Preserving Avid Sound Work in Pro Tools

I recently co-supervised the sound editing on K-19. This was my second OMF show with Walter Murch, who does very elaborate sound work that he wants presented at the mix. Although it's been four years since my first OMF project, I found that the interaction between Pro Tools and Avid is still not as smooth as many had hoped it would become. OMF makes possible things we couldn't do with EDL assemblies, but getting everything we want is still time-consuming and complicated. I'd like to share some information about the process we

All the sound work done by picture editors shoul

used on K-19, and how it helped solve some of the shortcomings inherent in OMF work.

Open Media Framework Interchange (OMFI or OMF) is a file format that Avid created to exchange edit information and digital media files between different types of workstations. There are two flavors of OMF files -- "composition with external media," which is preferred by most feature and television sound editors, and "composition with embedded media." This second option creates new media every time you do a cut, which cannot be referenced later if the cut is revised. As a result, it is of limited usefulness. (Final Cut Pro currently supports only "embedded media," but Apple is apparently planning on changing that in the near future -- editors should keep the pressure on them to do so!)

There are many benefits to using OMF, but only if the Avid audio is a high-quality transfer of the production audio (preferably a D-to-D copy of original digital sources). If the audio in the Avid is the result of several analog generations, we'll have to use the old EDL method to reproduce it in Pro Tools; but if it is of high quality and loaded correctly, then the picture editor's work can be preserved. This saves time and money in sound editorial and mixing, but it adds costs initially for the picture department. The net result is probably a cost savings to the production, but since picture comes first, producers may view the extra steps needed to load good audio as an unnecessary cost. The picture and sound departments need to work together to convince them of the eventual savings and other benefits of this process.

There are several ways to get high quality audio into the Avid, including the use of a digital (i.e. "magless") dailies system [see our July/August 2001 issue] or by loading audio from DAT and syncing in the Avid. These methods require careful setup, and picture assistants who haven't used them before should do some research before starting such a project. It is very important that each audio take is loaded as a separate media file. If entire sound rolls are loaded as audio master clips and then broken into subclips for Avid autosyncing, it causes problems for the sound department --regardless of how small a piece of sound we need, we have to use the entire sound roll, and it is also more difficult for us to set up a database.

Ideally, the sound department should be in touch with the picture department and the production sound mixer before shooting begins to discuss loading methods (there are sometimes hidden analog steps the picture assistants aren't aware of), sample rate and bit depth.

Unfortunately, Avid doesn't yet support 24-bit audio, which both Pro Tools and many digital production recorders can handle, and this creates yet another hurdle. We have developed a workaround, but the picture and sound departments must work out the process before shooting begins. Basically, the 24-bit production sound files are converted to 16-bit for import into the Avid; the original 24-bit files are then sent to the sound department. A naming convention must be established to ensure that the 16-bit and 24-bit files have the same names. When we get an OMF, we link what was cut on the 16-bit files in the Avid to the 24-bit files in the production sound library. This method was refined and used successfully by Roy Wauldsberger on The Shipping News and thoroughly discussed in the February issue of Mix magazine. But isn't it time that Avid handled 24-bit audio, so that we can avoid yet another convoluted and potentially problematic procedure?

Early in an OMF job, even before the sound crew starts work, the picture assistant needs to copy all the audio media from the Avid to the sound department's drives. This will be much easier if the picture department has consistently kept all audio media separate or on separate drives. Then simply doing a Finder copy will give us what we want. Once the initial turnover is complete, the Avid assistant should isolate all media digitized or created after the turnover date and periodically send us updates.

Next, we need a set of OMF compositions containing all the production master clips so that we can build a database for the OMF library. It's not enough to send us cut sequences with all associated media. We want all outtakes, as well. In fact, the outs are a secret weapon for sound, allowing us to fix, repair and smooth tracks in ways that the picture department can't. To give us all the source sound tracks, the Avid assistant typically creates a series of sequences that contain every clip from the sound rolls, generally putting about 10 sound rolls into each sequence. These sequences are exported as OMF files, which we convert to Pro Tools sessions and export lists. This allows our database to link the regions (clip names) to the sound files and their paths (what folder on what drive).

