[whatwg] <video>/<audio> feedback

David Singer singer at apple.com
Sun May 10 18:56:27 PDT 2009

At 14:09  +1000 9/05/09, Silvia Pfeiffer wrote:
>  > you might try loading, say, the one-page version of the HTML5 
>spec. from the
>>  WhatWG site...it takes quite a while.  Happily Ian also provides a
>>  multi-page, but this is not always the case.
>That just confirms the problem and it's obviously worse with video. :-)
>>  The reason I want clarity is that this has ramifications.  For example, if a
>>  UA is asked to play a video with a fragment indication #time="10s-20s", and
>>  then a script seeks to 5s, does the user see the video at the 5s point of
>>  the total resource, or 15s?  I think it has to be 5s.
>I agree, it has to be 5s. The discussion was about what timeline is
>displayed and what can the user easily access through seeking through
>the displayed timeline. A script can access any time of course. But a
>user is restricted by what the user interface offers.

Sure.  I think we are probably in agreement.  Logically, the UA is 
dealing with the whole resource -- which is why it's 5s in this case. 
The UA is also responsible for focusing the user on the fragment, and 
(implicitly) for optimizing the network for what the user is focusing 

For example, some UAs would essentially invoke the same code if the 
user immediately did a seek to a time, if the javacsript did a seek 
to a time, or the initial URI had a fragment indicator starting at a 
time.  In all three cases, the UA tries to start at that time as best 
it can, optimizing network access to do that.

>  > But we can optimize for the fragment without disallowing the seeking.
>What do you mean by "optimize for the fragment"?

I mean, the UA can get support from the server for time-based access, 
helping optimizing the network access for the fragment to be 
presented, while at the same time allowing seeking outside that 

>  Of course none of the
>discussion will inherently disallow seeking - scripts will always be
>able to do the seeking. But the user may not find it easy to do
>seeking to a section that is not accessible through the displayed
>timeline, which can be both a good and a bad thing.

How easy a particular user interface is to use for various tasks is 
(I hope) not our worry...
David Singer
Multimedia Standards, Apple Inc.

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