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CameraConfig.md

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CameraConfig.md

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Dictionary

Either create dictionary in your program or import ti from the config folder e.g. examples/configs/all_capture_configs.py

  1. set appropriate resolution and frames per second.
  2. determine the exposure and autoexposure settings.
  3. consider white balancing.

Video Flip

method name description
0 none Identity (no rotation)
1 clockwise Rotate clockwise 90 degrees
2 rotate-180 Rotate 180 degrees
3 counterclockwise Rotate counter-clockwise 90 degrees
4 horizontal-flip Flip horizontally
5 vertical-flip Flip vertically
6 upper-left-diagonal Flip across upper left/lower right diagonal
7 upper-right-diagonal Flip across upper right/lower left diagonal
8 automatic Select flip method based on image-orientation tag

Exposure and Autoexposure

The config keys exposure and autoexposure are interpreted differently depending on the capture backend (OpenCV, GStreamer, Picamera2/libcamera, legacy picamera).

key what it does typical values
exposure Manual exposure request. >0: time/value (often µs on PiCamera2/libcamera and Jetson nvargus). Some OpenCV webcam drivers use negative “stops-like” values (e.g. -5 ≈ $2^{-5} = (1/32)$ on some devices; not portable). 0/-1: often means “auto/leave default”, depending on backend.
autoexposure Auto-exposure (AE) on/off request. OpenCV: -1 keep, 0 manual, 1 auto; many V4L2 cams also accept 0.25 (manual) / 0.75 (auto). Other backends either ignore this key or map it differently.

Backend details:

  • OpenCV (cv2Capture):

    • autoexposure = -1 leaves AE unchanged; 0 requests manual AE mode; 1 requests auto AE mode.
    • Some Linux/V4L2 drivers commonly accept 0.25 (manual) and 0.75 (auto). Windows/macOS backends can differ.
    • exposure > 0 requests manual exposure and the code attempts to disable AE first. The numeric meaning of CAP_PROP_EXPOSURE is driver-specific (some cameras use negative values, others use milliseconds/microseconds-like scales).
    • To inspect what your OpenCV backend/camera supports, run python3 examples/list_cv2CameraProperties.py.

  • GStreamer (gCapture):

    • gCapture builds a pipeline and the meaning of “exposure” depends on the selected source element:
      • Jetson nvarguscamerasrc: exposure is treated as microseconds (converted internally) and applied via exposuretimerange when supported.
      • libcamerasrc: exposure/AE are controlled via libcamera controls, but the exact property interface is element-version specific. Use gst-inspect-1.0 libcamerasrc and set the element’s control-related properties via gst_source_props_str, or provide a complete custom source with gst_source_str.
      • v4l2src: exposure is typically controlled via V4L2 controls (recommended: v4l2-ctl from v4l-utils). Some GStreamer builds expose an extra-controls-style property on v4l2src, but it is not consistent across platforms/drivers.
      • Windows ksvideosrc / dshowvideosrc: many cameras do not expose manual exposure controls through these elements. If the element exposes a property for it, you can set it via gst_source_props_str; otherwise use vendor tools / OS camera settings (or configure exposure through a separate API).
    • Use gst-inspect-1.0 <element> to discover supported properties and set them via gst_source_props_str or a fully custom gst_source_str.

  • FLIR/Teledyne Spinnaker (spinCapture, PySpin):

    • exposure is in microseconds and maps to ExposureTime (requires ExposureAuto off and ExposureMode=Timed).
    • autoexposure: 0 off, 1 on (continuous/once depending on camera settings).

  • Raspberry Pi Picamera2/libcamera (piCamera2Capture):

    • exposure is interpreted as microseconds and mapped to libcamera ExposureTime.
    • autoexposure maps to libcamera AeEnable (>0 enables, 0 disables, -1 leaves unchanged).

  • Raspberry Pi legacy picamera (piCapture):

    • Exposure is controlled via shutter_speed in microseconds.
    • In this backend, exposure <= 0 uses automatic exposure (exposure_mode='auto'); exposure > 0 requests manual exposure (exposure_mode='off' plus shutter_speed).

Maximum usable exposure time is typically limited by frame interval. Roughly, max exposure is about $\frac{10^6}{\mathrm{fps}}$ microseconds (camera/driver may clamp differently).