W3C home > Mailing lists > Public > whatwg@whatwg.org > May 2010

[whatwg] Timestamp from video source in order to sync (e.g. expose OGG timestamp to javascript)

From: David Singer <singer@apple.com>
Date: Mon, 24 May 2010 09:18:59 -0700
Message-ID: <14E33FAC-4F71-4163-B3C5-C11A73038E49@apple.com>
I think it rather important that the format define "where you are" in time, precisely so that temporal fragments, or syncing with other material, can work.

For most video-on-demand, the program starts at zero and runs to its duration.  But for 'streaming', knowing 'where you are' in a stream depends on a lot of things.  The 3G HTTP streaming solution explicitly anchors the timeline, so that two players playing the same program at the same point in it will see the same time, no matter when they tuned it. 

On May 18, 2010, at 2:46 , Silvia Pfeiffer wrote:

> On Tue, May 18, 2010 at 7:28 PM, Robert O'Callahan <robert at ocallahan.org> wrote:
>> On Tue, May 18, 2010 at 8:23 PM, Odin Omdal H?rthe <odin.omdal at gmail.com>
>> wrote:
>>> 
>>> Justin Dolske's idea looks rather nice:
>>>> This seems like a somewhat unfortunate thing for the spec, I bet
>>>> everyone's
>>>> going to get it wrong because it won't be common. :( I can't help but
>>>> wonder if
>>>> it would be better to have a startTimeOffset property, so that
>>>> .currentTime et
>>>> al are all still have a timeline starting from 0, and if you want the
>>>> "real"
>>>> time you'd use .currentTime + .startTimeOffset.
>>>> 
>>>> I'd also suspect we'll want the default video controls to normalize
>>>> everything
>>>> to 0 (.currentTime - .startTime), since it would be really confusing
>>>> otherwise.
>> 
>> 
>> That's exactly what I've advocated before. I lost the argument, but I forget
>> why, probably because I didn't understand the reasons.
> 
> 
> To be honest, it doesn't make much sense to display the "wrong" time
> in a player. If a video stream starts at 10:30am and goes for 30 min,
> then a person joining the stream 10 min in should see a time of 10min
> - or better even 10:40am - which is in sync with what others see that
> joined at the start. It would be rather confusing if the same position
> in a video would be linked by one person as "at offset 10min" while
> another would say "at offset 0min". And since the W3C Media Fragments
> WG is defining temporal addressing, such diverging pointers will even
> end up in a URL and how should that be interpreted then?
> 
> Cheers,
> Silvia.

David Singer
Multimedia and Software Standards, Apple Inc.
Received on Monday, 24 May 2010 09:18:59 UTC

This archive was generated by hypermail 2.4.0 : Wednesday, 22 January 2020 16:59:23 UTC