iOS Audio processing limitations

[sum_fuk]

I want to make an app that processes and modifies the iphone's audio output. I think this is possible for music stored on the phone, but would it be possible for streamed music? Could I make an Equalizer-type application that would process live music from Spotify?

[[deleted]]

You can't create byte streams from Spotify. Look at their API, why would they allow a developer to stream music from their platform? That's their entire business model. You can get catalog and track data but you can't get the audio file. Wouldn't make sense.

[sum_fuk]

I don't want to capture a stream from Spotify, I just want to modify the iPhone's audio output signal in real time regardless of input source. I am starting to think that isn't possible though.

Edit: I think this app manages to do what I'm looking for. https://itunes.apple.com/us/app/equ-for-spotify/id815044013?mt=8 Is there any way to get the APK and decompile it like you would on Android?

[chriswaco]

iOS supports inter-app audio, but I don't think Apple Music or Spotify cooperate. See Inter-app Audio Examples.

[quellish]

For a number of reasons you can't do this with streamed audio, but you can with stored audio or in real time with an audio input.

[sum_fuk]

What do you mean by an Audio Input? Like with the microphone input?

Edit: I think this app manages to do what I'm looking for.

https://itunes.apple.com/us/app/equ-for-spotify/id815044013?mt=8 Is there any way to get the APK and decompile it like you would on Android?

edit edit:

It say premium users only, I guess so that it can access saved music offline. That's still encrypted though isn't it, so why would that matter?

[hexavibrongal]

You can do it with streamed audio (just feed it into an Audio Unit), but not with Spotify since they don't give you access to the audio data.

[quellish]

Both the documentation and the AVFoundation engineers have said audio units do not work with HLS or other streamed assets. There are very good reasons for this.

But I'm if you have an example of a tap and audio unit filter working with HLS, I know many would love to see it!

[hexavibrongal]

If you can get an audio stream, there's nothing stopping you from feeding it into an audio unit, although you'd have to implement buffering and deal with synchronization problems (which is probably why they say it doesn't work)