1394 slow when opening port or changing shutter speed

[rkrijger]

Please... don't kill the messenger... 😉

[DelphiDan]

I change shutter speed a lot and immediately before a Grab and never had any problems.   I'm using 8 AVT Guppy cameras off 2 Dual port IEEE1394 PCI boards.   I'm doing color LED inspection which requires a lot of shutter speed changes to adapt to different wavelengths.  Maybe you're not clearing the buffer before getting the next image.    I've attached my VB code with 2 procedures.  One procedure opens the camera port and that other procedures grabs an image.  Maybe you will notice something different.  You will notice that I once used the "SnapCw" function, but it is now commented out because of being a cycle time hog.

[danilo]

Hello!

Looks like we hav esimilar application. My aplication is also mentioned for LED testing.

But anyway I don't see any diference, except that before acquisition I readjust all camera parameters
not only shutter time.

Regards!

[DelphiDan]

I've never tried to change a lot of camera parameters before doing a Grab.  Maybe it's the collection of parameters that's causing the problem or maybe one isolated parameter causing the problem.   I would debug this by going through 1 parameter at a time to see if it's a particular parameter first.  What video mode are you using?   I had some problems with Format 7, mode 0, which I don't use anymore.   I use standard mode (1280 X 960 15fps)

From JoAnnS on a previous post:

For a standard mode (1280 x 960 15fps) there are very few registers to write. For a partial scan mode (Format 7, mode 0 1392 x 1040) there are a LOT more register to write

Maybe this is causing the extra time you are seeing.

[danilo]

I also use standard mode 1280*960 and nothing elese.

Regards!

[Jaidev]

Hi danilo,

Different parameters are written to the camera differently. If you change parameters during a grab, the driver sometimes needs to stop acquisition in order to write to the camera. Shutter speed is definitely one of these parameters. Now for some parameters, it might be faster to write directly to the registers than for the driver to execute the action. This however, needs you to have precise information about the parameter you are writing and the registers that you are writing to. If you have this information from the camera datasheet, you could use the Read register/Write register VIs that ship with both our IEEE1394 drivers. In this case, you will also need to check that parameter was written correctly by parsing the return string, if any.

-Jaidev

[danilo]

To DElphiDan: What did you mean with clear buffer after shuter time is adjusted?


Message Edited by danilo on 01-29-2008 03:04 AM

[danilo]

Hello!

In VB there is no Read/Write Buffer commands. Is there any other way?

DAn

Hi danilo,

Different parameters are written to the camera differently. If you change parameters during a grab, the driver sometimes needs to stop acquisition in order to write to the camera. Shutter speed is definitely one of these parameters. Now for some parameters, it might be faster to write directly to the registers than for the driver to execute the action. This however, needs you to have precise information about the parameter you are writing and the registers that you are writing to. If you have this information from the camera datasheet, you could use the Read register/Write register VIs that ship with both our IEEE1394 drivers. In this case, you will also need to check that parameter was written correctly by parsing the return string, if any.

-Jaidev

 

National Instruments
Applications Engineer

[danilo]

Hello!

I'm still thinking on use of camera in SNAP mode nad for me firewire is too slow. What do you think about GigE camera?
Do you think I can expect increase of speed in SNAP mode?

Regards!

Danilo

[Jaidev]

Hi Danilo,

GiGE cameras can certainly acquire fasters than firewire cameras in most cases. But again, For a snap, a session needs to be created every time so it represents some finite overhead per frame.

-Jaidev