[AAX] Idiosyncrasies of ProTools/AAX Audio Processing?

I’m sorry if this question is a bit vague, but i’m having a problem right now that seems to be related to some quirks in the way ProTools handles audio processing.

Just as an example of an idiosyncrasy from another DAW, Reaper has an “anticipative fx processing” option that causes problems for my setup.

Some quirks i’ve found out so far:

  • blocksize is always 1024, no matter how i set the hardware blocksize
  • when measuring the time between calls to processBlock, the time is sometimes faster than expected

To give you a bit of background and a brief description of the problem, I have an experimental setup where i’m exchanging data between two audio applications over a shared memory ringbuffer. One application is the DAW (and the plugin), the other application is a generic audio application, and the exchange is only in one direction, the DAW plugin only writes and the other application only reads.

Now, this works fairly well (surprisingly) from most DAWs, but ProTools seems to block the reading applications’ audio thread, causing glitches. I’ve currently no idea why this happens, i’ve tried several sync mechanisms, but that doesn’t seem to be the problem.

Thus, I’m looking around if there’s any other ProTools oddities, whether it’s resource handling, anticipative processing, etc.

Does anybody have a hint ? Any information appreciated …