Feedback from audio source on Android/iOS devices?

Question

Android

Good day.
A friend who does visualizations for music, among other things, asked me for advice and, to be honest, stumped me.
I must say right away that I do not develop for iOS at all, but I have a relatively distant relationship with development for Android.
The essence of the task in general terms:

1. You need to make an iOS application that runs on a tablet or smartphone. It renders a pre-created visualization (a video file, perhaps some kind of its own format - it doesn't matter yet), and broadcasts it to Apple TV. As far as I understand, it's not overly complicated.
   
2. Let's assume that the visualization is interactive. When working with a tablet / smartphone screen, you can, say, change the focus points for animation, or scroll it / adjust the speed of its playback. Again, intuition suggests that this is also feasible, although the complexity increases significantly.
   
3. The most important thing is feedback. Is it possible to make an iOS device receive a sound signal from an external source and render dynamic animation accordingly (like audio players like Winamp/AIMP do)? Without losing the opportunity to fulfill the previous two points.
   

The question is - how realistic is it to do and what are the potential labor costs?
Question 2 - how realistic is it if you use Android instead of iOS (respectively, you need to find an equivalent for Apple TV)?