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OMF files are an essential component for audio post workflow.   OMF or Open Media Framework is a file format developed by Avid Technology as a way to more conveniently transfer digital data.  It was originally released in 1990 and then updated in ’96 , it’s a standard and it’s a bit long in the tooth.  But we’ll get to that soon enough.

Simply put an OMF file is a digital container of all the audio files, edits, crossfades, pans and volume automation from your non-linear video editing platform.  It is a mighty handy tool compared to the old way of doing things. 

Here is a screenshot from Final Cut Pro.  You can see that there are eight tracks of audio, the top four of which are muted.

There is volume automation, panning information and a general temp mix in this edit timeline.  When we export the OMF from this timeline it will include tracks 5 – 8 only.  The OMF sees those muted tracks and leaves them out of the final export.  Most sound editors will want it all.  So I’d say unmute before the OMF creation.

Also a small FYI for those of you still using Final Cut 5 and below, the OMF is not a full spec OMF file.  It will not include volume automation, which if it’s feature length can create whole lot of extra work.  Not that you won’t re-mix from the ground up which is usually the case, but the temp mix can be a real time-saver for long projects.

I’ve also included a screenshot of the actual export of the OMF from the Final Cut Program.  Nothing fancy just a simple pull-down under File/Export – you can see – Audio to OMF.

You’ll get another dialog box after that which will give you a few options.  One is the handle length or the amount of audio that will be included on either side of any cut.  Handles are very important and contain loads of valuable information for a sound editor.  I generally ask for handles to be at lease five seconds if possible.  The default in FCP is 30 frames or one second.  Another option is to include volume automation and I would also add that functionality as well.  You can also choose to include crossfades which can be re-created by ProTools or the program that will be importing the OMF if they are not included.  There was a bug a while back in OMF exports that was related to crossfades.  This is no longer an issue.

What has just been detailed here is merely the mechanics of creating the OMF file.  As you can see it is a pretty simple and straightforward process.  Avid, FCP and other leading non-linear video editors offer some sort of OMF functionality and exporting them are all about the same process.  Make sure to mark an in and an out point create the accompanying movie file as well as the OMF from these same stop and start points.

Now that we have detailed the process of the OMF export what should be on the timeline in your non-linear video editor?  In my humble opinion, in a world of “less is more”, for audio post I would say that “more is more”.  If you have alt takes of lines, include them.  If you have roomtones include them.  Please.  Pretty please.

In fact I’m going to stop there.  Roomtones are a key component in audio post.  Period.  Notice the use of the word – key.  Not optional, not “if I can get to it”, not anything other than – key.  Not having roomtone is like writing without an eraser, a delete key or white-out.  Whoever digitizes the original camera tapes or dats will surely come across them.  Digitize them and stick them in a folder to give the sound editor or better yet as I advised cut them into your timeline and export them with the OMF.

I often ask the production recordist why they did not include roomtones and am generally told that they did indeed record them.  But somehow they never found their way to audio post.  So what happens to them?  They get lost in the shuffle with the mistaken assumption that they are not all that important.

In general picture editing gets a bit of time to complete their process.  Sometimes months and sometimes a year will be spent creating the final locked picture edit.  At the end of that they want the audio edited, mixed and output pronto.  So the best picture editors assemble their audio in a meaningful way to make the audio editors task simpler.  One thing that must be remembered is that all of that audio will be picked through, sorted, rearranged and cut to different tracks by the sound editor since it is their’s and the mixer’s job is to create a set of mix stems.  The editor had to create only one stem – a stereo temp mix.  And because of that many picture editors get lazy and just have their audio fall any where there is is room on an audio track.  This is fine for their temp mix but will not do to create a proper mix.  If Sound effects and music and dialog are all jumbled in the timeline – they will also be jumbled in the OMF.

Who cares?  “The audio guy will sort it all out ….”  The person who will care is the person who foots the bill.  Why?  Because they are going to be paying good money for studio time and an experienced sound professional to do basic housecleaning on the OMF.  It may sound minor but audio post deliveries are always tight and getting tighter and to waste a whole lot of time on things that have nothing to do with sound design and mixing is also a waste of the Producer’s money.  If you have a feature length project where the audio tracks were assembled willy-nilly it will take considerable time to sort out.    I have received OMF’s when opened reveal that the boom track and the lav track swap from take to take.  My job is to find “the best” sound and make that sound better.  If the boom sounds best then that means I have to audition and sort every single sound bite to determine whether it is the boom or the lav.  There may be thousands of these audio files in the timeline.  If the editor has diligently always put the boom on one track and the lav on another then he has cut my prep time considerably and I can concentrate on the task of making the movie sound even better.  Feel free to comment with questions since this is a huge topic that I’ve barely touched on.

One Comment

  1.   marc specter wrote:

    excellent site mr woody! Heres a list of my main dialogue editing pains, some frequent, some rare (unique I hope in the case of the first one):
    – boom combined with scratchy lav for unknown reason
    – no handles
    – no region naming
    – no sound reports/lined script
    – no room tones
    – unnecessary overlaps tainting otherwise useful dialogue
    -camera noise
    – dialogue too close to ‘action’ or ‘cut’
    I could go on for a long, long time. 🙂
    Sorry for the whinge I could also list the good things, but most of them can be summed up by ‘clear, clean and close dialogue on boom’. 🙂

    Monday, June 15, 2009 at 3:25 pm | Permalink