WebVTT Chapters and WebVTT Metadata

[nathangathright]

After Apple announced its support for the transcript tag and the WebVTT format, I learned that the WebVTT spec also supports chapter and metadata payloads. I took a stab at writing a JSON chapter to WebVTT converter.

WebVTT Chapter files have widespread adoption in HTML5 video players, but they only support chapter titles and no additional metadata. WebVTT Metadata files can contain JSON objects, which could contain the title and other properties, but existing players don’t recognize them.

If the namespace were to support WebVTT in the chapters tag, I’d suggest we copy the HTML <track> element by introducing a new kind attribute and allowing multiple chapter tags per episode. Like transcripts, apps only need to pick one to ingest. No need to reconcile discrepancies between them.

<podcast:chapters type="application/json+chapters" url="...chapters.json"/>
<podcast:chapters type="text/vtt" kind="metadata" url="...metadata.vtt"/>
<podcast:chapters type="text/vtt" kind="chapters" url="...chapters.vtt"/>

As best I can tell, the only advantage WebVTT has over our existing JSON spec is compliance with web standards. Still, I can’t imagine many developers will find that compelling for no tangible benefit to listeners. I’d love to hear if there are benefits I haven’t considered.