Report of the meeting of the SC-02-08 Working Group on Audio-File Transfer and Exchange of the SC-02 Subcommittee on Digital Audio, held in Vienna, Austria, 2007-05-06
The meeting was convened by chair M. Yonge.
The agenda and the report of the previous meeting, held on 2006-10-06 in , were accepted as written.
Open projects
AES-R1-R: Task Force on High-Capacity Digital Audio Carriers (AES-R1)
It was felt that it would be unlikely that this report could usefully be revised but that other reports might be produced in the future to extend this topic. Consequently, it was proposed to retire this formal project - its work is done.
AES31-1-R: Review of AES31-1-2001 (r2006): AES standard for network and file transfer of audio - Audio-file transfer and exchange - Part 1: Disk format
AES31-1-2001 was reaffirmed on 2006-10-18. There was some discussion about whether there was any meaningful competition for the current standard as a basis for interchanging large audio files between dissimilar computer platforms. No suitable candidate was identified. A discussion of file-sizes in FAT32-formatted disk indicated that a limit of 4 GB existed when formatted using a normal Windows computer, although this limit could be increased by special formating using larger block sizes.
AES31-2-R: Review of AES31-2-2006: Part 2: File Format for Transferring Digital Audio Data Between Systems of Different Type and Manufacture
The specification of the Broadcast Wave Format (BWF) in AES31-2 has enjoyed good takeup since its publication last year.
A question was raised about the fundamental file-size limit of Wave files set by its inherent 32-bit address space. Larger interleaved multi-channel audio files, for example, are likely to exceed the 4 GB Wave limit.
The European Broadcasting Union (EBU) in Technical Publication T3306, "RF64: An extended File Format for Audio", offers a solution with backwards compatibility. A. Holzinger explained this scheme: audio file sizes below 4 GB are recorded as completely standard AES32-2 Broadcast Wave Format (BWF) files. When the recording crosses the 4 GB boundary, a change is made to the RIFF header that switches to 64-bit addressing and enables file sizes of virtually unlimited size. These "RF64" files require different software to replay them and are not directly compatible with BWF files, however the difference is largely confined to the 64-bit addressing change and no significant additional complexity is needed. The format is already in use by a number of European broadcasters where long programme segments of interleaved multi-channel audio are encountered.
An amendment was proposed to specify the file-size limit solution from the EBU RF64 document T3306 as an annex to AES31-2.
A second part of T3306 that relates to channel-mask flags was not felt suitable for adoption because it was unnecessary to address the file-size issue, and was too restrictive in application.
AES31-3-R: Review of AES31-3-1999, AES standard for network and file transfer of audio - Audio-file transfer and exchange - Part 3: Simple project interchange. including maintenance of annex F.
The anticipated editorial revision is due in the next few weeks. (See also below under "New Projects").
AES46-R: Review of AES46-2002: AES standard for network and file transfer of audio - Audio-file transfer and exchange - Radio traffic audio delivery extension to the broadcast-wave-file format
This standard is due for review in 2007. It was proposed to reaffirm this standard at the earliest opportunity.
Development projects
AES-X068: A Format for Passing Edited Digital Audio Between Systems of Different Type and Manufacture That Is Based on Object Oriented Computer Techniques
This project needs an expert contributor to make progress. It was felt that it may be necessary to study metadata mapping between AES31, AES3 and MXF, for example.
AES-X128 : Liaison with AAF Association
It was noted that the AAF Association has now become the AMW Association and embraces both Advanced Authoring Format (AAF) files and Material Exchange Format (MXF) streaming files. It was also understood that they are developing a series of workflow documents that may be of interest to the AES. U Henry and D Ackerman expressed interest in pursuing this path as it related to issues of MXF files passing through audio post production.
AES-X149: Format and Recommend Usage of the Direct Stream Digital Interchange File Format (DSDIFF)
A draft for this file format for Direct Stream Digital (DSD) audio has been posted to this group. The next step is is for this draft to be secretariat-formatted. An annex containing a table of manufacturers' IDs, to be administered by the AES, needs to be be added.
Liaisons
There were no other liaison issues.
New Projects
Simple project interchange in XML form
D. Ackerman discussed a scheme for expressing the functionality of AES31-3, "Simple project interchange" in formal XML language. This would be simpler to incorporate in more generalised metadata management schemes, such as those used in libraries and archives, and would prompt more precise implementations. It would also allow, unlike AES31-3, the use of multi-byte, Unicode, characters for wider international acceptance.
Ackerman demonstrated a working example of the proposed XML format, complete with a style-sheet conversion to show EDML-formated text on the screen to provide human readability. Yonge will raise a project initiation request.
New business
There was no new business.
The next meeting will be scheduled in conjunction with the AES 123rd Convention in New York, NY., US, 2007-10.
