[whatwg] Start position of media resources

Silvia Pfeiffer silviapfeiffer1 at gmail.com
Tue Apr 7 15:29:39 PDT 2009

On Wed, Apr 8, 2009 at 8:21 AM, David Singer <singer at apple.com> wrote:
> At 8:02  +1000 8/04/09, Silvia Pfeiffer wrote:
>> Note that in the Media Fragment working group even the specification
>> of http://www.example.com/t.mov#time="10s-20s" may mean that only the
>> requested 10s clip is delivered, especially if all the involved
>> instances in the exchange understand media fragment URIs. During a
>> transition period, while the infrastructure does not support media
>> fragment URIs yet, the full resource will be delivered and it is up to
>> the UA to deal with the consequences. It could either terminate the
>> connection and decide that the resource is too long to accept and
>> report an error to the user. Or it could receive the full resource,
>> but decide to just play back the requested segment. Since ultimately
>> the aim is to have only the requested clip downloaded, I think the UI
>> presentation should be identical to the one where a query is used.
>> BTW: the media fragment WG will make suggestions as to what a UA
>> should do, but ultimately every application may have its own
>> motivations for what to display, so you will not see definite
>> specifications for what a UA is supposed to do UI-wise with media
>> fragments. Think, e.g., about a playlist that consists of fragments
>> from multiple Web resources (including different servers). Such a
>> mash-up should probably best be represented with on continuous
>> timeline that overrides the original timing of each clip. Only when
>> you drill into the clip will you actually get the original in and out
>> times.
> Ah, OK.  I agree that telling UAs what they should do, ought to be for the
> most part, out of scope.  But if there is material that the page author does
> NOT want to have shown, they probably need to know whether the # syntax will
> assure them that the user is restricted. (Always understanding that if they
> copy-paste the URL, neitehr # nor ? syntax stops them from changing the
> selection range).  Think of presenting a K-12 class with a clip from a
> movie...
> My mental analogy was HTML, where an acnhor takes you to that part of the
> page as a convenience, but nothing stops you from navigating away.  And in
> the case where the UA optimizes for showing that section (by suitable
> handshakes/translations with the server), again, it could present a UI which
> offers other times -- at the expense of more handshakes.

Yes, I understand that analogy. But because video can be a very long
resource, media fragment URIs cannot be restriced to client-side
offsetting. Think e.g. about wanting the last 2 minutes out of a 5
hour discussion downloaded to your mobile phone.

The media fragment WG decided that fragment addressing should be done
with "#" and be able to just deliver the actual fragment. (BTW: this
is in contrast to the temporal URIs that were specified for Annodex,
where chopping happened in the UA for "#"  and on the server for "?").


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