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Showing posts from April, 2014

What does the MSID attribute in the SDP mean?

There is a work in progress in the IETF [1] to define a new MSID attribute to be used in the SDP. This attribute has been defined in the context of WebRTC and it is already being sent by WebRTC endpoints (Firefox and Chrome). This is a typical SDP generated by Chrome:

v=0 o=- 658899108507703479 2 IN IP4 127.0.0.1 s=- t=0 0 a=group:BUNDLE audio video a=msid-semantic: WMS FmJZgkjbR2gBS25U0hP3qoUSjvfDddQl4UjJ m=audio 1 RTP/SAVPF 111 103 104 0 8 106 105 13 126 ... a=ssrc:1400694016 cname:Yk4LvPXyWNZKkW6S a=ssrc:1400694016 msid:FmJZgkjbR2gBS25U0hP3qoUSjvfDddQl4UjJ a228df45 a=ssrc:1400694016 mslabel:FmJZgkjbR2gBS25U0hP3qoUSjvfDddQl4UjJ a=ssrc:1400694016 label:a228df45-515e-49b6-be8f-0d044b65de64 m=video 1 RTP/SAVPF 100 116 117 ... a=ssrc:1484622160 cname:Yk4LvPXyWNZKkW6S a=ssrc:1484622160 msid:FmJZgkjbR2gBS25U0hP3qoUSjvfDddQl4UjJ 00f2f3d2 a=ssrc:1484622160 mslabel:FmJZgkjbR2gBS25U0hP3qoUSjvfDddQl4UjJ a=ssrc:1484622160 label:00f2f3d2-974e-48a6-b8dc-0f70194949d5 But what is it for and why…