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

ACTION-202: draft the paragraph that the group will propose to HTML5 regarding how the control of media fragment URI should be done

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Wed, 1 Dec 2010 22:05:12 +1100
Message-ID: <AANLkTinHmmLDY1XLC7ZddeTzmL-YQLP613jSpyesUvCi@mail.gmail.com>
To: Media Fragment <public-media-fragment@w3.org>
Hi all,

I started putting some thought together as to what browser vendors
would need to implement to support media fragments. It's at
https://wiki.mozilla.org/Accessibility/Video_Media_Fragments . The
required additions to HTML5 can be extracted from there as below.
Please have a thorough read so we can figure out if we have missed
something.

Cheers,
Silvia.


(1) Temporal Media Fragments

As per: http://www.w3.org/TR/media-frags/#naming-time

Relevant to: audio & video

Recommended approach to support temporal media fragments: byte range
requests, see http://www.w3.org/TR/media-frags/#URIfragment-user-agent

Two uses:

1. URL in address bar

When a media fragment URL is pasted into a Web browser address bar and
the browser is able to decode the media resource, the user should see
a video or audio file that starts playing from the fragment start time
and stops at end time. Also, since the browser will display controls,
we need to introduce markers on the controls for the fragment, see
http://www.youtube.com/watch?v=LfRRYp6mnu0 for an example
implementation.

The means towards interpreting the fragment should be by starting to
download the resource, then, as it is confirmed that it is a media
resource, download will stop and byte range requests will be applied.

Note further that for any video or audio that is playing in this way,
it makes sense to update the URL bar when pausing and to include the
fragment offset, such that users can cut and paste the new URL for
sharing. Also, it might make sense to add the new URL to the browser
history when pausing, allowing the user to jump back and forth between
pause points through navigating the browser history.

2. URL in @src attribute of video/audio element

When a media fragment URL is used in a video/audio element, the user
will similarly expect the media resource to start playing from
fragment start time and stops at end time.

If no @controls attribute is given, this equates to playing back a
media fragment without context and may be useful for video editing
applications or playlists of media snippets (so-called mash-ups).

If the @controls attribute is given, there is a need to introduce
markers for the fragment, see e.g.
http://www.youtube.com/watch?v=LfRRYp6mnu0 for an example
implementation.

Note that if the @loop attribute is given, the fragment will loop and
not the resource.


(2) Spatial Media Fragments

As per: http://www.w3.org/TR/media-frags/#naming-space

Relevant to: images & video

Recommended approach to support spatial media fragments: CSS-like,
i.e. hide unwanted pixels

A spatial media fragment URI can be used in the URL address bar or in
the @src attribute of video/img element.

The user will expect a cropped (spliced) image/video display of the resource.


(3) Track Fragments

As per: http://www.w3.org/TR/media-frags/#naming-track

Relevant to: audio & video

Recommended approach to support track fragments: hide unwanted tracks

A track media fragment URI can be used in the URL address bar or in
@src attribute of video/img element. One example use case has been
shown at https://labs.ericsson.com/developer-community/blog/beyond-html5-conversational-voice-and-video-implemented-webkit-gtk
.

The user will expect that only the enumerated tracks (audio, video
etc) will be displayed.
Received on Wednesday, 1 December 2010 11:06:07 GMT

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