At present, our EasyGBS, EasyRTC, EasyDSS and other platforms have implemented weBRTC protocol video playback, in the development of WeBRTC, information interaction needs to use SDP data format, while using FFPlay RTP data stream needs to obtain SDP file information first.

SDP session description protocol: describes SAP, SIP, and RTSR sessions. It is a file description protocol that describes the encoding information of media files generated by the server and the link to the server. In a multimedia session, the SDP transmits information about the media stream and causes the participants of the session description to join the session. The SDP is mainly used on the Intemet network, but can also be used on other networks.

SDP is very general and can describe sessions in other network environments, but it is mainly used in Intemet. SDP format:

v=<version>
o=<username> <session id> <version> <network type> <address type> <address>
s=<session name>
i=<session description>
u=<URI>
e=<email address>
p=<phone number>
c=<network type> <address type> <connection address>
b=<modifier>:<bandwidth-value>
t=<start time> <stop time>
r=<repeat interval> <active duration> <list of offsets from start-time>
z=<adjustment time> <offset> <adjustment time> <offset> ....
k=<method>
k=<method>:<encryption key>
a=<attribute>
a=<attribute>:<value>
m=<media> <port> <transport> <fmt list>
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Explanation:

V = (protocol version) o = (owner/creator and session identifier) s = (session name) I = * (session information) u = * (URI description) e = * (Email address) p = * (phone number) c = * (connection information) b = * (Bandwidth information) z = * (time zone adjustment) K = * (encryption key) a = * (0 or more session attribute lines)Copy the code

Time description:

T = (session activity time) r = * (0 or number of repetitances)Copy the code

Media description:

M = (Media name and transport address) I = * (media title) c = * (Connection information - optional if included at the session layer) b = * (bandwidth information) K = * (Encryption key) a = * (0 or more media attribute lines)Copy the code

During RTSP interactions, SDP messages are sent only when the client makes a Describe request and the server responds. The following is an SDP information printed by EasyRTSPClient.