1394 slow when opening port or changing shutter speed

[BruceAmmons]

I am not aware of a specific limit on the number of cameras.  If it exists, it is pretty large.  As long as the sum of the bandwidths used by each camera doesn't exceed the total bandwidth of the firewire connection, you shouldn't have any problems.  However, if you have too many cameras the frame rate for each camera will be very, very slow.

Bruce

[danilo]

Helo!

Thanks for reply.

But in case that I don't take simoultaniously picture from all cameras then

frame rate should be the same or not. For better understanding I don't need to grab images from

all cameras at once, but sequentionally one after another. Should then frame rate also drop down?

Dan

[BruceAmmons]

Even if you aren't using images from all the cameras at once, you are still doing all the Grab operations in the background.  The pictures are continuously being acquired and are ready for use when you need them.  Therefore, you still need the bandwidth for each camera.

If you were to start and stop different grab operations, you could use higher bandwidth per camera, but the starting and stopping is the slow part of the acquisition.  It would only work if you were using a large number of cameras and wanted to rotate between them.

Bruce

[danilo]

What if I have several IEE1394 controlers? Does it change anything?

Dan

[rkrijger]

On my computer, multiple controllers did not help. I think the problem is the bandwidth of PCI.

[danilo]

Hello!

I have new problem. I started testing my system with 2 Firewire cameras.
Because of speed reasons I switched from SNAP to GRAB mode. The speed
looks OK, but I don't acquire correct images. Before GRAB image command I allways
change parameters of camera( shutter time) and after that I get wrong image.
If I put big Delay betwen camera parameterization( shutter time ) and GRAB image command
then I get good picture, but time requiered for that is long as SNAP mode acquisition.
I don't now if this is normal??? Please help!

Dan

[rkrijger]

Try taking two snapshots and skip the first one.

If you immediately grab or snap your image after setting shutter speed or brightness/gain stuff, you might get the image from the buffer *before* the brightness/shutter/gain was modified.

I got the same problem when setting LEDs, and this was the solution for me.

Let us know if it works!

[danilo]

Hello!

Yes it is better, but it is far too time consumptive, so acquisition takes more than SNAP.

Anyway thanks! Maybe other solutions???


Message Edited by danilo on 01-25-2008 12:55 PM

Message Edited by danilo on 01-25-2008 12:56 PM

[rkrijger]

Another solution is other hardware. You might want to consider a framegrabber.

I had time issues with IEEE1394.

I solved it with a redesign of my software and performing several tasks parallel.

But it *is* a pain in the ass anyhow!

Hope this helps...

[danilo]

That are not good news..