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still image on <video> (was: width='' and height='' on <video>)

From: Håkon Wium Lie <howcome@opera.com>
Date: Wed, 10 Oct 2007 11:25:00 +0200
Message-ID: <18188.39532.123754.216243@gargle.gargle.HOWL>
To: Henri Sivonen <hsivonen@iki.fi>
Cc: HTMLWG WG <public-html@w3.org>

Also sprach Henri Sivonen:

 > The <video> element currently lacks width and height attributes on  
 > the grounds that:
 >   1) They'd be presentational.
 >   2) YouTube and the like put all videos in the same box.
 >   3) Different dimensions are called for different media, so the  
 > <div><style scoped media='...'> video { width: ...; height: ...; } </ 
 > style><style scoped media='...'> video { width: ...; height: ...; } </ 
 > style><video>...</video></div> would encourage media-independence  
 > while <video width='...' height='...'>...</video> would not.
 > 
 > And, yet, for *practical* purposes, authors seem to *expect* to have  
 > width and height attributes at their disposal. (Based on expectations  
 > voiced on IRC.) I suggest adding width and height attributes to <video>.

I support this. 

While on the subject of pragmatic attributes, I would also like to
propose another attribute -- still -- to point to an image that is
shown until the video itself is played. The current specification
indicates that the first frame of the video should be used for this.
Often, the first frame will be black or otherwise not representative
for the video that follows. Being able to explicitly set a still image
is a basic function in my DVD recorder; this is very useful as the
first frame of my home video snippets are often blank. Wikimedia have
started using the <video> element on their pages, but they start out
as <img> elements:

  http://commons.wikimedia.org/wiki/Category:Video

That is, they don't instantiate the <video> element until the user has
pressed play. A simple attribute would address their needs:

   <video src="foo.ogg" still="foo.jpg">

Other names for the attribute could be "img" or "index".

>From a performance perspective, it seems simpler to fetch a small
still image of fixed length rater than fetching a part of the video
file and hoping that a full frame is included.

>From an authoring perspective, it seems simpler to use the attribute
rather than editing the video file (e.g., by inserting the desired
still image in the beginning of the file).

I don't think the proposed attribute add any new accessibility issues
as the still image -- one must assume -- is taken from within the video.

An alternative approach is to specify a time -- say, "3.5s" -- into
the video from where the still should be fetched.

The HTML5 spec, in section 3.4.6 has an example showing how to encode still images:

  <p>
   <input type="image" src="frame.png" alt="Play Video"
     onclick="   if (nextSibling.load) nextSibling.load();
                 disabled = true;
                 return false;"
   ><video src="video.ogg" controls="" irrelevant=""
     onloadedfirstframe="
                 irrelevant = false;
                 previousSibling.irrelevant = true;
                 autoplay = true"
     onerror="   parentNode.irrelevant = true;
                 parentNode.nextSibling.irrelevant = false">
   </video>
  </p><p irrelevant="">
   Playback unavailable.
   <a href="video.ogg">Download Video</a>
  </p>

This seems complex to me; I'm a simple person.

-h&kon (who only speaks for himself on this issue)

              Håkon Wium Lie                          CTO °þe®ª
howcome@opera.com                  http://people.opera.com/howcome
Received on Wednesday, 10 October 2007 09:25:23 UTC

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