Ok. I didn't check the docs so far :) Well in that case they must be doing a sAPO (as already pointed out) although its been said several times on this list that hooking your own sAPO toa generic audio device via registry hacking (i.e. not via the driver .INF file) is a big NO-NO according to official MS policy.
I'm not sure what they are doing, but I don't think they have patched in an sAPO.
I plugged in a USB audio device after TotalRecorder had already been installed and it captured audio played back to that new device also. It would be pretty tricky to have the sAPO approach work for this case.
They claim they are using a "kernel mode filter driver". Searching on that term leads you to some general MS descriptions of a filter driver being an optional component that you can create that sits between the kernel level standard driver and the higher level calls for the purposes of adding additional functionality.
But the examples all seem to be for general purpose file reading and writing, not audio systems.
Is it possible that there is an undocumented method for adding a "filter driver" to the windows audio system and these guys figured out how to do it?
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