I want load ogg file and then convert to memory wav.
Win api have function for this ?

I might using audacity and save ogg to wav. But 1 mb ogg sound 10 mb on wav.
I not want have big wav sound, ogg more comfortable.
Maybe someone has a code convert ogg to wav.

There were quite a lot of multimedia APIs in Windows. I’d say, a lot depends on the way you’re going to use the WAVE data. For example, if you just want to play it with waveOut*-functions, you’d better have a look at DirectShow (and let it do the whole decompression and playing magic on its own), whereas if you’re going to do complex processing… well, even in that case DirectShow or its newer super-modern-cool something Windows something Media something Foundation something might be a better choice.

BTW, if my guess is right and you don’t want to deal with object-oriented APIs like DirectShow and prefer waveOut-like APIs, I’d start with looking at acm*-functions. All of them might be deprecated by now but even these days Microsoft tries to do a good job in backwards compatibility, so they’re going to be supported for quite a long time.