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Recovering lost audio from a computer crash while recording
Mon, 12/13/2004 - 12:48
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.
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.