CoreAudio: get bytes from audio stream

Hello,

After solving my first quest of macosx programming, thanks by this forum, I have to start a new thread with another subject...

I need getting audio stream from the default input (microphone or line-in) to process it (for example getting the signal volume) in a loop.

I don't need to store audio data after getting it.

I suppose that CoreAudio is the right place, but as a noob, I cannot understand how to accomplish it...

I would like to do it in pure C++, because this is the first part of a project that will involve OpenGL.

Could someone put me on the right way again

excuse me again if my english is bad...I hope is clear enough...

Thanks a lot!