We need a couple of tcpdump/Wireshark files using a rooted Android phone (your phone) showing the full SIP session setup and RTP data for a VoLTE call, including the call handover to WiFi. Specifically, we need packet captures to show:
1) Setup a call on mobile network with VoLTE, handover to WiFi and then shut down call. PCAP should include both the decrypted IPSec data and the WiFi physical interface data (may be split into 2 different simultaneous captures or combined into one). In other words, we want the WiFi interface packets included (e.g. the WiFi adapter such as wlan0).
2) Setup a call on WiFi, handover to mobile network w/ VoLTE and then shut down call. Need the same data as above.
Attached is a PDF from a blog explaining one way the capture and decryption of the IPSec tunnel can be done on a smartphone.
We would prefer at least ~15 seconds of voice data both before and after the handover.