Video overlay - Window updating

[Barry Scott]

On 11/03/10 20:50, Aaron Plattner wrote:
> On Mon, Mar 08, 2010 at 04:41:46AM -0800, Iban Rodriguez wrote:
>    
>>    Good Morning,
>>
>>    I have a question about video overlay and window repainting. I have
>> a project in which I need to show a video on a non-rect part of an
>> application window. After some attempts I decided to use play the
>> video on one window (window 1) and over it put the application window
>> (window 2) where the zone I want the video to show is painted using
>> the color key of the video overlay. With this configuration the video
>> should be shown as if it were embedded in window 2. However, it works
>> only in some situations, which I describe bellow:
>>
>>    1.- If window 1 (video) is completely covered by window 2, the video
>> doesn't show.
>>    2.- If window 1 (video) is not completely covered by window 2 (app)
>> by the left, the video is only show on the part that is not covered.
>>   3.- If window 1 (video) is not completely covered by window 2 (app)
>> by the bottom, the video is only show on the part that is not covered.
>>   4.- If window 1 (video) is not completely covered by window 2 (app)
>> by the bottom and by the left simultaneously, the video is shown on
>> the parts not covered and also on the parts of window 2 (app) which
>> are painted using the color key of the video overlay.
>>      
>    
>>   For my project, I need to reproduce the behaviour of case 4 in the
>> situation of case 1 but I don't know how to do it. I have tried it
>> with and without a window manager with the same result. I don't know
>> very much about the X server but the problem seems to be that when it
>> needs to update a window, it repaints the minimum rectangle which
>> cover all pixels that need to be updated so it only shows the video in
>> case 4 where the minimum rectangle is the entire window 1 (because of
>> the parts not covered). So my question is, is there a solution for
>> this problem? Can I tell the X server that some windows must be always
>> completely repainted? Is there any other way for managing the video
>> overlay that avoids this problem?
>>      
> The problem is that this is not a valid use of the overlay.  Among other
> things, you can't assume that the driver really uses a hardware overlay or
> just fakes it.  I suspect what's happening here is that the server is
> clipping the rendering against the occluding window, and simply skips it
> for the parts that it thinks are not visible.  The X server doesn't know
> that the hardware would let the video show through into parts of the
> occluding window.
>
> If you want to overlay stuff on top of the video, you'll need to either
> render it into the original video stream before sending it to Xv or use
> something that explicitly supports sub-pictures, like VDPAU or XvMC.
>    
Or use SHAPE extension to allow the video to show through.
Or use compositing if you need to alpha blend on top of the
video.

Barry