How does an OS know which visual data from a browser is okay to share with a screen capture application, and which should be blacked out?

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Data passed to my physical monitors is separate from the data passed to screen captures. I am sure of this, because if I run a screen capture while playing a movie on chrome (but not Firefox!), most popular services will just show a black screen. This implies that visual data passed from a browser to your desktop is separate from the data going from your desktop to a screen capture application. But how? What are they doing to keep these separate? How does my OS know which data from the browser is fine to show to the screen capture program and which is not?

Another example of this phenomena is when certain less-than-ethical streamers use video game cheats that will show hidden player locations on their monitor's screen, but not to their audience on a live-stream.

screen-recording screen-capture live-streaming operating-system google-chrome
1 Answers

When you play video using DRM and encryption, the decryption of that video isn't capturable via usual methods. In fact, if done correctly that video will be encrypted all the way up to the monitor via HDCP. Reality is that the whole stack of components used for DRM is unreliable, so it's more common you'll just get lower quality video if your system cannot ensure encryption.

Some resources:

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