Al,
We thought that AVAudioEngine is too complicated for our task, without examples of the code on FPC.
I saw that you tried to use Audio Queue Services.
Do you know, Audio Queue Services is NOT deprecated yet, right?
If I understand rightly, Audio Queue Services (or AudioToolBox in general) are base for OpenAl and AVAudioEngine. So Apple should not deprecate this low-level audio API.
We have all sound processing with buffers (volume control, fading, dissolves) in a cross-platform code. And we simply need to organize a queue of sound buffers for a playback of audio from memory buffers. We use FFmpeg to decode various audio formats.