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[whatwg] <video>/<audio> feedback

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Sat, 9 May 2009 14:09:32 +1000
Message-ID: <2c0e02830905082109t64fa89aaj5dd50933c3d9283@mail.gmail.com>
On Sat, May 9, 2009 at 2:25 AM, David Singer <singer at apple.com> wrote:
> At 23:46 ?+1000 8/05/09, Silvia Pfeiffer wrote:
>> On Fri, May 8, 2009 at 9:43 AM, David Singer <singer at apple.com> wrote:
>>> ?At 8:45 ?+1000 8/05/09, Silvia Pfeiffer wrote:
>>>> ?On Fri, May 8, 2009 at 5:04 AM, David Singer <singer at apple.com> wrote:
>>>>> ?At 8:39 ?+0200 5/05/09, K?i"tof ?elechovski wrote:
>>>>>> ?If the author wants to show only a sample of a resource and not the
>>>>>> ?full
>>>>>> ?resource, I think she does it on purpose. ?It is not clear why it is
>>>>>> ?vital
>>>>>> ?for the viewer to have an _obvious_ way to view the whole resource
>>>>>> ?instead;
>>>>>> ?if it were the case, the author would provide for this.
>>>>>> ?IMHO,
>>>>>> ?Chris
>>>>> ?It depends critically on what you think the semantics of the fragment
>>>>> ?are.
>>>>> ?In HTML (the best analogy I can think of), the web page is not trimmed
>>>>> ?or
>>>>> ?edited in any way -- you are merely directed to one section of it.
>>>> ?There are critical differences between HTML and video, such that this
>>>> ?analogy has never worked well.
>>> ?could you elaborate?
>> At the risk of repeating myself ...
>> HTML is text and therefore whether you download a snippet only or the
>> full page and then do an offset does not make much of a difference.
>> Even for a long page.
> 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.

>> So, the difference is that in HTML the user agent will always have the
>> context available within its download buffer, while for video this may
>> not be the case.
> I'm sorry, I am lost. ?We could quite easily extend HTTP to allow for
> anchor-based retrieval of HTML (i.e. convert a 'please start at anchor X'
> into a pair of byte-range responses, for the global material, and then the
> document from that anchor onwards).

Yes, but that's not the way it currently works and it is not a
proposal currently under discussion.

>> This admittedly technical difference also has an influence on the user
>> interface.
>> If you have all the context available in the user agent, it is easy to
>> just grab a scroll-bar and jump around in the full content manually to
>> look for things. This is not possible in the video case without many
>> further download actions, which will each incur a network delay. This
>> difference opens the door to enable user agents with a choice in
>> display to either provide the full context, or just the fragment
>> focus.
> But we can optimize for the fragment without disallowing the seeking.

What do you mean by "optimize for the fragment"? 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.

Received on Friday, 8 May 2009 21:09:32 UTC

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