Also, I don't know how native dsound / xaudio are implemented on Windows, but it would be weird if that was using some direct driver interfacing these days bypassing WASAPI, maybe using something undocumented there of course which we are not aware about.
Hmm, it seems you're right, that's also suggested by Microsoft's documentation: https://learn.microsoft.com/en-us/windows/win32/coreaudio/user-mode-audio-co...
Still, either they're using some private interface, or I can't see how they're doing format support checking, given that `IsFormatSupported()` is both documented and tested to always return false if channel count or sampling rate is different from the mix format, and it has no flags to alter its behavior.
Did you test all the same with audio IAudioClient3? It might behave overall different in theory.
You mean calling, say, `IAudioClient3_Initialize()` instead of `IAudioClient_Initialize()`? I can test that, but shouldn't they point to the same code in theory? Is it common to have the same method implemented differently in the subinterface and superinterface?