calculating RTP delay at receiver side since the packet was sent from sender.

i am using direct peer to peer browser–> gstreamer
using webrtcbin element in gstreamer

previously I tried this with mediasoup browser–>mediaosup->gstreamer
but the NTP time in RTCP was incorrect .
came to know that mediasoup changes the RTP time and NTP time form here Forwarding NTP timestamp from source - #5 by oto313