[directfb-dev] Re: Seeing "tearing" using mplayer dfbmga

[Antonino Daplas <adaplas@pol.net>]

On Mon, 2002-12-09 at 18:25, Denis Oliver Kropp wrote:
> Quoting Antonino Daplas (adaplas@pol.net):
> > Some possibilites that can be considered:  
> > 
> > 1.  Direct rendering implies writing to the video memory directly, which
> > is not just slow, but can be cached. In some hardware, you actually need
> > to do a read of the video memory (even just one byte, just to flush the
> > contents) to ensure that everything is in sync.  Especially true with
> > MTRR.  MTRR accumulates all those little writes and after a certain
> > threshhold, burst write everything at once.
> 
> Writing to the video memory is even faster than writing to system
> memory on my P3 800 system with a G400 AGP. However, reading from video
> takes ten times as long as reading from system memory.
> Also I don't think that caching is the cause as the amount of data is
> fairly big.
> 
You're right, I just mentioned it because I just cleaned up rivafb (for
linux-2.5) using an old riva128 pci card.  And everything is slow, had
some weird problems such as disappearing cursors and what-not :-).

> > 4.  Which is why we really need an AGP surface in DirectFB for things
> > like video :)
> 
> Yes, we really need that, but I'm too lazy to refactor the surface manager
> stuff for such an extension.
> 
Attempted it once too, but it will need someone who knows the ins and
outs of DirectFB :-)

Tony




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