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Note that stream transcoding on server is enabled when stream published as H264 is played as VP8 and vice versa.
11. When playing WebRTC broadcast in Firefox on macOS Catalina, displayed system warning and block on playing H264 stream.
Symptoms: when playing WebRTC broadcast in Firefox on macOS Catalina, displayed system warning "libgmpopenh264.dylib" was blocked from opening because it is not from an identified developer" and block of playing H264 stream.
Solution: Firefox uses a third-party library unsigned by the developer to work with H264. In accordance with macOS Catalina security policies, this is prohibited. To add an exception, go to System Preferences > Security & Privacy > General > Allow apps downloaded from > App Store and identified developers> "libgmpopenh264.dylib" was blocked from opening because it is not from an identified developer" > tap Open Anyway.