[whatwg] HTML 5 video tag questions

Ian Hickson ian at hixie.ch
Mon Jul 27 17:53:59 PDT 2009

There were some proposals to change <video>'s fallback model to allow 
markup to be used as an alternative to a video stream, so that once the 
various alternative videos had been tried, the user agent would make 
<video> act as a regular display:block element and no longer act as a 
video viewport.

I haven't changed <video> to do this, for the following reasons:

 * We tried this with <object> and we had years of pain. I'm not at all 
   convinced that we wouldn't have the same problems here again.

 * We won't need fallback as soon as we resolve the common codec issue, 
   which is still being worked on. I don't think we should redesign the 
   model to address a transient problem in the platform.

 * This model would either have to make <video> not dynamic -- once you 
   fail to load a video, you can no longer use it, because it's showing 
   fallback -- or would require us to introduce yet more state to keep 
   track of whether we should be displaying fallback or not.

 * If it's not dynamic, we'd have to define what happens when you use the 
   API when the fallback is being shown. Especially for cases like off- 
   page <audio>, this would lead to a quite confusing authoring experience.

 * We'd need to have an explicit way of triggering the behaviour for 
   <source>, given the way the media loading algorithm works.

 * It's a change, and I really would like to put the brakes on the number 
   of non-critical changes we make.

When the element was designed, we explicitly didn't do this -- that's why 
we have <source>, and is why the fallback is explicitly intended for 
legacy user agents, and not user agents that don't support the given 
videos. Which is to say, we didn't accidentally stumble into this design.

All in all, I'm very skeptical that this is a good idea.

What's more, any solution would almost certainly involve scripting anyway, 
and once you're doing things with script, it's really trivial to do the 
fallback manually, especially with all the hooks <video> provides, so the 
use cases don't seem that compelling.

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'

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