You can already do this in UE4. I added support to get a delegate callback from an audio component to get the playback progress percent. This is only guaranteed to be accurate currently on PC, other platforms use the “app clock” which obviously is not sample accurate. For the new audio engine, this is implemented so will work on all platforms. As I said in a previous post, if you want to get ultra-accurate, you’ll be able to make a source effect and setup a timer/scheduler, etc.
I have some ideas with how I might bring audio-sample accurate timing to BP but it’s tricky since BP runs on the game thread. I think it’s possible though and with the new audio engine, I’ll be able to do stuff like this with more efficiency since I only need to think about it and solve it once rather than re-approach the problem differently for each platform.
Right out of the gate though, any audio event that is triggered on the same game frame is gauranteed to happen at the same time in the audio thread. That alone has dramatically improved efforts to write procedural music. Robo Recall uses a music stitching system written by our talented Seth Weedin in BP that does plenty of beat-matching, loop splicing, etc. It’s a pretty sweet system and works great in the new audio engine. The day we turned on the new audio engine btw, Seth was extremely excited because of the automatic timing improvements. The shakiness of the old audio engine was such that they were on the verge of cutting his painstakingly authored BP music system but the new audio engine saved it 