Entrepreneur, music lover, player of video games, and futurist.
The number 1 thing people usually struggle with when setting up a dual PC stream is audio. Today I would like to give a really simple solution to this problem.
First of all, this method works for the capture card method. I have no experience with NDI. To do this you must have a capture card, and a program called Elgato Sound Capture (free).
Elgato Sound Capture allows your computer to output audio to multiple devices at once. By default windows will not allow this.
Output audio to whatever devices you want for your own use, PLUS the capture card you are using. Now all of your PC audio will output to the stream PC alongside the video in the same data output.