ASIO vs WASAPI audio host?

I’m running Windows 10 64 bit, vers 1809/build 17763. I recently purchased a Behringer UMC202HD USB audio interface to do some recording with Audacity. Originally I believed I wanted the ASIO audio host for superior low latency and performance, so I went to the work of building my own version of Audacity 2.3.1 to include support for the ASIO audio host interface.

I subsequently installed the Behringer drivers for the UMC202HD, and discovered that that driver set supported not only the ASIO audio host, but also the Windows WASAPI audio host. Curious, I did some trial and error experimenting with both interfaces.

In that testing I determined that the WASAPI audio host provides lower latency that the ASIO host does - the WASAPI audio host requires -97 msecs latency compensation, whereas the ASIO audio host requires -102 msecs for latency compensation.

So both the WASAPI and ASIO audio interfaces provide similar latency performance (with the WASAPI interface actually performing marginally better).

So… is there some other advantage(s) to the ASIO audio host interface over the WASAPI interface that makes it worthwhile to perform the additional work of building an ASIO capable version of Audacity? Inquiring minds would like to know!


Behringer doesn’t supply true ASIO drivers.

ASIO drivers were originally designed for low(er) latency, but Windows drivers may have caught-up in performance since then.

If I understand correctly, ASIO drivers won’t resample so you can only record & playback at sample rates supported by the hardware. That can be a good thing or a bad thing. You won’t be fooled by resampling happening behind your back but some sample rates may be incompatible with your hardware.

I believe that interface has zero-latency hardware monitoring so you should be able to use a larger buffer and latency shouldn’t be an issue.