W3C home > Mailing lists > Public > public-media-fragment@w3.org > June 2010

Media Fragment Question

From: Chris Double <chris.double@double.co.nz>
Date: Thu, 1 Jul 2010 01:39:37 +1200
Message-ID: <AANLkTikrGHOrH9ohWcQ84cpqIkDLWcPUTp3Fc9MzbLtx@mail.gmail.com>
To: public-media-fragment@w3.org
When a user requests a user agent to make a request with a URL
containing a media fragment, how should the user agent decide when if
it needs to send Range headers? For example, the media fragment spec
shows the request for URL http://www.example.com/video.ogv#t=10,20:

GET /video.ogv HTTP/1.1
Host: www.example.com
Accept: video/*
Range: t:npt=10-20

Is it expected that for every URL request with a fragment that matches
the syntax of media fragments that the user agent will attempt to send
the Range header? It can't know in advance if a request is for a media
file. Or does it first make a request, identify it as a media file,
then does another request with a Range?

A user agent that does not support a particular media type (eg. a
browser that doesn't support .ogv) obviously can't play a file. But if
the page presents a link of the form:

<a href ='http://example.com/video.ogv#t=10,20>right click me and save</a>

Is it expected that the user agent, which supports media fragments,
would send the range requests to ensure only the correct time range is
saved even if the user agent itself can't play the file? If so, that
seems to indicate that the Range request needs to be sent on every
single request made by the user agent which doesn't sound like a good

A couple of minor nits:

1) "unnecssary" is incorrect spelling in one place.
2) "If the server doesn't understand these query parameters, it
typically ignores them and returns the complete resource. This is not
a requirement by the URI or the HTTP standard, but the way it is
typically implemented in Web browsers." Should that be "typically
implemented in Web servers"?
3) "Wall-clock time codes are a way to address real-world clock time
that is associated typically with a live video stream. These are the
same time codes that are being used by ... and by HTML5 HTML 5." Were
are wall clock time codes with dates used in HTML 5 media?
'currentTime' is seconds for example.
4) "This section defines the different exchange scenarios for the
different situations explained in section 3 URI fragment and URI query
over the HTTĘprotocol. " That should be "HTTP protocol" I think.

Received on Wednesday, 30 June 2010 13:40:11 UTC

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