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Frame Rate Control


When the camera is in free run mode (default setting), the image acquisition happens at the fastest frame rate allowed by the current settings of the camera.
It is possible to switch the camera to a frame rate mode and control the acquisition frame rate.

Feature parameters

xiApi parameters

Feature related parameters
XI_PRM_ACQ_TIMING_MODE = Timing mode*
XI_PRM_FRAMERATE = Frame Rate in Hz

XI_ACQ_TIMING_MODE_FREE_RUN

For camera families MQ, MD the XI_PRM_FRAMERATE reports current frame rate with same minimum and maximum.

For camera families CB, MC, MT, MX the XI_PRM_FRAMERATE reports the last frame-rate-limit set regardless of current frame-rate of the camera.

XI_ACQ_TIMING_MODE_FRAME_RATE

In TIMING_MODE_FRAME_RATE the acquisition of next frame is triggered from exact period generator in FPGA (e.g. 25.000Hz).
This mode is supported by camera families MQ, MD.

  • The maximum value of XI_PRM_FRAMERATE is dependent on various factors (camera type, available bandwidth, exposure time etc.) and can be read out using the API parameter modifier XI_PRM_INFO_MAX.
  • The minimum value of XI_PRM_FRAMERATE minimum is constant for all cameras = 0.8Hz

XI_ACQ_TIMING_MODE_FRAME_RATE_LIMIT

In TIMING_MODE_FRAME_RATE_LIMIT the acquisition of next frame is triggered by control engine in FPGA that limits the frame rate to frequency defined by parameter XI_PRM_FRAMERATE.
If real frame-rate of sensor is higher than limit - it is limited.
If real frame-rate is lower than limit - it is NOT limited.
This mode is supported by selected camera families: CB, MC, MT, MX

  • The maximum value of XI_PRM_FRAMERATE is typically constant like 10000Hz represents value that is normally not reached by real sensor acquisition frame rate.
  • The minimum value of XI_PRM_FRAMERATE minimum is constant like 0.01Hz

Sample code

// set acquisition to frame rate mode
xiSetParamInt(h,XI_PRM_ACQ_TIMING_MODE, XI_ACQ_TIMING_MODE_FRAME_RATE);
// set frame rate
xiSetParamInt(h,XI_PRM_FRAMERATE,20);
// Start acqusition
xiStartAcquisition();

NOTE: The order of parameters setting is mandatory.

GenICam reference (SFNC)

AcquisitionTimingMode = FrameRate
AcquisitionFrameRate = Frame-rate-in-Hz |