Cast Mirroring Component (//components/mirroring)

This component provides the service implementation and browser integration for Cast Mirroring.

The Mirroring Service runs in its own sandboxed utility process. It uses Mojo message pipes to communicate with the privileged browser process to:

• Acquire media inputs, such as screen capture video or tab audio capture.
• Communicate with remote Cast devices using Cast Channel messaging (see //components/cast_channel).
• Open UDP network sockets for Cast Streaming packets.
• Switch between screen mirroring and content remoting modes.

The Service encapsulates all session-management logic and interfaces with //media/cast to encode and packetize media in real-time. Through the ResourceProvider Mojo interface, it requests necessary resources (like GPU access, video/audio capture streams, and network contexts) from the browser process.

*** note For details on the Cast Streaming session protocol, see the Cast Streaming Specification in the Open Screen library.

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Directory Breakdown

• browser/: Browser-side implementation and integration. Additional browser integration code can be found in //chrome/browser/media/cast_mirroring_service_host.h and //chrome/browser/media/router/providers/cast/.

• mojom/: Mojo interfaces for communication between the Mirroring Service and the browser process (e.g., MirroringService, ResourceProvider, SessionObserver).

• service/: The core Mirroring Service implementation. This directory contains all logic for session management, media capturing, content remoting, and packetization. See the Service README for detailed information on internal data flow, session negotiation, and core classes.