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

[Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de>]

Chris Worley wrote:
> 
> Klaus Schmidinger wrote:
> 
> > Chris Worley wrote:
> > You can have 1, 2, 4 or 8 bpp. However, since OSD memory is very limited,
> > using more than 4bpp leaves you with only a very small usable OSD area.
> >
> > Another drawback of the DVB card's OSD is that it isn't very fast.
> > Drawing a lot of text with many separate calls is way too slow to be
> > useful. That's why VDR mainly uses the OSD_SetBlock call to transfer
> > a bitmap (or parts of it) from VDR's memory to the OSD. This works fast
> > enough to be useful (IMHO).
> 
> Klaus,
> 
> Thanks for responding.
> 
> 4bpp works, 8bpp doesn't (for SetPixel, FillBlock, or SetBlock).  The
> routines all return zero, but nothing is drawn.  I fill all 256 color
> palette entries with a valid color (and 0xf0 blend), but no graphics.
>   It works fine if I switch to 4bpp (and make a 16 entry color table).
> Where can I learn more about OSD memory (and what I need to handle
> 8bpp graphics correctly)?

I guess all you need to do is make your OSD window smaller.
With 8bpp you need twice the amount of memory, and if you request
an OSD window that is too large (so the OSD runs out of memory)
it just does nothing. Start with a small window (say, 100x100 pixel)
and gradually increase the size until it isn't displayed any more.
That's the only way I know of to find out how big the OSD window can get.

Klaus
-- 
_______________________________________________________________

Klaus Schmidinger                       Phone: +49-8635-6989-10
CadSoft Computer GmbH                   Fax:   +49-8635-6989-40
Hofmark 2                               Email:   kls@cadsoft.de
D-84568 Pleiskirchen, Germany           URL:     www.cadsoft.de
_______________________________________________________________


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