Hi! According to the User Manual, “if you set your FMOD Studio project to be 5.1 Surround, but the player only has stereo speakers, FMOD automatically maps the outputs to the two available speakers”.
So I have a question regarding this topic.
I tested downmixing in FMOD Studio and in Unity with FMOD plugin, and I got really different results there. As far as I understand, in Unity, FMOD downmixes 5.1 to stereo according to the ATSC standard, using this formulae:
Lo= L + C/sqrt(2) + Ls/sqrt(2)
Ro= R + C/sqrt(2) + Rs/sqrt(2)
But in FMOD Studio I got different results. First of all, all sounds that have been placed behind the listener, (from -180° to -90° and from 90° to 180°) downmix in antiphase. For example, when sound was placed at 180° degrees, two channels had the same amplitude, but one of them had reversed phase.
Also, somehow, sound from Rs exists in L output channel and vice versa.
So, my questions are:
What downmix formulae does FMOD really use?
Shouldn’t the differences between downmixing algorithms in Studio and in the Engine be considered a bug, and why is there such a difference?