Make sure to have the latest stable Wireshark release (v2.4.4), with SpanDSP support build in.
Steps are rather simple, no 3rd party software required.
- Open Capture file with RTP packet in them
- Select from the menu Telephony | RTP Streams
- From the list select the stream you want to hear
- Click Analyse
- Click Play Streams
- This brings you to the RTP player with the waveform of the audio in the RTP packets.
- Click play to output the audio to the selected output device
