Harris reported that the CS8420 sample rate converter IC recognises this code point but does not preserve the AUX bits. The conclusion was that as annex A (in AES3-2003, B in the new draft) is only 1 page there is little benefit in removing it, and leaving it in would be the safest option.

New goal: final draft of PTD, date 2006-05; also target should be 2007.

AES-3id-R: Review of AES-3id-2001: AES information document for digital audio engineering -- Transmission of AES3 formatted data by unbalanced coaxial cable
Assigned to: SC-02-02, Status: Review
Intent: Review, Initiated: 2001, Target: 2006
Current goal: Status report, Goal date: Continuing

No action required or proposed. This document will become redundant once the new versions of AES-2id and AES3 are published.

AES5-R: Review of AES5 2003: AES recommended practice for professional digital audio - Preferred sampling frequencies for applications employing pulse-code modulation
Assigned to: SC-02-02 , Status: Review
Intent: Review, Initiated: 2003, Target: 2008
Current goal: Review, Goal date: Continuing

No action required or proposed.

AES10-R: Review of AES10-1991 (r1997): AES Recommended Practice for Digital Audio Engineering -- Serial Multi-channel Audio Digital Interface (MADI)
Assigned to: SC-02-02, Status: Revised 2003
Intent: Review, Initiated: 2003, Target: 2008
Current goal: Status report, Goal date: continuing

No action required or proposed.

AES-10id-R: Review of AES-10id-2005: AES information document for digital audio engineering -- Engineering guidelines for the multi-channel audio digital interface (MADI) AES10
Assigned to: SC-02-02, Status: Revised 2005
Intent: Review, Initiated: 2005, Target: 2010
Current goal: Status report, Goal date: continuing

No action required or proposed.

AES11-R: Review of AES11-2003: AES Recommended Practice for Digital Audio Engineering - Synchronization of digital audio equipment in studio operations
Assigned to: SC-02-02, Status:
Intent: Amendment, Initiated: 2003, Target: 2008
Current goal: PWD imminent, Goal date: 2005-10

Annex B: There was no dissent to the TG draft of 4th June. R Caine to send the .doc file for secretariat formatting.

Annex D has been submitted to AESSC for approval.

It was also noted that there are new frame rates that should be added to Table 1 next time the normative part is revised.

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
Assigned to: SC-02-02, Status:
Intent: Review, Initiated: 2002-04, Target: 2007
Current goal: Status report, Goal date: Continuing

Caine reported that he had asked IABM whether any of their members were using AES18, and there had been no response.

AES41-R: Review of AES41-2000: AES standard for digital audio - Recoding data set for audio bit-rate reduction
Assigned to: SC-02-02
Intent: Reaffirmation, Initiated: 2000, Target: 2005
Current goal: CFC, Goal date: 2005-10-20

Reaffirmation was requested after the Barcelona meeting. A. Mason reported that the BBC has a patent on audio Mole for which there are no licensees, and the patent is likely to be allowed to lapse.

AES47-R: Review of AES47-2002: Digital Audio in asynchronous transfer mode (ATM)
Assigned to: SC-02-02, Status: Review
Intent: Amendment, Initiated: 2002-04-19, Target: 2007
Current goal: PCFC, Goal date: 2005-10

The TG draft posted on 19th July was agreed subject to a few minor changes. J Grant to call for comment from the WG preparatory to sending the document for CFC (already done).

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
Assigned to: SC-02-02 , Status: Review
Intent: Revision, Initiated: 2005, Target: 2005
Current goal: PTD for revision, Goal date: 2005-10

J Grant to review and update following the revision of AES47 and finalisation of X143 and X148. New goal date 2005-12.

AES50-R: Review of AES50-2005: High Resolution Multichannel Audio Interconnection (HRMAI)
Assigned to: SC-02-02
Intent: Review, Initiated: 2005-07, Target: 2010
Current goal: Status report, Goal date: Continuing

No action required or proposed.

AES-R6-R: Review of AES-R6 2005: Guidelines for High Resolution Multichannel Audio Interconnection (HRMAI)
Assigned to: SC-02-02
Intent: Review, Initiated: 2005, Target: 2010
Current goal: Status report, Goal date: Continuing

No action required or proposed.

