Reducing audio file size ADPCM, plugins, etc.

This “Audio Files” section about Unreal Engine 4…WAV/index.html
says “Specifications PCM, ADPCM, DVI ADPCM”

I’m pretty sure the original Unreal engine supported ADPCM. It is 25% of the size of PCM (aka 4-bit). I did a quick test and CD audio sounds pretty much the same to me. The point is that I want to use some kind of compressed audio format (rather than about 10 Mb/min). I tried IMA and MS ADPCM but UE4 converted them to raw uncompressed PCM.

I tried installing the FMOD plugin but couldn’t get it to work. Are there other plugins that could be used? Ultimately I’d like to use OGG but I’d also be pretty happy with ADPCM.

It looks like in the Unreal Engine 4 source code, there is ADPCMAudioInfo.h !!!

How can I use it?