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Unread 01-02-2010, 10:05
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Doug Norman Doug Norman is offline
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Re: Camera lag...again

I did some testing and didn't see any difference with lag between Developer and Driver accounts. For me, using LabVIEW, a compression of 5% helped. Beyond that didn't make much difference - except very high compression lost sight of the target. While checking loop rates I started out doing some averaging, but I also watch individual loop times. There were occasions when the individual times were obviously too fast (like 2 ms). We did a little poking around and found a timeout in the vision code that was set to 100ms. This means if we took longer, it would return anyway with empty data. The next time through the loop the data might be there after only another millisecond or two. This means for two loops, we really only got one set of vision data, but the timing seemed twice as fast (or at least faster) when averaging.

This doesn't affect actual performance much, but we will be fixing it in the near future. If you want to look at this, you can find it in Program Files\National Instruments\LabVIEW 8.6\vi.lib\Robotics Library\WPI\Camera\Send Images To PC.vi where the Wait for Raw Image String subVI has 100 wired to it.