I cannot get Still Color operation using ImgGrab. Is there a reason why?

[PBatson]

I am using a 1409 grabber to acquire a monochrome slow scan signal using ImgGrab.  I would like to acquire 3-4 signals simultaneously using the same slow scan synchronization and assumed that setting up for RGB32 acquisition while feeding the additional channel inputs with the extra signals would accomplish this. It does not work.  I have looked at the Still Color C application and can manipulate this, making it do sensible things.  But it uses ImgSnap, rather than ImgGrab.  Is Still Color Mode compatible with ImgGrab, and if not how can I get an RGB acquisition with ImgGrab?  I am using NI-IMAQ in an MS C windows application.   

[DJ_L.]

Hey PBatson,

NI-IMAQ features a standard continuous acquisition routine that uses the high-level grab functions. StillColor, however, is only supported by the high-level snap function. In order to simulate the results of a grab, you must perform a snap, call IMAQ Init to reinitialize the IMAQ device, perform another snap, and so on to obtain a series of images. You can actually create a high-level routine for a continuous StillColor acquisition without reinitializing your IMAQ device at the start of each new image, such as using a while loop with the imgSnap.

I hope this answers your question. Please let me know if you have any further questions about this. Thanks, and have a great day.

Regards,

DJ L.

[PBatson]

Thank you.  I suspected this, but it wasn't clear in the documentation.  It doesn't fullfill my need, though, because I have a slowscan use at 5 frames per second.  Using multiple Snaps interleaves signals at the frame level.  I need signals interleaved at the pixel level so the channel information is obtained more or less simultaneously.  I thought that the availability of "color", and the presence of 4 hardware inputs, indicated an ability to digitize 3 or 4 signals simultaneously.  A block diagram of the signal processing in the advertising literature would have prevented this misconception. 

[DJ_L.]

Hey PBatson,

There actually is some documentation on the NI website about the 1409 and connecting multiple signals. There is a KnowledgeBase document called How Can I Connect Multiple Video Signals to an Analog IMAQ Device? This document explains "The NI 1409 has only one analog to digital converter (ADC) to digitize the incoming video. The board can acquire from up to four different cameras, but only from one camera at a time. Similar to most NI Data Acquisition (DAQ) boards, the incoming video signals are multiplexed to the single onboard ADC."

Sorry for the misconception. If you need the ability to digitize three or four signals simultaneously, then you might want to consider multiple framegrabbers. Just an option.

Regards,

DJ L.