Optimal setDSPBufferSize parameters for PSVita

I’m hearing some crackle when playing ordinary one-shot sound effects like a button press. I have experimented with setDSPBufferSize to different values and can certainly make the crackling -worse- doing this, but… what -should- they be?

My situation:
Running on PSVita - fmod studio - 1.06.17
All my source assets are 44.1 khz
For the vita build target they are all FADPCM @ 22.1 khz
Frame rate varies between 10-60 (but the intention is that it will be 30, and it is 30+ in the specific situation im testing) (this also corresponds to the frequency that ‘fmod update’ will be called).

News update:

I set up the simplest test case possible.

The only thing loaded is the master bank and one other bank that contains a couple non-streaming sounds. I press a button, it plays one sound. Nothing else is going on. It is running flat out at 60 fps, with a timer verifying that < 20 ms is elapsing between fmod update calls.

Yet I am hearing some poping sounds at random points through the duration of the sound effect (~50% of the time it sounds normal) (the poping seems to be more frequent towards the middle/end of the sound, might not ever actually occur right at the beginning, but i can’t really say definitively).

Any ideas what this could be? Or how do I diagnose? Because I’ve tried twiddling every fmod parameter i could find with no effect other than sometimes making it pop more. So I think i’ve exhausted my ability to find this through trial and error.

I also tried changing the compression type and bit rate on the bank and rebuilding it, also to no audible effect.

See below answer Any luck playing the event in our examples? If you still have trouble please contact support@fmod.com.

I found that the particular devkit I was testing on was the problem - running on a different device, a testkit, the audio sounded fine.

The optimal DSP buffer size for PS Vita is 4 buffers of 512 samples, this is the default.

Issue resolved, suspected faulty devkit.