> For the complete documentation index, see [llms.txt](https://docs.theiamarkerless.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.theiamarkerless.com/apollo-v2024/troubleshooting/error-messages/required-camera-parameter-groups-not-present.md).
# Required camera parameter groups not present
### Explanation
This error message arises when loading a calibration file. It indicates that the selected calibration file does not contain the required calibration parameters to calibrate the camera system of the loaded videos. The calibration file may be missing intrinsic parameters, extrinsic parameters, or a combination of both, which prevent it from calibrating the camera system for the video data.
### Possible Solutions
1. Check that the calibration file is an extrinsic calibration file. The selected calibration file may be a lens intrinsic calibration file, rather than an extrinsic calibration file. Confirm that you selected the correct calibration file, which was either saved after processing a chessboard or object calibration in Theia3D, or was generated by third party software such as Qualisys Track Manager or Vicon Nexus following wand calibration.
2. Check that the calibration file has not been modified. The selected calibration file may have been modified, and some calibration parameters may have been deleted. If parts of the calibration file have been modified or deleted, you may need to replace it with a backup of the original calibration file (if generated from third party software), or generate a new calibration file by reprocessing the chessboard or object calibration trial in Theia3D.
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