One problem is that Avid sound files have ridiculous names that don't make sense, full of numbers and letters. Fortunately, working with two talented sound editors, Phil Benson and Eric Dachs, we have developed a database that enables us to search for takes by their clip names instead of filenames. If you're a dialog editor looking for an alternate take, you can audition all the takes in that scene and mark the ones you like, then the database will copy the desired files onto your cut drive and import them directly into your open Pro Tools session. (Eric has incorporated this into a robust post-production intranet solution. It was used on Panic Room and hopefully will soon be available commercially. Meanwhile, e-mail me if you're interested in acquiring it for your show.)

There is also an Avid console command ("RenameMediaFiles") that is not supported by Avid but is well known to some picture assistants, which allows you to rename all the media files with names constructed out of a show name prefix, the audio ch#, and the master clip name. Then we can look at the file and know immediately what take it is. Many assistants are nervous about doing this, because it irreversibly renames all the audio media and is unsupported by Avid. It generally works without problems, especially if it is applied to clips before they are used for editing, but assistants should seek the guidance of someone who has been through the process before trying it. [See the topic "Changing Media File Names" on the Guild discussion groups for more information.]

After setting up the library and database, it's important to do a test reel. Get an OMF composition and a videotape with guide tracks of the test reel, as well as a track assemble list so that you can make sure you received everything that was in the Avid sequence. Go through the same process as you would with an actual reel to check that the system is working correctly.

Walter Murch does a lot of careful sound work in the Avid, including EQ and other effects to get takes to match. Unfortunately, much of this is missing after the conversion to Pro Tools. Even though Pro Tools and Avid use essentially the same AudioSuite plug-ins, effects don't get translated at all, and the sound crew just receives the original unaffected clip. Even worse, clips that have pitch or time compression or expansion effects on them often disappear entirely after OMF conversion and we have to manually find and assemble the clips that have disappeared. Walter does keyframe volume automation (rubber-banding), in addition to clip-based volume automation, and rubber bands also don't translate. According to Digidesign, with the recently-released Pro Tools 5.1.3, DigiTranslator 2.0, and Avid version 10.1 or later, volume automation is properly translated and AudioSuite effects are handled better than they were in the past. Unfortunately, many editors are still working on older systems.

All of the sound work that Walter has done on the Avid needs to show up at the mix, especially the temps, when there is no time to redo work that has already been done elsewhere. For the final, we also want the unprocessed and unmixed versions of everything, as well.

Once the editor is ready to turn reels over to sound, we'll start getting OMF compositions for each reel and any new media to add to the library. I usually work in the Bay Area, while picture is edited in Los Angeles. If there isn't a huge amount of media, we'll use a secure FTP site to transfer the files because it's so much faster than shipping. (I compress both compositions and media with StuffIt to avoid corruption.)

The picture assistant first makes a regular OMF of all tracks in the reel for sound (we call it the base OMF). To do this, first select the sequence in your bin. Then choose Export from the Avid's File menu and select options for OMFI 2.0, SD2 files and separate media for each (Figure 1). (In version 7.x, you'll notice that the "With Media" checkbox is both selected and inactive. This is the Avid's strange way of indicating that the OMF composition you're creating will reference copies of the media files on the Avid, which is what we want.)

Media Composer Version 7, this OMF will ignore AudioSuite effects. The solution is to render them -- but in Pro Tools, the rendered version will no longer contain any reference to the original, unaffected track. We need both the Avid-effected clip and its source, so that we can do additional work on it. The result is that the picture department must do two OMFs, one normal, and one with rendered effects. The picture assistant typically isolates clips with effects on them by copying them to separate tracks and then deleting all other tracks from the sequence. These effect clips can then be rendered and sent to us as a separate OMF, along with all rendered media.

With recent software versions, AudioSuite effects are imported with a choice: We can have either the underlying clip or a rendered version of the affected clip -- but not both. Digidesign says that pitch and time effects no longer disappear during import, but I don't have first-hand knowledge of this.

