[whatwg] Start position of media resources

[Chris Double]

Ogg based media resources can start from a time position that is not
zero. Examples of files that do this are those generated by the
program oggz-chop. For example:

http://ia331342.us.archive.org/2/items/night_of_the_living_dead/night_of_the_living_dead.ogv?t=0:20:00/0:20:50

If this is played in VLC the start time of the video is 0:20:00. When
seeking the time requested for the seek must be between 0:20:00 and
0:20:50. Does the HTML5 spec allow media resources that don't start
from 0? I see in the spec mention:

"Media elements have a current playback position, which must initially
be zero. The current position is a time."

In the case of the Ogg file above, the current playback position would
initially be zero, but when the first frame is loaded it will be
0:20:00.

Is this valid per the spec?  If so, would we need an attribute on the
media object so the web page author can retrieve the start time of the
video (in the same way they can get the duration). They would need
this to be able to display progress bars/scrubbers to position the
thumb correctly based on the currentTime. Detecting the first frame or
metadata loaded events and getting the position of the that won't work
as some of the video may have been played by the time that event is
handled by user code.

Chris.
-- 
http://www.bluishcoder.co.nz