m=audio 12548 RTP/AVP 0 8 101
It’s a field from SDP protocol, describing parameters of media (“m” is for “media”). Next, the type of media is “audio”, not video, for example. (m=audio). 12548 is a port address for streaming media. “RTP/AVP” means “RTP Audio/Video
Profile” and representing one of RTP profiles, which are coded by 0, 8 and 101. 0 is PCMU 8000 Hz, 8 is PCMA 8000 Hz, and 101 is payload type for DTMF digits sending.