Finally, we need the original tracks used in any mix-downs or renders that the editor has already done, which often requires some nifty detective work by the picture assistant. Most of these mix-downs and renders wouldn't be necessary if the Avid didn't have decade-old track and performance limits based on outdated CPU and drive speed issues.

Once we have downloaded everything from the FTP site and copied it to our OMF library drives, we use DigiTranslator to convert the OMF compositions to Pro Tools sessions (Figure 2). Since it's easier to use Session Browser to locate the media, hit Skip when asked for media; DigiTranslator will generate a list of missing media, which we generally ignore. We then have Session Browser resolve the sessions to the OMF library drives, which will reveal any missing media (called "unresolved files"). Then we'll get the missing files from the picture department and copy them to the library drives. When all the media is there, we use Session Browser to archive the reel to a cut drive (if we aren't cutting on a network).

For subsequent delivery of changed reels, we use the same process, but resolve to the cut drive for that reel instead of the OMF library drives. Session Browser will then generate a list of needed media (Figure 3), which we copy from the library to the cut drive. If the media doesn't exist in the library, we get it from the picture department.

Finally, we have all the media for that version of the reel on the drive -- but it doesn't end there. This is only the media that the Pro Tools session knows to look for. What about clips that did not get translated from Avid to Pro Tools via OMF? Those, we have to find the old fashioned way --by listening!

So far, we have two sessions for each reel -- the base and the rendered session. We combine these into one session with all rendered material going onto tracks called rendered 1, 2 and so on (Figure 4). The editor will now have both versions to work with and they'll both be present at the mix.

But before editing can begin, the dialogue assistant will listen to the session with the A guide track (which should have all the production sound and only that) on one side of headphones and the OMF production tracks on the other side. They will note footages and descriptions of anything on the guide track that is missing in the OMF, then call or e-mail the picture assistant. Often, it will be clips that had an effect, usually a pitch shift or time compression or expansion, though at times there seems no logical explanation for clips that were rendered but are nevertheless missing. In those cases, we get a timeline screen shot or assemble list of the rendered sequence so we can see footages for missing elements, then call to see what media was supposed to be at that footage. We often have this media, but the session did not know to look for it. Eventually, we get the missing pieces sorted out, and the session is finally ready for the editor. This is a time-consuming and extremely frustrating dance that we have to do every time we receive a new version of a reel.

Walter will lock the picture and (usually) the production tracks a few days before a temp, so that we can go ahead with our OMF session preparation. He will then continue to work on editing and mixing the music and some effects in his Avid. He will probably finish the last reel the night before the mix. As he finishes a reel, his assistant will bounce the music and effects tracks to preserve Walter's keyframe volume automation and EQ, then put the sound files with footages on the FTP site. We'll then download them and spot them into the Pro Tools session.

The next day, when Walter sits at the console to do the temp mix, all the work he's done on the Avid is playing out of Pro Tools. He has all the benefits of random access, and the ability to further split, smooth, slip or tweak, under the microscope of a mix stage, without having to waste time trying to recreate what he spent precious time and energy doing on the Avid.

We should be able to achieve these results without all the time and energy described above. With post budgets constantly shrinking, it's a waste of valuable resources to spend hundreds of man-hours and thousands of dollars, not only in sound and picture editorial, but also in wasted stage time, doing unnecessary work that would be eliminated if only OMF worked as promised! I think I speak for many sound and picture editors when I say that Avid (and Apple) should address these issues now. All the sound work done by picture editors should be easily translated into Pro Tools without a fight and it should be just as easy to move Pro Tools sessions back into the Avid, as well. Newer versions of Avid and Pro Tools systems are supposed to address some of these issues. I hope they work in the real world as advertised, and I look forward to finding the OMF process simpler and more reliable on my next show.

Larry Schalit is a Bay Area sound editor whose credits include Bandits,
The Talented Mr. Ripley, AI, Cast Away, Fight Club and Chocolat.
He can be reached via email