Synchronising a GoPro HERO 9 and an audio interface with an iPad and a metronome app

If you shoot video with a camera and an audio recorder without either having a built-in timecode generator and/or genlock feature, you will know what a pain it is, because you always end up with synchronisation problems. The advice usually is that you need to spend your money on a timecode generator and preferably one which also has genlock (that’s the feature that ensures your devices stay in sync). What if you don’t have the money or want to spend it on a couple of Tentacle Syncs or Denecke Syncboxes? Here’s a solution for footage of under 20 minutes long.

Your GoPro doesn’t have timecode; heck, it doesn’t even have a port that allows you to hook it up to a timecode generator. Your Mac doesn’t know about timecode either and I don’t know of many audio interfaces or recorders that sell for under 500 EUR.

Yet, although your HERO’s microphone is capable of a decent quality of sound, it’s always better to record audio with a proper mic on a proper sound recorder. It just sounds better. So, here is what you’ll need and do when you want to sync the sound and frames on your GoPro with sound recorded to an audio interface like a Focusrite Scarlett, an Apogee Duet — or Element 24, which is my setup.

I’ll be assuming you are recording a presentation for YouTube or similar output medium.

CAVEAT: You should be willing to Set the GoPro’s “Anti-flicker” setting to 50Hz. None of this will work with your GoPro set to 60Hz — I tested this out with 60Hz thoroughly and it always fails!

What you’ll need

  • A Mac (or a PC, but I only have experience with a Mac, so with a PC you’ll have to fill in the blanks yourself).
  • An audio interface with at least two microphone inputs hooked up to your computer.
  • A GoPro HERO 7 or later, preferably with the Media Mod.
  • Two microphones to hook up to the audio interface on your Mac, of which one has a directional shotgun-like pickup pattern (which means not a lot of sound is picked up from the sides and back of the mic). I personally find the sE Electronics V7 equipped with a Dynamite or T.N.T. pre-amp an excellent and inexpensive option.
  • One microphone to hook up to the GoPro — this is optional; it makes things easier, but your GoPro’s internal mic will do fine as well. If you do use one, it doesn’t have to be directional. It’s even better if it’s not.
  • An iPad, iPhone or other tablet and a metronome app (my favourite is Polynome because it allows you to choose the sounds it generates yourself from a large number of them).

What you’ll do

Set up your two mics that connect to your Mac DAW or recording app. I prefer to use Audio Hijack as it gives you plenty of flexibility and many sound quality settings. Put one of the mics as close to your mouth as possible (mic 1) and turn up the audio gain for optimum capture of your voice.

Put your smartphone or tablet with the metronome app as far away as you possibly can from where you are going to be talking in the first mic. If you don’t have a mic to connect to your GoPro, then make sure the device with the metronome app is as close to the GoPro as possible with the mobile device’s speakers turned away from where you are going to be talking as much as possible. Set up the metronome app so that the mic you’re talking into barely picks up the sound.

Put the second mic (mic 2) connected to your audio interface right besides the metronome output and set its gain to a good level (-18dB is OK).

Put the GoPro-connected mic (mic 3) close to the metronome and make sure the camera picks up the sound from you talking as well as sound from the metronome. The latter should be louder than your voice.

Timecode with metronome: instructions

The idea is that you’ll record your voice with mic 1, and the metronome with mic 2 and mic 3. In your NLE, you’ll then put the audio from mic 1 and 2 on their own tracks. When you start your video, clap your hands so you have a clear starting point to synchronise from.

For a video recorded at 50fps, you’ll set the metronome to a beat of 150bpm. For video recorded at higher speeds 300bpm is the best setting.

The best is to start by turning on the metronome, then start your GoPro and finally start the audio interface recording. That way, you can drag the audio tracks in your NLE along the video track which will be longer.

Look at the three tracks and find the clap signal. It should show up as a clear peak level, often with the sound going in the red. Cut and drag the audio to where the clap is and sync with the video. Then check further down the footage if your audio is drifting away from the metronome. If it is, you can correct by cutting a few frames.

I have tested this process with a 17 minutes recording and there was no drifting. With the GoPro set to 60Hz, though, drifting occurs after only a few minutes and renders the entire process as much a pain as not having any synchronisation at all.