August 2003|It's been more than five years since Avid and Microsoft publicly launched efforts to define and promote the Advanced Authoring Format (AAF). AAF is intended to facilitate interoperability in the content creation workflow through standardized exchange of digital media and metadata. For the end-users of production tools in fields such as video post, broadcast, and audio post, the concept is a welcome one. But for vendors of the tools, implementation of interoperability is a complex issue involving both technical and marketing considerations. So progress toward standardizing and then implementing AAF hasn't exactly been swift. At this year's NAB, however, there were some hopeful signs that AAF might eventually become an industry-wide phenomenon, which makes this an opportune time for an update on the standard's status and outlook.
AAF's origins are in Avid's Open Media Framework Interface (OMFI), but it utilizes a "structured storage" container format developed by Microsoft. Implemented in an object-oriented C++ environment, it incorporates a vendor-neutral plug-in architecture, supports a broader range of media formats and temporal data, and allows the integration of 2D, 3D, text, HTML, and XML objects.
Beyond simply passing along media data (video, audio, graphics, animation, and text), AAF's emphasis is on interchange of metadata (data about the data), including compositional information that describes how sections of media data are combined and modified. It also supports version control, allowing an AAF file's data to be edited and revised while retaining the history of the changes, as well as media derivation information about the original source. Unlike formats such as QuickTime, AAF is not intended to serve as a delivery format, but rather is exclusively designed to serve the needs of the production community.
The increasing attention vendors are paying to AAF reflects the reality that today's production environments are diverse rather than monolithic, involving many specialized tools from multiple vendors. "The post-production market," says Rick Keilty, director of 844/X product marketing at Media 100, "includes a wide array of products and tools—video, audio, input/output, graphics, and 3D workstations—from a wide range of suppliers across multiple platforms, including Windows, Macintosh, Linux, and Unix, and supporting multiple formats such as DV, MPEG, and uncompressed 601."
This diversity is great when it comes to choosing the right tool for the job, but it creates a big challenge in terms of workflow. "Particularly with large projects," says Mike Nann, technical marketing manager for post-production at Leitch Technology, "collaborative and multi-platform workflows are the norm. Collaborative might mean between multiple users, such as visual effects artists working on different segments of a project, or between multiple types of users with distinct skills and specialties, such as editors exchanging project sequences with compositors and animators. It could be between multiple facilities, or even just a single user that might use two different compositing software packages."
What makes an interchange standard for production so appealing is the promise that this collaboration can work smoothly and efficiently, thus boosting productivity. "Collaboration and interchange are very critical in this segment," Keilty says, "in order to improve efficiency and thus provide cost and time savings. The entire content creation food chain has been pushed to deliver higher-quality, more visually sophisticated material in a shorter time frame for less money. Running around with tapes and paper copies of notes on editorial decisions is time-consuming, inefficient, and ultimately impacts design quality. So the need to share data between disparate systems and applications has reached a critical point."
The business pressures are occurring simultaneously with the long-term technological transition from linear to non-linear storage and production techniques. "The content creation industry," says Tim Claman, director of interoperability and standards at Avid Technology, "is moving away from workflows based on interchange of baseband signals and tape storage to workflows based on IP networks and storage."
As the technological foundation of the industry has changed, the methods available for facilitating heterogeneous workflow haven't kept up. "The complexity of today's post-production and broadcast workflows," says Paul Saccone, Final Cut Pro product manager at Apple, "makes it nearly impossible for any one vendor's products to handle everything. Seamless collaboration technologies are becoming a critical necessity. For years we've dealt with either inadequate or proprietary solutions."
The Collaboration Problem
"Fundamentally," says Christian Schormann, VP of engineering and chief strategist at Pinnacle Systems, "there are a few pieces to the problem of collaboration in the environment of IT-based video production systems. There is the interchange of media and the interchange of compositional metadata, meaning the information that explains how pieces of media are combined into a single production. And there is network workflow and asset management."
How do existing approaches to interchange measure up in each of these areas? "SDI has the widest compatibility," Schormann says, "but it is a pure push model of content; the receiver must take what is on the wire in a synchronous fashion. And SDI defines and transports very little metadata. In particular, there is no notion of compositions or compositional metadata. So the interchange is happening on such a low level that it is not particularly supportive for a content production workflow."