Why auto-scroll video capture fails when page, compositor, and encoder run on separate clocks

A developer building an auto-scroll screen capture tool discovered that the browser page, display compositor, and video encoder each operate on independent timing cycles, making synchronization difficult. Attempts to force a single shared clock worsened recordings, causing visible jumps when large catch-up scroll steps were captured in a single paint frame. The encoder produces variable frame rate WebM output tied to actual screen paints rather than a fixed metronome, which many players interpret as stutter. Fixes included capping catch-up scroll steps, preserving sub-pixel remainders to avoid staircase artifacts, and dropping resolution instead of demanding higher frame rates from an overloaded encoder. The key insight was that live capture must follow the compositor's natural cadence rather than imposing an artificial frame rate at the recording layer.