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[directfb-users] Re: YUY2 video + RGBA osd alpha blending
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[directfb-users] Re: YUY2 video + RGBA osd alpha blending



On Mittwoch, 28. Juli 2004 10:59, Kristof Pelckmans wrote:
> Quoting Stefan Lucke <stefan@lucke.in-berlin.de>:
> > Code is available via http://www.lucke.in-berlin.de
> > It is used in vdr-softdevice plugin. File of interest is video-dfb.c
> > (somewhere in .. tar.bz2) .
> I looked at your code and saw that you have 2 scenarios :
> YUY2 :
> osd rendering :
> - copy into srcSurface
> - srcSurface->Flip
> video rendering :
> - copy into videoSurface
> - videoSurface->Flip

That is the one where alpha blending is available.

> 
> YV12 || I420 :
> osd rendering :
> - copy into osdSurface
> - osdSurface->Flip
> video rendering :
> - copy into videoSurface
> - srcSurface->StretchBlit( videoSurface )
> - srcSurface->Blit( osdSurface ) (alpha blending)
> - srcSurface->Flip

Oh, in these formats I do no stretchblit and only colorkeyd OSD is present.
That is when OSD color == colorkey (black) I see video, else I see OSD.

> 
> Now I am still stuck with two questions :
> 1) I conclude that the alphablending will only work when you have a
> pixelformat YUY2 for your video surface ? 

Yes.

> Is this because your Matrox card
> does only support this for this pixelformat ? 

No my card support all 3 formats but stretchblit works for me only
in YUY2.

> If you don't have alphablending
> for this specific scenario, is there a fallback to software aided
> alphablending ?

There is some work in directfb for software emulated stretchblit, but
I didn't test that with a card that has not hw-stretchblit

> 2) What happens during the first scenario ? You do a flip on the primary
> surface, but is it shown when the video surface covers it ? Do you use
> destination color keying here ?

> 
> Thanks for your comments,

I'll put my answer on the list because my knowledge of dfb programming is
rather limited and someone my correct me if I'm wrong.


Stefan Lucke





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