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  • Writer's pictureSheldon Kessel

Perspective on OMF back in the day

I was going through a ton of old reference materials I've collected over the years and came across this interesting article about OMF files from back in '97. I teach about OMF and have been more-than-a-little surprised by how many "professionals" out in the "real world" aren't even aware that file exchange formats exist. least my students entering the "real world" know what's up. Anyway, check out this perspective on OMF from back in the day.


It's A Mob Mentality Out There: OMF Gains Followers

AV Video Magazine June 1997 by Bill Ferster

In 1991, Avid Technology introduced a new concept to the video production community: the Open Media Framework. OMF promised to unify the digital facility, by trying to create a common file format.

This new format would be able to describe an entire show; with its edits, audio work, effects and animation. The files would be able to be read on any computer system and by any workstation whose supported OMF.

It's taken six years, but OMF is starting to gain some acceptance in the video industry. One manufacturer commented, "In an age of the all digital facility, most people are still using punch-card era technology to exchange information about a show," referring to the CMX list's continued role as the Rosetta Stone for EDL interchange.

A Political Hot Potato

Avid introduced OMF with a fair amount of fanfare, which was met with very little industry acceptance. This was primarily due to the political baggage OMF carried by being a prodigy of Avid, who was aggressively marketing their nonlinear editors. Avid's nonlinear competitors at the time, EMC and LightWorks were hesitant t to support any standard proposed by a competitor.

This stance has weakened over the years, with LightWorks just now beginning to offer OMF support in their editors, and other nonlinear vendors likely to follow. Avid has been sensitive to the issue, and has sought assure competitors that OMF is an open standard.

A SMPTE/EBU standards committee, charged with harmonizing the rat's nest of production standards, is currently evaluating adopting the OMF spec as a new media interchange standard. If that happens, any competitive fears about Avid's OMF connection should be allayed.

In addition to any political hesitancies, OMF's acceptance has also been hampered by its perceived difficulty in adding it to an existing product. OMF is based on a fairly complex object-oriented software base. Adding OMF support is a significantly more difficult task than adding a simple CMX or Grass Valley EDL output to a system.

What exactly is OMF?

The overall idea behind OMF, is that it provides an abstract way of describing a show in its entirety. The video format, the timings, the edits, the images, audio and where they can be found, and the transitions between them. The actual media, such as the digitized audio and video can be imbedded within the file, or be specified by name.

OMF is based upon Bento, an extremely versatile, but complicated object-oriented developed by Apple Computer for their ill-fated OpenDoc system. Bento is completely cross-platform compatible, making OMF files completely agnostic as to the computer system they were created on, or where they are read.

Traversing Bento accounts for much of the difficulty manufacturers experience when trying to add OMF to their products. Avid offers a software tool kit at no charge which insulates developers from having to know much about Bento, making the job somewhat easier.

OMF consists of a number of definitions (constructed in Bento objects) that relate to the description and control of streaming media (i.e. audio and video). OMF encapsulates a lot of knowledge about this media, such as the difficult task of audio resampling and frame rate control and audio/video synchronization.

OMF has added a new meaning to the word "mob." In the vernacular, a mob is a "Media OBject." A mob is a way of grouping things, such as clips, transitions and even complete projects together.

A typical OMF project file is made up a number of these mobs, called "composition mobs." Each composition is a collection of "track mobs," such as audio and video channels, coupled with an overall timing information about the scene(s) they describe.

Each track then is made up of the individual media elements called "clip mobs." These clip mobs are what define the media itself, either by naming the source, such as the reel name, if it is a tape, or where the digital data itself resides, or both. Transition mobs define how the individual clips transition from one to another, such as dissolves, DVE, etc..

Audio Applications for OMF

The most compelling application for OMF up to this point has been audio finishing. Audio workstation manufacturers were the first companies to pony up to the bar. Traditional EDLs could not adequately describe the complex virtual track layouts that the nonlinear editing systems could produce. The makers of digital audio workstations embraced OMF early on as a means for directly translating the editorial and preliminary sweetening done in the offline.

An OMF file will accurately describe all the editing, including the to-and-from track designations, EQ and level settings, making manual layout unnecessary. Some systems, such as ProTools, AudioVision and AudioFile, are able to read the audio directly from a disk containing OMF audio files, eliminating the time consuming importing and translating processes.

Video Applications for OMF

Video manufacturers have been slower to adopt OMF as an interchange format than their audio chums. This is primarily because the current interchange formats (i.e. traditional EDLs) meet an on-line video editor's need more closely. However, the more complex the show, the more value OMF brings to video projects, particularly when animation and complex compositing is involved.

OMF allows these projects to be worked on at lowered resolutions, (in the offline editing concept), and later rerendered at full broadcast resolution when the creative decision making is over. Descreet Logic and Kodak Cineon systems make extensive use this powerful capability.

The ability to act as an EDL interchange format has not been widely adopted by many of the on-line editing system manufacturers. A product called EDLMAX fills this gap by providing a way to convert to and from OMF to any of the traditional EDL formats, such as Sony, Grass Valley and CMX.

In the emerging multimedia world, Apple's latest version of QuickTime has direct support for OMF media. This means than any of the hundreds of software applications that support QuickTime 3.0 will play OMF files directly, with no need for time consuming translations.

Married to the Mob

OMF is a clearly robust way to exchange media around a facility and between various pieces of equipment, regardless of their manufacturer. It has already become the defacto standard in the audio world, and studios are regularly using it for complex animation and compositing projects.

Avid has done a great job developing and evangelizing this emerging standard. Hopefully, it will get the endorsement of SMPTE/EBU, and thereby remove any vestiges of competitive feelings from other video manufacturers.


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