Report of the meeting of SC-02-12 Working Group on Audio Applications Using the High Performance Serial Bus (IEEE 1394) of the SC-02 Subcommittee on Digital Audio, held in San Francisco, CA., US., 2006-10-07

The meeting was convened by Chair J. Strawn.

The agenda and the report of the previous meeting were approved as written.

Development projects

AES-X075: IEC TC100 Liaison for IEC 61883
Project scope: Prepare recommendations and assist the work of IEC TC100 regarding the development and maintenance of relevant parts of IEC 61883. Any assigned task group shall report project progress to SC-02-12 and shall ask SC-02-12 for its advice on content. Administrative review of the project shall follow AESSC rules.

Assigned to: SC-02-12, Initiated: 1998
Intent: Liaison, Target: Continuing Current goal: Status report, Goal date: Continuing
Status: Ongoing

J. Yoshio reported:

For IEC 61883-6, edition 2 was published in 2005-10. No further changes to this IEC document are currently proposed, however the 1394 Trade Association (1394TA) is preparing Version 2.2 of their document which will contain clarifications on a) flow control and b) relationship with IEC 60958-3, Edition 3, concerning high sampling frequencies.

In IEC there is a new proposal for multichannel linear PCM for new disks such as HDTV, Blue Ray. Currently IEC 61883-6 has no entries for this. The DVD Forum also has a focus group discussing this issue. Yoshio has proposed adding loudness information; some broadcasting companies in Japan want to control loudness. The time scale is not fixed; IEC will probably publish a draft in the middle of next year.

For IEC 61883-8 concerning Consumer Audio/Video Equipment for video transmission with ITU 602.1, Fujitsu have proposed new codecs to be included, such as the codec described in ITU-R BT.601. The application is the transmission of video and audio in an automotive environment.

A discussion of ITU-R BT.601 clarified that this is a lower-latency video compression scheme. Applications include automotive rear-view cameras.

IEC 60958-3, Edition 4. New sampling frequencies will be added to transmit new compressed audio formats from DTS and Dolby that require high sampling frequencies to transmit high-frequency audio data through HDMI and the IEEE 1394 bus. Loudness data is also being considered in this revision.

AES-X101: Data Type, Properties, and Method Definitions for Audio Device Application Program Interfaces (API)

Project scope: Define and publish recommended data types, properties, and methods for use in the control of common audio devices.
Assigned to: SC-02-12, Initiated: 1999-12
Intent: Report, Target: 2006
Current goal: PWD, Goal date: 2006-09
Status: Sec- formatted report awaited

No progress by Secretariat in reformatting report, low on priority list.

AES-X137: Liaison with 1394 Trade Association (1394 TA)

Project scope: Liaison with 1394 Trade Association (1394 TA)
Assigned to: SC-02-12, Initiated: tba
Intent: Liaison, Target: Continuing
Current goal: Status report, Goal date: Continuing
Status: Liaison in progress

Deferring discussion of the use cases from task groups SC-02-12-H, -J, and -K until later in the meeting, Yoshio and R. Gurdan report that there was nothing in particular to report.

N. Warren reported that Apple is working actively to extend AV/C specifications to accomodate what breakout box manufacturers want; regarding latency, for example.

Strawn suggested that latency would be a use case. Warren stated that, while continuing to participate in use-case discussions, he wants to focus on the needs of manufacturers of breakout boxes. Discussion that having a breakout box does not constitute a use case, however the use of a breakout box is possible in all use cases under discussion.

Strawn noted that there had been progress on the issue of 1394TA documents as normative references for AES standards. [A positive conclusion was reached subsequent to this meeting].

AES-X126 : Profile for professional audio over 1394 Project scope: to describe unique requirements for professional audio carried over 1394

Assigned to: SC-02-12-G, Initiated: 2001-05
Intent: Standard, Target: 2006
Current goal: PCFC, Goal date: 2007-01
Status: Output to comprise several documents. First, on "32-bit generic transport", currently in draft

B. Moses reported on the meeting of SC-02-12-G that took place on the previous day.

SC-02-12-G is proposing to merge two documents: a professional baseline audio document will be combined with a so-called "L1_L2" document.

Discussion about AV/C and Open Generic Transporter (OGT). AV/C does not not seem complete enough to support pro audio devices. Yamaha is expected to share open source sample code if possible.

