Introduction


WAVE files have become a de facto standard for exchanging audio among diverse systems and applications in the radio business, much the same way that " magnetic tape was in the past. But as low tech as magnetic tape seems to us now, no one ever had a problem sticking a label on a reel or cart to fully describe the audio contents of that tape. The Cart Chunk standard addresses this issue, allowing users to embed the common labeling information that radio users need, directly into a WAVE file. Based on the RIFF file format, the Cart Chunk format is a non-proprietary standard that allows additional metadata to be attached as an integral part of a WAVE file in the form of "chunks", or integral units of data.

INSPIRATION
Several years ago, we saw the need for sharing data between different manufacturer's PC-based systems used in the radio industry; for example, taking finished commercials or promos from a production system and sending them to an on-air control system. In engineering several connections between one brand of system and another, it became obvious that each connection required a huge amount of engineering effort, because each had its own unique set of properties and requirements. These custom connections were expensive to implement and difficult to maintain. Finally, having recognized that virtually all systems being used for broadcast audio production, storage and delivery share a large subset of common attributes, and we sought to define a common interface format to them all.

WORKING FOR A COMMUNITY STANDARD
Inspired by the European Broadcast Union's BroadcastExtension (or 'bext') chunk standard, AKA the "Broadcast Wave File", we formulated a strawman proposal for a public-domain, license-free interchange standard using the industry-standard WAVE file format. This new chunk, dubbed the 'Cart' chunk, contains fields and attributes that a large number of broadcast system use to describe an audio file. But rather than try to impose a fixed, proprietary standard on the industry, as some companies have tried in order to obtain a competitive advantage, we decided from the beginning to seek the participation of members of the radio community, including users and vendors (some, complete rivals) alike.

Our strawman proposal was presented officially to the radio community at the NAB '99 convention in Las Vegas, where it was enthusiastically accepted (even garnering the first Radio World Cool Stuff Award presented to a non-product candidate). From that point, we conferred actively with a number of participants, and set up a free mailing list dedicated to discussion of the standard. By the end of the summer of 1999, we had received valuable advice and suggestions from all corners of the community, and in the fall of 1999, submitted it as a proposal to the Audio Engineering Society's Standards Commitee on File Interchange (SC-06-01) where it has now (June 10, 2002) been formally ratified as AES Standard AES46-2002.

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