Thanks, that’s helpful. I suspect (though can’t yet confirm experimentally) that some added latency is the price for Audio Queue’s relative simplicity and ease of use. IMHO it would kick the most ass if it was possible to achieve as close as possible to minimum system audio I/O latency with SDL, but I also acknowledge that this is irrelevant for most SDL use cases, unless you’re trying to do something crazy like write a DAW that depends only on SDL.
If I can get some more substantive information on comparitive low-latency performance of Audio Queue vs. Audio units I’ll post that here just as an FYI.