AAF Import and Export: Pro Tools + Digital Performer, Logic etc

My goal is to hand off a Digital Performer Session to a Pro Tools studio, retaining as much as I can of the DP session. Handing off loose audio files is easy. Handing off those files arranged in a session file used to be very hard... Let's see if AAF makes it easier.

[ Keep in mind that all versions of Pro Tools must have the optional DigiTranslator ($495) or DV Toolkit ($1295) installed to be able to import or export AAF. ]

As an initial test of AAF's possibilities, I exported a live recording (straight multitrack, with no edits) from Digital Performer 4.61 to an AAF session, and then imported the AAF session back into DP. My test session is a 27 track, 24-bit, 2-hour live recording (27 GBs of audio). The live recording had a break in the middle, so there are two audio soundbites on each track, with no gap between them. Here's my report...

When DP exports an AAF session, you have a few choices. Here's a snap of the options I chose (not the default settings):

Note that the option "Export references to soundbites" is greyed out, it is not an option. (This seems only available during an OMF export, which uses the same dialog box.) Too bad, bacause it would make this process a lot quicker if the original audio could be referenced instead of creating all new audio files too. So, new audio files must be created. (And in this version of DP, they can only be WAV or AIFF, not SDII.)

I chose to export all of the audio files as individual WAV files (as shown, "copy all sound files"). One alternative during an AAF or OMF export is to embed all of the audio into one huge file. This might have benefits in a closed production environment, but I need to keep my options as wide open as possible. Not having independent audio files would severely limit the possibilities.

When DP exports to new audio files, it puts them in the same folder as the AAF session. So make a folder for your new AAF session first.

The export process took a while. My 27 GBs of audio (27 tracks of a 24-bit, 2-hour recording) took about 50 minutes to export. (Another 32 GB session took 75 minutes.)

Then, I opened the new AAF session with DP. It created a new DP session, and made fresh copies of all of the audio files as Sound Designer II files. (Since for some bizarre reason MOTU has still not made DP wav-capable.) This also took a long time, about 50 minutes. (The other, 32 GB project took an hour.)

I don't think my Mac's processor (G5 1.8G) was a major factor in the speed of these two conversions. I use MenuMeters to track CPU usage, and the processor was not maxing or even working that hard.

So it's important to make sure you've got enough extra disk space for the new audio files. In this test case, I needed three times the disk space (original, AAF wav export, DP sdII import). In normal use, you'll only need twice the space.

An interesting side note, it seems that the wav files are slightly smaller than the sdII files. But when DP recreated the sdII files during the import, they were almost exactly the same size as the originals, just a few bytes smaller.
Original: 906.1MB (950,088,030 bytes)
Wav: 903.7MB (947,619,515 bytes)
Re-imported sdII: 906.1MB (950,087,829 bytes)

Maybe the sdII file format has more header info than wav, but what's lost in translation?

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Results
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So, when the DP session went through the AAF export/import process, what was retained and what was lost? All in all it was perfect for my needs- a simple hand-off to a Pro Tools studio.

Keep in mind that I was just dealing with a basic 27-track, 24-bit live recording, with no fades, edits, plug-ins etc. Also, I'm not sure which stage (the export or the import) was responsible for these.

The basic items are retained:

Track names are the same.
Soundbites remain in place within each track, including sequential soundbites (from pausing recording during the live show).
Empty tracks are still there.

Some things ARE changed by the AAF export/import:

The session's bit depth setting was lost- the original was 24 bit, after export-import it was 16 bit. Don't panic: the audio files are still 24 bit. It's just the session setting, which is one click to change, but until you change it back, the 24-bit files won't play.

Most mixer settings: panning, level, plug-ins etc. This might be a dealbreaker for studios wanting to handoff a mixing project from DP to PT. But I'm just handing off simple live multitrack recordings, so I'm OK with losing these. An important question remains: which stage stripped this info- the export as AAF from DP, or the import of the AAF session back into DP? I'll investigate...

Tracks that were "hidden" (not currently showing in the expanded sequence window) become "visible", and other minor stuff like track colors are lost. No biggie.

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So, the bottom line for me is that AAF keeps the basics. Now I can hand off live recordings to the next stage of production (the mix studio) with a session that is much more likely to be opened up in their DAW of choice. They will be saved the hassle of setting up the right number of tracks in the right order, naming those tracks, and importing all the audio files.

