Getting played time in RTSP video

[Bruno Gonzalez]

Hi,

I have a server-client video streaming using gstreamer and RTP. So basically:
[source storage] --> [server] ---------> [client] --> [frames rendered
on screen]

Is there any way to know, for each rendered frame, what was the
original playing time in the video source of the server?

For example.
 - At 10 fps, after 30 seconds of playing, the "playing time" would be
300.0 seconds.
 - But if the network is slow, the playing time could very well be
only 276.4 seconds.
 - Or maybe some frames could be lost if using UDP.
 - Also, if the source storage has variable framerate, I cannot use
"10fps" or any other average fps for any calculations.

How could this be achieved?

Thanks!