Video overlay - Window updating

[Iban Rodriguez]

2010/3/12 Barry Scott <barry.scott at onelan.co.uk>:
> 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
>
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>

Thank you very much for your suggestions.

I finally solved the problem using X11 composite extension, making the
application transparent and showing the video behind it using xv in
textured mode insted of overlay mode.

Iban.