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Video Sync For Audio Minds

A few tips for those considering a move into the video side

By Andrew Dawson June 14, 2012

Have you decided to take the big plunge into pictures by turning your once humble audio room into a full-fledged video facility?

Or perhaps you merely wish to have some basic audio-for-video capabilities so you can do audio for TV commercials as well as radio spots.

Either way, welcome to the world of synchronization. Despite what you my think about sync to picture, it isn’t as easy as it seems.

“Hey, I deal with timecode every day,” you say. Sure, in our own private world. The real challenge, however, is making your studio work with coming in from, and going out to, other facilities.

First, some questions to ask yourself before taking the leap. Above all, does the added income of work justify the expense of the new gear? Is there a video post demand in your city/locale? Are you going to add video editing capabilities as well? What will you say when the client wants you to edit out two seconds of the video—and they WILL ask that—what then?

If you really plan on doing video in house, be prepared to plop down at least the cost of a new SSL for a “decent” video-editing suite such as an Avid workstation?

An alternative is to find a local video studio, one that doesn’t do much audio, and buddy up with them. You throw them video work, they throw you audio—kind of and I’ll scratch your back and you scratch mine situation.

Here’s where you need to be prepared when dealing with video. What format is the client (or video house) going to give you: 24fps, 25fps, 29.97fps, or 29.97df ? What format is this intended for? What is the delivery medium?

From the point the material comes into your studio until point that it goes back out, there are a distressing number of things that can go wrong.

If I haven’t scared you away, I’ll get into the good stuff. FIRST LAW OF AUDIO TO PICTURE: When dealing with film/video, ALWAYS use 48k as your sample rate. Why should you use 48k? Because it’s the standard. If you try to take your project anywhere else, or get a project from anywhere else, you’ll be quickly grabbing for the aspirin if you’re working at the wrong sample rate.

When dealing with video, you must think of two sync signals: “speed” and “location”. Where are we (location)? How fast are we going (speed)? When dealing with SMPTE timecode in a purely audio world, SMPTE is both speed AND location. However, in video, SMPTE is “location” and video sync/house sync defines “speed”.

SMPTE contains the location, or address. Address answers the question, “Where are we?” How fast we get to where we are is determined by the frame rate. Common frame rates are 30fps (frames per second), 29.97fps, 29.97df (drop frame), 24fps, and 25fps.

For audio work, 30fps is the standard, and you (hopefully) will stripe your 2-inch and ADATs with 30fps when dealing with a purely audio session. Note that 30 fps is simply that: in the period of one second thirty video frames will pass.

However, the film standard is 24fps: in one second of film 24 frames will pass. Adding to the confusion, 25fps is the standard for most of Europe, Asia, and South America. (This 25fps standard is commonly referred to as PAL or SECAM.)

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