Re: [sdw] WebVMT: Investigate better out-of-band link handling (#1107)

**Playlist Use Case**

This use case is designed to demonstrate why linked media information is required, even if it's not present in HTML.

Consider media and VMT files loaded into a webpage to dynamically create a media playlist. The user loads multiple files via an input element to play the media in sequence, in a similar way to a YouTube playlist. Note that the HTML contains no URLs for either the media or VMT files.
```
<input id="vmt-load" multiple type="file" accept="video/*,video/mp4,.vmt">
<video id="vmt-video" controls src="">
   <track kind="metadata" map-id="vmt-map" tile-url="https://{s}.tile.openstreetmap.com/{z}/{x}/{y}.png?apikey=MY_KEY" />
</video>
```
The browser must create a playlist and correctly pair the media and VMT files, though no association details exist in the HTML. The only sources of information are the files that are loaded by the user and the media files are unmodified by WebVMT, so the only place this information can be recorded is in the VMT file.

It should be noted that:
  * HTML successfully supports this use case without WebVMT content;
  * This use case is equally applicable to WebVTT content.

-- 
GitHub Notification of comment by rjksmith
Please view or discuss this issue at https://github.com/w3c/sdw/issues/1107#issuecomment-452765967 using your GitHub account

Received on Wednesday, 9 January 2019 16:46:15 UTC