I would also add that if you are recording and streaming a lecture in a hall with a screen and speakers, you need to make sure your system sound output is the hall's screen (not "OBS Audio Capture"), make the hall's screen the target of "Fullscreen Projector (Preview)" in OBS, and make sure none of your sound sources in OBS have the output muted. I bring two small monitors to the hall. I start the Powerpoint slideshow in presenter's view, using one of the small monitors as the target screen and the other as the preview screen. Then I bring OBS to the front, and put its control window in front of the Powerpoint preview window, but make it small enough so that it lets me see my presenter's notes. To advance to the next slide, click on the other small screen. OBS should remain in front of the preview screen while you click the other screen. And of course, in OBS, you need to do a window capture of the Powerpoint window. Using the above setup, any audio in your Powerpoint slideshow should output to both the hall's speakers and your stream. Your mic will pick up the sound from the speakers, but so far I've had no problems with that. It took me six weeks to get this right.
