[linux-dvb] Re: Need help understanding OSD ioctls, mostly SetColor and SetBlock.

[Chris Worley <cworley@liberate.com>]

Ralph Metzler wrote:

> Chris Worley writes:
>  > Another reply to this post said DirectFB works for the DVB cards.  Is 
>  > that true?  If so, then there should be some way to get a memory 
>  > mapped pointer directly into the DVB-S cards graphics framebuffer memory?
> 
> No, we use DirectFB on the graphics card of the PC instead of the
> OSD of the DVB card. The video of the DVB card is then overlayed with the 
> video of the PCs VGA card. You will need a VGA card with TV-out of
> course. Most "PC-Set-Top-Box" solutions use boards with on-board VGA 
> with TV-out and this works very well. 

Ralph,

Thanks for responding!

That solution would be okay if I could overlay graphics atop the 
video, and have alpha blending.

I could go without alpha blending, but graphics overlay atop the video 
is necessary, and it's not always nice rectangles.

If I draw the video from the DVB card into the video cards 
framebuffer, would I be able to overlay graphics on top (without 
getting into a race with the DVB card, which would overwrite my graphics)?

Maybe chromakey or colorkey?  For example, If I could draw black 
pixels onto the areas where I didn't want video, using the OSD 
routines, setting the blend to 0xf0, then have the DVB card draw into 
the video cards framebuffer memory, might I be able to get it to skip 
drawing regions of the frame buffer where I wanted to draw graphics? 
That idea wouldn't work; it would just draw my black pixels into my 
framebuffer, and it would overwrite any graphics drawn into the same 
framebuffer area.  Maybe a video card with z-order capability?

How do you do this?

Thanks,

Chris



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