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 San Francisco, CA., US., 2008-10-03
The meeting was convened by chair S. Harris.
The agenda and the report of the previous meeting held on 2007-10-06 were approved as written.
Open Projects
AES-6id-R Review of AES-6id-2006: AES information document for digital audio - Personal computer audio quality measurements
No action was requested or required.
AES-12id-R Jitter specifications.
References to AES3 and AES2id jitter sections will be added to the next
printing of AES-12id.
AES17-R: Review of AES17-1998 (r2004): AES standard method for digital audio equipment - Measurement of digital audio equipment
A PTD is still under development. Some questions arose regarding the direction of this document. The primary target audience was felt to be both manufacturers of audio equipment and manufacturers of audio test equipment.
It was also noted that IEC 61606 has 2 parts: one descriptive explanation of the equipment and setup, and a second section which describes the detailed measurement technique. The meeting felt that the revision of AES17 should be done in such a way that the material could be cut and pasted into the next revision of IEC 61606-3 Basic measurement methods of audio characteristics - Part 3: Professional use, as appropriate. The secretariat will discuss with M. Furukawa about harmonising the words and figures from IEC 61606-3 with AES17.
It was pointed out that the format of IEC 61606-3 refers back to IEC 61606-1 Basic measurement methods of audio characteristics - Part 1: General, but in practice it overwrites most of the general requirements.
A task group to update AES17 was formed, currently I. Dennis, T. Kite and
D. Foley. Dennis reminded us about the history of comments about AES17 on the document site. Kite will make a report about updates and new sections for the AES17 revision before the end of January 2009, including the content of the notes and comments history document on the web site. Foley and Harris will find additional people to join the task group for updating AES17.
Development Projects
AES-X102: Liaison with IEC TC100 PT 61606
IEC 61606-3 Ed.1, Audio and audiovisual equipment - Digital audio parts - Basic measurement methods of audio characteristics - Part 3: Professional use, has completed its final draft stage and is expected to be published by IEC later this month. The maintenance result date for the next revision of IEC 61606-3 is 2012, so any AES-proposed text would need to be submitted by 2010. To correspond with this, the next revision of AES17 needs to be complete by 2010.
AES-X118: ITU-R study group 6 liaison
C. Todd observed that the active ITU-R group is now called WP6C, "production aspects". ITU-RWP6B handles assembly of audio and video.
Regarding the ITU-R work on loudness, the peak metering text from AES-R7-2006 has been incorporated in ITU-R BS.1770. The loudness metering algorithm is done, but implementation details are still being discussed. There is a general interest in short-term loudness displays to support audio operations, however the ITU does not feel that it should be designing equipment and there is a possible role for the AES in this area.
In another field; ITU-R BS.775, "Multichannel stereophonic sound system with and without accompanying picture", discusses the LFE loudspeaker channel having a gain offset of +10dB. It was felt that BS.775 should now be updated to specify positively the +10dB offset for the LFE channel.
AES-X177 Techniques for measurement of audio-video synchronisation error
Mason's AES preprint 7518, Factors affecting prception of audio-video synchronization in television, was presented at the convention and discussed in this meeting. Mason will upload the paper to the SC-02-01 doc site for information.
Todd said that Dolby has an old MPEG test file that could be used as an objective reference for audio-video syncronization. Mason will contact Todd to get a copy. Mason asked what format for a test file would be most generally useful. AVI is available but may not be very useful, however Mason will post the test file to the document site for information.
Mason will also post a circuit diagram for a simple measurement system.
IEC 62503, Multimedia quality - Method of assessment of synchronization of audio and video, is the draft IEC doc for lip sync measurement, currently at CDV stage. Yonge has posted a copy of the CDV to the SC-02-01 document site.
Liaisons
With regard to the discussion under AES-X118 and the proposed new project, below, a closer liaison with ITU-R is desirable. It is noted that ITU can only work with approved organisations. As matters curently stand, ITU can not send a liaison statement to AES, and AES can not send a liaison statement to ITU.
Yonge is considering attending the next ITU meeting, if that could be made possible. A suggestion was made for him to register through existing liaison groups such as SMPTE. Mason will help to provide relevant contact information.
New Projects
S. Lyman suggested that the AES consider producing a report on audio level measurements to introduce measurements of both true peak level and ITU-R BS.1770 loudness as a replacement for more traditional - and more diverse - metrics. Lyman will write a draft and post it to the document site by the end of 2008-10.
New Business
D. Foley is interested in electroacoustics and mentioned IEEE 269 Standard Methods for Measuring Transmission Performance of Analog and Digital Telephone Sets . Foley will arrange to post this to the SC-02-01 document site. Kite and Dennis will consider if some element of electroacoustics test can or should be included in the revision to AES17.
The next meeting will be scheduled in conjunction with AES 126th convention in Munich, Germany, 2009-05.
