all apis i'm familiar with (asio, jack, portaudio) provide api functions that can query the driver to get the input and the output latency ...
Wow, that's great. But it seem to easy to be true :-) Do they really provide the delay between start of playing a buffer and start of appearing the analog signal at the output?
in theory .... yes ... they also provde the delay between the time, a signal appears on the input and the time it's sent to the software ...
I use Hammerfall/Digiface with some attached D/A-Cs. Do the driver know what's the latencies of D/A-C, especially if connected to a digital sound card output, like mine? Or do the API just deliver the value what can be set in settings of the Hammerfall "Buffer Size (Latency)", which, unfortunately, is not the latency between the software layer and analog output.
i doubt that the hdsp would know about the attached hardware and their latencies ... but it should be possible to query the driver for the specific digital ports and read the specs of the dacs you're using for the additional latency ...
cheers ... tim