March 2014

Audition Video Audio Sync

How to sync audio tracks recorded separately to your video tracks so that the audio from both the camera and your recording match up.

In the March issue’s “Lights Camera Audition” article, we talk about getting good sound for video. The best way to do this is to use plug good mics into your camera and place them close to the source—in this case, the person auditioning.

But what can you do if you don’t have access to a camera that can work with good mics? You can record sound separately on an audio recorder that either has built in mics (place this close to the source) or one that can accept input from good mics (for example, using music software and an audio interface). Either way, you’ll need to sync it to video after the fact.

In order to do this, you can use audio software that supports video—which is a common feature found in programs ranging from GarageBand to Pro Tools, Cubase, Ableton Live, Logic, StudioOne, Cakewalk, and others.

You can also use any video editing program that allows multiple audio channels, such as iMovie or more advanced software like Final Cut and Adobe Premier.

Either way, your goal is to the start time of both recordings so that the sound plays in sync. Here’s an easy way to do it.

1. Save every take as a separate recording on both the video camera and the audio recorder. Label the takes so that your sure which audio goes with which video.

2. Hit record on both devices and create an audio mark by clapping or using another percussive sound. Percussive sounds will show up the audio track display of both the video editor and the audio editor. Do this for every take.

3. Once you choose a take, load the video file and the audio file that goes with it into your editing software.

4. Make sure the software is set to show audio waveforms. If possible, trim the audio waveform so that it starts right on the clap. This can make it easier to match the two audio tacks.

5. Using the clap as a guide, slide the audio waveform over so that the clap in the audio lines up with the video. Start by zooming out to get close, then zoom in to get as precise a match as you can.

6. Play the video and mute the video’s original audio track, and check your work. If the audio sounds a bit out of sync, you can move it back and forth one frame at a time (this command is often called “nudging”) until it lines up. If you feel like it’s still off, turn on the original audio and check it. If it’s off by more than a few milliseconds, you’ll hear an echo. If it’s slightly off, you may hear a sweeping sound. If it’s on, the sound should be similar to what you’d hear from two microphones recorded at the same time.

7. Once you’ve got the video and audio lined up, play with the mix a bit: sometimes, a little ambience from the camera’s mic can sound good mixed with the a close mic from the audio recorder.

9. Use your software to export a new version of the video with the new audio track in place. Then save the original audio and video files in case you need to go back to them later. Check the resulting video. If it matches, you can now use this to do any additional editing (such as trimming excess at the beginning of the video, adding titles, etc.).

The following video offers a tutorial discusses some of the options, problems, and their solutions.