Cloudflare releases Streamline, an open-source playground for custom video pipelines

Cloudflare has released Streamline, an open-source developer platform that demonstrates how to build custom video processing pipelines using Workers, Containers, and Cloudflare Stream. The system allows developers to modify video in real time, supporting operations such as animated overlays, burned-in subtitles, and filters, with output published as livestreams or hosted video.

Architecture and Components

Streamline consists of two main components: a Media Engine and a controlling Application. The Media Engine runs in a Container to handle media input/output and processing (currently using FFmpeg), ensuring a lifecycle independent of the controlling request. The Application, built on Workers, manages session creation, configuration, and observation. Durable Objects are used for orchestration and preview relaying, allowing the media process to continue even if the controlling application disconnects.

API and Operations

Developers interact with Streamline via a high-level API exported as @cloudflare/streamline/client. Key methods include session.start() to define the pipeline configuration, session.ingest() to send video chunks (e.g., from a webcam), and session.annotation() to update overlay graphics dynamically. The system supports a fixed order of operations: filter (blur, saturation), overlay (images or PNGs), subtitle (burning in text), and encode. Preview video is delivered back to the application via WebSockets.

Security and Deployment

Security is integrated via Workers Access, ensuring only authorized users can create or control sessions. Stream RTMPS keys are stored as secrets and never exposed to the controlling application. Cloudflare has released the source code for both the Media Engine and an example application on GitHub, along with a public playground for developers to test the capabilities.