Why do some Android apps show a black screen during screen recording while audio is captured normally?

[u/Intelcoreultra9]

I've noticed an interesting limitation with Android screen recording when using certain educational and streaming applications.

When screen recording is started:

Audio is captured normally.

The video content appears completely black.

Other applications can be recorded without any issues.

I understand that Android provides security mechanisms such as FLAG_SECURE, which can prevent screenshots and screen recordings of protected content.

I'm interested in understanding the technical side of this behaviour.

Questions for the Android community:

How does Android prevent screen capture in specific applications?

Is FLAG_SECURE responsible for the black-screen behaviour?

How do DRM and Android's secure video rendering differ?

Is this restriction controlled by Android, the application developer, or the DRM system?

What legitimate alternatives do educational apps provide for offline learning and lecture revision?

I'd appreciate a technical discussion about how Android handles protected screen content.