Introduction and Overview of Advanced Authoring Format and

mats such as Philips with Digital Picture Exchange. (DPX), and ... While MXF's metadata capabilities are quite extensive, at their ... firm in 1997. He graduated ...
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Introduction and Overview of Advanced Authoring Format and Material Exchange Format By Brad Gilmer

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he film, post, and broadcast communities have been proactive in developing and adopting new technologies. Many companies are now building IT-based production facilities—facilities where content is created, moved, stored, modified, distributed, and consumed in a digital environment. These new facilities would not have been possible without the expertise and dedication of many people in the European Broadcast Union and SMPTE technical community. These individuals recognized early that IT-based facilities would only be possible if the industry came together on Standards that promote the free interchange of content in this networked environment. Many from the computer industry have also participated extensively in development of new Standards and key enabling technologies. At the International Broadcast Convention on September 12, 1996, the EBU and SMPTE created the EBU/SMPTE Task Force for Harmonized Standards for the Exchange of Program Material as Bit Streams. This group, commonly referred to as the EBU/SMPTE Task Force, began to tackle the issues of interoperability and interchange of content in a networked environment. The group published its final report1 in July of 1998, and to its credit, many of the recommendations in that report have held up in implementations which are now becoming available. The industry has learned a great deal. Some things we thought would be relatively straightforward, turned out to be rather difficult. Other areas that were expected to be difficult have actually been relatively easy to work out. For example, the concept of a unique identifier is quite simple. It is intuitive that computer systems require a unique identifier to keep track of each piece of content. This concept is quite simple, but has proven quite difficult to implement. An example of a SMPTE

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more complex issue is the adoption of common object model for the representation of metadata. At first this seemed to be a huge task. However, adoption of the well developed data model used in both AAF and MXF have made agreement in this area much easier. Companies that have been at the forefront of file formats such as Philips with Digital Picture Exchange (DPX), and Thomson Grass Valley with General eXchange Format (GXF) have demonstrated a willingness to share what they have learned with others as we have worked to create the next generation of file formats. Additionally, several companies from the computer industry are now participating in this area, reconizing that this work will affect their industry as much as it affects ours. In this issue of the SMPTE Motion Imaging Journal, we take a look at two file formats that are poised to become the cornerstone of IT-based production—the Advanced Authoring Format (AAF), and the Material eXchange Format (MXF). (AAF has been developed by the AAF Association2—MXF has been developed by the Pro-MPEG Forum.3)

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In 1996, the Task Force attempted to develop a proposal for a single file format for film editing, post-production and distribution. The Task Force concluded early on that user requirements in these areas were sufficiently different and required two file formats.4 The Task Force report describes these two formats as a Complex Content Package and the Simple Content Package, in recognition of the fact that a file format used to describe project information in the film editing and post-production space is necessarily more complex than a format used to describe finished program material. AAF is primarily intended for the interchange of video, audio, data, and metadata in a creative environment where the content is not completed. As such, an AAF file might contain multiple pieces of video, audio and graphics, along with metadata that describes how these pieces are to be combined to create a completed program. Because of this, the AAF data model is rich, and is able to fully describe the content and the actions to be taken on that content in the environment of film edit and post-production. MXF is primarily intended for the exchange of completed programs. It provides a simple structure for the expression of metadata, and will likely find extensive use in electronic news gathering, broadcast, and archiving applications. While MXF’s metadata capabilities are quite extensive, at their root, these capabilities are intended to replace the tape label and shot log that used to accompany videotapes. It is a credit to the industry that both AAF and MXF use the same data model. This is good news for imaging and IT professionals. It means that metadata can be more easily interchanged between AAF and MXF applications. Hans Hoffmann points out in the File Interchange Handbook,5 “The results of the EBU/SMPTE Task Force have initiated the appropriate actions in all the technology areas concerned with future server and network-based content production environments. Traditional broadcast as well as IT companies are discovering new business opportunities in professional media and have created IT-based solutions for the broadcasters. These will result in

enhanced services: more flexibility, new processes, more effective workflows in program-making, and promising economic benefits. In this environment, interoperability, and consequently standardization, is mutually advantageous for users and manufacturers.”

References 1. EBU/SMPTE Task Force for Harmonised Standards for the Exchange of Program Material as Bit Streams, “Final Report: Analyses and Results,” July 1998, available via www.ebu.ch or www.smpte.org. 2. AAF Association, www.aafassociation.org. 3. Pro-MPEG Forum, www.pro-mpeg.org. 4. EBU/SMPTE Task Force for Harmonised Standards for the Exchange of Program Material as Bit Streams, “First Report: User Requirements,” April 1997, available via www.ebu.ch or www.smpte.org. 5. B. Gilmer, File Interchange Handbook, Focal Press: New York, 2004.

THE AUTHOR Brad Gilmer is president of Gilmer & Associates, Inc., a technology and management consulting firm and is also the editor-in-chief of the File Interchange Handbook. He currently serves as the executive director of the Advanced Authoring Format Association and as executive director of the Video Services Forum. Gilmer was also co-chair of the File Interchange committee of the Pro-MPEG Forum and a participant in the EBU/SMPTE Task Force. Gilmer held various posts during a 14-year career at Turner Broadcasting Systems, Inc., before he left to start his own firm in 1997. He graduated Summa Cum Laude with a degree in business from Georgia State University.

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