Re: Dislpay problems
From: Chris P. [MVP] (msdn_at_chrisnet.net)
Date: 05/21/04
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Date: Fri, 21 May 2004 09:52:53 -0400
The Slow Onw wrote:
> We had EXACTLY the same problem with an IEI board (IVC200) which is a
> four input card (four BT878's)
>
> Initial development was fine. When it came time to ship the product
> we bought a new card, installed it, and suddenly we had noise
> consisting of horizontal streaks. A way to visualise the effect was
> as if, say, the odd frame was fixed and only the even frame updated
> (though the truth was partially inbetween).
>
> The solution was to install the _old_ driver and the problems went
> away. Completely !
>
> If you do the maths on the amount of data bytes you need for 4 large
> images across the PCI bus it is about 120MB/s, ISTR the bus is
> 133MB/s ??? Dropping frames I could accept, but not corruption !
>
> Incidently, changing the source from RGB32 to say YUY2 improved the
> situation but never effected a complete cure.
He was using the ADLink RTV.
I did the math, for 4 x full frame PAL requires 85MB/s plus overhead. So
one card is fine as expected. 2 cards is going to require 170MB/s, just not
going to happen on a standard 33MHz PCI bus which has a total bandwidth of
133MB/s. The card does support 66MHz PCI so with an appropriate motherboard
it might be possible to have 2 cards running on a single 66MHz PCI bus
(which has a bandwidth of 266MB/s) however, like you say, there still could
be driver issues. Best to just use a server class motherboard with split
PCI buses.
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