[whatwg] [media] startOffsetTime, also add startTime?

Philip Jägenstedt philipj at opera.com
Thu Mar 8 02:55:55 PST 2012

On Thu, 08 Mar 2012 11:11:06 +0100, Philip Jägenstedt <philipj at opera.com>  

> As hinted above, I don't think that startOffsetTime should really be the  
> first choice for trying to sync live streams. However, knowing the date  
> of a video is still useful, potentially even for the streaming case, so  
> we do want to expose the DateUTC field from WebM. However,  
> startOffsetTime is a bad name for it, since it's not using the same unit  
> as currentTime. I suggest offsetDate, to go with offsetTime.

We discussed this some more internally, specifically if the date is an  
offset at all and if so what it is relative to. In WebM, the DateUTC field  
is defined as "Date of the origin of timecode (value 0), i.e. production  
date." [1] Exposing this directly would mean that it is the date at  
currentTime=-offsetTime, an origin time that you can't actually seek to in  
the streaming case.

We discussed the concatenation of two clips and how to represent the date.  
At least chained WebM and chained Ogg should be able to represent this.

To reduce the possibility for confusion about what date is represented and  
to allow the recording date to be preserved in editing, how about exposing  
currentDate instead?

[1] http://www.webmproject.org/code/specs/container/

Philip Jägenstedt
Core Developer
Opera Software

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