"IMAQdx Configure Grab" vs "IMAQdx Configure Acquisition " on 1394 wrt buffers.

[AndyN]

What is the real difference between those two functions with respect to internal image buffers and execution efficiency? I assume that IMAQdx Configure Grab have two buffers(space for two frames) by definition (I think I read it somewhere...)

I am doing continuous acquisition and processing at 60fps and I am long done before the next frame comes. Even, if somehow I lose frame ( ie. don't have time to process), it is not a problem for me. Considering this, is there any benefit of using IMAQdx Configure Acquisition and setting like 3 buffers instead of using standard IMAQdx Configure Grab?  I guess the real question is about the existence of any execution/performance gains when going form High Level functions on the Image acquisition palette to Low Level functions, assuming that I do not care if once per a few hundred frames I skip one?

The IMAQdx manual strongly suggests using the LL functions for continuous acquisition but the only reason it gives, is the possibility of loosing a frame. Can someone, please clarify? Thanks

LV 2009 SP1 RT. 1394 with Basler A601F

[BruceAmmons]

I think you are right that it is mainly the number of buffers.  With Grab, your only option is the last buffer that was acquired.  With the LL functions, you can configure a large buffer to allow for delays.  Very important if you can't afford to miss a single frame.  If you aren't worried about missing an occasional frame, Grab works just fine.

I think the acquisition itself works the same way no matter what, and there are no performance differences between the two methods.

Bruce

[AndyN]

Can anyone confirm the number of buffers on High Level Grab in IMAQ and IMAQdx? 

From the online resources it seems IMAQ has two but IMAQdx? Based on the property of the Overwrite it can have three? That is just my guess.

I did not see OverWrite property for IMAQ.  My guess is that It would not make sense just with the two buffers?

Thanks.

[Matt_McLaughlin · Accepted solution]

Hi Andy,

If you open up the Block Diagram of the IMAQdx Configure Grab, it calls the IMAQdx Configure Acquisition VI. The inputs to the Configure Acquisition set it to continuous acquisition with the number of buffers set to 5. Is what you were wondering about regarding the High Level Grab and its number of buffers, or am I simplifying te question?

[AndyN]

Thanks, my bad for not checking if I can get inside that function.