Description of Media parameter in SIP "m=audio 12548 RTP/AVP 0 8 101"

Question

Can anyone describe each parameter in following media information

m=audio 12548 RTP/AVP 0 8 101

Thanks

Answer 1

It's a field from SDP protocol, describing parameters of media ("m" is for "media"). Next, 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. There are some links that can be useful:

• https://www.rfc-editor.org/rfc/rfc4566
• https://en.wikipedia.org/wiki/Session_Description_Protocol
• http://www.3cx.com/blog/voip-howto/sdp-voip2/
• http://en.wikipedia.org/wiki/RTP_audio_video_profile