Filter Guide: Calibration Tool - Crowsinc/LiveVisionKit GitHub Wiki

A tool for creating camera calibration profiles to use in other filters.

This tool uses a calibration pattern to facilitate the creation of calibration profiles for use in camera/lens specific filters, such as the Lens Correction filter. Check out the Instructions section learn how to perform calibrations.

Specifications

  • Filter Type: Video or effects filter
  • HDR Support: No
  • Performance Impact: N/A
  • Special Requirements:
    • Must have an OpenCL capable GPU.
    • Should be used on raw, unaltered video from the desired camera and lens combination.
    • You will need a black and white printer for the calibration pattern.

Settings

  • Profile Name: The chosen name of the new or existing calibration profile which will be created or replaced.

  • Square Size: The side length, in millimeters, of the black squares in the calibration pattern.

  • Capture Frame: Advances the calibration process by capturing the current frame. Once all frames are captured, it is used to generate the calibration profile instead.

  • Reset: Resets the calibration progress, starting a new calibration.

Instructions

Read all instructions before attempting.

  1. Download and print the calibration pattern on white paper. Then use clear tape on the corners to adhere it flat to a white rigid surface such as a door, within a brightly lit area. You should also measure the side length of the black squares in millimeters. If no scaling was applied during printing, they should be 24mm long.

  2. Set up OBS so the calibration tool filter can be applied to unaltered video taken by the camera and lens combo being calibrated. We recommend recording a video and loading it into OBS through the VLC Video Source with the calibration tool applied. It can also be done with a live video feed but you may need two people; one to control the camera and one to control the calibration tool. Note that the calibration tool will overlay the following useful information onto the video:

    • Profile: The chosen profile name.
    • Square Size: The measured square size.
    • Captures Remaining: The remaining number of captures required to finalize the calibration.
    • Status: The calibration status and any issues which must be resolved before finalization of the calibration.

  3. Fill in the desired name of the calibration profile and the measured square side length in millimeters.

  4. Stream/Record a video that replicates this example video. As shown, the video should present the calibration pattern straight ahead and then at 45 degrees left, right, up and down. For each of those 5 angles, pan the camera so the full pattern appears in focus at the center and corners of the frame.

  5. Press the 'Capture Frame' button as shown in this example video for each of the positions mentioned in step 4. The corners of the inner squares of the pattern will be briefly highlighted and the 'Captures Remaining' overlay element will decrement. If this does not happen, or the corners do not match up with the inner squares, then the calibration tool is unable to locate the pattern. You should aim to imitate the conditions of the provided example video and try again.

  6. The 'Capture Frame' button will become a 'Calibrate button' once all 25 captures are completed. When pressed while the 'Status' overlay element shows 'ready for calibration', the button will finalize the calibration and save it to the profile. The status will update to 'calibration successful!' if the profile was successfully saved. If 'calibration failed!' is displayed, the calibration tool was unable to save the calibration to the desired profile.

  7. Your calibration profile should now appear for selection in filters which require it. The filter may be removed if no longer needed.