问题
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.
回答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).
来源：https://stackoverflow.com/questions/14333752/how-to-use-portaudio-to-read-audio-data-output-from-sound-card