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Weird frame rate with binning pixels




  • Official comment
    Community team
    Expert (Gold)

    Hello Nghia,

    For some of the sensors such as the ones you mention, the framerate is limited by the sensor, and not by the bandwidth.  Depending on the size of the image, the ISP on the camera sometimes can not keep up as well.

    Since these cameras do not support on-sensor binning, and binning is done in the FPGA, we are reading the whole image off the sensor.  We can do 2x2 binning outside of our ISP, but 4x4 has to be done in the ISP, which can slow down the max framerate.

    To help explain what is happening on the cameras, here is an example with your 12MP model:

    For example for the BFS-PGE-122S6C:

    No Binning, 4096x3000, 8.99fps
    2x2 binning,  2048x1500, 15.11fps
    - note that this is only if ISP is disabled.  We can do the 2x2 binning outside the ISP, so we get a framerate increase.  There is more link bandwidth available here, but we are hitting the max sensor full res framerate.
    - if you enable the ISP in 2x2 binning mode, the max framerate is 10fps.  This is because this is the max speed of the ISP
    4x4 binning, 1024x720, 10fps - This is because we need to run through the ISP to do the 4x4 binning, and the max framerate through the ISP for this resolution is 10fps

    If the binning could be done on the sensor, then the framerate would certainly increase more.  But some of these sensors do not support color binning on the sensor.

    For the BFS-PGE-50S5C, I expect something similar as above, but I don't have the camera handy to verify exactly.  The camera should be able to do 24fps full res no binning, and 24fps 4x4 binning (ISP limit).  2x2 binning with ISP should also be 24fps, but with ISP turned off is when you likely get the higher 36fps.

    I hope this helps explain what is going on.  In summary, 4x4 binning needs to run through our on-camera ISP, so that is what is slowing down the framerate in 4x4 mode.  The framerates are not going to be 4x and 16x, as we are limited by the sensor framerate (not link bandwidth) since binning is not done on the sensor so we are still reading out the full frames.

    If I can help clarify further, please let me know.

    Thank you,



  • Nghia Ho

    Thanks, that's very helpful to know!


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