[AVT] new I-D on temporal URI addresses

[Silvia.Pfeiffer@csiro.au]

Hi all,

we have submitted a proposal to specify temporal URI fragments on 
time-continuous Web resources (such as audio and video files/streams). I 
would like to ask for your brains on whether this is a problem that 
you've stumbled across, too, and whether you like the solution that we 
are proposing.

http://www.ietf.org/internet-drafts/draft-pfeiffer-temporal-fragments-00.txt

THE PROBLEM:
------------
We can see a need for the direct specification of points of interest in 
a URI for a/v. There are several uses for it:

1) Representation of search results:
When typing a search term into your favourite search engine, you would 
like it to search on a/v and bring up the link to an offset in a video 
where the search term matches. e.g. goal in last week's soccer matches

2) Favourite links:
When sending a link to a video to a friend, you'd really like to be able 
to specify the main part of your interest in it. e.g. look at my new 
cool sunglasses in my friend's wedding video


THE SOLUTION:
-------------
What we want is to address fragment offsets into videos. Therefore, the 
"#fragment" part of a URI naturally lends itself for including this 
address specification. For specification of the time points, we were 
inspired by the timestamp specification in RTSP. Therefore, we are 
proposing the following pattern:

#@npt=14.5

-> the "#" part signifies a fragment specification
-> the "@" tells us to look "at" that time specification
-> the "npt=" part is a time scheme just like in RTSP and we are also 
proposing npt, smpte, smpte-30-drop, smpte-25, and clock
-> the time format itself depends on the time scheme, this one 
signifying a 14.5 seconds offset

[for more details refer to the I-D]


THE USE:
--------
Here are examples for temporal URI fragment offsets:

http://foo/bar.mov#@smpte=00:00:14:15
(start downloading at 14 seconds and 15 frames into bar.mov)

rtsp://foo/bar.avi#@utc=20030308T143000.00Z
(start streaming at 8th March 2003 at half past 2pm)

http://foo/bar.mpg#@start
(start downloading from the start)

rtsp://foo/bar.rm#@now
(start streaming now)

---
We wanted to make it simple, intuitive and human readable and have 
therefore come up with this solution. Please let me know what you think.

Cheers,

Silvia.
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