[Qt-interest] Intercepting Phonon VideoWidget frames as they are pushed

[Kaleb Pederson]

On Tuesday 24 March 2009 11:50:56 am Trenton Tuggle wrote:
> Interesting update...
> 
> I've been unable to "capture" VideoWidget paint events at all -- it  
> appears as if it somehow gets drawn outside of a PaintEvent -- but how  
> could it then be captured and redirected onto a  
> QGraphicsViewProxyWidget?

Wouldn't you really need a proxy QPaintDevice?  The QPaintDevice could then render onto whatever it wanted. 

Please let us know how it goes.

Thanks.

--Kaleb

> What's the mechanism that QGraphicsViewProxyWidget uses to "capture"  
> the paint events of its children and "redirect" them to be drawn on  
> the appropriate Graphics View/Scene?
> 
> Thanks in advance for any pointers...
> 
> -Trent Tuggle <Trent at Tuggle.Org>
> 
> 
> On Mar 21, 2009, at 11:39 AM, Trenton Tuggle wrote:
> 
> > I have an interesting challenge I've been working on:
> >
> > I'm working on video processing, and am investigating using Phonon for
> > platform-independent back-ends.
> >
> > My interest is not the usual, though -- I have little interest in
> > showing the video on-screen (although that would be nice, also) but
> > primarily, I'm interested in obtaining the video frames.
> >
> > Now I know it's easy to render() a widget (such as VideoWidget) onto a
> > pixmap or other, but I'm really interested in obtaining the frames in
> > a more automated way -- such as getting a signal when the next frame
> > is ready, etc.  My thought is that since VideoWidget can be embedded
> > in a graphics scene, it must be possible to intercept its painting
> > events and redirect it to a qimage or something: but so far I've  
> > failed.
> >
> > So that's my question: how can I embed a VideoWidget in something that
> > can intercept paint events, redirect them to a QImage, then signal a
> > processor that a frame is ready for processing?
> >
> > I've tried stuff along these lines:
> >
> > http://www.kdedevelopers.org/node/3644
> >
> > The thought was that I'll create a Phonon path to play on a
> > VideoWidget embedded in something like that which would capture the
> > frame, then signal my processor....
> >
> > But so far, I've been unable to get the widget I create to receive any
> > paint events, or intercept anything at all -- it doesn't even get
> > resized properly when a video is loaded!
> >
> > If anyone has any advice or input on this, I'd really appreciate it!
> >
> > Thanks in advance!
> >
> > Trent Tuggle <Trent at Tuggle.Org>
> > _______________________________________________
> > Qt-interest mailing list
> > Qt-interest at trolltech.com
> > http://lists.trolltech.com/mailman/listinfo/qt-interest
> 
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