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.
Assigned to: SC-02-02-G, Status: Sec formatted PTD including editorial changes
Intent: Standard, Initiated: 2000-09, Target: 2005
Current goal: PWD imminent, Goal date: 2005-08

The document has been passed up to SC-02. The proposed standard has now been designated AES52.

AES-X119: Standard, Connector for AES3 interfaces
Project scope: to consider the specification of an alternative connector for AES3 interfaces.
Assigned to: SC-02-02-F, Status: Questionnaire results available
Intent: Amendment of AES3, Initiated: 2001-03, Target: 2004
Current goal: Draft questionnaire, Goal date: 2003-12

A. Eckhart reported that Switchcraft do not intend to manufacture the XLD as they do not foresee a sufficient demand for it.

Caine recommended that the XLD should be added to AES3 as an option once a specification has been standardised by SC-05-02.

The meeting recommends closure of Project X119 as the remaining work can be done in AES3-R.

AES-X121: Synchronisation of digital audio over wide areas
Project scope: to study the measures that may be taken either to ensure that the two clocks are frequency-locked or to cope with the consequences of samples not being used at the same rate as they arrive; and to recommend practices or write specifications.
Assigned to: SC-02-02-G, Status: PTD to be revised
Intent: Report, Initiated: 2001-05, Target: 2005
Current goal: PTD, Goal date: 2006-01

C. Chambers reported that BBC Research may be able to provide some input for this document.

AES-X139: Liaison with EBU P/AGA
Project scope: Liaison with EBU P/AGA
Assigned to: SC-02-02, Status: Continuing
Intent: Liaison, Initiated: 2002-03, Target: Continuing
Current goal: Status report, Goal date: Continuing

R. Chalmers reported that P-AGA met in Amsterdam on 12th September but very little of the discussion concerned items of interest to SC-02-02. Chambers reported to them on AES-X111.

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.
Assigned to: SC-02-02-E
Intent: Standard, Initiated: 2004-02, Target: 2005
Current goal: PWD, Goal date: 2005-10

The draft was posted to the Working Group on 22nd September. There having been no dissent, it is ready to be passed to SC-02.

New goal: PCFC. New target date: 2006.

AES-X148: Sample-accurate timing in AES47
Project scope: to specify how the timing markers specified in 4.1.4.1.1 and 4.5 of AES47 may be used to associate an absolute timestamp with individual audio samples
Assigned to: SC-02-02
Intent: Standard, Initiated: 2004-09, Target: 2005-10
Current goal: PTD, Goal date: 2005-06

The draft awaits secretariat reformatting as a PWD.

New goal: PWD, date: 2005-11. New target date: 2006.

Liaisons

IEC TC100
J. Yoshio reported from IEC TC100, which met on 26-30 September in San Jose. IEC 60958-3 (digital audio interface -- consumer applications) has added SMPTE time code and latency information, and is now at the CDV stage (voting closes in February). PT 62312 "Guidelines for synchronization of audio and video" is writing a new standard to address the problem of maintaining lip sync when there is a significant processing delay in the display device; this will be a new part of the command set for IEEE 1394. PT 62379 (Common Control Interface for networked audiovisual equipment) is adding Part 8 to address issues specific to consumer equipment; the PT met immediately before the SC-02-02 meeting - Part 1 is essentially complete, while Part 8 is at the stage of collecting ideas on requirements.

M. Yonge reported that IEC 60958-4 (digital audio interface -- professional applications) is due for review, and any contributions must be received before the end of 2005. It is currently aligned with AES3-1992, but the additional sampling frequencies etc in AES3-2003 ought to be added. Yoshio thought it was already too late to provide input to the current revision, but it should be kept for the 2008 revision. Yonge to investigate, and ensure the right things are done at the right time.

Yoshio reported that the studio equipment group in ARIB is investigating how to carry metadata; for consumer use (60958-3) it would be carried in the U-bit, but it is not yet clear how it should be carried in the professional case. S. Lyman pointed out that most legacy professional equipment does not carry the U-bit transparently.

New Projects

No new projects were proposed

New business

Chambers reported that Neutrik now produce an LC-compatible optical fibre connector in a ruggedised shell.

The next meeting will be scheduled in conjunction with the 120th AES Convention, Paris, May 2006
(NOTE that it will not be possible to hold meetings before the convention, so the likely options are May 20th (first day of convention) or 24th (day after the last)

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