Video Stream In TOP frameTime Timestamp to figure out delay

I am using the Video Stream In TOP with a rtsp stream. I am trying to figure out the exact timestamp of each frame so that I know the exact delay to my local time on the machine. The member “timeStamp” from the python class returns a floating number in seconds, it seems to show seconds since starting stream? Is that correct? Digging deeper into rtsp it doesn’t seem to have an easy way to extract a timestamp, its somewhere deeper in the RTP stream and its header.
Maybe somehow has been there and knows another way finding out the delay of the feed itself??

Many thanks

The value we output is the timestamp contained in the packet we get out of FFmpeg’s library. How this is filled is a level beyond what we control.