Multiple SoundCard Inputs

I tried searching, but I couldn’t find the answer/solution if this can be done.

I’m interested in recording multiple sound card inputs (external usb mixer and a-likes) and/or the external sound card input and the internal sound card output both at the same time into a wave file.

I found no easy way of doing it until I stumbled upon the JUCE library which might seems like it is advanced enough to do just that.
Though I failed to understand where to start from nor could I find any examples to show me the way.

Any comments/ideas/examples would be greatly appreciated.

You can certainly use juce to open multiple audio devices, but the tricky bit would be syncing up the incoming data. AudioIODevice is the place to start.