End Google Ads 201810 - BS.net 01 --> How to acquire the sound signal from a 4-channel sound blaster?

I have a 4-channel sound blaster. I wanna to acquire sound signal from each channel respectively. Is there any advice for this prolem? Maybe WAVEFORMATEXTENSIABLE is one way to carry out the problem. However, it is very hard to find a example about it.

If you have any kind idea is ok, just tell me. Thanks very much.