Streamline: custom video pipelines with Cloudflare Stream and Workers

This post introduces Streamline, a new developer playground for building custom video pipelines on Cloudflare's Developer Platform. It details the architecture involving Cloudflare Containers for the Media Engine (using FFmpeg for processing) and Workers/Durable Objects for the controlling Application. Key technical contributions include: overriding `onActivityExpired()` in Containers to maintain long-running media processing, a session-based API (`@cloudflare/streamline/client`) for controlling pipelines, support for RTMP and HLS inputs, and the ability to update annotations dynamically. It also outlines the configuration structure for defining input, operations (e.g., overlay, encode, subtitle), and output.