API to get live stream position as Date, not relative to video timeline

[aletorrado]

Is it possible using Shaka to get the current live playback time, from a live streaming MPD, such as .timeAsUTC() of Dash.js?

Thanks!

[tdrews]

You can use player.seekRange().end. This will give you the effective live-edge in seconds. However, this value will be a number of seconds less than just now - MPD@availabilityStartTime. Does that work?

[aletorrado]

.seekRange doesn't work for me. I need the time of the current playback position. Btw, seekRange does not seem to be documented.

I could use the current seek value (for example, getting the HTML Video DOM element, and getting .currentTime), but I don't know how to access MPD@availabilityStartTime using Shaka either.

[tdrews]

If you just need the playhead position then you should use video.currentTime; it will correspond to the position in the live stream.

[aletorrado]

Nope, I need the real time (UTC) of the playhead, like MPD.availabilityStartTime+video.currentTime. But I have no access to the MPD.

[tdrews]

Ah, got it. We could add an API for that. You could also try

var timeBehindLiveEdge = player.seekRange().end - video.currentTime;
var streamPosition = (Date.now() / 1000) - timeBehindLiveEdge;

although, since player.seekRange().end is offset a little from the true live-edge, it may not work exactly how you want (seekRange() available from the master branch).

[aletorrado]

It may work but it won't be precise. I'm thinking about accesing .manifest_ to get the availabilityStartTime, but it would be really nice to have .timeAsUTC() as dash.js have. Why don't you export the manifest?

[aletorrado]

This works great:

var playHeadDate = new Date(player.manifest_.presentationTimeline.presentationStartTime_*1000 + videoElm.currentTime*1000)

[tdrews]

Why don't you export the manifest?

Modifications to the manifest by the application could have many unintended consequences.

var playHeadDate = new Date(player.manifest_.presentationTimeline.presentationStartTime_*1000 + videoElm.currentTime*1000)

We could provide an equivalent API for this.