How to Take Advantage of SamsungVR’s Quad-binaural Audio Format for 360 Video
A guide to help you showcase your 360 video with spatial audio
A few weeks ago I wrote an article about how to prepare audio deliverables and achieve the best quality spatial audio for YouTube. I highly recommend you read that first, as a lot of the first-half of that article makes sense here in regards to what you should be asking your audio team to deliver back to you.
Today, I want to dive into one of my favorite spatial audio formats: quad-binaural. To my knowledge, I think SamsungVR is the only major 360 video platform supporting it, which is a shame for two reasons:
- It sounds incredibly realistic.
- It has almost no compute overhead, making it an idea choice to maximize video quality or take advantage of streaming.
The concept behind quad-binaural is that you record four pairs of binaural audio for each direction (often referred to as North, West, South, East) and the software cross fades between them based on the direction your head is turning. To my ears, it’s very accurate and sounds particularly good for live music.
One of the best microphones I’ve used with this audio format is Hear360’s 8-Ball. It’s what they refer to as omni-binaural — meaning it captures 360° of sound, but really it’s capturing four pairs of high quality binaural microphones arranged to give a very accurate sound. We record it to a Zoom F8 recorder and the best part is that we don’t need to do any post-processing in order to use our files. All we need to do is to sync it up with our video, make sure the odd track numbers (1, 3, 5, 7) are panned left and the even track numbers (2, 4, 6, 8) are panned right.
Pro Tip: If using FCPX, you can assign roles to your stereo pairs to make output a ton easier. The way the 8-ball records is tracks 1–2 are North, tracks 3–4 are West, tracks 5–6 are South, and tracks 7–8 are East. Assigning roles allows you to do all sorts of cool stuff such as turning on and off directions when you are checking your work, to easily outputting your stereo binaural pairs (more on that shortly).
So, how do we go about preparing files for SamsungVR?
Output the Binaural Stems
Before we marry the audio with the video track, we’ll need to get the North, East, South, and West binaural stereo files generated. There are a few ways to do this.
- Use the Facebook Spatial Audio Encoder to convert your 8 channel .wav master to Quad-Binaural.
This will output four audio tracks labeled with degrees (0, 90, 180, 270).
2) Use the roles feature in FCPX to discretely output your audio channels separate from your video. Share your master file and in the settings tab, choose “Roles as Separate Files”. Then add your four stereo audio files and select the correct roles for each.
Use iFFMPEG to Join the Audio & Video
The next step is to marry the audio and video. For this, I use iFFMPEG. If you are on PC, there is a something called myFFMPEG or if you are a command line lover, by all means use FFMPEG in all it’s geeky glory.
We’ll bring in our H.264 audio file that we’ve already compressed according to these specifications. Set your container to .mp4 and your video file to “pass through”.
Then we’ll bring in our four audio tracks. The order here is very important.
- North (0 degrees/Front)
- East (90 degrees /Right)
- South (180 degrees/Rear)
- West (270 degrees/Left)
The default settings of AAC in iFFMPEG work well. Then hit play and watch it marry the files together. This should all be really fast.
Upload to SamsungVR
When uploading your video to SamsungVR, it’s important that you select binaural and not quadraphonic. Our audio is still binaural, there are just four channels for complete 360 coverage.
If you are sideloading your content onto your Samsung GearVR, you’ll place your video into a MilkVR folder and be sure to add “_binaural” to the end of the filename so that the app knows to decode it correctly.
So there we have it! Hopefully this quick walkthrough helps you showcase your 360 video work with spatial audio on SamsungVR’s platform. You can check out a project we did with this technique on SamsungVR. To experience the spatial sound, you must watch in a headset.
Bonus tip! The guys over at Midnight Coffee Creative have put together an iOS app for VR that not only is a great way to showcase your work to clients running iOS, but also supports both the Facebook 360 audio format, AND quad-binaural (through technology provided by Hear360.io). If you are in the market for a custom app, I’d check them out. We recently had them code Light Sail VR an iOS app and we’re loving it.
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