SD2 File Recovery: A Problem We Have Solved
Using a modern Pro Tools setup (on either Mac or Windows) you might run into problems opening sessions created in the 90s to early 2000s (PT 1 through PT 8) on Mac System 7.x, 8.x, OS 9.x, or OS X 10.0.x-10.4.x which may report missing audio files. Even after searching and locating the files on the hard drive, Pro Tools will often still be unable to bring them into the session.
This happens because Sound Designer II (SD2) files, the default audio file format for Pro Tools 1 through 7, stored critical metadata (sample rate, bit depth, and channel count) in the Mac resource fork. When SD2 files are transferred through non-Mac file systems (FAT32, ExFat, NTFS, cloud storage) without being zipped first, this metadata is stripped away. The raw audio data survives, but Pro Tools cannot identify or play the files without the metadata.
Deep Signal Studios has developed proprietary tools to solve this problem. We can extract the sample rate and bit depth from Pro Tools session files and use this information to rebuild the resource fork metadata on every SD2 file in the session. We have successfully restored sessions containing thousands of damaged SD2 files. Typical turnaround is 48 hours.
What We Can Recover
| Pro Tools Version | Session Extension | Session Recoverable if the files left the HFS/HFS+ file system? |
SD2 Files Recoverable? |
|---|---|---|---|
| PT 3, 4, 5 | none (Mac-only) | No (data stored in resource fork) | Yes, as WAV files |
| PT 5.1 | .pts | Yes | Yes, fully restored |
| PT 6 | .pts | Yes | Yes, fully restored |
| PT 7 | .ptf | Yes | Yes, fully restored |
| PT 8 | .ptf | Yes | Yes, fully restored |
| PT 9+ | .ptf/.ptx | Yes | N/A (uses WAV or AIF formats) |
When can PT 3/4/5 Sessions Be Recovered?
Pro Tools versions 3, 4, and 5 stored all session data entirely in the resource fork. The data fork of these files is completely empty, 0 bytes. If these files pass through a non-Mac file system, the resource fork (containing 100% of the session data) is discarded. There is nothing left to recover. If they were always on a Mac, they will be fine and they can be fully converted to the current version of Pro Tools.
The SD2 audio files from these sessions can still be converted to WAV since the raw audio survives. However, simply converting SD2 to WAV does not restore your session. The session file contained all the information about where each audio file sits on the timeline, which portions of each recording were used, what edits were made, and how tracks were arranged. Without the session file, you would need to either manually relink each WAV file in a new session and guess at their placement on the timeline, or start over with raw recordings. If you have hundreds of audio files, this becomes impractical. If the sample rate is unknown, common values are 44100 Hz (CD quality) or 48000 Hz (video standard).
Why PT 5.1-8 Sessions Can Be Recovered
Starting with Pro Tools 5.1 (released 2001-2002), Digidesign moved session data from the resource fork to the data fork. This was done to support Windows, which has no concept of resource forks. As a result, PT 5.1 and later session files survive transfers through non-Mac file systems with their session data intact.
When a PT 5.1-8 session and its SD2 files are transferred incorrectly:
- The session file loses its resource fork but retains all session data (tracks, edits, regions, automation)
- The SD2 files lose their resource fork metadata but retain all audio data
- We extract the sample rate and bit depth from the session file
- We rebuild the resource fork on every SD2 file with the correct parameters
- The session opens normally with all audio relinking automatically
This is the key advantage of our recovery process: we use the original session file to restore the SD2 files with the correct parameters. The session retains all track assignments, edits, regions, fades, and timeline positions. Once the SD2 files are healed, Pro Tools recognizes them and relinks everything automatically with no manual relinking or guesswork required. If you have Pro Tools 5.1 or newer we can restore your session to any Pro tools session version (5.1 .pts, PT 6/7/8 .pff, PT 9/10/11/12+ .ptx) with the audio files aw WAV files which will not only allow you to open and work on the session but also prevent it from being damaged again in the future.
Pro Tools History
Over the years, Pro Tools has released many versions of the software, ranging from HD (aimed at the professional market) and more basic versions like Pro Tools SE and LE. In 1995, AVID acquired Digidesign and over the years, Pro Tools has gone through many changes, including dropping TDM and then RTAS plugin support formats, introducing the AAX format in Pro Tools 11, and also changing the native audio file format from SD2 to WAV while AIFF remains an option.
Pro Tools, originally named "Sound Tools" was first launched in 1989. At that stage it was a basic audio editor for stereo files. After further enhancement, a new version of the program was developed and renamed Pro Tools, which offered 4 tracks of digital audio recording. Digidesign continued to enhance the Pro Tools software, added a MIDI sequencer and multitrack recording at 16-bit / 44.1 KHz. By 1997, Pro Tools reached 24-bit, with support of up to 48 tracks. Since the late 1990s Pro Tools has become the industry standard for disk-based digital audio recording. Pro Tools files on OS X and Windows can be identified by the file extensions .PTS, .PTF, and .PTX. Pro Tools on Mac System 7.x, 8.x, and OS 9.x have no file extension.
We can also convert Pro Tools sessions made in 10 or 11 to PT7, PT8, or PT9 sessions. In addition to repairing and restoring Pro Tools files, we can convert your Pro Tools projects for use in other 2024 DAW formats including Logic, Digital Performer, Cubase, Ableton, GarageBand, or any other DAW or sequencer file format you wish by exporting each track as a .wav file. We can retrieve sessions from Jaz, Zip, DDS tapes, or DVD-RAM.
Please read these details on the right way to transfer old Mac files to a modern computer while keeping the resource fork intact for the purpose of emailing a download link to us so we can convert them.
If your Pro Tools session files have one of these icons below that is visible in current macOS (or still using a machine from that period) they, along with your SD2 files, will probably be OK as long as you zip them. Pro Tools Windows session files will not have any of the above problems.