Sure, there are other ways for them to save time importing without AAF, like QuicKeys, but anything I can do to save them studio time makes my work more valuable.

The only significant downside I see to AAF is that I have to plan for some extra time and disk space.

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Next time on... "Adventures in AAF"...
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• See how Pro Tools, Logic etc import these DP AAF exports and vice-versa.
• See if the new DP 5 changes AAF export/import.
• Experiment with other DP AAF export settings: "Enforce Logic Compatibility" etc.

A few random notes...
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From the Digital Performer 4.6 Read Me:

re MXF Import:
Pro Tools 6.9 has added the ability to export audio files in the MXF file format. As this is a relatively new audio file export standard, Digital Performer 4.6 does not open .mxf files.

re OMF/AAF Export options (Enforce Logic compatibility):
Logic supports embedded audio in OMF files, but not AAF files.

re OMF/AAF Export options (Embed audio data in OMF/AAF file
and Export audio data as SDII/AIFF/WAV files):
The update notes state that these will be grayed out if "Export references to sound files" is selected. They are in fact still available, and will be used for any audio that must be copied instead of references (such as fades, or audio that must be converted from 24-bit to 16-bit).

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OMF 2 can handle 24 bit audio, but OMF 1 can not. DigiTranslator 2 can do 24 bit/OMF 2, but DigiTranslator 1 does not.

OMF 1 Tool (precurser to Digitranslator) is free but only works with 16 bit files, and is OS 9 only.

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Pro Tools 7 LE can save a session as older versions of PT via the "Save Copy In..." (NOT Save As..."!) This can be helpful, because there are standalone apps out there that can read PT 5 and earlier.

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Release dates and versions for DigiTranslator:

12/01/99 version 1.0 (initial release)
04/05/00 version 1.0cs1 (maintenance release)
03/29/01 version 1.0cs2 (maintenance release)
05/10/01 version 1.0cs3 (maintenance release)
05/30/01 version 1.0cs3 (cp fix to cs3)

?/?/? version 2

I've learned a bit more about AAF from a contact at Digidesign, which spurred me to do more comprehensive research. I had been under the impression that some versions of PT could import or export AAF without additional software, but this is not true. No version of PT can import or export AAF without buying either DV Toolkit ($1295) or DigiTranslator ($495). (I have updated the above article to reflect this clarification.)

DigiTranslator is often on EBay (click here to search). EBay also sometimes has DV Toolkit (click here to search). But double-check the version #. Buying these used usually involves transferring a license to your iLok key. Or, you can go to any Digidesign dealer.

My new research has also shown that the next topic to learn about is AES-31, and in particular, AES31-3. AES31 is the official interchange standard of the Audio Engineering Society.

Here's a great article to get the background on AAF and AES31 (Nov 2002, by Ron Franklin):
http://www.mixonline.com/news/profiles/file-format-futures/374070

I consider that article to be "required reading" on this topic!

In summary, AES31 has four sections:

AES31-1 describes the audio file format (Broadcast Wave)

AES31-2 describes the disk file system (FAT32)

AES31-3 describes session interchange (Simple Project Format)

AES31-4 describes session interchange (Object-Oriented Project Format)

The AES31-3 standard is a free download, with examples (ie. page 33) here:
http://www.aes.org/publications/standards/courtesy.cfm?ID=32

AES31-3 and AES31-4 are two methods of achieving the same end goal: interchange of sessions. As I read it, they differ in how they are used by the manufacturer to develop product features.

OMF was object-oriented and not open source. It was difficult to develop, which limited it's adoption. Plus, it allowed for too many variations, resulting in inconsistent interchange and unpredictability. The worst of both worlds.

AAF is also object-oriented but is supposedly open source. The open-source-ness of it should have spurred development, but the object-oriented-ness of it has slowed development. And AAF is controlled by a consortium of companies, not an independent standards organization like the AES.

So AES31-3 development is not object-oriented. It's specifications are determined by the AES to ensure standardization, and it should be much easier for manufacturers to add to their products. It aims for compatibility with a narrow focus instead of a more complicated wide focus.

But to cover their bases, AES31-4 is there as an alternative with a wider focus (covering video etc.). As of the above 11/2002 article, the prediction was that AAF would be adopted as AES31-4. As of 5/2007, this still does not seem to have been settled.