AVGuesser

This is an extremely simple utility for guessing the filetype of audio/video files. It can identify all common audio/video formats (including image formts) and is extremely tiny.

The goal of AVGuesser is simply to be a tiny “step zero”. Paired with libav.js's modular builds, you can use this tool to choose which demuxer to load, then load the appropriate demuxer without loading every other demuxer. Because it pairs with libav.js, all¹ names are in libav.js format.

¹ With the exception of image files, which are supported in weird ways in libav.js anyway.

Using AVGuesser

Slice the first 12 bytes off of the file and pass it to AVGuesser.guess as an ArrayBuffer:

import * as AVGuesser from "avguesser";

const file = ... // some File or Blob object
const result = AVGuesser.guess(await file.slice(0, 12).arrayBuffer());
console.log(result);

Results are of one of two forms. If the file could not be identified, the result is simply

{
    success: false
}

If the file could be identified, the result is

{
    success: true,
    audio: boolean,
    video: boolean,
    image: boolean
}

The audio, video, and image fields correspond to whether this file type can contain the given type of data, and not whether the file in question does contain it. You will need to use an actual demuxer to find what's in the file.

Non-ES6-module builds of AVGuesser expose a global object AVGuesser.