With video, an hour of shooting (or less) might fill up a card, where-as with audio, a day’s worth of work might fit in the same space. Even so, the production mixer needs to make sure the files make it to the right place.
In the problem you mentioned, it wasn’t a matter of missing files, but corrupt files. There are many reasons a file can become corrupt. It could have happened during the initial recording—particularly at the end of the recording when the file is officially "closed." It also can become corrupted during file-copy procedures.
One technique to avoid problems during the initial recording is to make sure the recorder has adequate power. This means avoiding plugging in to power that’s coming from generators or that’s used for lighting. It might mean using batteries—batteries that are in good shape with a significant charge. (Don’t try to eke out the last few milliamps. It’s not worth it.)
But those are common-sense suggestions. With file copying, some similar common-sense recommendations also pop up: Adequate power and attention to detail are just a couple ideas.
By attention to detail, I mean pay attention to what you’re doing. A friend recently told me about a post session that was delayed a day because the shooter thought he was copying his files to a hard drive attached to his laptop, but instead copied everything to his laptop’s desktop.
Keep people away from your equipment. Some connections like USB and FireWire (and even card readers) often aren’t the most mechanically secure connections. Moving a cable during a copy procedure may cause some transfer errors.
Another suggestion is to use a more robust file-verification system to do your copying. Computer operating systems do some file checking after the file has been transferred, but the verification isn’t as thorough as that of a third-party application.
One popular application is ShotPut Pro, which allows you to make verified copies of files (www.imagineproducts.com). Besides being able to deal with all sorts of directory structures created by cameras like the ALEXA and DSLRs, several levels of verification include byte-by-byte comparison. It works well with audio files, too.
While I’m on the subject of double-system sound, I thought I’d mention syncing using software. Singular Software’s PluralEyes software uses a sophisticated waveform-matching algorithm to line up the production audio files with the reference audio recorded with the video files. The PluralEyes software works with most popular editing applications.
Note: Remember that you need to record audio on your video files. The better the quality, the more success you’ll have automatically syncing the files. You might ask why someone would use PluralEyes with an application like Final Cut Pro X that has built-in syncing. PluralEyes allows you to sync in multicam situations, requires less preparation and allows you to sync multiple video takes across a single audio roll. Their DualEyes product allows you to do your syncing before you get in to edit. Check out the Singular Software website at www.singularsoftware.com.