good video capture card

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bartus
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Joined: Mon Apr 19, 2004 10:43 pm

good video capture card

Post by bartus » Thu Apr 22, 2004 1:17 pm

what's a good video capture card in terms of video and build quality? are the grandtecs ok? i've checked ebay and looked at those cheap cards, and am skeptical of the quality of its components. thanks.

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zoneminder
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Post by zoneminder » Thu Apr 22, 2004 2:21 pm

I can't comment on any experience with GrandTec or any cards off eBay in particular as I haven't got any from either of those places. However there are a couple of things to keep in mind. Firstly make sure you know how many video capture chips are on the card, cheap cards will share one between all inputs and more expensive ones will have one bttv chip per input. This make a big difference to the performance, and usually the cost. You can normally work out how many chips are on the card from just looking at the picture but it's worth checking with the vendor to be on the safe side.

The other thing that you can't usually tell until you try a card, and which only applies to the single chip cards, is the switching performance between inputs. If you are using multiple inputs on the cheaper cards they have to switch the input through the chip each time an image is captured. Good cards will do this quickly, bad ones will take a while. So while you may get 25 frames per second in both cases for a single input if you have two it may drop to 12 on a good card and 8 on a bad one and so on as you add more inputs. You may also get artefacts or ghost frames from the wrong inputs as well. The only way to to know if this is going to be an issue is to try one, or find someone else who has, so you're definitely doing the right thing by asking!

Oh, and of course, the card needs to be supported by Linux, though most BT8x8 ones are anyway though some may need tweaked drivers for best performance or features.

Phil,

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davide
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Post by davide » Fri Apr 23, 2004 5:20 pm

I have successfully used GrandTec cards in zoneminder.

Theese cards are very cheap in cost and performances:
all cards (4ports, 9ports, 16ports) have just 1 BT878 chip.
I repeat: 1 single chip.

this means very low FPS

capture size is also little:
gray: maximum 640x480
colours: maximum 384x288

4 ports card is autodetected by BTTV
16 ports card is NOT autodetected, I had to add manually
"options bttv card=103" in modules.conf

If you are looking for a great performances card GrandTec is NOT the solution

If you are looking for a very cheap card GrandTec IS the best solution (at least here in Italy)

regards,

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davide
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Location: Italy

Post by davide » Tue Apr 27, 2004 6:38 pm

Reading old messages from the forum I found this one:
http://www.zoneminder.com/forums/viewtopic.php?t=306
(the search feature is cool)
I successfully got my GrandTec working on 24bit colours at 768x576 (max buffers images:36)

It still has 1 single BT878 chip, then FPS is very low...

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