Is there a way to capture the audio outputted by only a single application, and not the system as a whole? With WASAPI I can capture the entire system audio, but I wish to only capture the audio from one application (there will be many applications, all playing audio at once.)
Detours is used for hooking. Using the lib to hook IAudioRenderClient interface, including GetBuffer and ReleaseBuffer, and read data from the buffer.
Depending on the APIs used by the application to play the audio, you could write an AppInit DLL that will wrap the built-in waveIn\waveOut functions and would pass along the audio data. I know this works with the waveIn\waveOut functions, but not sure what other audio playback interfaces there are on Windows 7 and whether they are compatible with the AppInit trick.
来源：https://stackoverflow.com/questions/6084550/capture-audio-of-a-single-application-on-windows-7