Lost frames at high frame rates

[asrm]

Hi!

I am using a bonito camera that can acquire colour image at 200 fps with a resolution of 2320 x 1723 (MAX display). In order to save this amount of information I got a NI PCIe - 1433 Frame grabber and a solid state disk that can write up to 500 MB/s (OCZ SSD Agility 3 120GB SATA III).

I am also using the "LL Ring.VI" example to grab and save the movies. However I always lost some frames.

What can I do to avoid this situation?

Thanks

Ana

[toto26]

Hi,

How did you save your sequence? If you save it in avi format, don't use compression codec which is time expensive.

You can use a fifo architecture in your code to have a little more flexibility and avoid losing frames.

I suggest to benchmark your write to disk function. If this is the weakest link, then you should have a look at low level stream to disk: http://zone.ni.com/devzone/cda/epd/p/id/5348

Hope this help

[asrm]

Hey!

Thanks for your email! I am not using any compression codec.

Can you help me to build this fifo architecture in the "LL Ring. VI" example? I don't know how to do it.

Thanks

Ana 

[toto26]

HI

Have a look at this post: http://forums.ni.com/t5/LabVIEW/How-does-labview-deal-with-enqueuing-dequeuing-images/m-p/871875

[BruceAmmons]

With rough calculations, each image (2320x1723) is 4 MB, assuming they are 8 bit grayscale.  At 200 fps, that would be 800 MB/s.  If your hard drive can only write 500 MB/s, you are going to lose some frames!!!  And that is assuming it is perfectly optimized, which may be impossible.  You should be able to get close to that rate, perhaps 400 MB/s.  I would aim for 100 fps or reduce the image size, or get another hard drive and split the load.

Bruce