How to Sync Audio and Video (The Manual Way)
Most of the time, audio/video synchronization is not something you think about when you’re recording video, as the camera takes care of everything for you.
If you record your video and your audio separately, however, making them match up can be quite the challenge. Thankfully, we can draw upon the decades of expertise from Hollywood film editors, made much easier with modern audiovisual editing software.
Why the “Clap board” is Your Best Friend
You may not know what a clap board is by name, but you’ve certainly seen these iconic objects many times before.
They are the little black items that have scene information written on them, and with a yell of “Take!” and “Action!” the filming begins and the actors know to begin acting out the scene.
The clap board is not just an easy way to signal the start of action for the cast and crew. The sharp, piercing snap of the clap board has been a simple, yet invaluable, tool for film editors tasked with synchronizing the video and the audio for their movies.
How so? Most audio/video editing software displays a visualization of the audio. This can take on a bevy of different looks, but the most common is of a simple graph, with the sound appearing as a very busy wave snaking across a baseline.
In general, the louder the sound, the more that line will variate from the baseline.
This is useful for isolating individual sounds, and the clap board editing technique takes advantage of this phenomena.
That loud snap is very easy to see on such a visualization, not just because it will stand out on the graph, but because it will likely be at one end or the other of that graph.
If you do not have a clap board, clapping your hands is also a great substitute.
NEVER Use the Audio From Your DSLR Camera
In this example, there is a video file shot with a DSLR camera.
The DSLR camera is capable of recording audio, and has done so. However, the microphone on the camera is not very good.
The sound will be muffled, tinny, and if used in windy conditions, it will be plagued by clipping (that unpleasant effect you get with audio that is too loud for the recording device).
That is why this video was shot along with an external recording device.
That means there is a video segment that has its own audio accompaniment, but we also have a second audio segment recorded on the external audio recorder in higher quality, and the goal is to synchronize that with the original video segment.
Upload both the video and the external audio files into the A/V editing software of your choice. It doesn’t matter which, because they are similar enough for this simple task.
Synchronizing in your Video Editing Program
Obviously, the audio that is attached to the video needs to be replaced, but not just yet, because there is a use for it.
If you line up both audio segments together on the timeline, you may or may not be able to notice how similar they are, even though the original audio file probably looks messier and more clipped.
This is what the clap board technique is for.
Finding the spike on the graph where the clap sounds is not very hard to do, and this is the focal point you’ll use to synchronize. Once those are lined up, it’s easy to go down the rest of the graph and see how similar they are.
However, you will want to zoom in closely on the audio segments, so that you can make the most precise synchronization you can.
A delay of even a quarter of a second may not seem like much, yet be impossible to ignore in a finished product.
A bit of careful nudging can make all the difference.
Depending on the software that you are using, you may be a feature that automatically does this for you, but once you know what it is you have to look for, it is not difficult to get it right simply by eyeballing it.
Once you’ve achieved satisfactory synchronization, you can now discard the video’s original audio file and play back the new coupling.
If your video happens to feature scenes of people talking, watching their lips and listening to the words is a great way to tell how good a job you’ve done.
That’s all there is to it. Now, you’ve got the great audio to go with your great video!
How to Sync Audio and Video (The EASIER Way)
For a much easier approach on how to sync audio and video, there are two solutions:
If you are using the latest versions of Final Cut Pro X or Adobe Premiere CC, then we recommend trying out PluralEyes by RedGiant.
And if you’re using a simple editing software like Vegas Pro, iMovie, or even Final Cut 7 or Adobe Premiere Pro 6, DreamSync is absolutely the answer for you.
This little tool will save you tons of time in post-production and make it super simple to piece your audio and video content together.