[AG-TECH] Quad Capture card performance

[Natalia Costas Lago]

Thanx a lot Derek!!

That was enlightening!!

----- Original Message ----- 
From: "Derek Piper" <dcpiper at indiana.edu>
To: "John Hodrien" <johnh at comp.leeds.ac.uk>
Cc: "ag-tech" <ag-tech at mcs.anl.gov>; "Natalia Costas Lago" 
<natalia at cesga.es>
Sent: Monday, April 25, 2005 3:29 PM
Subject: Re: [AG-TECH] Quad Capture card performance


>
> Of course if the system you're installing on only supports 32-bit x 33Mhz 
> slots (as many do) then you're not going to get a lot of benefit. Natalia, 
> what are the hardware specs on the capture machine you're upgrading or 
> rebuilding?
> It's important to note too that however many PCI *slots* you have, you 
> (normally) only have one PCI *bus*. And the TOTAL bandwidth of that bus is 
> 32bit x 33Mhz = 132MBytes/sec. So however the cards are arranged (singly 
> or quad) you're going to run into that same bandwidth limitation. Of 
> course the quad capture card might be slightly more efficient due to it 
> being the only card on the bus and thus eliminating bus contention between 
> the capture cards.
> To reiterate the math here?
>
> 33000000 x 32 = 1056000000 bits/sec PCI max
>
> = 132000000 bytes/sec PCI max
>
> 1 frame (24 bit color) = (768 x 576 x 24 / 8 ) = 1327104 bytes
>
> 25 fps = 33177600 bytes/sec
>
> x 2 captures = 66355200 bytes/sec
>
> x 3 captures = 99532800 bytes/sec
>
> x 4 captures = 132710400 bytes/sec
>
> Derek
>
> John Hodrien wrote:
>> On Mon, 25 Apr 2005, Natalia Costas Lago wrote:
>>
>>>
>>> We are about to purchase a Spectra8 capture card or Winnov Videum 4400. 
>>> It's
>>> a very good point not to have to use 4 PCI buses, that's what I like 
>>> most of
>>> both cards, however I am concerned to performance issues, I mean, a PCI 
>>> bus
>>> allows 132 Mbps more or less, and the Spectra8 delivers 4 videostreams 
>>> at
>>> 30fps 768x576 (it can be less, that's the worst case) (similar values 
>>> for
>>> the Videum 4400 card). So, it seems to me that the PCI bus cannot 
>>> transmit
>>> so much information, that means, does it drop frames? Maybe I cant get 
>>> the
>>> highest resolution at 30fps (25fps for the Winnov card)?.
>>
>>
>> It won't be 30fps at 768x576 will it?  That's PAL resolution at NTSC 
>> frame
>> rates.  If you drop that to 25fps, the back of my envelope looks like 
>> you'd
>> indeed be rather close to 32 bit PCI limits.  The 4400 supports 64bit 
>> PCI,
>> thus solving that problem.
>>
>> jh
>>
>
> -- 
> Derek Piper - dcpiper at indiana.edu - (812) 856 0111
> IRI 323, School of Informatics
> Indiana University, Bloomington, Indiana
>