# fmp4 v0.1.0 - API Reference

## Modules

- [Fmp4](Fmp4.md): Reads the shape of a fragmented MP4 as ffmpeg writes it: the header (`ftyp` +
`moov`) and then `moof` + `mdat` pairs, one per fragment. A file still being
written is read as far as it is complete, so a playlist can be made of it
while it grows — which is how a conversion plays as it runs, with the server
spending a fraction of a core instead of an HLS segmenter's worth.
- [Fmp4.RangeFile](Fmp4.RangeFile.md): Serves a file to a video element with HTTP range requests, including a
file that is still being written. Any file: a fragmented MP4 a playlist
from `Fmp4.playlist/3` points at, a plain MP4, a Matroska release.