Image acquisitio​n slower than expected on Win 7 64bit

Question

Hi all,
I wanted to know if anyone had issue after upgrading OS from Windows XP to Windows 7 64bit.
I had a fairly big project the runs fine on Windows XP, hardware is computer + PCIe 1433 + Basler A504 + external trig source. The frame size 1000*128 pixel so I can acquire at 4kHz. This works fine. NI Software is LV 2011 SP1 + lastest VDM and VAS.
I've tried to switch to Windows 7 64bit with LV 2011 SP1 + VDM + VAS all in 64bit versions and the acquisition doesn't work as I expect.
I've put together a test VI that configures the acquisirion in a similar way that my app does (triggered ring acquisition) with my external trig source set at 4kHz, when I run it, instead of having a 4kHz frame rate I get ~250Hz frame rate.
I also tried triggered acquisition in MAX because I know MAX gives me 2 information : display frame rate and acquisition frame rate, both appear to be ~250Hz.
I contacted NI about this issue, an application engineer has been able to reproduce the issue with similar hardware and we're trying to identify the reason.
Anyone has a clue?
ps : here's the code used to test the acquisition on Win 7 64bit.
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Attachments:
TestAcqu_64bit.zip ‏99 KB

Answer 1

Hi TiTou,
Please make sure that you are not triggering the camera and the frame grabber board.Sending a trigger signal to the camera in order to trigger acquisition of every frame.  In this case, there is no need to trigger the frame grabber board as well because the camera is being triggered directly.  What was causing the acquisition to run at half the triggered frame rate was the way the signals lined up.  The camera begins acquiring on the rising edge of the trigger pulse.  Once a rising edge is received, FVAL goes high and remains high as long as the camera is exposing.  It then goes low until another trigger pulse is received. 
At the same time, if you are triggering each buffer on the frame grabber, the frame grabber waits to begin reading data from the camera until a rising edge is received, and then begins read out once FVAL goes low.  The result is that the frame grabber begins reading out the current frame, which takes about as long as the camera takes to acquire a frame.  So while the frame grabber is reading out the data, the camera receives the next trigger pulse and begins acquiring the next frame.  However, the frame grabber is still reading out the previous frame and thus ignores the trigger pulse until it finishes, resulting in an acquired frame rate that is exactly half of the triggered rate.  At lower rates, there is enough time for the camera and the frame grabber to acquire the frame off the same trigger pulse and "re-arm" before the next pulse arrives.
Elmar
PS: Please also make sure the exposure time is lower as 161us.