How to use portAudio to read audio data output from sound card?

Question

I was wondering if it is possible to read data that is going from the sound card to the speakers with the PortAudio API. After looking through the documentation, I found an example (http://portaudio.com/docs/v19-doxydocs/paex__record_8c_source.html) where they read data from the microphone. However, I would like to be able to capture the audio that is coming from the sound card. Is there a way to do this in PortAudio and if not please point me in the right direction. Also, it is important that this works on Windows, Mac, and Linux computers and I would prefer to write this in C.

Answer 1

This cannot be done. Someone recently submitted a patch that allows this to be done on one of the windows APIs, but that is a special case, and you would have to ask on the mailing list.

It cannot be done cross platform from a simple, single library. For example, on OS X, you need to install special system extensions (or whatever they are called).