Dear Lazyweb, is there some way for JavaScript to know the timestamp of a VIDEO tag's currently-playing live HLS stream? Bu this I mean the wall clock at the time the video was encoded, not played. Think of this as a subtitle-sync problem. Apple references something called "HLS Timed Metadata" which I gather is in-band ID3 frames within the MPEG stream, but the doc is an atrophied stub. On this demo page there is stuff visible in HTMLMediaElement.textTracks but I don't know how to make OBS and/or nginx-rtmp insert these sorts of ID3 tags, or whatever they are. (Remember, this is for a live stream, not a pre-recorded static file.)

The HLS RFC has a thing about EXT-X-SESSION-DATA but I have no idea what that's for or how it differs from just some random comment-line in the file; and it seems to only be for Master Playlists, not Media Playlists.

Things that don't work:

• HTMLMediaElement.currentTime -- this is the elapsed time since the user pressed play.
• Scanning the .m3u8 file from the SRC attribute directly -- there's no way to know which of those segments is currently playing, or where within that segment the play-head is.

Previously.