missing frames with IEEE 1394b firewire camera

[Ward T]

I am using a Teli Toshiba Firewire b camera with labview 8.5 in a Dell Laptop computer.  The camera is externally triggered at 30 Hz and the video is displayed in various Labview VI's including Triggered Grab and also in MAX.   The laptop is a Dell Latitude D600 with 1.7 GHz Pentium M processor and 1 GB RAM running Windows XP Pro SP2.  Some times the system will display a steady full image at the full 30 Hz or at least 29 frames/second.  Then, without changing anything, it will only operate at 19 or 20 frames/second and the image breaks up on the lower half.  I have tried removing running processes in Windows and giving Labview a high priority and sometimes get better performance, but still have missing frames.  The device/processor window in Windows shows that the processor is only operating at 20 % capacity, so the computer does not seem to overloaded. 

Any suggestions on how to get stable camera operation?  I have switched to a newer dual core processor notebook system, but still see the same issues. 

Ward T

[Nate.H]

Hi Ward,

Just to clarify, do you experience this trouble when preforming a grab in MAX? From your post I am unsure if you are having trouble in all the LabVIEW VIs & in MAX, or if some VIs and MAX run fine, but you are having the problem in a particular VI.

What are your Video Mode, Speed, and Packet Size settings in MAX under "Acquisition Attributes"? These settings will determine what framerate is achievable.

Do you have a FireWire B card in the computer? If you have a FireWire B camera and a FireWire A card, you will be limited to 400Mb/s instead of the 800Mb/s possible with FireWire B.

Is there any pattern that you notice when you start getting only 19 or 20 fps, or is it seemingly random?

If you acquire without the external trigger at the same frame rate, do you get the same behavior?

Hopefully the answers to the above questions will help in narrowing down why you are experiencing this behavior.

Best Regards,

~Nate

[Ward T]

Hi Nate,

Thanks for the response. 

Yes, this problem occurs in both MAX and various VI's.  However, the strange thing is that sometimes I can get the full 30 frames/sec.

I am using a Firewire B card plugged into the labtop.  It does run at 800 MB/sec, but that speed required rolling back the driver to the windows XP SP1 version.  The driver with windows XP SP2 reduces the speed to 100 MB/sec.

When using MAX, the video mode is 640x480 RGB 8 packed 30 fps.  Speed:  800 MB/sec.  Packet:  3840 bytes

When the frame rate is 19 fps, generally the top half of the image is stable and the bottom half jumps vertically frame to frame.

I tried operating without a trigger and have the same problem.

When I tried operating at 60 frames/sec. triggered, I got frame rates from 33 to 44 frames/sec.

When I tried 15 frames/sec, the image and frame rate were stable at 15 fps.

I will work at 15 frames/sec until I find a solution.  I think the problem may be related to various windows services, but not sure yet.

Ward

[Nate.H]

Hi Ward,

This certainly is strange. Here are a couple of troubleshooting suggestions:

1) Could it be that the camera is not being provided sufficient power over the FireWire bus from the Laptop? Can you try out the camera on a desktop machine to see if there is any difference there?

2) Are there any Format 7 options under the video modes? I am curious to see if operating in a Format 7 mode (camera specific format) makes a difference.

3) When you say the bottom half of the image jumps from frame to frame, does this mean that the break between the stable top half and the unstable bottom half is at the same location every time, or does it vary height wise in the image? Maybe you could post a sample of an unstable frame(s)?

I am still puzzled on this one. The fact that your performance is intermittent makes this an interesting problem. Good luck on the troubleshooting! Let me know how it goes.

Best Regards,

~Nate

[klaus0]

Hello,

two observations I've made that might be of help:

• I've seen similar behaviour and it was caused by the antivirus software getting active at regular intervals.
• The broken-up images you're seeing may actually be intact but only displayed in a distorted way. Have you tried saving images and looking at them offline? 

Cheers,

Klaus