Q I ran into a situation recently that has me a bit worried. I was shooting double-system sound, which I've done many, many times. I heard back from the person who was doing the post, and they were asking for some files that had already been delivered. At first, I thought I must have done something wrong. There does seem to be a sort of dance you have to do to make sure you don't mess up the file structure. But after a few phone calls, I realized that the problem wasn't with my video files, but with the audio. There were several audio files that wouldn't open. I'm not sure what happened, as I didn't have anything to do with that part of the production. It seems like missing or corrupt files might be a more common event. Are there things that people do to prevent this?
Via the Internet
A For those not familiar with the term, double-system sound is where the production audio is recorded on a device that's separate from the image-capture device. This method of sound recording was developed because film cameras weren't capable of capturing sound. Today's electronic cinema cameras are capable of recording sound. Even so, double-system sound may be used by the production sound mixer for a number of reasons:
• If you're shooting with cameras that have limited audio quality, like DSLRs, you might use double-system to increase the audio recording quality.
• If you're shooting multiple audio sources, you might exceed the number of channels that the camera can record.
• If the camera is located a distance away from the audio mixer, like on a crane.
• If you're shooting with multiple cameras.
In analog days, the audio recording device was a portable reel-to-reel tape recorder like a Nagra. These days, it's usually a file-based audio recorder. The audio is recorded to a hard drive or memory card. If recorded to a hard drive, the files are transferred either to a memory card or to another storage device via a cable.
At the beginning of each recording, a clapper (usually on the top of a slate) is used to create an audio and visual cue that's used to line up the video and audio. In postproduction, the audio and video files are then synced.
That's how it's all supposed to happen. But the files—video and audio—need to make it to the edit suite in good condition. By good condition, I mean without losing any digital bits.
If you talk to any digital imaging technician (DIT), you'll hear his or her methods for making sure all of those files get to the right place. It's a bigger challenge for a DIT than the production mixer because the file sizes are greater. So the DIT needs to move files off of the recording media cards so the cards can be reused.