camera_info_url is located where?

[vxgu86]

https://github.com/NVIDIA-AI-IOT/redtail/wiki/Testing-in-Simulator said that:
trailnet_debug.launch file runs several nodes, including camera (uses settings for left ZED camera by default), DNN (uses TrailNet DNN by default), debug and other necessary nodes. Check the file for more details. Instead of camera, you can use image_pub node to play video or images, make sure to set parameters frame_id and camera_info_url accordingly.

but where is the camera_info_url located?
what is the meaning of it?
I changed it to
home/nvidia/ws/src/zed-ros-wrapper/zed_wrapper/params/zed.yaml
which is from the zed_ros_wrapper, but the launch said error:
[ INFO] [1570013434.619257418]: camera calibration URL: file:////home/nvidia/ws/src/zed-ros-wrapper/zed_wrapper/params/zed.yaml
[ERROR] [1570013434.619931300]: Exception parsing YAML camera calibration:
yaml-cpp: error at line 0, column 0: bad conversion
[ERROR] [1570013434.620008935]: Failed to parse camera calibration from file [//home/nvidia/ws/src/zed-ros-wrapper/zed_wrapper/params/zed.yaml]

[mtbsteve]

I just ran into the same issue when I try to launch gscam. gscam is expecting the camera calibration file as apparently mandatory input. The different zed launch scripts define a camera info file like:
<arg name="camera_info_url" default="file:///home/nvidia/zed_wvga.yaml" />
Such file does not exist in the repo nor I found a way how to create it. Any hints welcome!