How to access FMOD banks in an install-time asset-pack on Android?

I’m working on a game in Xamarin Android (C#) where we have been using FMOD (2.0.9 since this is a bit long-going project, but I think this should not matter). We are trying to access FMOD banks that are part of an Android install-time asset pack (since they are over 150 MB, you need to do this to get them to Google Play). Xamarin Android’s AssetManager.Open finds the banks just fine with Open("banks/"):

AssetManager assets = mainActivity.Assets;
Stream s = assets.Open(fullsourcepath)

where fullsourcepath = "banks/". So I can for example copy the banks to a file, but this takes disk space. But when I call FMOD directly with

res = _system.loadBankFile(bank_path, LOAD_BANK_FLAGS.NORMAL, out tmpbank);

where bank_path = "file:///android_asset/banks/", I get a file not found error from FMOD.

To my understanding FMOD should supply “banks/” to AAssetManager_open in this case, which is probably exactly the same function call as AssetManager.Open in C#. I think this may have something to do with install-time asset-packs, but I’m not entirely sure, since AssetManager.Open in Xamarin works just fine.

I fact found out the reason: I had forgotten to add Org.Fmod.FMOD.Init(this); to MainActitivity.OnCreate. However, it turns out that streaming the voice lines etc. from the assets directory is hopelessly slow (maybe takes a 2-3 sec delay to load) compared to great performance if the banks were saved on disk. I will make another question on this topic.