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Thread: UVC cameras for computer vision , ways to improve latency?

  1. #1
    Join Date
    May 2018
    Posts
    56

    Default UVC cameras for computer vision , ways to improve latency?

    Any computer vision geeks here?

    In a budget the expensive high framerate vision cameras aren't much of option.
    I have manage to find good 120-330 fps UVC cameras at reasonable price but their latency (total latency from sensor capture to display on monitor) is 50ms. I wish to improve that a little.

    I can't use USB3 and need to use USB2 and mjpeg compression because of the singleboard computer bandwith limitations and API requirements. I understand that adds to latency. I imagine compression and decompression on the computer adds a lot to the total latency.

    1) first question is can't we set the compression level of mjpeg to basically no compression or absolute minimum? Because even then the USB2 standard should provide enough bandwith (320x240 resolution at 120 fps at 24 bit color is 221 Mbit/s which USB2 should handle).

    2) Using grayscale capture for NIR camera lenses? From what I understand camera sensors work similar to LCD (subpixels) screens rather than DLP/LCoS (color sequential) but even then the latency may improve because less (1/3) of the photosensors will be read and even if that wasn't the case converting RGB to grayscale from the cameras IC then to mjpeg will probably waste a ms or two.
    If I am right in any of these (please mention which) what does it take to make the camera capture in grayscale?

    And if anyone has experience with this and results they got please share.

    PS: If you are interested in these USB 2 cameras I can provide links to buy them (cost is 12 usd to 75 depending on fps)

  2. #2
    Join Date
    Oct 2012
    Location
    Germany
    Posts
    1,478

    Default

    ... I was using industrial BW-cameras, extracted out from old dentalscanners -- but Win7 (and 10 too) didn't support the old drivers, so fixed to XP for them.

    Have newer cameras with USB2 and 60fps, but eventually interested in faster grabbing too ...

    Viktor

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