[MPlayer-users] stripes in image with (x)mga and ffmpeg on G200

Diego Biurrun diego at biurrun.de
Tue Jan 29 17:51:02 CET 2002

Hello Brent!

Lowering the vertical refresh rate from 100Hz to 85Hz did indeed
help.  No more stripes in my image!  Thanks.

This probably explains why the windows driver does not offer more than
85Hz refresh rate.  Mplayer now plays videos at least as good as
Windows Media Player, and I have no real reason left to boot into
Windows now and then.  Thanks, guys!

Brent, now that you have been so kind in answering my questions, may I
bug you some more?  Do you have any idea why this would go away when
resizing the image or watching fullscreen?


Brent Roman writes:
 > > One more question, what is RAM access contention supposed to mean in
 > > this context?  I would be most delighted if somebody could educate me
 > > on the matter.
 > This occurs because the RAM on the video card is accessed by both
 > the video hardware (to drive the Video DAC) and the low-level software
 > drivers.  There must be some mechanism to insure that at both do not
 > try to access the RAM at the same instant.  When you run the 
 > card at high resolution, refresh rate or color depth, it increases
 > the memory bandwitch necessary to drive the Video DAC.  This leaves
 > less time left over for software to update the Video RAM and, thus,
 > makes RAM contention more likely.
 > If it is RAM contention, you will find that just lowering the 
 > vertical refresh rate from say 85hz to 60hz will improve the
 > situation.  If you are already at 60hz, then you probably have
 > to start thinking about another video card or try to find out
 > if there's something that can be done to the software to have it
 > time its accesses to avoid RAM contention.  Any such
 > hypothetical software fix is likely to hurt proformance, so if
 > you're already "on the edge" to CPU utilization, don't even bother.
 > Hope this helps.
 > - brent

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