Session description
      v=  (protocol version)
      o=  (originator and session identifier)
      s=  (session name)
      i=* (session information)
      u=* (URI of description)
      e=* (email address)
      p=* (phone number)
      c=* (connection information -- not required if included in
           all media descriptions)
      b=* (zero or more bandwidth information lines)
      One or more time descriptions:
        ("t=", "r=" and "z=" lines; see below)
      k=* (obsolete)
      a=* (zero or more session attribute lines)
      Zero or more media descriptions

   Time description
      t=  (time the session is active)
      r=* (zero or more repeat times)
      z=* (optional time zone offset line)

   Media description, if present
      m=  (media name and transport address)
      i=* (media title)
      c=* (connection information -- optional if included at
           session level)
      b=* (zero or more bandwidth information lines)
      k=* (obsolete)
      a=* (zero or more media attribute lines)