Proposal: canPlay(a local file) api

[hanguokai]

Hi, I created a web video player that focus on playing local video files (not online streaming media).

I want to know whether a video element can play a local file. Currently, I use try-catch statement to detect it. But sometimes it can play audio track but can't play video track, and don't throw error.

The problem is isTypeSupported(), canPlayType() and decodingInfo() asking for a (MIME type + codec) string as a parameter. But for local files scene, I don't know this info in advance. To get this info, I need to analyze the file content, for example use mp4box.js or mediainfo.js library.

So I would like to propose a new method canPlay(file). The parameter is a file object URL or a file. If Media Capabilities API supports whether browser can play a local file, I don't need to know (MIME type + codec) in advance.

Use case is:

if (browser can play this file) {
   play it
} else {
  prompt user: "cannot play this file"
}