How MP4 to OGG Conversion Works
AnyTool converts MP4 audio to OGG entirely in the browser using a self-hosted single-threaded ffmpeg.wasm engine — the core (ffmpeg-core.js + the 32 MB wasm) is bundled from npm and served as a same-origin asset, so nothing is fetched from a CDN. The video track is dropped with -vn and the audio is re-encoded with -c:a libvorbis at a VBR quality (-q:a) setting, producing an Ogg Vorbis file. Because Vorbis is a lossy codec this is a true re-encode rather than a copy. Single-threaded is deliberate: the multi-threaded core needs SharedArrayBuffer + cross-origin isolation (COOP/COEP), which would block cross-origin ad iframes, so it is avoided.
- Runs client-side — the video is never uploaded
- Self-hosted ffmpeg core (bundled) — no CDN
- -vn drops video; -c:a libvorbis with VBR quality (-q:a)
- Lossy re-encode to Ogg Vorbis
- Single-threaded (keeps ads working); no backend, no cap
- Works offline after first load
