| 摘要 |
A method is provided for use in a push to talk type service. A message is received (3) at a server (S) from a second terminal (B) inviting a first terminal (A) to establish a push to talk type session. The message comprises a list of media types that the second terminal (B) may send to the first terminal (A) during the session. Prior to that, the server (S) is notified (1) by the first terminal (A) of information specifying, for the or each of at least one media type, in what circumstance, if at all, the first terminal (A) would accept that media type in a push to talk type session. In response to receipt of the invite message, and based on the information, the list of media types is reviewed by the server (S) to leave out any media types that the first terminal (A) would not accept from the second terminal (B). If there remains at least one media type in the list, the invite message, with the reviewed list, is then forwarded (5) to the first terminal. In one embodiment, the invite message is an Invite message of the Session Initiation Protocol (SIP), and Session Description Protocol (SDP) parameters are used to specify the list of media types. The push to talk type service may be a push to talk over cellular service (PoC). The push to talk type service may be a conferencing service.
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