Libav-wasm NPM

LibAV WASM

This library can be used to remux from MKV -> MP4, it could technically do any remux but i haven't had the need for it, create an issue if you'd like it.

src/test.ts Contains a full example of a MKV video player

Basic usage

const remuxer = await makeRemuxer({
  // the path at which the wasm file is getting served
  publicPath: new URL('/dist/', new URL(import.meta.url).origin).toString(),
  // url of the worker file of libavWASM
  workerUrl: new URL('../build/worker.js', import.meta.url).toString(),
  // reads are done in 2.5mb chunks
  bufferSize: 2_500_000,
  // byte length of the video file
  length: contentLength,
  // fetch returning a ReadableStream
  getStream: async (offset, size) =>
    fetch(
      VIDEO_URL,
      {
        headers: {
          Range: `bytes=${offset}-${size ? Math.min(offset + size, contentLength) - 1 : ''}`
        }
      }
    ).then(res => res.body)
  ,
  // callback where you'll receive the subtitle chunks
  subtitle: (title, language, subtitle) => {
    // console.log('SUBTITLE HEADER', title, language, subtitle)
  },
  // callback where you'll receive the attachments
  attachment: (filename: string, mimetype: string, buffer: ArrayBuffer) => {
    // console.log('attachment', filename, mimetype, buffer)
  }
})

// Returns a chunk that looks like {
//   isHeader: boolean,
//   offset: number,
//   buffer: Uint8Array,
//   pos: number,
//   pts: number, // timestamp
//   duration: number
// }
// buffer can be appended to the MediaSource API(MSE API)
const chunk = await remuxer.read()

// allows you to seek to timestamp and start reading from there
await remuxer.seek(number)

await remuxer.read()

Intellisense

To have C++ autocompletion, put a ffmpeg repo clone folder in the root git clone https://github.com/FFmpeg/FFmpeg & git clone https://github.com/emscripten-core/emscripten