Recovering lost audio from a computer crash while recording

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Joined: 02/12/2009

Quick note: This is a method which has worked for me. Since lost recordings are such a mission-critical topic, I take NO RESPONSIBILITY or support for this. Use at your own risk. If you're reading this at all, you're likely desperate enough to try anything. But this method works best if you prepare for it beforehand. Good luck!

I do live recordings. There's a very good reason why nobody wants to do this kind of work, because it is a house of cards. Any one of dozens of pitfalls can ruin the whole project. This article describes one of the worst, a computer crash during a recording. It also applies to a surprise power outage. All may not be lost, but don't get your hopes up.

Summary:
I bring two drives (or two partitions on one drive), and record to the smaller one. If there's a crash, switch to the big one to continue recording. Then, after the show, dig out the remains of the pre-crash recording from the first partition, using the method described below.

[edit 8/2005: This first method is for an OS 9 crash. See the next post for an OS X crash. See the third post if you crash in OS 9 AND have OS X too.]

This example is with Digital Performer in Mac OS 9, your system may vary:

When you first hit "record", your audio recording application grabs the whole hard drive, divided up into the number of record-enabled tracks. If there's a hard crash or a power failure, those huge temporary files are never closed because the "stop" command never happened. For example, the temp files may be 2 Gigabytes each. (The file size limit of many older systems is 2GB.) Some software allocates on-the-fly, so the whole drive's space might not be taken up after a crash.

To understand what's in these temp files, a little background is necessary. When a file is deleted, it isn't actually wiped from the drive. The Operating System just removes the pointer to the file. The space taken up by the old file is now available for future new files. Until something new is written, the old file's data is still lurking there.

So if there is a crash while recording, the temp files will contain pieces of whatever was in that space, interspersed with your recording up to the point of the crash. If your drive was used exclusively for audio recording (which it should be), you'll also find a hodgepodge of previously deleted audio and random noise.

In Mac OS 9, post-crash files will appear in a folder called "recovered items" in your trash. (I welcome feedback on other OSes.) It's very important to get these files out of your trash immediately when you reboot. Otherwise you might delete them, so DON'T EMPTY THE TRASH until you pull these files out.

If you open these files in your audio editing application, it will take some time to search through them. You might find a few minutes at a time of various recordings, hopefully including your new recording. A little cut-and paste and you might reassemble your lost recording.

Once you’ve reassembled things, bounce these clips to disk as new files. Then you can throw out the huge temp files.

To make things easier on you in the future, set up your drives so that you record on your smaller drive (while still being big enough for your recording of course), then use the bigger one to make a backup copy of your recordings. If you reinitialize the smaller one occasionally (or even after every recoding), there will be fewer ghost recordings lurking.

It's not perfect, but it might save your butt.

Related links:

Silent Way's Ultimate Track Sheet and Digital Audio Hard Drive Storage Calculator

Back That Mac Up (and that PC too): Simple cheap backup tips

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Joined: 02/12/2009

It took a while, but I finally had an OS X crash during recording, so now I can report on the OS X version of the method to pull your fat out of the fire.

Unlike an OS 9 Digital Performer crash, an OS X DP crash doesn't create huge files which take up most of your disk. In OS X, the files are only as big as they would have been had you stopped recording on purpose.

This OS X method is similar to the OS 9 method, but there are a few key differences.
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First emergency response: Do nothing until you can attempt recovery. Don't record any more to that drive, don't restart, and don't empty the trash! If you can, try recovery first. If there is another crash/power outage, your recovery chances get slimmer!

DON'T EMPTY THE TRASH or restart until you recover these files! To play it safe, don't do any more recording on that drive, because the temporary files won't be there for long. After a restart, they may get moved to the trash:
http://docs.info.apple.com/article.html?artnum=11280
http://docs.info.apple.com/article.html?artnum=301913
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This example comes from Digital Performer 4.5, running in OS 10.3.9. The user is "503".

[A quick note on user names and IDs: In OS X, you're familiar with being identified by name, but in the underlying Unix subsystem, users are known by number, based on the order the user account was created. So the first user account is "501", the second account is "502" etc. All pro recording Macs should have a dedicated user set up for recording sessions, with all the bells and whistles turned off. In the following examples, the user is "503".]

Instead of OS 9's "recovered items" folder, recovered files are put in an invisible directory here:

Root level of the session's drive (NOT necessarily your user's drive/ boot drive)-->Temporary Items-->503-->Temporary Items

That's not a typo. There is a sub folder within the user "503" which is also called "Temporary Items".

Check the size of the "Temporary Items" folder at the root level, which should not be invisible. It might show a significant size... there's something in there! The next step is to peek inside.

The trick is that the subfolder is invisible. You need to change it's visibility and then restart (or relaunch the Finder). There are a few different ways to do this.

The easiest seems to be TinkerTool. TinkerTool can switch ALL invisible files to become visible (careful not to screw up other important system files- switch back after you're done):
http://www.bresink.com/osx/TinkerTool.html

Another application to try is called Invisible Finder. It allows you to browse folders and change their visibility. It's less user-friendly than TinkerTool, but allows more precise control of what's turned visible:
http://www.ragesw.com/invisiblefinder.php

Another one which looks good, a Contextual Menu called Folder Contents CM:
http://www.naratt.com/FolderContents.html

If you are experienced with the Terminal, that can do it too.

Remember that depending on the method you've used, you'll probably have to relaunch the Finder to see the visibility changes. Use Command-Option-Escape to relaunch the Finder. But be careful not to restart if there is a "Recovered Items" folder in the trash. (Restarting the computer is different than relaunching the Finder.)
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In another example, I had a situation with multiple power outages during a recording, and I didn't have time to attempt recovery until a day later. Instead of finding the audio files in Root-->Temporary Items-->503-->Temporary Items, I found them in "Recovered Items" in the Trash. Because the trash is user-specific, the audio didn't appear to other logged-in users.

So the moral is to attempt recovery ASAP, with minimal restarts, logins, etc. And don't empty the trash!
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Once you've found the files, copy them ASAP to another location, preferably on a different drive.

The next step is to make sure those files are readable audio files. In my case, because of the crash Digital Performer wasn't able to properly create the end of the files. So they needed to be re-imported into Digital Performer.

Each file had a generic name, such as "Take4-1089465748" instead of the proper name. The "Take4" matched the analog input #4 on my MOTU 896HD. That shows which file belongs on which track. I just dragged them back into the session and waited for a minute as DP imported the file (it made a new copy in the session's Audio Files folder).

Also, be careful because all these orphaned files might not be of equal lengths, which makes it harder to line up in your session.
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More on invisible files:
http://www.cnet.com/8301-13727_7-10344207-263.html?tag=mfiredir

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If you need a much more advanced service for recovering lost files, here's my discount code for the Drive Savers service:
http://www.silentway.com/node/1212[/b]

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Joined: 02/12/2009

I've discovered another method for recovering "missing files". This method is for a crash in OS 9. You need to boot into OS X or mount the drive with an OS X Mac. Then use one of the ways listed above to find the recovered items in this invisible location:

(Root level of the drive)--> Trash -->Rescued items from(name of the drive)

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