I have an installation project (Unity) that runs in 5.1 in the venue, but needs a stereo version for documentation purposes. What’s the best way to turn a 5.1 mix into stereo via FMOD? My group channels and spatializers are all 3D/5.1, my master is set to “platform (5.1 surround)”.
Is all I need to do setting my “speaker mode” in platform settings of the Unity integration to stereo and adjusting my group channels levels if needed? Will the panning then just work as before but in stereo? My content is just mostly game objects passing left and right in front of the static camera/listener, but in the 5.1 also going through the center of course. I am trying to avoid artifacts from the downmix. Just setting to stereo as explained above did not sound bad in my initial test but I am wondering if it s the proper way to do it.
Bonus question: What happens if a 5.1 FMOD mix/project is set to stereo platform, is it just applying gain factors to the channels, if so which factors to which ones? Because we already capture the 5.1 audio to wav and our stereo mix does not need to be realtime and can be done in post, I might as well keep FMOD to 5.1 only. And later do the stereo downmix in a DAW using the same channel factors as FMOD does based on the captured 5.1 wav file. This would keep our FMOD versioning etc simpler. or is there some FMOD magic happening that would be lost here?
There are multiple different ways to do this, each with its own advantages and disadvantages. Which of them is “best” is subjective.
The method you’re currently using is extremely easy to implement. However, the downmix from 5.1 channel format to stereo channel format may result in a slight increase to the output signal volume, and the changes to panning may result in the sound’s panning being slightly muddier than would otherwise be the case.
Another option would be to create a second platform in the “build” tab of FMOD Studio’s preferences dialog, and set that platform’s surround speaker mode to “headphones.” This automatically sets every spatializer effect in your project (as well as every bus with the “platform” channel format) to use a stereo channel format while that platform’s banks are loaded. Because this method spatializes your audio in a stereo channel format to begin with, it eliminates the need to downmix from 5.1 channel format to stereo and the disadvantages of doing so; however, because the headphones speaker format assumes a 180 degree separation between the two speakers rather than the ~45 degree separation between the left/front left and right/front right speakers that’s more common in other speaker channel formats, the resulting output may be distributed differently to what you expect.
I recommend testing these options to see which best fits your project’s unique requirements.
You can read about how different speaker channel formats are upmixed and downmixed to other speaker channel formats in our documentation on the topic. In the specific case of downmixing a 5.1 surround signal to stereo speaker channel format, the left speaker channel receives the full signal of the front left speaker and 0.707 times the signal from both the center and back left speakers, and the right speaker channel receives the full signal of the front right speaker and 0.707 times the signal from both the center and back right speakers.
Thanks very helpful advice. I set the FMOD integration in Unity to be “multi platform” so I can have the stereo Build and the 5.1 built at the same time. I then built for all platforms from FMOD studio so stereo and 5.1 banks are in seperate subfolders. However, I can only add one Windows build via the Unity integration. Once I add one and set it to be my 5.1 folder, I can not add a second Windows build. Am I missing something?