how_to_setup_code.txt

Install Windows 10 SDK and at least Visual Studio Express 2019

The directshow baseclasses example is no longer part of the Windows SDK. Get
the samples by cloning https://github.com/microsoft/Windows-classic-samples 
to D:\build

mkdir D:\build
cd /d D:\build
git clone https://github.com/microsoft/Windows-classic-samples

Build directshow baseclasses from the SDK: 
Open 
D:\Build\Windows-classic-samples\Samples\Win7Samples\multimedia\directshow\baseclasses\baseclasses.sln
in Visual Studio, let Visual Studio upgrade the version and build
it (all combinations Debug x86, Release x86, x64... especialy for the platform you want to build 
audio_sniffer.dll for).

Clone the virtual-audio-capture-grabber-device repository

cd /d D:\build
git clone https://github.com/rdp/virtual-audio-capture-grabber-device
cd virtual-audio-capture-grabber-device
git submodule update --init --recursive

then open the visual studio project file \source_code\acam\acam.vcxproj 

let Visual Studio upgrade the version and build it.

It outputs a .dll file that you "register" via (in administrator console) 
$ regsvr32 XXX.dll (and unregister when you're done with regsvr32 /u XXX.dll)

In essence this is the "WASAPI loopback" sample
https://blogs.msdn.microsoft.com/matthew_van_eerde/2008/12/16/sample-wasapi-loopback-capture-record-what-you-hear/

combined with the "capture source filter" http://tmhare.mvps.org/downloads.htm but with many improvements :)

So go to those two to learn the basics.

This is meant to provide a "directshow filter" you can use in your graph, not a demo of how to do graphs.