Report of the meeting of the SC-02-01 Working Group on Digital Audio Measurement Techniques of the SC-02 Subcommittee on Digital Audio, held in Munich, Germany, 2009-05-09
The meeting was convened by chair S. Harris.
The agenda and the report from the previous meeting were approved.
Open Projects
AES17-R, Review of AES17-1998 (r2004): AES standard method for digital audio equipment - Measurement of digital audio equipment
T. Kite has sent a document to the group with some proposals. I. Dennis has also made some comments on the document privately, and has been asked to send his comments to the SC-02-01 reflector.
We re-affirmed the need to update AES17, rather than just rely on IEC 61606, so we can continue with our own document and development direction.
We proposed to split the next version of AES17 into two complementary documents. A revision of the standard will focus on documenting measurements precisely. A second document will be more tutorial in nature to discuss the relevance of the measurements.
The next AES17 should be harmonised with IEC 61606 as far as possible. The secretariat has received approval to use text and drawings from IEC 61606.
This development work will be handled under new project IDs to avoid confusion with the current publication. PIRs will be raised by M.Yonge:
AES-X187A - Revision of standard AES17-1998 containing definitions of how to make each measurement. This can be compact and precise.
x187B - New information document - Measurement Tutorial. This can be more open-ended and discussion-oriented, and may include options about each measurement.
Kite will chair the task group to write both the new standard (AES-X187A) and the tutorial (AES-X187B). If you would like to join this task group, please send an email to the reflector and volunteer. Kite will organise the task group work by phone calls or emails.
There was some discussion about how to agree about some technical issues, for example, defining full scale. We stated that we work by consensus, consensus means lack of sustained objection. So if anyone disagrees, they must provide alternative text. For example, we could specify that if the digital audio signal is available then Full Scale should be defined by digital FS. If the digital audio is not available, then use 1% distortion point as FS. In any case, the FS definition method should be indicated by anyone claiming an AES17 compliant measurement.
AES-12id-R, Review of AES-12id-2006: AES information document for digital audio measurements - Jitter performance specifications
No action requested or required.
AES-6id-R, Review of AES-6id-2006: AES information document for digital audio - Personal computer audio quality measurements
J. Ekeroot is interested in updating AES-6id to add information about what happens to the audio in the computer software, which AES-6id-2006 does not discuss. There has been some work on this in the game-audio space; there is a AES technical council group on audio for games and they organised an AES conference in London, 2009-02, on the general subject. There may be additional standards work concerned with computer audio quality.
Ekeroot will send an introductory email to the SC-02-01 reflector, asking for contributors. Harris will use this email to find the proper people at Microsoft and Apple who may want to contribute to this work.
Development projects
AES-X177, Techniques for measurement of audio-video synchronisation error
A. Mason is unable to continue this work at BBC Research, but he can finish off the current work.
A paper was presented last October at AES convention in October 2008. There is an EBU technical review document, and a BBC white paper, about impact of Dolby E on latency in the BBC audio chain. The test example file has been posted to our document site. A tutorial on lip sync, chaired by F. Gierlinger IRT Munich, was held elsewhere at this convention.
Mason will make a AESSC report on AV synchronisation by way of finishing off this project. This will be a combination of the AES paper and BBC white paper about Dolby E impact on AV sync and any other thoughts.
There was a suggestion to retain a liaison project on audio-video synchronisation. Work in EBU/SMPTE may change the way sync is handled in the future. It seems posible that in the future, because of the prevalence of IT-based technical infrastructures, audio and video will not be automatically synchronous unless specified. M. Yonge is involved in this work.
AES-X102 Liaison with IEC PT61606-3 Audio and audiovisual equipment - Digital audio parts - Basic measurement methods of audio characteristics - Part 3: Professional use
Result of voting was approved, as of Dec 2008. Document is now published.
AES-X118 Liaison with ITU-R study group 6C
Mason reported that he is involved in an update to BS 1770 loudness meter, in particular adding gating to loudness measurement and making measurement [gated with a threshold that is relative to the un-gated level*]. Some documents about this have been posted to the 0201 document site.
There was a discussion about short, medium and long term metering.
A tutorial about loudness metering was presented elsewhere at this convention that will be available on the AES web site in the future.
Liaisons
None
New Projects
None, except the AES-X187 proposed above.
New Business
None
The next meeting will be scheduled in conjunction with the AES 127th Convention in New York, 2009-10.
[* amended after correction by A Mason, 2009-05-20]
