Library 
This is not related to ExoPlayer.
This builds some of the extensions from source code. This is primarily used by Voice
Install
repositories {
maven { url "https://jitpack.io" }
}
dependencies {
// important: add the core dependency and set transitive to false on the extensions
implementation 'com.google.android.exoplayer:exoplayer-core:2.X.X'
implementation "com.github.PaulWoitaschek.ExoPlayer-Extensions:extension-opus:X.Y.Z" {
transitive = false
}
implementation "com.github.PaulWoitaschek.ExoPlayer-Extensions:extension-flac:X.Y.Z" {
transitive = false
}
}