WebVTT File For Live Stream

Question

I am trying to implement the closed captioning for live stream.

The video is generated from the source and converted to m3u8 + ts file through the encoder and put in the server. video is in 3 bit rates for adaptive streaming.

The speech to text convertor is giving the XML files for the speech along with the timestamp in UTC (I could change to any time zone) which binds with the video stream for which it is generated.

Is it possible to use the XML data in WebVTT File. In My understanding WebVTT consists of captions with the time(in hh:mm:sss.mmm format) when it will come in video. like

 WEBVTT X-TIMESTAMP-MAP=MPEGTS:900000,LOCAL:00:00:10.000 00:00:30.006 --> 00:00:30.706 Instant Folgers! 00:00:30.900 --> 00:00:31.900 Instant Folgers? 00:00:32.646 --> 00:00:33.800 Tastes good as fresh-perked. 00:00:34.446 --> 00:00:36.646 Good as fresh-perked? I'll try it. 00:00:39.446 --> 00:00:41.746 Jean, this coffee is delicious, do you know that? 00:00:41.846 --> 00:00:43.722 Mm mm 00:00:43.822 --> 00:00:45.822 It's not the same kind we've been using, is it? 00:00:45.922 --> 00:00:47.922 Mm mm 00:00:48.022 --> 00:00:49.022 Don't just shake your head. 00:00:49.122 --> 00:00:50.909 Explain why the coffee's so good 00:00:51.009 --> 00:00:53.700 Good taste. 00:00:55.409 --> 00:00:57.370 Tastes good as fresh-perked. 00:00:57.734 --> 00:01:00.134 Instant Folgers. 

But in Livestream do we need to pass the date information along with it(hh:mm:sss.mmm) as only time will not serve the purpose as the time may be repeated for another day, led to confusion.

And How the video time is linked with the WebVTT time information in live streaming, as VOD videos have the constant time duration.

Please share any info If you have already implemented the closed caption for live stream using any technologies

Answer 1

Apples developer site has all this information, and it easy to search and navigate.

They even have videos:

https://developer.apple.com/videos/play/wwdc2012/512/