[whatwg] Using <video> as a source for canvas.drawImage

Oliver Hunt oliver at apple.com
Mon Aug 18 18:48:58 PDT 2008

On Aug 18, 2008, at 5:58 PM, Robert O'Callahan wrote:

> On Tue, Aug 19, 2008 at 11:24 AM, Oliver Hunt <oliver at apple.com>  
> wrote:
> Cool -- I wonder though if it would be better if it were placed in a  
> different method, drawFrame or something (very much an up in the air  
> sort of question)
> drawImage is already overloaded, so why not carry on with that,  
> unless we change the API as you suggest below.
I'm  not sure that drawImage overloading was a good idea in the first  
place *but* canvas and image are fairly similar in both image-like,  
whereas video is quite clearly different.  I was also thinking it  
would work better given the additional frame argument, however...
> AFAIK we'd basically have to implement that by creating a second  
> video stream, seeking it and then capturing the frame, and you  
> really don't want to do that synchronously! Then we'd want to cache  
> that stream so that another drawFrame with a nearby frame index was  
> efficient ... ick. So I suggest not offering that API. Authors can  
> always use a second, hidden video element to achieve the same effect.
... I had failed to consider streaming content (where random seeking  
may not be possible) :-/

I still think it would be useful to be able to specify an exact frame,  
but as you say it may not be really feasible


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