If I only have photo data, how can I estimate the camera's internal and external parameters

[smart4654154]

If I only have photo data, how can I estimate the camera's internal and external parameters？

I have read the code:

Edit path to the folder containing the renders

DATASET_PATH = "./small_room"

Edit path to the folder containing the cube calibration images.

OBJ_DATASET_PATH = "./cube_calib"

Edit marker size in meters

MARKER_SIZE = 0.48 * 0.575

Check which IDs are used

MARKER_IDS = list(map(str, range(24)))

dataset = Dataset(root=DATASET_PATH)
obj_dataset = Dataset(root=OBJ_DATASET_PATH)

I find that I must have cameras.json.
cameras.json has camera's internal and external parameters
but I only have photo data,so I do not have cameras.json.I am unable to continue executing the code.
how can I estimate the camera's internal and external parameters？
thank you