There was some discussion of software code. Some participants want to look at software code before advancing the document. What Warren really wants is a source code for generic hardware abstraction layer (HAL) implementation. Warren added that they would like to see source code for an independent implementation of the HAL, and not transporter code. Strawn clarified that concensus needs to be established before the document moves forward. There was a discussion of whether Yamaha should be asked to release code to this group.

R. Foss asked whether it would be possible to verify with a binary. Warren felt that it would have to be a very full implementation and that an open standard woud need to be supported by open source software.

Gurdan asked whether anyone else would be interested in the software code. Warren clarified that Apple wants to see code running on its platform and is willing to do the port if needed.

AESSC secretary, M. Yonge, pointed out that a letter of compliance with the AESSC policy on patents would be required from Yamaha before their code could be included in an AES standards document.

Warren said that Apple would need HAL code at minimum, but would also want enabler code and transporter code if at all possible. Apple will want to do an end-to-end test of a complete system. Foss clarified that the HAL code is relevant to the OGT specification.

AES-X132: Synchronisation of audio over IEEE 1394

Project scope: to specify methods of audio clocking and sampling-frequency synchronisation in a professional audio network based on the IEEE 1394 high performance serial bus. Include techniques to ensure devices function correctly in a network which includes IEEE 1394.1 compliant bridges Assigned to: SC-02-12-G, Initiated: 2005-10, Intent: Standard, Target: 2006 Current goal: Sec-formatted PWD, Goal date: 2006-12 Status: Awaiting Sec-formatted PWD

X132 being secretariat formatted, high in queue.

1. There was one comment from C. Travis on the definition of synchronization. S. Harris has discussed with Travis. Travis' intention was not to hold up publication of the document. He can also agree to publishing the document as it stands. Harris to discuss further with T. Thaler, to be done after the document has been secretariat-formatted. Yonge expects to have document formatted document by end of November.

Goal: call for comment early 2007.

2. Foss mentioned that in the Paris meeting the issue of jitter across bridges had been discussed. Had the document changed after M. Mora's question about jitter in Paris? Warren added concerns about the jitter per node, resulting in cumulative jitter. Foss offered to follow up with an email with suggested wording concerning a) more precise meaning of "synchronization" b) how to minimize cumulative jitter.

Warren brought up the amount of jitter that can be tolerated. Harris reported on discussion in SC-02-01 and discussed whether AES standards should set minimum acceptable levels. Harris added that the nature of the jitter, and the amount tolerated, are influenced by converter or digital amplifier architecture. The document being considered in SC-02-01 will attempt to define how jitter is measured, not state a minimum acceptable level.

AES-X156: Use cases for IEEE 1394 in professional audio: Recording

Project scope: to identify and clarify use cases for IEEE 1394 in professional audio in Recording applications Assigned to: SC-02-12-H, Initiated: 2006-06-01
Intent: Use case draft, Target: 2007
Current goal: PTD, Goal date: 2006-10
Status: Use cases under development
Leader: F. Saelen

AES-X157: Use cases for IEEE 1394 in professional audio: Live sound

Project scope: to identify and clarify use cases for IEEE 1394 in professional audio in Live sound applications Assigned to: SC-02-12-J, Initiated: 2006-06-01
Intent: Use case draft, Target: 2007
Current goal: PTD, Goal date: 2006-10
Status: Use cases under development
Leader: S. Peer

AES-X158: Use cases for IEEE 1394 in professional audio: Audio installations

Project scope: to identify and clarify use cases for IEEE 1394 in professional audio in Audio installation applications Assigned to: SC-02-12-K, Initiated: 2006-06-01
Intent: Use case draft, Target: 2007
Current goal: PTD, Goal date: 2006-10
Status: Use cases under development
Leader: R. Gurdan

Of the three leaders of these task groups, Gurdan was present and reported. These three groups met the previous day. Basic use cases are drafted and the discussions are intended to continue. The next meeting is intended to be convened at the next 1394TA meeting, with a goal of finalizing three use cases per group in November.

A. Goldstein asked where documents will be deposited. Strawn asked the secretariat and AES Webmaster to tighten links from AES web site to forums, which can be found at https://secure.aes.org/standards/index.cfm.

Liaisons

There were no other liaison issues.

New Projects

No new projects were received or proposed.

New business

It was noted that Moses has resigned as chair of SC-02-12-G. Strawn has appointed himself as chair of SC-02-12-G.

The next meeting will be scheduled in conjunction with the AES 122nd Convention in Vienna, Austria, 2007-05.