Camera Timestamp From Camera Server Question

[mkriesel]

Hello, I am pulling images from the voxl-camera-server of a ar0144 camera over the modal pipe and was wonder what was meant by " int64_t timestamp_ns; ///< timestamp in apps-proc clock-monotonic of beginning of exposure", if this is the case if I am looking for the "center of exposure time" does this mean I take the "exposure_ns" and add half of that to the timestamp_ns?

[Alex Kushleyev]

@mkriesel,

For global shutter camera like AR0144, the center of exposure will happen at the time that you suggested:

int64_t center_of_exposure_ns = start_of_exposure_ns + exposure_time_ns / 2;

For rolling shutter cameras, this is not true because different lines are exposed at different times. In this case, the center of exposure, which means the center of exposure of the middle line ( ) will be:

int64_t center_of_exposure_ns = start_of_exposure_ns + (exposure_time_ns + readout_time_ns)/2;

This means that you will need to know the readout_time (which is time it takes for the full image to be transferred from the camera). It is not currently exposed in camera server or the camera metadata.

Take a look at this resource, it should help understand the rolling shutter case if you need : https://www.1stvision.com/cameras/IDS/IDS-manuals/en/basics-shutter-mode.html , specifically:

Alex