How to get the timestamp on the start of a capture using LibArgus?

My program has a while loop calling capture and then acquireFrame. I have got the timestamp right after a capture, and got the SensorTimestamp in the metadata of a frame. But there is about 0.1 second delay between these two timestamps. So it seemed like the SensorTimestamp wasn’t on the start of a capture. Is there any other method to get a more accurate timestamp?

The SensorTimestamp is the real SOF time. However the acquireFrame from APP not the really time to start capture. They have queue for the capture request from the APP.

May I ask what is SOF? I only captured once in each loop so I think there was no delay caused by queuing.

Start Of Frame.