WebCodecs Packages

Record MediaStream to MP4, Use Webcodecs API encode VideoFrame and AudioData, [mp4box.js](https://github.com/gpac/mp4box.js) as muxer. 录制 MediaStream 到 MP4，使用 Webcodecs API 编码 VideoFrame、AudioData，mp4box.js 封装。

Build bleeding edge video processing applications

A bridge between libav.js and WebCodecs, to allow easier decoding of files demuxed by libav.js

A WebCodecs polyfill (ponyfill, really), using libav.js