| 摘要 |
A media exchange monitor is disclosed that selectively (i) introduces a mixer into a two-party call when the two-party call becomes a conference call (ad-hoc conference), and (ii) removes the mixer when one or more conference call participants drop out, leaving only two participants behind. When a party to a two-party call requests to convert the call into a conference call, the packet telephony system responds to the conference call request by connecting a mixer to service the conference call between the parties. When parties drops out of a conference call, leaving only two parties behind, the mixer is removed from the conference call. In one implementation, the mixer is removed from the conference call only if the two remaining parties can exchange media directly. When the media connection among the parties must be changed to introduce or remove the mixer, the media exchange monitor achieves the desired connectivity by initially querying the parties for their capabilities. Thereafter, the media exchange monitor instructs the parties to establish a direct connection for a two-party call or to connect to the mixer for a conference call. The media exchange monitor processes the results of the capability query to select a compatible compression algorithm.
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