mp4-muxer

jMuxer - a simple javascript mp4 muxer that works in both browser and node environment.

Lightweight local-first desktop app for Windows/macOS: Visual SRT timeline editing, local speech-to-text, and lossless multi-track MP4 subtitle embedding without re-encoding.

Design a spinning vinyl record label in the browser and export it as MP4, a seamlessly looped GIF, or self-contained embed HTML. Vanilla JS, zero runtime dependencies — hand-rolled MP4 muxer and GIF encoder included.