Hi there-
Sounds like you’re working on something exciting in the audio game genre- can’t wait to hear about it :). UE4 currently does not have a function like Audio.GetSpectrumData, but we are working on a similar feature for the engine. Alas, I don’t know if and when it will be ready for release, so it will likely not be a help you on your current project.
The engine also currently only supports PCM .wav file import, 16 bit up to 48khz. When these .wav files are imported into the engine, they are converted to different platform-based formats. For the PC, the .wav files are converted to Ogg Vorbis format; you can then set an Ogg encoding quality on each asset.
Hope these answers at least clarify the current audio pipeline; we are constantly working to improve it. I’ll mention the Audio.GetSpectrumData request, and see if I can’t get that prioritized :).
Best-
Zak