The VoIP Calls window shows a list of all detected VoIP calls in the captured traffic. It finds calls by their signaling.

More details can be found on the https://wiki.wireshark.org/VoIP_calls page.

The RTP Player window lets you play back RTP audio data. In order to use this feature your version of Wireshark must support audio and the codecs used by each RTP stream.

More details can be found on the https://wiki.wireshark.org/VoIP_calls page.