publishing calibration data with bag file

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Hi,

I recorded a bag file with a video sequence. The corresponding bag file does only contain the image_raw topic, as by the time I recorded the sequence I had not calibrated the camera yet.

Now I have calibrated the camera, and I would like to play the bag file and simultaneously publish the camera_info data so that, for example, I can undistort the images from the bag file using image_proc.

How can I start a publisher that only publishes the camera_info ? Or could I add this camera_info in some way to the pre-existing bag file ?

Thanks